QT60486 [QUANTUM]

32 & 48 KEY QMATRIX ICs; 32和48个重点QMATRIX集成电路


型号：	QT60486
厂家：	QUANTUM RESEARCH GROUP
描述：	32 & 48 KEY QMATRIX ICs 32和48个重点QMATRIX集成电路
文件：	总32页 (文件大小：881K)
中文：	中文翻译
下载：	下载PDF数据表文档文件

QT60326, QT60486

32 & 48 KEY QMATRIX™ IC

z Advanced second generation QMatrix™ controller

z Keys individually adjustable for sensitivity, response

time, and many other critical parameters

z Panel thicknesses to 50mm through any dielectric

z 32 and 48 key versions

44 43 42 41 40 39 38 37 36 35

MOSI

MISO

SCK

/RST

Vdd

Vss

XT2

XT1

Y3B

Y2B

Y1B

Y0B

Vdd

Vss

Vdd

z 100% autocal for life - no in-field adjustments

z SPI Slave and UART interfaces

QT60326

QT60486

z Sleep mode with wake pin

z Adjacent key suppression feature

z Synchronous noise suppression pin

z Spread-spectrum modulation: high noise immunity

z Mix and match key sizes & shapes in one panel

z Low overhead communications protocol

z FMEA compliant design features

TQFP-44

13 14 15 16 17 18

20 21 22

z Negligible external component count

z Extremely low cost per key

z 44-pin Pb-free TQFP package

APPLICATIONS -

y Security keypanels

y Industrial keyboards

y Appliance controls

y Outdoor keypads

y ATM machines

y Touch-screens

y Automotive panels

y Machine tools

These digital charge-transfer (“QT”) QMatrix™ ICs are designed to detect human touch on up 48 keys when used with a scanned,

passive X-Y matrix. They will project touch keys through almost any dielectric, e.g. glass, plastic, stone, ceramic, and even wood, up to

thicknesses of 5 cm or more. The touch areas are defined as simple 2-part interdigitated electrodes of conductive material, like copper

or screened silver or carbon deposited on the rear of a control panel. Key sizes, shapes and placement are almost entirely arbitrary;

sizes and shapes of keys can be mixed within a single panel of keys and can vary by a factor of 20:1 in surface area. The sensitivity of

each key can be set individually via simple functions over the SPI or UART port, for example via Quantum’s QmBtn program, or from a

host microcontroller. Key setups are stored in an onboard eeprom and do not need to be reloaded with each powerup.

These devices are designed specifically for appliances, electronic kiosks, security panels, portable instruments, machine tools, or

similar products that are subject to environmental influences or even vandalism. It can permit the construction of 100% sealed,

watertight control panels that are immune to humidity, temperature, dirt accumulation, or the physical deterioration of the panel surface

from abrasion, chemicals, or abuse. To this end the device contains Quantum-pioneered adaptive auto self-calibration, drift

compensation, and digital filtering algorithms that make the sensing function robust and survivable.

The parts can scan matrix touch keys over LCD panels or other displays when used with clear ITO electrodes arranged in a matrix.

They do not require 'chip on glass' or other exotic fabrication techniques, thus allowing the OEM to source the matrix from multiple

vendors. Materials such as such common PCB materials or flex circuits can be used.

External circuitry consists of a resonator and a few passive parts, all of which can fit into a 6.5 sq cm footprint (1 sq inch). Control and

data transfer is via either an SPI or UART port.

These devices make use of an important new variant of charge-transfer sensing, transverse charge-transfer, in a matrix format that

minimizes the number of required scan lines. Unlike older methods, it does not require one IC per key.

AVAILABLE OPTIONS

T_A

# Keys

Part Number

QT60326-AS-G

QT60486-AS-G

-40⁰C to +105⁰C

QT60486-AS R8.01/0105

Contents

4.15 Return Last Command - 0x0f

. . . . . . . . . . . . . . . . . . 16

4.16 Internal Code - 0x10

1 Overview

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1.1 Part differences

1.2 Enabling / Disabling Keys

. . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . 16

4.17 Internal Code - 0x11

4.18 Internal Code - 0x12

4.19 Sleep - 0x16

. . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . .

2 Hardware & Functional

2.1 Matrix Scan Sequence

. . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . 16

2.2 Burst Paring

2.3 Response Time

2.4 Oscillator

4.20 Data Set for One Key - 0x4k

. . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . 16

4.21 Status for Key ‘k’ - 0x8k

4.22 Cal Key ‘k’ - 0xck

4.23 Command Sequencing

. . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . 16

. . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . 16

2.5 Sample Capacitors; Saturation Effects

. . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . 16

. . . . . . . . . . . . . . . . . . . 18

Table 4.2 Command Summary

2.6 Sample Resistors

2.7 Signal Levels

2.8 Matrix Series Resistors

2.9 Key Design

2.10 PCB Layout, Construction

. . . . . . . . . . . . . . . . . . . . . . . .

5 Setups

. . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

5.1 Negative Threshold - NTHR

. . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . 20

5.2 Positive Threshold - PTHR

5.3 Drift Compensation - NDRIFT, PDRIFT

5.4 Detect Integrators - NDIL, FDIL

. . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . 20

2.10.1 LED Traces and Other Switching Signals

. . . . . . . . . . . .

. . . . . . . . . . . . . . . . . 21

2.10.2 PCB Cleanliness

5.5 Negative Recal Delay - NRD

. . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . 21

2.11 Power Supply Considerations

2.12 Startup / Calibration Times

5.6 Positive Recalibration Delay - PRD

5.7 Burst Length - BL

. . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . 21

. . . . . . . . . . . . . . . . . . . . . . . . 22

Table 2-1 Calibration Timings

5.8 Adjacent Key Suppression - AKS

. . . . . . . . . . . . . . . . 22

. . . . . . . . . . . . . . . . . . . 22

. . . . . . . . . . . . . . . . . 22

2.13 Reset Input

2.14 Spread Spectrum Acquisitions

2.15 Detection Integrators

2.16 FMEA Tests

5.9 Oscilloscope Sync - SSYNC

5.10 Negative Hysteresis - NHYST

5.11 Dwell Time - DWELL

. . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . 22

. . . . . . . . . . . . . . . . . . . . . 22

. . . . . . . . . . . . . . . . . . . . . . . 23

5.12 Mains Sync - MSYNC

5.13 Burst Spacing - BS

5.14 Serial Rate - SR

. . . . . . . . . . . . . . . . . . . . . . . . . .

2.17 Wiring

. . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Table 2.2 - Pin Listing

. . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . 23

Figure 2.7 Wiring Diagram

5.15 Lower Signal Limit - LSL

5.16 LED / Alert Output - LED

5.17 Host CRC - HCRC

. . . . . . . . . . . . . . . . . . . . . . 10

. . . . . . . . . . . . . . . . . . . . . 11

. . . . . . . . . . . . . . . . . . . . 23

3 Serial Communications

3.1 DRDY Pin

3.2 SPI Communications

. . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

. . . . . . . . . . . . . . . . . . . . . . . 23

. . . . . . . . . . . . . . . . . . . . . . . 24

Table 5.1 Setups Block

. . . . . . . . . . . . . . . . . . . . . . 11

. . . . . . . . . . . . . . . . . . . . . 12

. . . . . . . . . . . . . . . . . . . . . . . 13

. . . . . . . . . . . . . . . . . . . . . . 13

Table 5.2 LED Function Control Byte Bits

Table 5.3 Key Mapping

3.3 UART Communications

. . . . . . . . . . . . . . . 25

4 Control Commands

. . . . . . . . . . . . . . . . . . . . . . . 25

Table 5.4 Setups Block Summary

4.1 Null Command - 0x00

. . . . . . . . . . . . . . . . . . 26

4.2 Enter Setups Mode - 0x01

4.3 Cal All - 0x03

4.4 Force Reset - 0x04

4.5 General Status - 0x05

4.6 Report 1st Key - 0x06

4.7 Report Detections for All Keys - 0x07

Table 4.1 Bit fields for multiple key reporting and key

numbering . . . . . . . . . . . . . . . . . . . . . . . . . . . .

4.8 Report Signals for All Keys - 0x08

4.9 Report References for All Keys - 0x09

4.10 Report Deltas for All Keys - 0x0a

4.11 Report Error Flags for All Keys - 0x0b

4.12 Report FMEA Status - 0x0c

4.13 Dump Setups Block - 0x0d

4.14 Eeprom CRC - 0x0e

6 Specifications

. . . . . . . . . . . . . . . . . . . . 14

. . . . . . . . . . . . . . . . . . . . . . . . . . 27

6.1 Absolute Maximum Electrical Specifications

6.2 Recommended operating conditions

. . . . . . . . . . . . . . . . . . . . . . . . . . 14

. . . . . . . . . . . 27

. . . . . . . . . . . . . . . . . . . . . . . 14

. . . . . . . . . . . . . . . . . . . . . . 14

. . . . . . . . . . . . . . . . . . . . . . 15

. . . . . . . . . . . . . . . 27

. . . . . . . . . . . . . . . . . . . . . . . . 27

. . . . . . . . . . . . . . . . . . . . . . 27

6.3 DC Specifications

6.4 Timing Specifications

6.5 Mechanical Dimensions

6.6 Marking

. . . . . . . . . . . . . . 15

. . . . . . . . . . . . . . . . . . . . . 27

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29

7 Appendix

. . . . . . . . . . . . . . . . 15

. . . . . . . . . . . . . . 15

. . . . . . . . . . . . . . . . 15

7.1 8-Bit CRC Software C Algorithm

7.2 16-Bit CRC Software C Algorithm

7.3 1-Sided Key Layout

. . . . . . . . . . . . . . . . . 29

. . . . . . . . . . . . . . . . 29

. . . . . . . . . . . . . . . . . . . . . . . 30

. . . . . . . . . . . . . 15

7.4 PCB Layout

. . . . . . . . . . . . . . . . . . . . . . . . . . . 30

. . . . . . . . . . . . . . . . . . 15

. . . . . . . . . . . . . . . . . . . 15

. . . . . . . . . . . . . . . . . . . . . . 15

QT60486-AS R8.01/0105

QmBtn software for the PC can be used to program the

operation of the IC as well as read back key status and signal

levels in real time.

1 Overview

QMatrix devices are digital burst mode charge-transfer (QT)

sensors designed specifically for matrix geometry touch

controls; they include all signal processing functions necessary

to provide stable sensing under a wide variety of changing

conditions. Only a few external parts are required for operation.

The entire circuit can be built within a few square centimeters of

single-sided PCB area. CEM-1 and FR1 punched, single-sided

materials can be used for possible lowest cost. The PCB’s rear

can be mounted flush on the back of a glass or plastic panel

using a conventional adhesive, such as 3M VHB 2-sided

adhesive acrylic film.

The parts are electrically identical with the exception of the

number of keys which may be sensed.

1.1 Part differences

Versions of the device are capable of a maximum of 32 or 48

keys (QT60326, QT60486 respectively).

These devices are identical in all respects, except that each is

capable of only the number of keys specified. These keys can

be located anywhere within the electrical grid of 8 X and 6 Y

scan lines.

