MAX1234EGI-T [MAXIM]
Consumer Circuit, 5 X 5 MM, 0.80 MM HEIGHT, QFN-28;型号: | MAX1234EGI-T |
厂家: | MAXIM INTEGRATED PRODUCTS |
描述: | Consumer Circuit, 5 X 5 MM, 0.80 MM HEIGHT, QFN-28 商用集成电路 |
文件: | 总44页 (文件大小:636K) |
中文: | 中文翻译 | 下载: | 下载PDF数据表文档文件 |
19-2512; Rev 0; 7/02
1ꢀ5k ꢁEDꢂ-rotected TouchꢂEcreen
Controllers Include DAC and Keypad Controller
General Description
Features
The MAX1233/MAX1234 are complete PDA controllers in
a 5mm × 5mm, 28-pin QFN package. They feature a
12-bit analog-to-digital converter (ADC), low on-resis-
tance switches for driving resistive touch screens, an
internal +1.0V/+2.5V or external reference, 2°C accu-
rate, on-chip temperature sensor, direct +6V battery mon-
itor, keypad controller, 8-bit digital-to-analog converter
(DAC), and a synchronous serial interface. Each of the
keypad controllers’ eight row and column inputs can be
reconfigured as general-purpose parallel I/O pins (GPIO).
All analog inputs are fully ESD protected, eliminating the
need for external TransZorb™ devices.
o ESD-Protected Analog Inputs
15kV IEC 1000-4-2 Air-Gap Discharge
8kV IEC 1000-4-2 Contact Discharge
o Single-Supply Operation
+2.7V to +3.6V (MAX1233)
+4.75V to +5.25V (MAX1234)
o 4-Wire Touch-Screen Interface
o Internal +1.0V/+2.5V Reference or External
Reference (+1.0V to AV
)
DD
o SPI™/QSPI™/MICROWIRE™-Compatible 10MHz
The MAX1233/MAX1234 offer programmable resolution
and sampling rates. Interrupts from the devices alert the
host processor when data is ready, when the screen is
touched, or a key press is detected. Software-
configurable scan control and internal timers give the user
flexibility without burdening the host processor. These
devices consume only 260µA at the maximum sampling
rate of 50ksps. Supply current falls to below 50µA for
sampling rates of 10ksps. The MAX1233/MAX1234 are
guaranteed over the -40°C to +85°C temperature range.
Serial Interface
o 12-Bit, 50ksps ADC Measures
Resistive Touch-Screen Position and Pressure
Two Auxiliary Analog Inputs
Two Battery Voltages (0.5V to 6V)
On-Chip Temperature
o 8-Bit DAC for LCD Bias Control
o 4 × 4 Keypad Programmable Controller Offers Up
to Eight GPIO Pins
Applications
o Automatic Detection of Screen Touch, Key Press,
Personal Digital Assistants
and End of Conversion
Pagers
o Programmable 8-, 10-, 12-Bit Resolution
o Programmable Conversion Rates
Touch-Screen Monitors
Cellular Phones
o AutoShutdown™ Between Conversions
MP3 Players
Portable Instruments
Point-of-Sale Terminals
o Low Power
260µA at 50ksps
50µA at 10ksps
6µA at 1ksps
-in Configuration
0.3µA Shutdown Current
TOP VIEW
o 28-Pin 5mm × 5mm QFN Package
Ordering Information
DV
AV
1
2
3
4
5
6
7
21 C4
20 C3
19 C2
18 C1
17 R1
16 R2
15 R3
DD
DD
PART
TEMP RANGE
-40°C to +85°C
-40°C to +85°C
PIN-PACKAGE
*X+
*Y+
*X-
MAX1233
MAX1234
MAX1233EGI
MAX1234EGI
28 QFN (5mm × 5mm)
28 QFN (5mm × 5mm)
*Y-
GND
TransZorb is a trademark of General Semiconductor Industries,
Inc.
SPI and QSPI are trademarks of Motorola, Inc.
MICROWIRE is a trademark of National Semiconductor Corp.
AutoShutdown is a trademark of Maxim Integrated Products, Inc.