QMatrix parts employ transverse charge-transfer ('QT') sensing,

a technology that senses changes in electrical charge forced

across an electrode by a pulse edge (Figure 1-1).

Unused keys are always pared from the burst sequence in

order to optimize speed. Similarly, in a given part a lesser

number of enabled keys will cause any unused acquisition burst

timeslots to be pared from the sampling sequence to optimize

acquire speed. Thus, if only 40 keys are actually enabled, only

40 timeslots are used for scanning.

Figure 1-1 Field flow between X and Y elements

overlying panel

1.2 Enabling / Disabling Keys

The NDIL parameter is used to enable and disable keys in the

matrix. Setting NDIL = 0 for a key disables it (Section 5.4). At

no time can the number of enabled keys exceed the maximum

specified for the device in the case of the QT60326.

element

On the QT60326, only the first 4 Y lines (Y0..Y3) are

operational by default. On the QT60326, to use keys located on

lines Y4 and Y5, one or more of the pre-enabled keys must be

disabled simultaneously while enabling the desired new keys.

This can be done in one Setups block load operation.

cmos

driver

QMatrix devices allow for a wide range of key sizes and shapes

to be mixed together in a single touch panel. The approximate

design rules for these keys can be seen in Figure 2-6.

2 Hardware & Functional

The actual internal pattern style is not as important as is the

need to achieve regular X and Y widths and spacings of

sufficient size to cover the desired graphical key area or a little

bit more; 2mm overhand is acceptable in most cases, since the

fields drop off near the edges anyway. The overall key size can

range from 10mm x 10mm up to 100mm x 100mm. The keys

can be any shape including round, rectangular, square, etc.

The internal pattern can be as simple as a single bar of Y or as

complex as the interleaved structure shown in Figure 2-6.

2.1 Matrix Scan Sequence

The circuit operates by scanning each key sequentially, key by

key. Key scanning begins with location X=0 / Y=0 (key #0). X

axis keys are known as rows while Y axis keys are referred to

as columns. Keys are scanned sequentially by row, for example

the sequence X0Y0 X1Y0 .... X7Y0, X0Y1, X1Y1... etc. Keys are

also numbered from 0..47. Key 0 is located at X0Y0. A table of

key numbering is located on page 25.

Each key is sampled in a burst of acquisition pulses whose

length is determined by the Setups parameter BL (page 22),

which can be set on a per-key basis. A burst is completed

entirely before the next key is sampled; at the end of each burst

the resulting signal is converted to digital form and processed.

The burst length directly impacts key gain; each key can have a

unique burst length in order to allow tailoring of key sensitivity

on a key by key basis.

For better surface moisture suppression, the outer perimeter of

X should be as wide as possible, and there should be no

ground planes near the keys. The variable ‘T’ in this drawing

represents the total thickness of all materials that the keys must

penetrate.

A picture of an actual board made using similar key geometries

is shown on page 30.

The devices use both UART and SPI interfaces to allow key

data to be extracted and to permit individual key parameter

setup. The interface protocol uses simple single byte

commands and responds with single byte responses in most

cases. The command structure is designed to minimize the

amount of data traffic while maximizing the amount of

information conveyed.

2.2 Burst Paring

Keys that are disabled by setting NDIL =0 (page 21) have their

bursts pared from the scan sequence to save time. This has the

consequence of affecting the scan rate of the entire matrix as

well as the time required for initial matrix calibration. It does not

affect the time required to calibrate an individual key once the

matrix is initially calibrated after power-up or reset.

In addition to normal operating and setup functions the device

can also report back actual signal strengths and error codes.

QT60486-AS R8.01/0105

increasing BL to a high count and watching what the waveform

does as it descends towards and below -0.25V. The waveform

will appear deceptively straight, but it will start to flatten even

before the -0.25V level is reached.

2.3 Response Time

The response time of the device depends on the scan rate of

the keys (Section 5.13), the number of keys enabled (Section

5.4), the detect integrator settings (Section 5.4), and the serial

polling rate by the host microcontroller (or the use of the LED

pin as an interrupt to the host; Sections 5.16, and Table 5.2 on

page 25). An example timing:

A correct waveform is shown in Figure 2-3. Note that the

bottom edge of the bottom trace is substantially straight

(ignoring the downward spikes).

Keys enabled (KE) = 20

Burst spacing (BS) = 1ms

NDIL = 3

Unlike other QT circuits, the Cs capacitor values on QT60xx6

devices have no effect on conversion gain. However they do

affect conversion time.

FDIL = 5

Unused Y lines should be left open.

Host polling rate (PR) = 10ms

The worst case response time is computed as:

((KE + FDIL) x NDIL x BS) + PR = Worst case response

((20 + 5) x 3 x 1ms) + 10ms = 85ms

2.6 Sample Resistors

There are 6 sample resistors (Rs) used to perform single-slope

ADC conversion of the acquired charge on each Cs capacitor.

These resistors directly control acquisition gain: larger values of

Rs will proportionately increase signal gain. Values of Rs can

range from 220K✡ to 1M✡. 220K✡ is a reasonable value for

most purposes.

The use of the LED pin to trigger host sampling can reduce this

to ~75ms by saving the majority of the host polling time; see

Section 5.16.

Larger values for Rs will also increase conversion time and may

reduce the fastest possible key sampling rate, which can impact

response time especially with larger numbers of enabled keys.

2.4 Oscillator

The oscillator can use either a quartz crystal or a ceramic

resonator. In either case, the XT1 and XT2 must both be loaded

with 22pF capacitors to ground. 3-terminal resonators having

onboard ceramic capacitors are commonly available and are

recommended. An external TTL-compatible frequency source

can also be connected to XT1 in which case, XT2 should be left

unconnected.

Unused Y lines do not require an Rs resistor.

The frequency of oscillation should be 16MHz +/-1% for

accurate UART transmission timing.

Figure 2-1 VCs - Non-Linear During Burst

(Burst too long, or Cs too small, or X-Y capacitance too large)

2.5 Sample Capacitors; Saturation Effects

The charge sampler capacitors on the Y pins should be the

values shown. They should be X7R or NP0 ceramics or PPS

film. The value of these capacitors is not critical but 4.7nF is

recommended for most cases.

Cs voltage saturation is shown in Figure 2-1. This nonlinearity

is caused by excessively negative voltage on Cs inducing

conduction in the pin protection diodes. This badly saturated

signal destroys key gain and introduces a strong thermal

coefficient which can cause 'phantom' detection. The cause of

this is usually from the burst length being too long, the Cs value

being too small, or the X-Y coupling being too large. Solutions

include loosening up the interdigitation of key structures,

separating X and Y lines on the PCB more, increasing Cs, and

decreasing the burst length.

Figure 2-2 VCs - Poor Gain, Non-Linear During Burst

(Excess capacitance from Y line to Gnd)

Increasing Cs will make the part slower; decreasing burst

length will make it less sensitive. A better PCB layout and a

looser key structure (up to a point) have no negative effects.

Cs voltages should be observed on an oscilloscope with the

matrix layer bonded to the panel material; if the Rs side of any

Cs ramps more negative than -0.25 volts during any burst (not

counting overshoot spikes which are probe artifacts), there is a

potential saturation problem.

Figure 2-3 Vcs - Correct

Figure 2-2 shows a defective waveform similar to that of 2-1,

but in this case the distortion is caused by excessive stray

capacitance coupling from the Y line to AC ground, for example

from running too near and too far alongside a ground trace,

ground plane, or other traces. The excess coupling causes the

charge-transfer effect to dissipate a significant portion of the

received charge from a key into the stray capacitance. This

phenomenon is more subtle; it can be best detected by

QT60486-AS R8.01/0105

Figure 2-4 X-Drive Pulse Roll-off and Dwell Time

Figure 2-6 Recommended Key Structure

‘T’ should ideally be similar to the complete thickness the fields need to

penetrate to the touch surface. Smaller dimensions will also work but will give

less signal strength. If in doubt, make the pattern coarser.

Lost charge due to

inadequate settling

before end of dwell time

X drive

Dwell time

Y gate

Figure 2-5 Probing X-Drive Waveforms with a Coin

2.8 Matrix Series Resistors

The X and Y matrix scan lines should use series resistors

(referred to as Rx and Ry respectively) for improved EMI

performance.

X drive lines require them in most cases to reduce edge rates

and thus reduce RF emissions. Typical values range from 1K to

20K✡.

Y lines need them to reduce EMC susceptibility problems and in

some extreme cases, ESD. Typical Y values range around

1K✡. Y resistors act to reduce susceptibility problems by

forming a natural low-pass filter with the Cs capacitors.

It is essential that the Rx and Ry resistors and Cs capacitors be

placed very close to the chip. Placing these parts more than a

few millimeters away opens the circuit up for high frequency

interference problems (above 20MHz) as the trace lengths

between the components and the chip start to act as RF

antennae.

2.7 Signal Levels

The upper limits of Rx and Ry are reached when the signal

level and hence key sensitivity are clearly reduced. The limits of

Rx and Ry will depending on key geometry and stray

capacitance, and thus an oscilloscope is required to determine

optimum values of both.

Using Quantum’s QmBtn™ software it is easy to observe the

absolute level of signal received by the sensor on each key.

The signal values should normally be in the range from 250 to

750 counts with properly designed key shapes (see appropriate

Quantum app note on matrix key design). However, long

adjacent runs of X and Y lines can also artificially boost the

signal values, and induce signal saturation: this is to be

avoided. The X-to-Y coupling should come mostly from

intra-key electrode coupling, not from stray X-to-Y trace

coupling.

The upper limit of Rx can vary depending on key geometry and

stray capacitance, and some experimentation and an

oscilloscope are required to determine optimum values.

Dwell time (page 22) affects the duration in which charge

coupled from X to Y can be captured. Increasing the dwell will

increase the signal levels lost to higher values of Rx and Ry, as

shown in Figure 2-4. Too short a dwell time will cause charge to

be 'lost', if there is too much rising edge roll-off. Lengthening

the dwell time will cause this lost charge to be recaptured,

thereby restoring key sensitivity. In these devices, dwell time is

adjustable (see Section 5.11) to one of 3 values.

QmBtn software is available free of charge on Quantum’s web

site.

The signal swing from the smallest finger touch should

preferably exceed 10 counts, with 15 being a reasonable target.

The signal threshold setting (NTHR) should be set to a value

guaranteed to be less than the signal swing caused by the

smallest touch.

Dwell time problems can also be solved by either reducing the

stray capacitance on the X line(s) (by a layout change, for

example by reducing X line exposure to nearby ground planes

or traces), or, the Rx resistor needs to be reduced in value (or a

combination of both approaches).

Increasing the burst length (BL) parameter will increase the

signal strengths as will increasing the sampling resistor (Rs)

values.

One way to determine X settling time is to monitor the fields

using a patch of metal foil or a small coin over the key (Figure

QT60486-AS R8.01/0105

2-5). Only one key along a particular X line needs to be

observed, as each of the keys along that X line will be identical.

The chosen dwell time should exceed the observed 95%

settling of the X-pulse by 25% or more.

the device. Such signals should be routed away from the Y

lines, or the design should be such that these lines are not

switched during the course of signal acquisition (bursts).

LED terminals which are multiplexed or switched into a floating

state and which are within or physically very near a key

structure (even if on another nearby PCB) should be bypassed

to either Vss or Vdd with at least a 10nF capacitor of any type,

to suppress capacitive coupling effects which can induce false

signal shifts. Led terminals which are constantly connected to

Vss or Vdd do not need further bypassing.

In almost all case, Ry should be set equal to Rx, which will

ensure that the charge on the Y line is fully captured into the Cs

capacitor.

2.9 Key Design

Circuits can be constructed out of a variety of materials

including flex circuits, FR4, and even inexpensive single-sided

CEM-1.

2.10.2 PCB Cleanliness

All capacitive sensors should be treated as highly sensitive

circuits which can be influenced by stray conductive leakage

paths. QT devices have a basic resolution in the femtofarad

range; in this region, there is no such thing as ‘no clean flux’.

Flux absorbs moisture and becomes conductive between

solder joints, causing signal drift and resultant false detections

or transient losses of sensitivity or instability. Conformal

coatings will trap in existing amounts of moisture which will then

become highly temperature sensitive.

The actual internal pattern style is not as important as is the

need to achieve regular X and Y widths and spacings of

sufficient size to cover the desired graphical key area or a little

bit more; ~3mm oversize is acceptable in most cases, since the

key’s electric fields drop off near the edges anyway. The overall

key size can range from 10mm x 10mm up to 100mm x 100mm

but these are not hard limits. The keys can be any shape

including round, rectangular, square, etc. The internal pattern

can be as simple as a single bar of Y within a solid perimeter of

X, or (preferably) interdigitated as shown in Figure 2-6.

The designer should specify ultrasonic cleaning as part of the

manufacturing process, and in cases where a high level of

humidity is anticipated, the use of conformal coatings after

cleaning to keep out moisture.

For better surface moisture suppression, the outer perimeter of

X should be as wide as possible, and there should be no

ground planes near the keys. The variable ‘T’ in this drawing

represents the total thickness of all materials that the keys must

penetrate.

2.11 Power Supply Considerations

As these devices use the power supply itself as an analog

reference, the power should be very clean and come from a

separate regulator. A standard inexpensive LDO type regulator

should be used that is not also used to power other loads such

as LEDs, relays, or other high current devices. Load shifts on

the output of the LDO can cause Vdd to fluctuate enough to

cause false detection or sensitivity shifts.

See Figure 2-6 and page 30 for examples of key layouts.

2.10 PCB Layout, Construction

It is best to place the chip near the touch keys on the same

PCB so as to reduce X and Y trace lengths, thereby reducing

the chances for EMC problems. Long connection traces act as

RF antennae. The Y (receive) lines are much more susceptible

to noise pickup than the X (drive) lines.

Ceramic 0.1uF bypass capacitors should be placed very close

and routed with short traces to all power pins of the IC. There

should be at least 3 such capacitors around the part.

Even more importantly, all signal related discrete parts (R’s and

C’s) should be very close to the body of the chip. Wiring

between the chip and the various R’s and C’s should be as

short and direct as possible to suppress noise pickup.

2.12 Startup / Calibration Times

The devices require initialization times as follows:

Ground planes and traces should NOT be used around the

keys and the Y lines from the keys. Ground areas, traces, and

other adjacent signal conductors that act as AC ground (such

as Vdd and LED drive lines etc) will absorb the received key

signals and reduce signal-to-noise ratio (SNR) and thus will be

counterproductive. Ground planes around keys will also make

water film effects worse.

1. From very first powerup to ability to communicate:

2,083ms (one time event to initialize all of eeprom, or to

recover eeprom copy from FLASH in the event of

eeprom corruption)

2. From powerup to ability to communicate:

2,100 ms in the event the part is being forced to restore

the factory defaults.

Ground planes, if used, should be placed under or around the

QT chip itself and the associated R’s and C’s in the circuit,

under or around the power supply, and back to a connector, but

nowhere else.

3. From powerup to ability to communicate:

36 ms in the event the setups have been changed and

the part needs to backup the EEPROM to flash.

4. Normal cold start to ability to communicate:

See page 30 for an example of a 1-sided PCB layout.

3ms (Normal initialization from any reset)

5. Calibration time per key vs. burst spacings for 32 and 48

enabled keys (Table below):

2.10.1 LED Traces and Other Switching Signals

Digital switching signals near the Y lines will induce transients

into the acquired signals, deteriorating the SNR perfomance of

QT60486-AS R8.01/0105

QT60xx6 spread spectrum operates by using a frequency chirp

within each burst, in four different frequency bands.

Table 2-1 Calibration Timings

This feature is hardwired into the device and cannot be

disabled or modified.

Burst Spacing, Cal Time, ms, Cal Time, ms,

32 keys

48 keys

*Auto

0.50

0.75

1.00

1.25

1.50

1.75

2.00

2.25

2.50

2.75

3.00

see text

280

384

2.15 Detection Integrators

387

543

See also SR setup parameter, page 23.

UART mode is selected as soon as the QT receives any data

on the UART Rx pin. There is no other configuration required to

make the device operate in UART mode. Once UART is

selected after a power-up, the device cannot switch to SPI

mode unless the device is reset.

DRDY - Data Ready - active-high - indicates to the host that the

QT is ready to send or receive data. This pin idles high. This

pin includes an internal pull-up resistor of 20K ~ 50K. In SPI

mode this pin is an output only (i.e. open drain with internal

pull-up).

UART mode communications functions in the same basic way

as SPI communications. The Baud rate is adjusted by means of

setup parameter ‘SR’ (page 23). Once a new Baud rate has

been set, the device must be reset for the new rate to take

effect.

The MISO pin on the QT floats in 3-state mode between bytes

when /SS is high. This facilitates multiple devices on one SPI

bus.

The major difference with SPI mode is that the UART mode is

asynchronous and so the host does not clock the QT. No

framing /SS or clock signal is required, simplifying the interface

greatly. Return data is sent from the QT back to the host when

the data is ready.

Null Bytes: When the QT responds to a command with one or

more response bytes, the host should issue a null commands

(0x00) to get the response bytes back. The host should not

send new commands until all the responses are accepted back

from the QT from the prior command via nulls.

Figure 3-3 SPI Slave-Only Mode Timing (Fosc = 16MHz)

S1: m125ns

S2: [20ns

S3: m25ns

S4: [20ns

S9: m250ns

S5: [20µs S6: m1µs

S7: m125ns

S8: m125ns

high via pullup-R

DRDY

(from QT)

/SS

(from Host)

CLK

(from Host)

Data shifts in to QT on rising edge

MOSI

(Data from Host)

{Command byte}

Data shifts out of QT on falling edge

{optional 2nd command byte}

{null byte or next command to get QT response}

3-state

MISO

(Data from QT)

3-state

data response

QT60486-AS R8.01/0105

Multi-drop capability: Tx floats within 10µs after each

transmitted byte. This line can thus be shared with other UART

based peripherals. Tx includes an internal 20K ~ 50K pull-up

resistor to Vdd to prevent the line from floating down.

Figure 3-5 UART Connections

Host MCU QT60xx6

Rx Tx

Wake operation: The device can be put into sleep mode with a

serial command, 0x16 (page 16) and then be awaked with a

dummy byte from the host, if the Rx and WS pins are connected

together. The first received UART byte from the host after a

wake should be a 0xFF; any other byte value could create a

framing error. The start bit of the 0xFF forms a convenient

narrow wake pulse without being long enough to be interpreted

as a byte during the wake operation.

DRDY

P_IN

Simple RC networks and slower data rates are helpful to

resolve these issues. CRC checks have been added to critical

commands in order to detect transmission errors to a high level

of certainty.

The recommended method to reestablish communications after

Wake from Sleep is to send a 0x0F ('Get Last Command'

command) repeatedly until the correct response comes back

(the command's own compliment, i.e. 0xF0).

UART Timing Parameters: UART timings are as shown in

Figure 3-4. Delay timings for parameters U2 and U3 are

dependent on the specific command. See Section 4.

Rx - Receive async data. This pin is an input only.

Tx - Transmit async data. Drives out when transmitting but

floats within 10µs of the end of the stop bit, to allow bussing

with several similar parts. Tx should idle high, and it includes

an internal 20K ~ 50K resistor to Vdd. Tx is push-pull when

transmitting data for good drive characteristics.

4 Control Commands

Refer to Table 4.2, page 18 for further details.

Suggested command sequencing: See Section 4.23, page 16.

UART transmission parameters are:

The devices feature a set of commands which are used for

control and status reporting. The host device has to send the

command to the QT60xx6 and await a response.

Baud rate:

Start bits:

Data bits:

Parity:

9600 ~ 115,200

None

SPI mode: While waiting the host should delay for 20 µs from

the end of the command, then start to check if DRDY is or goes

high. If it is high, then the host master can clock out the

resulting byte(s).

Stop bits:

DRDY in UART mode: Section 3.1 applies.

DRDY is bi-directional in UART mode. DRDY can be pulled

down by either the QT or the host (wire-AND), so that either

device can be inhibited from sending data until the other is

ready. The host should obey this control line or transmission

errors can occur. The host should grant a 10µs grace period

after clamping DRDY low in which it can still accept the start bit

of a transmission from the QT.

UART mode: After the command is sent, the QT will send back

the response usually starting within 1ms. The host can clamp

DRDY low (wire-AND logic) to inhibit a response if the host is

not able to receive the transmission for a while.

Command timeouts: Where a command involves multi-byte

transfers in either direction, each byte must be transmitted

within 100ms of the prior byte or the command will timeout. No

error is reported for this condition; the command simply ceases.

As explained in Section 3.1, DRDY is not clamped low

immediately after the QT receives a byte; there can be up to a

20µs delay from the end of the stop bit before DRDY goes low.

Sampling of DRDY by the host should occur 20µs after the byte

has been fully sent; if DRDY is already high at this point, or

becomes high, then it is clear to send.

Word return byte order: Where a word or long word is

returned (16 or 24 bit number or bit pattern) the low order byte

is sent or received first.

Response delays: The device requires processing time to

complete command requests and respond with an answer to

the host. These timings are the same for SPI and UART modes.

Most commands respond with data in 1ms maximum; timing

parameters U2 and U3 in Figure 3-4 will thus be 1ms maximum

for these commands. The exceptions are:

Null Bytes: Unlike SPI mode, there is no reason to send null

bytes to the QT in UART mode. The QT device will respond to

commands with data when ready, subject to the DRDY line

being high.

UART Noise: In some designs it is necessary to run Tx and Rx

over a lengthy distance. This can introduce ringing, ground

bounce, and other noise problems which can corrupt data.

0x01 (Setups upload):

<20ms

0x0E (Get eeprom CRC):

0x16 (Sleep):

<5ms

Figure 3-4 UART Timing

4.1 Null Command - 0x00

Used to shift back data from the QT in SPI

mode. Since the host device is always the

master in SPI mode, and data is clocked in

both directions, the Null command is

U1: <=20us U2, U3: See text; U4: <10us

DRDY (handshake)

Rx (command from host)

required frequently to act as a placeholder

where the desire is to only get data back

from the QT, not to send a command.

floats high

Tx (response to host)

Stop bit

QT60486-AS R8.01/0105

In SPI communications, when the QT60xx6 responds to a

command with one or more response bytes, the host can issue

a new command instead of a null on the last byte shift

operation.