QFN
*PIN INCLUDES 8kV/15kV ESD PROTECTION.
________________________________________________________________ Maxim Integrated Products
1
For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at
1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com.
1ꢀ5k ꢁEDꢂ-rotected TouchꢂEcreen
Controllers Include DAC and Keypad Controller
ABSOLUTE MAXIMUM RATINGS
AV
DV
to GND............................................................-0.3V to +6V
All Other Pins..................................................................... 2.5kV
Maximum Current into Any Pin............................................50mA
DD
DD
to AV .......................................................-0.3V to +0.3V
DD
Digital Inputs/Outputs to GND.................-0.3V to (DV + 0.3V)
X+, Y+, X-, Y-, AUX1, AUX2,
Continuous Power Dissipation (T = +70°C)
DD
A
28-Pin QFN (derate 28.5mW/°C above +70°C) .................2W
Operating Temperature Range ...........................-40°C to +85°C
Storage Temperature Range.............................-60°C to +150°C
Lead Temperature (soldering, 10s) .................................+300°C
and REF to GND ..................................-0.3V to (AV + 0.3V)
DD
BAT1, BAT2 to GND.................................................-0.3V to +6V
Maximum ESD per IEC 1000-4-2 (per MIL STD-883 HBM)
X+, X-, Y+, Y-, AUX1, AUX2, BAT1, BAT2...................... 15kV
Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional
operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to
absolute maximum rating conditions for extended periods may affect device reliability.
ELECTRICAL CHARACTERISTICS
(DV
= AV
= +2.7V to +3.6V (MAX1233), DV
= AV
= +4.75V to +5.25V (MAX1234), external reference V
= 2.5V
REF
DD
DD
DD
DD
(MAX1233), V
= 4.096V (MAX1234); f
= 10MHz, f
= 50ksps, 12-bit mode, 0.1µF capacitor at REF, T = -40°C to
REF
SCLK
SAMPLE A
+85°C, unless otherwise noted. Typical values are at T = +25°C.)
A
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
ANALOG-TO-DIGITAL CONVERTER
DC ACCURACY (Note 1)
Resolution
Software-programmable 8/10/12 bit
12
2
Bits
Bits
No Missing Codes
11
12-bit mode
0.8
0.5
0.8
0.5
0.5
0.5
0.5
0.5
0.5
2
Relative Accuracy (Note 2)
Differential Nonlinearity
Offset Error
INL
LSB
LSB
LSB
10-bit and 8-bit modes
12-bit mode
2
DNL
10-bit and 8-bit modes
12-bit mode
4
10-bit and 8-bit modes
12-bit mode
4
Gain Error (Note 3)
10-bit mode
LSB
LSB
8-bit mode
12-bit mode
Total Unadjusted Error
TUE
10-bit and 8-bit modes
1
Offset Temperature Coefficient
Gain Temperature Coefficient
Channel-to-Channel Offset
0.4
0.4
0.1
ppm/°C
ppm/°C
LSB
Channel-to-Channel Gain
Matching
0.1
50
LSB
Noise
Including internal V
µV
RMS
REF
MAX1233
AV = DV
0.4
= +2.7V to +3.6V
= +5V 5%
DD
DD
DD
Full-scale
input
Power-Supply Rejection
PSR
mV
MAX1234
0.3
AV
= DV
DD
DYNAMIC SPECIFICATIONS (1kHz SINE WAVE, V = 2.5V
FOR MAX1233, V = 4.096V FOR MAX1234, 50ksps,
P-P
IN
P-P
IN
f
= 10MHz)
SCLK
Signal-to-Noise Plus Distortion
SINAD
69
dB
2
_______________________________________________________________________________________
1ꢀ5k ꢁEDꢂ-rotected TouchꢂEcreen
Controllers Include DAC and Keypad Controller
ELECTRICAL CHARACTERISTICS (continued)
(DV
= AV
= +2.7V to +3.6V (MAX1233), DV
= AV
= +4.75V to +5.25V (MAX1234), external reference V
= 2.5V
REF
DD
DD
DD
DD
(MAX1233), V
= 4.096V (MAX1234); f
= 10MHz, f
= 50ksps, 12-bit mode, 0.1µF capacitor at REF, T = -40°C to
REF
SCLK
SAMPLE A
+85°C, unless otherwise noted. Typical values are at T = +25°C.)