The host can monitor the progress of the recalibration by

checking the status byte, using command 0x05, during the

course of the calibration.

A key will show an error flag (using command 0x8k) indicating

the key has failed calibration if its signal is too noisy or if its

signal is below the low signal threshold. A key is deemed too

noisy if, at the end of calibration, the signal is no longer

between its computed negative hysteresis level and positive

thresholds.

New commands during intermediate byte shift-out operations

are ignored, and null bytes should always be used.

4.2 Enter Setups Mode - 0x01

This command is used to initiate the Setups block transfer from

Host to QT.

4.4 Force Reset - 0x04

The command must be repeated 2x within 100ms or the

command will fail; the repeating command must be sequential

without any intervening command. After the 2nd 0x01 from the

host, the QT will stop scanning keys and reply with the

character 0xFE. In SPI mode this character must be shifted out

by sending a null (0x00) from the host. This command

suspends normal sensing starting from the receipt of the

second 0x01. A failure of the command will cause a timeout.

The command must be repeated 2x within 100ms or the

command will fail; the repeating command must be sequential

without any intervening command. After the 2nd 0x04, the

device will reply with the character 0xFB just prior to executing

the reset operation.

After any reset, the device automatically performs a full key

calibration on all keys.

Each byte in the block must arrive at the QT no later than

100ms after the previous one or a timeout will occur. Any

timeout will cause the device to cancel the block load and go

back to normal operation.

The host can monitor the progress of the reset to see when the

chip is operating again by checking the status byte for

recalibration, by repeatedly issuing command 0x05 (see below).

If no response comes back, the command was not received and

the device should preferably be reset by the host just in case

there are any other problems.

4.5 General Status - 0x05

This command returns the general status bits. This command is

not as useful as the 0x06 command for routine use. The bits

returned from 0x05 are as follows:

If 0xFE is received by the host from the QT, then the host

should begin to transmit the block of Setups to the QT. The

DRDY line handshakes the data. The delay between bytes can

be as short as 10µs but the host can make it longer than this if

required, but no more than 100ms. The last two bytes the host

should send is the CRC for the block of data only (ie the CRC

should not include the command in its calculation).

BIT

Description

Reserved

1= communications failure

1= FMEA failure detected

1= eeprom corrupt

1= Mains sync error

1= calibration has failed on an

enabled key or, an LSL failure

1= any key in calibration

1= any key in detect

After the block transfer the QT will check the CRC and respond

with 0x00 if there was an error. Regardless, it will program the

internal eeprom. If the CRC was correct it will reply with a

second 0xFE after the eeprom was programmed.

If there was an error in the block transfer the device will restore

the last known good Setups from Flash memory the next time

the device is reset. However until that point, the device will

attempt to operate using the new Setups block even if it is

corrupt. Note that some Setups do not take effect until the part

is reset (e.g. Baud rate).

Notes:

Bit 6: Set if a communications failure. This can be reset by

sending command 0x0f (“last command command”) repeatedly

until a response of 0xf0 is received.

Bit 5: Set if an FMEA error was detected during operation. See

Section 2.16. A further amplification of what the FMEA error

consisted of is described in Section 4.12.

At the end of the full block load sequence, the device restarts

sensing without recalibration. Most of the setups in the block

will take effect immediately, but it is important to reset the

device after a block load to make all the changes effective

and permanent. See Section 4.4.

Bit 4: Set if eeprom corruption was detected. If this happens, it

is recommended that the device be reset. If a reset does not

cure the problem, the Setups block should be reloaded (Section

4.2) and the device reset again.

Command response timing: Responses to the bytes in the

setups block (both DRDY and return byte at the end) by the

part can take as long as 20ms each.

Bit 3: Set if there was a mains sync error, for example there

was no Sync signal detected within the allotted 100ms amount

of time. See Section 5.12. This condition is not necessarily fatal

to operation, however the device will operate very slowly and

may suffer from noise problems if the sync feature was required

for noise reasons.

4.3 Cal All - 0x03

This command must be repeated 2x within 100ms or the

command will fail; the repeating command must be sequential

without any intervening command.

Bit 2: Reports either a cal failure (failed in 5 sequential

attempts) on any enabled key or, that an enabled key has a

very low signal reference value, lower than the user-settable

LSL value (Section 5.15).

After the 2nd 0x03 from the host, the QT will reply with the

character 0xFC. Shortly thereafter the device will recalibrate all

keys and restart operation.

Bit 1: Set if any key is in the process of calibrating.

Bit 0: Set if any key is in detection (touched).

If no 0xFC comes back, the command was not properly

received and the device should preferably be reset.

QT60486-AS R8.01/0105

A CRC byte is appended to the response to the 0x05 command;

this CRC folds in the command value 0x05 itself initially.

4.10 Report Deltas for All Keys - 0x0a

Returns the delta signal values with respect to the reference

levels for all keys. Each value is an 8-bit unsigned number

representing {reference - signal}; negative results are truncated

to zero, i.e. those where the signal rises above the reference

value. This command returns 48 bytes. No CRC is appended to

the return, so the data should not be considered secure. The

byte for key 0 is returned first.

4.6 Report 1st Key - 0x06

Reports the first or only key to be touched, plus indicates if

there are yet other keys that are also touched.

The return bits are as follows:

BIT

Description

If the delta value attempts to exceed 255, the result is limited to

255.

1= more than 1 key is active

1= any error condition is present

Key bit 5

4.11 Report Error Flags for All Keys - 0x0b

Returns six bytes which show error flags as a bitfield for all

keys. Key 0 reports in bit 0 of the first byte returned; key 47 is

reported in bit 7 of the last byte returned. See Table 4.1 and

Table 5.3, page 25.

Key bit 4

Key bit 3

Key bit 2

Key bit 1

Key bit 0

One type of error reported with this command is the signal

being below its limit point (Section 5.15).

Bits 5..0 encode for the first detected key in range 0..47. If no

keys are active, these 6 bits are all 1’s (0x3F, 63 decimal when

bits 6, 7 are masked off).

A key that is in calibration also is reported as an error in the

response since it cannot operate as a key while it is calibrating.

This type of error flag is self-cleared once the key exits from

calibration. A calibration error flag due to an actual cal error can

be found thereafter using command 0x8k (Section 4.21).

If 2 or more keys in detection, bit 7 is set and the host should

interrogate the part via the 0x07 command to read out all the

key detections. This one command should be the dominant

interrogation command in the host interface; further commands

can be issued if the response to 0x06 warrants it. For example,

if there is an error flag, command 0x05 can be sent to find the

cause. If bit 7 is set, the command 0x07 can be sent to find

further keys in detection.

A CRC byte is appended to the response; this CRC folds in the

command 0x0b itself initially.

Note that these error bits exclude FMEA failure modes.

A CRC byte is appended to the response; this CRC folds in the

command 0x06 itself initially.

4.12 Report FMEA Status - 0x0c

Returns one byte which shows the FMEA error status of the X

and/or Y matrix scan lines. If an X line is in error, the

corresponding bit (below) is set. If a Y line has an FMEA error,

the entire field is set to ones (0xFF).

4.7 Report Detections for All Keys - 0x07

Returns six bytes which indicate all keys in detection if any, as a

bitfield. Key 0 reports in bit 0 of the first byte returned; key 47 is

reported in bit 7 of the last byte returned. See Table 4.1 and

Table 5.3, page 25.

Due to the physics of matrix wiring, a fault on any Y line will

cause faults to be reported on all X lines as well. It is not

possible to separate out these faults for reporting purposes.

A CRC byte is appended to the response; this CRC folds in the

command 0x07 itself initially.

A CRC byte is appended to the response; this CRC folds in the

command 0x0c itself initially.

Table 4.1 Bit fields for multiple key reporting and

key numbering

Key #

Bit Number (X line #)

For more information see Section 2.16.

4.13 Dump Setups Block - 0x0d

This command causes the device to dump the entire internal

Setups block back to the host.

If the transfer is not paced faster than 100ms per byte the

transfer will be aborted and the device will time out. This can

happen if the host is also controlling DRDY.

During the transfer, sensing is halted. Sensing is resumed after

the command has finished.

4.8 Report Signals for All Keys - 0x08

Returns the raw signal values for all keys. Each value is a 16-bit

number, and there are 48 words returned. No CRC is appended

to the return, so the data should not be considered secure. The

low byte of key 0 is returned first.

A 16-bit CRC is appended to the response; this CRC is the

same as the Setups table CRC and is sent LSByte first.

4.14 Eeprom CRC - 0x0e

4.9 Report References for All Keys - 0x09

Returns the reference values for all keys. Each value is a 16-bit

number, and there are 48 words returned. No CRC is appended

to the return, so the data should not be considered secure. The

low byte of key 0 is returned first.

This command returns the 16-bit CRC calculated from the

eeprom contents. The CRC is sent back LSByte first. The CRC

sent back is the same CRC that is appended to the end of the

Setups block.

QT60486-AS R8.01/0105

This command requires substantial amounts of time to process

and return a result; it is not recommended to use this command

except perhaps on startup or very infrequently.

A recommended method to reestablish communications after

Wake from Sleep is to send the QT device a 0x0F ('Last

Command' command) repeatedly until the correct response

comes back (the command's own compliment, i.e. 0xF0).

Command response timing: The response to this command

If Sync mode is also enabled, the part will assume the wakeup

pulse is also a sync signal, and resume scanning starting with

Key 0 (which is not necessarily where it left off scanning when it

went to sleep).

can take as long as 20ms.

No CRC is appended to the response.

4.15 Return Last Command - 0x0f

WS Note: The device checks the WS pin and waits for it to

return high before the part actually begins sleep. There is a

timeout limit on this wait of ~2s; if the WS pin has not gone high

after this time, the part will reset itself.

This command returns the last received command character, in

1’s complement (inverted). If the command is repeated twice or

more, it will return the inversion of 0x0f, 0xf0.

If a prior command was not valid or was corrupted, it will return

the bad command as well. This command also will reset the

communications error flag (Section 4.5).

4.20 Data Set for One Key - 0x4k

Returns the data set for key k, where k = {0..47} To form this

command, the key number is logical-OR’d into the byte 0x40.

This command returns 5 bytes, in the sequence:

No CRC is appended to the response.

Signal (2 bytes)

4.16 Internal Code - 0x10

Reference (2 bytes)

This command returns an internal code, as a value from 0..255.

Normal Detect Integrator (1 byte)

A CRC byte is appended to the response; this CRC folds in the

command 0x10 itself initially.

Signal and Reference are returned LSByte first.

No CRC is appended.

4.17 Internal Code - 0x11

This command returns an internal code word (3 bytes) of the

part for factory diagnostic purposes.

4.21 Status for Key ‘k’ - 0x8k

Returns a bitfield for key ‘k’ where k is from {0..47}. The bitfield

indicates as follows:

A CRC byte is appended to the response; this CRC folds in the

command 0x11 itself initially.

BIT

Description

1= reserved

4.18 Internal Code - 0x12

1= reserved

This command returns an internal code word (2 bytes) of the

part for factory diagnostic purposes.

1= reserved

1= key is enabled

1= key is in detect

No CRC is appended to the response.

1= signal ref < LSL (low signal error)

1= key is undergoing calibration

1= cal on this key failed 5 times

4.19 Sleep - 0x16

The command must be repeated 2x within 100ms or the

command will fail. After the 2nd 0x16 from the host, the device

will reply with the character 0xE9, then sleep. On wake from

Sleep, the device will issue a 0x01 character back to the host.

Bit 2 - LSL notes: See page 23.

A CRC byte is appended to the response; this CRC folds in the

command 0x8k itself initially.

Communications response timing: Responses to this

command may take from a few microseconds up to 5ms,

depending on what the device was doing at the moment the

command arrived.

4.22 Cal Key ‘k’ - 0xck

This command must be repeated 2x within 100ms or the

command will fail; the repeating command must be sequential

without any intervening command.

After the response, the device will enter low power sleep mode

until awakened by a >10µs low level on the WS pin. When it

wakes, it will resume current operation in the state from which it

exited and attempt to send a 0x01 code back to the host to

signal that it is ready to communicate again.

This command functions the same as 0x03 CAL command

except this command only affects one key ‘k’ where ‘k’ is from 0

to 47.

The chosen key ‘k’ is recalibrated in its native timeslot; normal

running of the part is not interrupted and all other keys operate

correctly throughout. This command is for use only during

normal operation to try to recover a single key that has failed or

is not calibrated correctly.

During Sleep the DRDY pin is held low, and released once the

device awakes and is ready to return the 0x01 code.

The WS pin can be connected to Rx or /SS to provide a ‘free’

wakeup connection from the host controller. In SPI mode with

/SS tied to WS, a /SS toggle (any low pulse of at least 10µs)

under software control from the host controller without an actual

SPI transmission will wake the device.

Returns the 1’s compliment of 0xck just before the key is

recalibrated.

In UART mode, with Rx tied to WS a 0xFF byte should be sent

to provide a pulse on WS. The start bit of the 0xFF forms a

convenient, narrow wake pulse without being long enough to be

interpreted as a byte during the wake operation.

4.23 Command Sequencing

To interface the device with a host, the flow diagram of Figure

4-1, page 17, is suggested. The actual settings of the Setups

block used should normally just be the default settings except

QT60486-AS R8.01/0105

Figure 4-1 Suggested Communications Flow

Power On or Hardware Reset

0x0F

Get

'Last command'

0x0E

Setups CRC

Check

0x01

Load Setups

Block

0x04

Force Reset

0xF0

returned

Setups CRC

failed 1x

0xF0 not

returned

CRC is OK

No key,

no error

Setups CRC failed 2x

0x06

Report 1st Key

~10ms Delay

0x05

Get

General Status

Any Error Flag

(highest

precedence)

2 Keys

Detected

0x0F

Get

Only 1 Key

in Detect

Comms

Error

'Last command'

(clear error)

0x07

Report all

detections

Keys OK

eeprom corrupt, or

calibration fail, or

FMEA fail, or

Internal Host

Processes

multiple errors

resolvable

error

Key Detection(s) Processing

Error Handling

Comms with

FMEA Calibration

Error

Stuck Key

Detected

Error

Note: CRC errors or incorrect

responses should cause

each transmission to retry

Done

0x0B

0x0C

Get

FMEA Status

0xck

Cal Key 'k'

Get

Errors for All

Keys

where changes are specifically required, such as for sensitivity,

timing, or AKS changes.

Error handling takes place whenever an error flag is detected,

or the device stops communicating (not shown). The error

handling procedure is up to the designer, however normally this

would entail shutting down the product if the error is serious

enough (for example, a key that will not calibrate, or a FMEA

class error).

The circles in this drawing are communications interchanges

between host and sensor. The rectangles are internal host

states or processing events. If any communications exchange

fails, either the device will fail to respond within the allotted time,

or the response CRC will be incorrect, or the response will be

out of context (the response is clearly not for the intended

command). In these cases the host should just repeat the

command.

Normally it is not required to reload the setups, since the device

itself stores a backup copy of these in Flash memory should the

eeprom become corrupt. However the host should reset the QT

so that the device will copy the Flash setups to eeprom, and

then the QT should check that the eeprom CRC code is correct.

Only if this fails should the eeprom be reloaded by the host.

One exception to this rule is just after powerup, since a CRC

error in the eeprom setups at this point is clearly a critical error

that would require reloading. This happens at the factory, during

the very first powerup cycle.

The control flow will spend 99% of its time alternating between

the two states within the dashed rectangle. If a key is detected,

the control flow will enter ‘Key Detection Processing’.

Stuck Key Detection processing (0xck) is optional, since the

device contains the max on-duration timeout function and can

therefore recalibrate the stuck key automatically. However, the

host can recalibrate stuck keys with greater flexibility if the

recalibration timeouts are set to infinite and the host recalibrates

them under specific conditions.

The ‘Last Command’ command can be used at any time to clear

comms error flags and to resynchronize failed communications,

for example due to timing errors etc.

QT60486-AS R8.01/0105

Table 4.2 Command Summary

Page

Hex

Name

Description

#/Cmd # rtnd Rtn range CRC

Notes

Flushes pending data from QT; one required to extract each response

0x00 Null command

Used to get data back in SPI mode

0..0xFF

byte.

First 0xFE issued when ready to get data, second 0xFE issued when

all loaded and burned; else timeout.

If 2 commands not received in 100ms, times out and no response is

issued. Part will timeout if each byte not received within 100ms of

previous byte.

Enter Setups, stop sensing; followed by block

load of binary Setups of length ‘nn’. Command

must be repeated 2x consecutively without any

intervening command in 100ms to execute.

Sensing auto-restarts, however, the device

should be reset after the block load to ensure

all new setups will take effect.

0xFE

+ 0xFE

If CRC failure, returns 0x00 instead of 0xFE

Enter Setups

2 + nn

+ 2

0x01

16 Data block length is ‘nn’ + 2 (CRC-16). LSL and CRC should be sent

low byte first. A CRC of 0x0000 is also acceptable in which case

the CRC is not checked.

mode

0xFE

+ 0x00 (err)

Internal EEPROM will update regardless of CRC health, but, if the

CRC is bad, the EEPROM will be declared invalid and thus on

reset the EEPROM will be restored from flash backup, overwriting

the desired (but corrupt) new setups.

Force device to recalibrate all keys; reenters

RUN mode afterwards automatically; 0x03

must be repeated 2x consecutively without any

intervening command in 100ms to execute

Force device to reset. Command must be

repeated 2x consecutively without any

intervening command in 100ms to execute

Returns 1’s complement of command to acknowledge cmd once the

cal has been initiated.

0x03 CAL all

0xFC

0xFB

If 2 commands not received in 100ms, times out and no response is

issued.

Returns 1’s complement of command to acknowledge command prior

0x04 Force reset

to reset. If 2 commands not received in 100ms, times out and no

response is issued.

Bit 7: reserved

Bit 6: 1= comms error: unrecognized command received

This bit can be reset by 0x0F cmmd

Bit 5: 1= FMEA failure

Bit 4: 1= eeprom is corrupt

0x05 General status

Get general part status.

0..0xFF

Bit 3: 1= line sync failure

Bit 2: 1= cal failed 5 times on an enabled key, or, an enabled key has

a low reference (Ref < lower sig lim)

Bit 1: 1= any key in calibration

Bit 0: 1= any key is in detect

Last return byte is CRC-8 of cmmd + return data

Bit 7: 1= indicates 2 or more touches if set.

Bit 6: 1= any of the following prevail: calibrating, key(s) failed cal 5

times, sync fail, comms error, FMEA failure, EEPROM corrupt.

Bits 5..0: indicates key number (0..47) of first key touched; reads

0x3F (63 decimal) if no touch. 2nd return byte is CRC-8 of cmmd

+ return data

0x06 Report 1st key

Get indication of first touched key + others

0..0xFF

6 bytes

0x07 Report all keys

0x08 Signals for all

Sends back all key detect status bits (bitfield)

Sends back all key signal levels

Last return byte is CRC-8 of cmmd + return data

0..0xFFFF

Returns block data for all keys’ signals

The low order byte is returned first.

48 words

QT60486-AS R8.01/0105

Page

Hex

Name

Description

#/Cmd # rtnd Rtn range CRC

Notes

0..0xFFFF

Returns block data for all keys’ references.

0x09 References for all Sends back all key reference levels

48 words

The low order byte is returned first.

0..0xFF

Returns block data for all keys’ signal deltas from refs,

{reference - signal}; Unsigned binary bytes, in range 0..255.

0x0a Deltas for all

Sends back all key delta signals from ref

48 bytes

0..0xFF

0x0b Error flags for all

0x0c FMEA status

Error bit fields

Last return byte is CRC-8 of cmmd + return data

6 bytes

FMEA bitfield on X, Y lines

0..0xFF

Last return byte is CRC-8 of cmmd + return data

Dump of fixed length ‘nn’ followed by CRC-16

Returns Setups block area followed by CRC.

Scanning is halted and then auto-restarted

after the cmd has completed.

CRC is same as CRC at end of Setups block load.

LSL and CRC words are sent back to host low byte first.

Part will timeout if each byte not transmitted within 100ms of previous

byte. (This can happen if DRDY is driven by the host).

0..0xFF

0x0d Dump Setups

0x0e Eeprom CRC

nn+2

nn+2 bytes

CRC-16 only on Setups array section of eeprom

Get eeprom CRC

0..0xFFFF

16 This CRC is the same as the CRC at the end of Setups block load.

This word is returned low byte first.

Returns 1’s compliment of last command even if bad. Resets the

0x0F Return last cmmd Returns last command received

0..0xFF

communications error flag.

Return internal

0x10

0x11

0x12

Diagnostic code for factory use.

Returns internal code. 2nd byte is CRC-8 of cmmd + return data

code

Return internal

Returns internal code. Last byte is CRC-8 of cmmd + return data.

The low order byte is returned first.

0..0xFFFFFF

0.0xFFFF

code

Return internal

code

Diagnostic code for factory use. The low order byte is returned first.

Returns 1’s complement of command to acknowledge; wakes on INT,

meanwhile sleeps in low power mode; 0x01 when restarted. If 2

commands not received in 100ms, times out and no response is

issued.

Enter sleep; Command must be repeated 2x

consecutively without any intervening

command in 100ms to execute.

0x16 Sleep

1 + 1 0xE9 + 0x01

DRDY is held low while the part is asleep. DRDY is released high

once awake and ready to return the 0x01.

Get signal, ref, Norm DI for key k {0..47}

0..FF

Diagnostic use only, not to be relied upon (no CRC). Signal and ref

0x4k Data for 1 key

Signal: 2 bytes; Ref: 2 bytes; Norm DI: 1 byte

Each byte

are Tx as 2 bytes, LSB first.

Bits 7..5: reserved

Bit 4: 1= key is enabled

Bit 3: 1= key is in detect

0x8k Status for key ‘k’

0xck CAL key ‘k’

Get status byte for key ‘k’ {0..47}

0..FF

Bit 2: 1= (Ref < LSL)

Bit 1: 1= key is in calibration

Bit 0: 1= calibration of this key failed 5 times

Second return byte is CRC-8 of cmmd + return data

Used in Run mode. Normal sensing of other keys not affected. CAL of

‘k’ only takes place in the key’s normal timeslot.