A
PARAMETER
Total Harmonic Distortion
Spurious-Free Dynamic Range
Full-Power Bandwidth
Full-Linear Bandwidth
CONVERSION RATE
Internal Oscillator Frequency
Aperture Delay
SYMBOL
THD
CONDITIONS
MIN
TYP
-84
84
MAX
UNITS
dB
SFDR
dB
-3dB point
0.5
50
MHz
kHz
SINAD > 67dB
8
11.5
70
MHz
ns
30
Aperture Jitter
<50
ps
Maximum Serial Clock Frequency
Duty Cycle
f
10
30
MHz
%
SCLK
AUXILIARY ANALOG INPUTS (AUX1, AUX2)
Input Voltage Range
0
V
V
REF
1
Channel not selected or conversion
stopped
Input Leakage Current
0.1
34
µA
pF
Input Capacitance
BATTERY MONITOR INPUTS (BAT1, BAT2)
Input Voltage Range
0.5
6.0
V
Sampling battery
Battery monitor OFF
Internal reference
10
1
kΩ
GΩ
%
Input Impedance
Accuracy
-3
+3
TEMPERATURE MEASUREMENT
Temperature Range
-40
+85
°C
°C
Differential method (Note 4)
1.6
0.3
3
Resolution
Single measurement method (Note 5)
Differential method (Note 4)
Accuracy
°C
Single measurement method (Note 5)
2
INTERNAL ADC REFERENCE
2.5V mode, T = +25°C
2.470
0.980
2.500
1.000
60
2.530
1.020
A
V
Reference Output Voltage
V
REF
1.0V mode, T = +25°C
A
Output Tempco
TCV
ppm/°C
Ω
REF
Reference Output Impedance
Reference Short-Circuit Current
Normal operation
250
18
mA
EXTERNAL ADC REFERENCE (INTERNAL REFERENCE DISABLED, REFERENCE APPLIED TO REF)
Reference Input Voltage Range
Input Impedance
(Note 6)
1.0
V
V
DD
CS = GND or V
1
GΩ
DD
V
V
= +2.5V at 50ksps (MAX1233)
= +4.096V at 50ksps (MAX1234)
5
10
15
REF
REF
Input Current
µA
8
Shutdown/between conversions
0.1
_______________________________________________________________________________________
3
1ꢀ5k ꢁEDꢂ-rotected TouchꢂEcreen
Controllers Include DAC and Keypad Controller
ELECTRICAL CHARACTERISTICS (continued)
(DV
= AV
= +2.7V to +3.6V (MAX1233), DV
= AV
= +4.75V to +5.25V (MAX1234), external reference V
= 2.5V
REF
DD
DD
DD
DD
(MAX1233), V
= 4.096V (MAX1234); f
= 10MHz, f
= 50ksps, 12-bit mode, 0.1µF capacitor at REF, T = -40°C to
SAMPLE A
REF
SCLK
+85°C, unless otherwise noted. Typical values are at T = +25°C.)