Returns the ones compliment of the cmd char, once the cal is

scheduled.

Force calibration of key # k where k= 0..47.

Command must be repeated 2x consecutively

without any intervening command in 100ms to

execute

~0xck

QT60486-AS R8.01/0105

occurs only after a recalibration when an object is touching

the key and is subsequently removed. The desire is normally

to recover from these events quickly.

5 Setups

The devices calibrate and process all signals using a

number of algorithms specifically designed to provide for

high survivability in the face of adverse environmental

challenges. They provide a large number of processing

options which can be user-selected to implement very

flexible, robust keypanel solutions.

Positive hysteresis: PHYST is fixed at 12.5% of the positive

threshold value and cannot be altered.

Positive threshold levels are programmed in using the Setup

process on a per-key basis.

User-defined Setups are employed to alter these algorithms

to suit each application. These setups are loaded into the

device in a block load over one of the serial interfaces. The

Setups are stored in an onboard eeprom array. After a

setups block load, the device should be reset to allow the

new Setups block to be shadowed in internal Flash ROM

and to allow all the new parameters to take effect. This reset

can be either a hardware or software reset.

Typical values:

1 to 4

(5 to 8 counts of threshold; 4 is internally added to

PTHR to generate the threshold)

Default value:

(6 counts of threshold)

5.3 Drift Compensation - NDRIFT, PDRIFT

Signals can drift because of changes in Cx and Cs over time

and temperature. It is crucial that such drift be compensated,

else false detections and sensitivity shifts can occur.

Refer to Table 5.1, page 24 for a list of all Setups.

Block length issues: The setups block is 247 bytes long to

accommodate 48 keys. This can be a burden on smaller host

controllers with limited memory. In larger quantities the

devices can be procured with the setups block

Drift compensation (Figure 5-1) is performed by making the

reference level track the raw signal at a slow rate, but only

while there is no detection in effect. The rate of adjustment

must be performed slowly, otherwise legitimate detections

could be ignored. The devices drift compensate using a

slew-rate limited change to the reference level; the threshold

and hysteresis values are slaved to this reference.

preprogrammed from Quantum. If the application only

requires a small number of keys (such as 16) then the

setups table can be compressed in the host by filling large

stretches of the Setups area with nulls.

Many setups employ lookup-table value translation. The

Setups Block Summary on page 26 shows all translation

values.

When a finger is sensed, the signal falls since the human

body acts to absorb charge from the cross-coupling between

X and Y lines. An isolated, untouched foreign object (a coin,

or a water film) will cause the signal to rise very slightly due

to an enhancement of coupling. This is contrary to the way

most capacitive sensors operate.

Default Values shown are factory defaults.

5.1 Negative Threshold - NTHR

The negative threshold value is established relative to a

key’s signal reference value. The threshold is used to

determine key touch when crossed by a negative-going

signal swing after having been filtered by the detection

integrator. Larger absolute values of threshold desensitize

keys since the signal must travel farther in order to cross the

threshold level. Conversely, lower thresholds make keys

more sensitive.

Once a finger is sensed, the drift compensation mechanism

ceases since the signal is legitimately detecting an object.

Drift compensation only works when the signal in question

has not crossed the negative threshold level.

The drift compensation mechanism can be made asymmetric

if desired; the drift-compensation can be made to occur in

one direction faster than it does in the other simply by

changing the NDRIFT and PDRIFT Setups parameters. This

can be done on a per-key basis.

As Cx and Cs drift, the reference point drift-compensates for

these changes at a user-settable rate; the threshold level is

recomputed whenever the reference point moves, and thus it

also is drift compensated.

Specifically, drift compensation should be set to compensate

faster for increasing signals than for decreasing signals.

Decreasing signals should not be compensated quickly,

since an approaching finger could be compensated for

partially or entirely before even touching the touch pad.

However, an obstruction over the sense pad, for which the

The amount of NTHR required depends on the amount of

signal swing that occurs when a key is touched. Thicker

panels or smaller key geometries reduce ‘key gain’, i.e.

signal swing from touch, thus requiring smaller

NTHR values to detect touch.

The negative threshold is programmed on a

per-key basis using the Setup process. See table,

page 26.

Figure 5-1 Thresholds and Drift Compensation

Typical values:

3 to 8

(7 to 12 counts of threshold; 4 is internally

added to NTHR to generate the threshold).

Reference

Default value:

(10 counts of threshold)

Hysteresis

Threshold

5.2 Positive Threshold - PTHR

The positive threshold is used to provide a

mechanism for recalibration of the reference point

when a key's signal moves abruptly to the

positive. This condition is not normal, and usually

Signal

Output

QT60486-AS R8.01/0105

sensor has already made full allowance for, could suddenly

be removed leaving the sensor with an artificially suppressed

reference level and thus become insensitive to touch. In this

latter case, the sensor should compensate for the object's

removal by raising the reference level relatively quickly.

If FDIL = 1, the device functions conventionally; each

channel acquires only once in rotation, and the normal detect

integrator counter (NDIL) operates to confirm a detection.

Fast-DI is in essence not operational.

If FDIL m 2, then the fast-DI counter also operates in addition

Drift compensation and the detection time-outs work together to the NDIL counter.

to provide for robust, adaptive sensing. The time-outs

If Signal [ NThr: The fast-DI counter is incremented towards

provide abrupt changes in reference calibration depending

on the duration of the signal 'event'.

FDIL due to touch.

If Signal >NThr then the fast-DI counter is cleared due to

lack of touch.

NDRIFT Typical values:

(2 to 3.3 seconds per count of drift compensation)

NDRIFT Default value: 10

(2.5s / count of drift compensation)

9 to 11

Disabling a key: If NDIL =0, the key becomes disabled.

Keys disabled in this way are pared from the burst sequence

in order to improve sampling rates and thus response time.

PDRIFT Typical values:

3 to 5

(0.4 to 0.8 seconds per count of drift compensation;

translation via LUT, page 26)

NDIL Typical values:

NDIL Default value:

FDIL Typical values:

FDIL Default value:

2, 3

4 to 6

PDRIFT Default value:

(0.6s / count of drift compensation)

5.4 Detect Integrators - NDIL, FDIL

NDIL is used to enable keys and to provide signal filtering.

To enable a key, its NDIL parameter should be non-zero (ie

NDIL=0 disables a key).

5.5 Negative Recal Delay - NRD

If an object unintentionally contacts a key resulting in a

detection for a prolonged interval it is usually desirable to

recalibrate the key in order to restore its function, perhaps

after a time delay of some seconds.

To suppress false detections caused by spurious events like

electrical noise, the device incorporates a 'detection

The Negative Recal Delay timer monitors such detections; if

a detection event exceeds the timer's setting, the key will be

automatically recalibrated. After a recalibration has taken

place, the affected key will once again function normally

even if it is still being contacted by the foreign object. This

feature is set on a per-key basis using the NRD setup

parameter.

integrator' or DI counter mechanism that acts to confirm a

detection by consensus (all detections in sequence must

agree). The DI mechanism counts sequential detections of a

key that appears to be touched, after each burst for the key.

For a key to be declared touched, the DI mechanism must

count to completion without even one detection failure.

The DI mechanism uses two counters. The first is the ‘fast

DI’ counter FDIL. When a key’s signal is first noted to be

below the negative threshold, the key enters ‘fast burst’

mode. In this mode the burst is rapidly repeated for up to the

specified limit count of the fast DI counter. Each key has its

own counter and its own specified fast-DI limit (FDIL), which

can range from 1 to 15. When fast-burst is entered the QT

device locks onto the key and repeats the acquire burst until

the fast-DI counter reaches FDIL, or, the detection fails

beforehand. After this the device resumes normal key

scanning and goes on to the next key.

NRD can be disabled by setting it to zero (infinite timeout) in

which case the key will never auto-recalibrate during a

continuous detection (but the host could still command it).

NRD is set using one byte per key, which can range in value

from 0..254. NRD above 0 is expressed in 0.5s increments.

Thus if NRD =120, the timeout value will actually be 60

seconds. 255 is not a legal number to use.

NRD Typical values:

NRD Default value:

NRD Range:

20 to 60 (10s to 30s)

20 (10s)

0..254 (∞, 0.5s .. 127s)

The ‘Normal DI’ counter counts the number of times the

fast-DI counter reached its FDIL value. The Normal DI

counter can only increment once per complete scan of all

keys. Only when the Normal DI counter reaches NDIL does

the key become formally ‘active’.

5.6 Positive Recalibration Delay - PRD

A recalibration can occur automatically if the signal swings

more positive than the positive threshold level. This condition

can occur if there is positive drift but insufficient positive drift

compensation, or, if the reference moved negative due to a

NRD auto-recalibration, and thereafter the signal rapidly

returned to normal (positive excursion).

The net effect of this is that the sensor can rapidly lock onto

and confirm a detection with many confirmations, while still

scanning other keys. The ratio of ‘fast’ to ‘normal’ counts is

completely user-settable via the Setups process. The total

number of required confirmations is equal to FDIL times

NDIL.

As an example of the latter, if a foreign object or a finger

contacts a key for period longer than the Negative Recal

Delay (NRD), the key is by recalibrated to a new lower

reference level. Then, when the condition causing the

negative swing ceases to exist (e.g. the object is removed)

the signal can suddenly swing back positive to near its

normal reference.

If FDIL = 5 and NDIL = 2, the total detection confirmations

required is 10, even though the device only scanned through

all keys only twice.

It is almost always desirable in these cases to cause the key

to recalibrate quickly so as to restore normal touch

The DI is extremely effective at reducing false detections at

the expense of slower reaction times. In some applications a

slow reaction time is desirable; the DI can be used to

intentionally slow down touch response in order to require

the user to touch longer to operate the key.

operation. The time required to do this is governed by PRD.

In order for this to work, the signal must rise through the

QT60486-AS R8.01/0105

positive threshold level PTHR continuously for the PRD

period.

larger keys can be altered to compensate for this without

causing problems with key suppression.

After the PRD interval has expired and the auto- recalibration Adjacent key suppression works to augment the natural

has taken place, the affected key will once again function

normally. PRD is set on a per-key basis.

moisture suppression of narrow gated transfer switches

creating a more robust sensing method.

The functioning of the PRD setting is determined by an offset

to a lookup table, found on page 26. The values of time can

range from 0.1s to 25s. Setting the parameter to 0 will

disable the feature.

AKS Default value:

0 (Off)

5.9 Oscilloscope Sync - SSYNC

Pin 43 (S_Sync) can output a positive pulse oscilloscope

sync that brackets the burst of a selected key. More than one

burst can output a sync pulse as determined by the Setups

parameter SSYNC for each key.

PRD Typical values:

PRD Default value:

PRD Range:

5 to 8 (0.7s to 2.0s)

6 (1 second)

0..15 (∞, 0.1 .. 25s)

This feature is invaluable for diagnostics; without it,

observing signals clearly on an oscilloscope for a particular

burst is very difficult.