A
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
DIGITAL-TO-ANALOG CONVERTER
DC ACCURACY
Resolution
8
Bits
LSB
LSB
mV
Integral Linearity Error
Differential Linearity Error
Offset Error
INL
(Note 7)
1.0
1.0
25
DNL
No missing codes
(Note 8)
V
1
1
OS
Offset Error Temperature
Coefficient
ppm/°C
%
Full-Scale Error
Code = 255, no load
Code = 255, no load
5
Full-Scale Error Temperature
Coefficient
10
ppm/°C
DYNAMIC PERFORMANCE
Voltage Output Slew Rate
Output Settling Time
Glitch Impulse
Positive and negative
0.5LSB; 50kΩ and 50pF load (Note 9)
Code 127 to 128
0.4
20
40
50
V/µs
µs
nV/s
µs
Wake-Up Time
From shutdown
DAC OUTPUT
✕
✕
✕
0.85
0.9
0.95
Internal DAC Reference
V
(Note 10)
V
REFDAC
AV
AV
AV
DD
DD
DD
Code = 255; 0 to 100µA
Code = 0; 0 to 100µA
Power-down mode
TOUCH-SCREEN CONTROLLER
Y+, X+
0.5
Output Load Regulation
Output Resistance
LSB
0.5
1.0
MΩ
7
9
On-Resistance
Ω
Y-, X-
Touch-Detection Internal Pullup
Resistance
X+ to AV
1
MΩ
DD
KEYPAD CONTROLLER
C4, C3, C2, C1 (Note 11)
R4, R3, R2, R1 (Note 11)
DIGITAL INTERFACE
Pullup Resistance
0.5
16
kΩ
kΩ
Pulldown Resistance
DIGITAL INPUTS (SCLK, CS, DIN, R_, C_)
✕
0.3
DV
Input Voltage Low
V
V
IL
DD
✕
0.7
DV
Input Voltage High
V
I
V
IH
DD
Input Leakage Current
0.1
1
µA
L
4
_______________________________________________________________________________________
1ꢀ5k ꢁEDꢂ-rotected TouchꢂEcreen
Controllers Include DAC and Keypad Controller
ELECTRICAL CHARACTERISTICS (continued)
(DV
= AV
= +2.7V to +3.6V (MAX1233), DV
= AV
= +4.75V to +5.25V (MAX1234), external reference V
= 2.5V
REF
DD
DD
DD
DD
(MAX1233), V
= 4.096V (MAX1234); f
= 10MHz, f
= 50ksps, 12-bit mode, 0.1µF capacitor at REF, T = -40°C to
SAMPLE A
REF
SCLK
+85°C, unless otherwise noted. Typical values are at T = +25°C.)
A
PARAMETER
Input Capacitance
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
C
15
pF
IN
DIGITAL OUTPUT (DOUT)
I
I
= 2mA
= 4mA
0.4
0.8
SINK
SINK
Output Voltage Low
V
V
V
OL
DV
0.5
-
-
DD
Output Voltage High
V
I
= 1.5mA
SOURCE
OH
DIGITAL OUTPUT (BUSY, PENIRQ, KEYIRQ, R_, C_)
Output Voltage Low
V
I
= 0.2mA
0.4
V
V
OL
SINK
DV
0.5
DD
Output Voltage High
V
I
= 0.2mA
OH
SOURCE
POWER REQUIREMENTS
MAX1233
2.7
3
3.6
5.25
5
AV
DV
/
DD
Supply Voltage (Note 12)
V
DD
MAX1234
4.75
5
Idle; all blocks shut down
0.5
150
150
670
Only ADC on; f = 20ksps
SAMPLE
500
230
900
Analog and Digital Supply
Current
I
+
AVDD
µA
I
DVDD
Only DAC on; no load
Only internal reference on
TIMING CHARACTERISTICS
SCLK Clock Period
t
100
40
40
40
0
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
CP
SCLK Pulse Width High
SCLK Pulse Width Low
DIN to SCLK Rise Setup
SCLK Rise to DIN Hold
SCLK Fall to DOUT Valid
CS Fall to DOUT Enabled
CS Rise to DOUT Disabled
CS Fall to SCLK Rise
t
CH
t
t
CL
DS
DH
t
t
C
C
C
= 50pF
= 50pF
= 50pF
40
45
40
DOV
LOAD
LOAD
LOAD
t
DV
t
DOD
t
40
0
CSS
CSH
GPO
CSW
CS Fall to SCLK Ignored
SCLK Rise to R_/C_ Data Valid
CS Pulse Width High
t
t
C
= 50pF (Note 13)
230
LOAD
t
40
Note 1: Tested at DV
= AV
= +2.7V (MAX1233), DV
= AV
= +5V (MAX1234).
DD
DD
DD
DD
Note 2: Relative accuracy is the deviation of the analog value at any code from its theoretical value after the offset and gain errors
have been removed.
Note 3: Offset nulled.
Note 4: Difference between TEMP1 and TEMP2; temperature in °K = (V
Note 5: Temperature coefficient is -2.1mV/°C. Determine absolute temperature by extrapolating from a calibrated value.
- V
) × 2680°K/V. No calibration is necessary.
TEMP1
TEMP2
Note 6: ADC performance is limited by the conversion noise floor, typically 300µV . An external reference below 2.5V can
P-P
compromise the ADC performance.
Note 7: Guaranteed from code 5 to 255.
_______________________________________________________________________________________
5
1ꢀ5k ꢁEDꢂ-rotected TouchꢂEcreen
Controllers Include DAC and Keypad Controller
ELECTRICAL CHARACTERISTICS (continued)
(DV
= AV
= +2.7V to +3.6V (MAX1233), DV
= AV
= +4.75V to +5.25V (MAX1234), external reference V
= 2.5V
REF
DD
DD
DD
DD
(MAX1233), V
= 4.096V (MAX1234); f
= 10MHz, f
= 50ksps, 12-bit mode, 0.1µF capacitor at REF, T = -40°C to
SAMPLE A
REF
SCLK
+85°C, unless otherwise noted. Typical values are at T = +25°C.)
A
Note 8: The offset value extrapolated from the range over which the INL is guaranteed.
Note 9: Output settling time is measured by stepping from code 5 to 255, and from code 255 to 5.
Note 10: Actual output voltage at full scale is 255/256 × V
.
REFDAC
Note 11: Resistance is open when configured as GPIO or in shutdown.
Note 12: AV and DV should not differ by more than 300mV.
DD
DD
Note 13: When configured as GPIO.
Timing Diagram
CS
t
CSW
t
CSH
t
t
t
CSH
t
CH
CP
CSS
t
CL
t
CSS
SCLK
t
DH
t
DS
DIN
t
t
DOD
DOV
t
DV
DOUT
R_/C_
NOTE: TIMING NOT TO SCALE.
t
GPO
6
_______________________________________________________________________________________
1ꢀ5k ꢁEDꢂ-rotected TouchꢂEcreen
Controllers Include DAC and Keypad Controller
Typical Operating Characteristics
(AV
= DV
= 3V (MAX1233) or 5V (MAX1234), external V
= +2.5V (MAX1233), external V
= +4.096V (MAX1234), f
SCLK
=
DD
DD
REF
REF
10MHz (50% duty cycle), f
= 20ksps, C = 50pF, 0.1µF capacitor at REF, T = +25°C, unless otherwise noted.)
LOAD A
SAMPLE
SHUTDOWN CURRENT
vs. ANALOG SUPPLY VOLTAGE
SHUTDOWN CURRENT
vs. TEMPERATURE
INTERNAL OSCILLATOR FREQUENCY
vs. ANALOG SUPPLY VOLTAGE
300
250
200
150
100
50
300
250
200
150
100
50
10.0
9.8
9.6
9.4
9.2
9.0
8.8
8.6
8.4
8.2
8.0
MAX1233/MAX1234
0
0
2.7
3.2
3.7
4.2
4.7
5.2
-40
-20
0
20
40
60
80
2.7
3.2
3.7
4.2
4.7
5.2
AV (V)
DD
TEMPERATURE (°C)
AV (V)
DD
INTERNAL OSCILLATOR FREQUENCY
vs. TEMPERATURE
TEMP1 DIODE VOLTAGE
vs. ANALOG SUPPLY VOLTAGE
TEMP1 DIODE VOLTAGE
vs. TEMPERATURE
9.8
9.6
9.4
9.2
9.0
8.8
8.6
0.70
0.68
0.66
0.64
0.62
0.60
0.58
0.56
0.54
0.52
0.50
0.80
0.75
0.70
0.65
0.60
0.55
0.50
0.45
0.40
MAX1234, AV = +5.0V
DD
MAX1233, AV = +3.0V
DD
-40 -20
0
20
40
60
80
2.7
3.2
3.7
4.2
4.7
5.2
-40 -25 -10
5
20 35 50 65 80
TEMPERATURE (°C)
AV (V)
DD
TEMPERATURE (°C)
TEMP2 DIODE VOLTAGE
vs. ANALOG SUPPLY VOLTAGE
TEMP2 DIODE VOLTAGE
vs. TEMPERATURE
0.80
0.75
0.70
0.65
0.60
0.90
0.85
0.80
0.75
0.70
0.65
0.60
2.7
3.2
3.7
4.2
4.7
5.2
-40 -25 -10
5
20 35 50 65 80
AV (V)
DD
TEMPERATURE (°C)
_______________________________________________________________________________________
7
1ꢀ5k ꢁEDꢂ-rotected TouchꢂEcreen
Controllers Include DAC and Keypad Controller
Typical Operating Characteristics (continued)
(AV
= DV
= 3V (MAX1233) or 5V (MAX1234), external V
= +2.5V (MAX1233), external V
= +4.096V (MAX1234), f
=
DD
DD
REF
REF
SCLK
10MHz (50% duty cycle), f
= 20ksps, C
= 50pF, 0.1µF capacitor at REF, T = +25°C, unless otherwise noted.)