5.7 Burst Length - BL

The signal gain for each key is controlled by circuit

parameters as well as the burst length.

This function is supported in Quantum’s QmBtn PC software

via a checkbox.

The burst length is simply the number of times the

charge-transfer (‘QT’) process is performed on a given key.

Each QT process is simply the pulsing of an X line once, with

a corresponding Y line enabled to capture the resulting

charge passed through the key’s capacitance Cx.

SSYNC Default value:

0 (Off)

5.10 Negative Hysteresis - NHYST

The devices employ programmable hysteresis levels of

6.25%, 12.5%, 25%, or 50%. The hysteresis is a percentage

of the distance from the threshold level back towards the

reference, and defines the point at which a touch detection

will drop out. A 12.5% hysteresis point is closer to the

threshold level than to the signal reference level.

QT60xx6 devices use a fixed number of QT cycles which are

executed in burst mode. There can be up to 64 QT cycles in

a burst, in accordance with the list of permitted values shown

in Table 5.4.

Increasing burst length directly affects key sensitivity. This

occurs because the accumulation of charge in the charge

integrator is directly linked to the burst length. The burst

length of each key can be set individually, allowing for direct

digital control over the signal gains of each key individually.

Hysteresis prevents chatter and works to make key detection

more robust. Hysteresis is used only once the key has been

declared to be in detection, in order to determined when the

key should drop out.

Apparent touch sensitivity is also controlled by the Negative

Threshold level (NTHR). Burst length and NTHR interact;

normally burst lengths should be kept as short as possible to

limit RF emissions, but NTHR should be kept above 6 to

reduce false detections due to external noise. The detection

integrator mechanism also helps to prevent false detections.

Excessive amounts of hysteresis can result in ‘sticking keys’

that do not release. Conversely, low amounts of hysteresis

can cause key chatter due to noise or minor amounts of

finger motion.

The hysteresis levels are set for all keys only; it is not

possible to set the hysteresis differently from key to key.

BL Typical values:

BL Default value:

BL possible values:

2, 3 (48, 64 pulses / burst)

2 (48 pulses / burst)

16, 32, 48, 64

NHYST Typical values: 0, 1 (6.25%, 12.5%)

NHYST Default value:

1 (12.5%)

5.11 Dwell Time - DWELL

5.8 Adjacent Key Suppression - AKS

These devices incorporate adjacent key suppression (‘AKS’ -

patent pending) that can be selected on a per-key basis.

AKS permits the suppression of multiple key presses based

on relative signal strength. This feature assists in solving the

problem of surface moisture which can bridge a key touch to

an adjacent key, causing multiple key presses. This feature

is also useful for panels with tightly spaced keys, where a

fingertip might inadvertently activate an adjacent key.

The Dwell parameter in Setups causes the acquisition

pulses to have differing charge capture durations. Generally,

shorter durations provide for enhanced surface moisture

suppression, while longer durations are usually more

compatible with EMC requirements. Longer dwell times

permit the use of larger series resistors in the X and Y lines

to suppress RFI effects, without compromising key gain

(Section 2.8).

This setup lets the designer trade off one requirement for

with the other.

AKS works for keys that are AKS-enabled anywhere in the

matrix and is not restricted to physically adjacent keys; the

device has no knowledge of which keys are actually

physically adjacent. When enabled for a key, adjacent key

suppression causes detections on that key to be suppressed

if any other AKS-enabled key in the panel has a more

negative signal deviation from its reference.

DWELL typical value:

DWELL default value:

1 (187.5ns)

DWELL possible values: 0, 1, 2 (125, 187.5, 312.5ns

)

5.12 Mains Sync - MSYNC

This feature does not account for varying key gains (burst

length) but ignores the actual negative detection threshold

setting for the key. If AKS-enabled keys have different sizes,

it may be necessary to reduce the gains of larger keys to

equalize the effects of AKS. The signal threshold of the

The MSync feature uses the WS pin. The Sleep and Sync

features can be used simultaneously; the part can be put into

Sleep mode, but awakened by a mains sync signal at the

desired time.

QT60486-AS R8.01/0105

External fields can cause interference leading to false

detections or sensitivity shifts. Most fields come from AC

power sources. RFI noise sources are heavily suppressed

by the low impedance nature of the QT circuitry itself.

The Baud rate can be adjusted to one of 5 values from 9600

to 115.2K baud.

SR Default value:

0 (9600 Baud)

Noise such as from 50Hz or 60Hz fields becomes a problem

if it is uncorrelated with acquisition signal sampling;

5.15 Lower Signal Limit - LSL

This Setup determines the lowest acceptable value of signal

level for all keys. If any key’s reference level falls below this

value, the device declares an error condition in the key

status bits (Sections 4.5, 4.6, 4.8, 4.11).

uncorrelated noise can cause aliasing effects in the key

signals. To suppress this problem the WS input allows bursts

to synchronize to the noise source. This same input can also

be used to wake the part from a low-power Sleep state.

Testing is required to ensure that there are adequate

margins in this determination. Key size, shape, panel

material, burst length, and dwell time all factor into the

detected signal levels.

The noise sync operating mode is set by parameter MSYNC

in Setups.

The sync occurs only at the burst for the lowest numbered

enabled key in the matrix; the device waits for the sync

signal for up to 100ms after the end of a preceding full matrix

scan, then when a negative sync edge is received, the matrix

is scanned in its entirety again.

This parameter occupies 2 bytes of the setups table. The low

order byte should be sent first.

LSL Default value:

100 (recommended value)

0..2047

LSL Possible range:

The sync signal drive should be a buffered logic signal, or

perhaps a diode-clamped signal, but never a raw AC signal

from the mains. The device will sync to the falling edge.

5.16 LED / Alert Output - LED

Refer also to Table 5.2 page 25 for details.

Since Noise sync is highly effective and inexpensive to

implement, it is strongly advised to take advantage of it

anywhere there is a possibility of encountering low frequency

(i.e. 50/60Hz) electric fields. Quantum’s QmBtn software can

show such noise effects on signals, and will hence assist in

determining the need to make use of this feature.

Pin 40 is designed to drive a low-current LED or to be used

as a status and error signaling mechanism for the host

controller, primarily for FMEA purposes.

One use for this pin is to alert the host that there is key

activity, in order to limit the amount of communication

between the device and the host. The LED pin should ideally

be connected to an interrupt pin on the host that can detect

an edge, following which the host can proceed to poll the

device for key activations.

If the sync feature is enabled but no sync signal exists, the

sensor will continue to operate but with a delay of 100ms

from the end of one scan to the start of the next, and hence

will have a slow response time. A failed Sync signal (one

exceeding a 100ms period) will cause an error flag (see

commands 0x05, 0x06).

Note that LED polarity can be reversed in the setups byte.

Table 5.2, on page 25 shows the possible internal conditions

that can cause the LED pin to go active. The various items in

the table are logical-OR’d together.

MSYNC Default value:

MSYNC Possible range:

0 (Off)

0, 1 (Off, On)

The LED pin can even be used as a watchdog for the host,

to reset it should the host fail to send regular transmissions

to the QT (bit 0 of LED byte). The comms timeout required to

generate the ‘reset’ signal is about 2 seconds of inactivity. If

this feature is enabled, it does not become effective until the

first command is received from the host; therefore, it is

assumed that there is at least some initial host activity for

this feature to work.

5.13 Burst Spacing - BS

The interval of time from the start of one burst to the start of

the next is known as the burst spacing. This is an alterable

parameter which affects all keys. The burst spacing can be

viewed as a scheduled timeslot in which a burst occurs. This

approach results in an orderly and predictable sequencing of

key scanning with predictable response times.

Shorter spacings result in a faster response time to touch;

longer spacings permit higher burst lengths and longer

conversion times but slow down response time.

Note that the LED state will be preserved during sleep.

LED Default value:

0x6c

(see Table 5.2, page 25 for details)

An automatic setting is also available that performs a ‘best

fit’ timeslot determination for each key’s acquisition burst.

The fit is determined on power-up each time and is fixed

thereafter until reset again.

5.17 Host CRC - HCRC

The setups block terminates with a 16-bit CRC, HCRC, of

the entire block. The formulae for calculating this CRC and

the 8-bit CRC also used in the device are shown in Section

7. The low order byte should be sent first.

See Table 5.4 (page 26) for possible values.

BS Default value:

0 (Automatic)

BS Possible range:

0..11 (Auto, 500µs .. 3ms)

5.14 Serial Rate - SR

The possible Baud rates are shown in Table 5.4. The rate

chosen by this parameter only affects UART mode. SPI

mode is slave-only and can clock at any rate from DC up to

4Mhz.

QT60486-AS R8.01/0105

Table 5.1 Setups Block

Setups data is sent from the host to the QT in a block of hex data. The block can only be loaded in Setups mode following two 0x 01 commands (page 14). The devices this

datasheet pertain to have the same block length. Refer also to Table 5.4, page 26 for further details, and all of Section 5.

Item

Key

Default

Byte Parameter

Symbol Bytes Valid range Bits Scope Value Description

Page

Neg thresh

NTHR

PTHR

NDRIFT

PDRIFT

NDIL

NTHR = 0..15

PTHR = 0..15

NDRIFT = 0..15

PDRIFT = 0..15

NDIL = 0..15

Lower nibble = Neg Threshold - take operand and add 4 to get value

Upper nibble = Pos Threshold - take operand and add 4 to get value

Lower nibble = Neg Drift comp - Via LUT

Pos Thresh

Neg Drift Comp

Pos Drift Comp

Upper nibble = Pos Drift comp - Via LUT

Normal DI Limit

Lower nibble = Normal DI Limit, values same as operand (0 = disabled burst)

Upper nibble = Fast DI Limit, values same as operand (0 does not work)

Range is in 0.5 sec increments; 0 = infinite; default = 10s (operand = 20)

Range is { infinite, 0.5...127s }; 255 is illegal to use

Lower nibble = PRD, via LUT, default = 6 (1 sec)

Fast DI Limit

FDIL

FDIL = 0..15

144 Neg recal delay

Pos recal delay

NRD

0..254

PRD

PRD = 0..15

BL = 0..3

Burst Length

Bits 5, 4: = BL, via LUT, default = 48 (setting =2)

192

AKS

AKS = 0, 1

Bit 6 = AKS, 1 - enabled

Scope Sync

Neg Hysteresis

240 Dwell Time

Mains Sync

SSYNC

NHYST

DWELL

MSYNC

SSYNC = 0, 1

NHYST = 0..3

DWELL = 0..2

MSYNC = 0, 1

BS = 0..11

Bit 7 = Scope sync, 1 = enabled

device

Lower nibble = Neg hysteresis, all keys; default = 12.5%

Bits 5, 4 = Dwell time, 3 values via LUT, default = 187.5ns

Bits 6 = Mains sync, negative edge, 1 = enabled; default = 0 (off)

Lower nibble = burst spacing; default = 0 (automatic)

Burst spacing

241

Serial rate

SR = 0..4

Upper nibble = serial rate via LUT - 9600, 19.2K, 38.4K, 57.6K, 115.2K (UART) 23

Lower limit of acceptable signal; below this value, device declares an error.