SAMPLE
LOAD
A
ADC INTEGRAL NONLINEARITY
vs. OUTPUT CODE
ADC DIFFERENTIAL NONLINEARITY
vs. OUTPUT CODE
1.0
0.8
0.6
0.4
0.2
0
1.0
0.8
0.6
0.4
0.2
0
-0.2
-0.4
-0.6
-0.8
-0.2
-0.4
-0.6
-0.8
-1.0
-1.0
0
500 1000 1500 2000 2500 3000 3500 4000
OUTPUT CODE
0
500 1000 1500 2000 2500 3000 3500 4000
OUTPUT CODE
ADC OFFSET ERROR
vs. ANALOG SUPPLY VOLTAGE
ADC OFFSET ERROR vs. TEMPERATURE
2.0
1.5
1.0
0.5
0
2.0
1.5
1.0
0.5
0
-0.5
-1.0
-1.5
-0.5
-1.0
-1.5
-2.0
-2.0
2.7
3.2
3.7
4.2
4.7
5.2
-40
-20
0
20
40
60
80
AV (V)
DD
TEMPERATURE (°C)
ADC GAIN ERROR
vs. TEMPERATURE
ADC GAIN ERROR
vs. ANALOG SUPPLY VOLTAGE
2.0
1.5
1.0
0.5
0
2.0
1.5
1.0
0.5
0
-0.5
-1.0
-1.5
-2.0
-0.5
-1.0
-1.5
-2.0
2.7
-40
-20
0
20
40
60
80
3.2
3.7
4.2
4.7
5.2
TEMPERATURE (°C)
AV (V)
DD
8
_______________________________________________________________________________________
1ꢀ5k ꢁEDꢂ-rotected TouchꢂEcreen
Controllers Include DAC and Keypad Controller
Typical Operating Characteristics (continued)
(AV
= DV
= 3V (MAX1233) or 5V (MAX1234), external V
= +2.5V (MAX1233), external V
= +4.096V (MAX1234), f
SCLK
=
DD
DD
REF
REF
10MHz (50% duty cycle), f
= 20ksps, C
= 50pF, 0.1µF capacitor at REF, T = +25°C, unless otherwise noted.)
SAMPLE
LOAD
A
ADC SUPPLY CURRENT
vs. SAMPLING RATE
ADC EXTERNAL REFERENCE INPUT
CURRENT vs. SAMPLING RATE
1000
100
10
8
MAX1233
= +2.5V
V
REF
6
4
2
0
1
0.1
1
10
100
1k
10k
100k
100
1k
10k
100k
f
(Hz)
SAMPLE
f
(Hz)
SAMPLE
ADC SUPPLY CURRENT
vs. TEMPERATURE
ADC SUPPLY CURRENT
vs. SUPPLY VOLTAGE
140
120
100
80
250
200
150
100
50
AV = +3V
DD
EXTERNAL REF
f
= 20ksps
SAMPLE
60
40
20
0
0
-40
-20
0
20
40
60
80
2.7
3.2
3.7
4.2
4.7
5.2
TEMPERATURE (°C)
AV (V)
DD
DAC DIFFERENTIAL NONLINEARITY
vs. OUTPUT CODE
DAC INTEGRAL NONLINEARITY vs. CODE
0.075
0.050
0.025
0
0.075
0.050
0.025
0
-0.025
-0.050
-0.075
-0.025
-0.500
-0.075
-0.100
-0.100
0
50
100
150
200
250
300
250
150
0
50
100
200
300
OUTPUT CODE
CODE
_______________________________________________________________________________________
9
1ꢀ5k ꢁEDꢂ-rotected TouchꢂEcreen
Controllers Include DAC and Keypad Controller
Typical Operating Characteristics (continued)
(AV
= DV
= 3V (MAX1233) or 5V (MAX1234), external V
= +2.5V (MAX1233), external V
= +4.096V (MAX1234), f
=
DD
DD
REF
REF
SCLK
10MHz (50% duty cycle), f
= 20ksps, C
= 50pF, 0.1µF capacitor at REF, T = +25°C, unless otherwise noted.)
SAMPLE
LOAD
A
DAC FULL-SCALE ERROR
vs. ANALOG SUPPLY VOLTAGE
DAC FULL-SCALE ERROR
vs. TEMPERATURE
MAX1233/34 toc21
MAX1233/34 toc22
0.75
0.50
0.25
0
1.2
0.8
0.4
0
1.2
0.8
0.4
0
0.75
0.50
0.25
0
-0.25
-0.50
-0.4
-0.8
-0.4
-0.8
-0.25
-0.50
-0.75
-1.2
5.5
-1.2
-0.75
2.5
3.0
3.5
4.0
4.5
5.0
-40
-20
0
20
40
60
80
AV (V)
DD
TEMPERATURE (°C)
DAC SUPPLY CURRENT
vs. ANALOG SUPPLY VOLTAGE
DAC SUPPLY CURRENT
vs. TEMPERATURE
250
200
150
100
50
200
175
150
125
100
75
50
25
0
0
2.7
3.2
3.7
4.2
4.7
5.2
-40
-20
0
20
40
60
80
AV (V)
DD
TEMPERATURE (°C)
ADC REFERENCE VOLTAGE
vs. TEMPERATURE
ADC REFERENCE VOLTAGE
vs. ANALOG SUPPLY VOLTAGE
MAX1233/34 toc26
MAX1233/34 toc25
2.60
2.55
2.50
2.45
2.40
1.250
1.125
1.000
0.875
0.750
2.550
2.525
2.500
2.475
2.450
1.020
1.010
1.000
0.990
0.980
V
= 1.0V
REF
REF
V
= 1.0V
= 2.5V
REF
V
REF
V
= 2.5V
2.7
3.2
3.7
4.2
4.7
5.2
-40
-20
0
20
40
60
80
TEMPERATURE (°C)
AV (V)
DD
10 ______________________________________________________________________________________
1ꢀ5k ꢁEDꢂ-rotected TouchꢂEcreen
Controllers Include DAC and Keypad Controller
Typical Operating Characteristics (continued)
(AV
= DV
= 3V (MAX1233) or 5V (MAX1234), external V
= +2.5V (MAX1233), external V
= +4.096V (MAX1234), f
=
DD
DD
REF
REF
SCLK
10MHz (50% duty cycle), f
= 20ksps, C = 50pF, 0.1µF capacitor at REF, T = +25°C, unless otherwise noted.)
LOAD A
SAMPLE
ADC REFERENCE SUPPLY CURRENT
vs. ANALOG SUPPLY VOLTAGE
REFERENCE SUPPLY CURRENT
vs. TEMPERATURE
750
700
650
600
750
700
650
600
550
550
2.7
3.2
3.7
4.2
4.7
5.2
-40 -25 -10
5
20 35 50 65 80
AV (V)
DD
TEMPERATURE (°C)
-in Description
PIN
NAME
FUNCTION
Positive Digital Supply Voltage, +2.7V to +3.6V for MAX1233, +4.75V to +5.25V for MAX1234. Bypass
with a 0.1µF capacitor. Must be within 300mV of AV
1
DV
DD
DD
.