242 Lower signal Limit

244 LED Function

245 Host CRC

LSL

LED

0..2047

0..255

0..65K

100

0x6c

The low order byte should be sent first.

device

Controls what the LED does; see table, below.

CRC-16 of above setups, does NOT include CRC of command itself. The low

order byte should be sent first. See also CRC notes, page 29.

HCRC

Block length

247

CRC Note: A CRC calculator for Windows is available free of charge from Quantum Research on request.

QT60486-AS R8.01/0105

Table 5.2 LED Function Control Byte Bits

See also page 23. The LED pin can be used to indicate a variety of things in combination. The LED control byte controls which states make the LED pin active. The active state can

also be set either high or low by changing bit 7 in this byte. One purpose for these functions is to provide an FMEA-compliant mechanism for fault detection via an alternative path to

the serial comms path. Another is to provide an interrupt signal to a host controller to reduce the amount of required comms traffic. Another reason is to simply light an LED on a

sensing fault, a keypress, or a comms failure for diagnostic purposes.

Bit

1 =

0 =

Default

LED pin is active high polarity

Active on any key error: (cal, cal failed, low sig)

Active on any keypress

Active while in sleep

Active on eeprom error

LED pin is active low polarity

Key errors have no effect

Not active on any keypress

Inactive on Sleep

Inactive on eeprom error

Inactive on Mains sync error

Active on Mains sync error

Active on comms error (unrecognized command): LED pin is set active on error,

inactive again when ‘get last cmd’ is called, or part is reset.

Inactive on comms error

Host watchdog. Active if no host comms within any 2s period. Host reset pulse

length is 150ms. The host watchdog is not enabled until the first valid cmd

is received from the host.

Communications unmonitored

Table 5.3 Key Mapping

Some commands return bit fields related to keys. For example, command 0x07 (report all keys) returns 6 bytes containing flag bits, one per key, to indicate which keys are reporting

touches. The following table shows the byte and bit order of the keys. The table contains the key number reported in each bit.

The key number is related to the X and Y scan lines which address each particular key. Each byte in the return stream represents one set of keys along a Y line, i.e. up to 8 keys.

Thus, key 0 is at location X0,Y0 and key 29 is at location X5,Y3. .

Bit (X line)

Byte

(Y line)

Note: Byte 0 is returned first.

QT60486-AS R8.01/0105

Table 5.4 Setups Block Summary

Typical values: For most touch applications, use the values shown in the outlined cells. Bold text items indicate default settings. The number to send to the QT is the number in

the leftmost column (0..15), not numbers from the table. The QT uses a lookup table internally to translate 0..15 to the parameters for each function.

NRD is an exception: It can range from 0..254 which is translated from 1= 0.5s to 254= 127s with zero = infinity.

Parameter

Index

NTHR

PTHR NDRIFT PDRIFT NDIL

FDIL

NRD

secs

PRD

Scope

Sync

Number counts counts

secs secs counts counts

secs

pulses

AKS

NHYST DWELL MSYNC

UART

Per key Per key Per key Per key Per key Per key

Per key

0 (Infinite)

0.5 .. 127s

Per key

0 (Infinite)

0.1

Per key Per key Per key Global

Global

- Off -

Global

- Auto -

500µs

Global

-9,600-

19,200

0.1

0.2

0.1

0.2

Key off

unused

- Off -

6.25%

125ns

-12.5%- -187.5ns-

- 6 -

0.3

- 2 -

0.2

- 48 -

25%

312.5ns

750µs

38,400

Default=

10s

0.4

0.6

0.8

0.4

0.3

0.5

0.7

- 1 -

1.5

50%

1,000µs

57,600

- 0.6 -

0.8

1,250µs 115,200

1,500µs

- 5 -

- 10 -

1,750µs

1.2

1.5

1.2

1.5

2,000µs

2,250µs

- 2.5 -

3.3

4.5

3.2

4.5

2,500µs

2.5

3.3

4.5

2,750µs

3,000µs

12.3

17.5

7.5

QT60486-AS R8.01/0105

6 Specifications

6.1 Absolute Maximum Electrical Specifications

Operating temp. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . -40^OC ~ +105^OC

Storage temp. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . -55^OC ~ +125^OC

VDD. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . -0.5 ~ +5.5V

Max continuous pin current, any control or drive pin. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ±10mA

Short circuit duration to ground, any pin. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . infinite

Short circuit duration to V , any pin. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . infinite

Voltage forced onto any p^Din^D. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . -0.6V ~ (Vdd + 0.6) Volts

Frequency of operation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17MHz

Eeprom setups maximum writes. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100,000 write cycles

6.2 Recommended operating conditions

DD. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . +4.75 ~ 5.25V

Supply ripple+noise. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5mV p-p max

Cx transverse load capacitance per key. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0 ~ 20pF

Fosc oscillator frequency. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16MHz +/-2%

6.3 DC Specifications

Vdd = 5.0V, Cs = 4.7nF, Freq = 16MHz, Ta = recommended range, unless otherwise noted

Parameter

Notes

Description

Min

Typ

Max

Units

Iddr

Idds

Supply current, running

Supply current, sleep

Vdd internal reset voltage

Low input logic level

High input logic level

Low output voltage

µA

bits

Vil

0.8

0.6

Vhl

Vol

Voh

Iil

Rrst

2.2

4mA sink

1mA source

High output voltage

Vdd-0.7

Input leakage current

Acquisition resolution

Internal pullup resistors

Internal /RST pullup resistor

±1

DRDY, /SS, TX pins

6.4 Timing Specifications

Vdd = 5.0V, Cs = 4.7nF, Freq = 16MHz, Ta = recommended range, unless otherwise noted

Parameter

Description

Min

Typ

Max

Units

Notes

Burst spacing

500

3,000

µs

Adjustable parameter via Setups

Pulse spacing, average

@ dwell = 125ns

1.80

1.90

2.00

2.75

2.80

2.92

Tpc

Fqt

µs

@ dwell = 187.5ns

@ dwell = 312.5ns

Burst frequency range

@ dwell = 125ns

364

357

342

556

526

500

kHz

Spread spectrum range

@ dwell = 187.5ns

@ dwell = 312.5ns

Fck

È /SS to first È CLK edge

È CLK to valid MISO

Last Ç CLK to Ç /SS

Ç /SS to 3-state MISO

Ç /SS to falling DRDY

DRDY low pulse width

CLK low pulse width

CLK high pulse width

CLK period

125

µs

SPI parameter controlled by host

SPI parameter controlled by QT

SPI parameter controlled by host

SPI parameter controlled by QT

SPI parameter controlled by host

125

250

SPI Clock rate

MHz

QT60486-AS R8.01/0105

6.5 Mechanical Dimensions

20 22

Package Type: 44 Pin TQFP

Millimeters

Inches

Max

SYMBOL

Min

Max

Notes

Min

Notes

9.90

10.10

12.21

0.20

0.75

0.15

1.20

0.45

0.80

8.00

0.386

0.458

0.003

0.018

0.002

0.394

0.478

0.008

0.030

0.006

0.047

0.018

0.031

0.315

11.75

0.09

0.45

0.05

0.30

0.80

8.00

0.012

0.031

0.315

BSC

6.6 Marking

TQFP Part

T_A

Number

Keys

Marking

QT60326-AG

QT60486-AG

-40⁰C to +105⁰C

QT60326-AS-G

QT60486-AS-G

QT60486-AS R8.01/0105

7 Appendix

7.1 8-Bit CRC Software C Algorithm

// 8 bits crc calculation. Initial crc entry value must be 0.

// polynomial = X8 + X5 + X4 + 1

// data is an 8 bit number; crc is an unsigned 8 bit number

// repeat this function for each data block byte, folding the result

back into the call parameter crc

unsigned char eight_bit_crc(unsigned char crc, unsigned char data)

{

unsigned charindex; // shift counter

unsigned charfb;

// intermediate test bit

index = 8;

// initialize the shift counter

// loop 8 times

{

fb = (crc ^ data) & 0x01;

data >>= 1;

crc >>= 1;

if(fb)

{

}

crc ^= 0x8c;

} while(--index);

return crc;

}

7.2 16-Bit CRC Software C Algorithm

// 16 bits crc calculation. Initial crc entry value must be 0.

// The message is not augmented with 'zero' bits.

// polynomial = X16 + X12 + X5 + 1

// data is an 8 bit number, unsigned

// crc is a 16 bit number, unsigned

// repeat this function for each data block byte, folding the result

back into the call parameter crc

unsigned long sixteen_bit_crc(unsigned long crc, unsigned char data)

{

unsigned char index; // shift counter

crc ^= (unsigned long)(data) << 8;

index = 8;

{

// loop 8 times

if(crc & 0x8000)

{

}

else

crc= (crc << 1) ^ 0x1021;

{

}

crc= crc << 1;

} while(--index);

return crc;

}

A CRC calculator for Windows is available free of charge from Quantum Research.

QT60486-AS R8.01/0105

0-ohm SMT Jumper

7.3 1-Sided Key Layout

This key design can be made on a 1-sided SMT PCB. A single 0-ohm jumper

allows the wiring to be done on a single side with full pass-through of X and Y

traces to allow matrix connections to be made across a large number of keys.

Key size, shape, and number of interleavings can be varied substantially from

this drawing. The below drawing shows 6 interleave white spaces; only a

double interleave is required in the case of smaller keys.

The PCB is bonded to a panel on its underside, and the fields fire through the

PCB, adhesive, and panel in that sequence. This results in a very low cost

design.

7.4 PCB Layout

Shown is an example 32-key PCB layout using inexpensive 1-sided CEM-1 or FR-1 PCB laminate. The key layouts follow the

design rules of Figure 2-6 (page 5) and as shown above.

QT60486-AS R8.01/0105

NOTES

QT60486-AS R8.01/0105

Patented and patents pending

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1 Mitchell Point

Ensign Way, Hamble SO31 4RF

Great Britain

Tel: +44 (0)23 8056 5600 Fax: +44 (0)23 8045 3939

admin@qprox.com

www.qprox.com

North America

651 Holiday Drive Bldg. 5 / 300

Pittsburgh, PA 15220 USA

Tel: 412-391-7367 Fax: 412-291-1015

The specifications set out in this document are subject to change without notice. All products sold and services supplied by QRG are

subject to our Terms and Conditions of sale and supply of services which are available online at www.qprox.com and are supplied with

every order acknowledgement. QProx, QTouch, QMatrix, QLevel, and QSlide are trademarks of QRG. QRG products are not suitable for

medical (including lifesaving equipment), safety or mission critical applications or other similar purposes. Except as expressly set out in

QRG's Terms and Conditions, no licenses to patents or other intellectual property of QRG (express or implied) are granted by QRG in

connection with the sale of QRG products or provision of QRG services. QRG will not be liable for customer product design and

customers are entirely responsible for their products and applications which incorporate QRG's products.

Development Team: Dr. Tim Ingersoll, Samuel Brunet, Hal Philipp

QT60486 [QUANTUM]

相关型号：

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QT60486-AS-G

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QT60645-AS

QT60645-S

QT60645B

QT60645B-A

QT60645B-AS

QT62C-SERIES

QT62E-SERIES

QT62HC-SERIES