DD
Positive Analog Supply Voltage, +2.7V to +3.6V for MAX1233, +4.75V to +5.25V for MAX1234.
2
AV
Bypass with a 0.1µF capacitor. Must be within 300mV of DV
.
DD
3*
4*
X+
X+ Position Input
Y+
X-
Y+ Position Input
5*
X- Position Input
6*
Y-
Y- Position Input
7
GND
BAT1
BAT2
AUX1
AUX2
Analog and Digital Ground
8*
Battery Monitoring Input 1. Measures battery voltages up to 6V.
Battery Monitoring Input 2. Measures battery voltages up to 6V.
Auxiliary Analog Input 1 to ADC. Measures analog voltages from zero to V
Auxiliary Analog Input 2 to ADC. Measures analog voltages from zero to V
9*
10*
11*
.
REF
.
REF
Voltage Reference Output/Input. Reference voltage for analog-to-digital conversion. In internal
reference mode, the reference buffer provides a 2.5V or 1.0V nominal output. In external reference
mode, apply a reference voltage between 1.0V and AV . Bypass REF to GND with a 0.1µF
DD
12
REF
capacitor in the external reference mode only.
13
14
15
16
17
18
DACOUT
R4
DAC Voltage Output; 0.9 × AV
Full Scale
DD
Keypad Row 4. Can be reconfigured as GPIO3.
Keypad Row 3. Can be reconfigured as GPIO2.
Keypad Row 2. Can be reconfigured as GPIO1.
Keypad Row 1. Can be reconfigured as GPIO0.
Keypad Column 1. Can be reconfigured as GPIO4.
R3
R2
R1
C1
______________________________________________________________________________________ 11
1ꢀ5k ꢁEDꢂ-rotected TouchꢂEcreen
Controllers Include DAC and Keypad Controller
-in Description (continued)
PIN
19
20
21
22
23
24
NAME
C2
FUNCTION
Keypad Column 2. Can be reconfigured as GPIO5.
C3
Keypad Column 3. Can be reconfigured as GPIO6.
C4
Keypad Column 4. Can be reconfigured as GPIO7.
KEYIRQ
PENIRQ
DOUT
Active-Low Keypad Interrupt. KEYIRQ is low when a key press is detected.
Active-Low Pen Touch Interrupt. PENIRQ is low when a screen touch is detected.
Serial Data Output. Data is clocked out at SCLK falling edge. High impedance when CS is high.
Active-Low Busy Output. BUSY goes low and stays low during each functional operation. The host
controller should wait until BUSY is high again before using the serial interface.
25
26
27
BUSY
DIN
CS
Serial Data Input. Data is clocked in on the rising edge of SCLK.
Active-Low Chip Select. Data is not clocked into DIN unless CS is low. When CS is high, DOUT is
high impedance.
Serial Clock Input. Clocks data in and out of the serial interface and sets the conversion speed (duty
cycle must be 30% to 70%).
28
SCLK
*ESD protected: ±±kꢀ Contact, ±15kꢀ Air.
open or floating. The point where the touch screen is
pressed brings the two resistive layers in contact and
creates a voltage-divider at that point. The data convert-
er senses the voltage at the point of contact through the
X+ input and digitizes it.
Detailed Description
The MAX1233/MAX1234 are 4-wire touch-screen con-
trollers. Figure 1 shows the functional diagram of the
MAX1233/MAX1234. Each device includes a 12-bit sam-
pling ADC, 8-bit voltage output DAC, keypad scanner
that can also be configured as a GPIO, internal clock,
reference, temperature sensor, two battery monitor
inputs, two auxiliary analog inputs, SPI/QSPI/
MICROWIRE-compatible serial interface, and low on-
resistance switches for driving touch screens.
12ꢂBit ADC
Analog Inputs
Figure 3 shows a block diagram of the ADC’s analog
input section including the input multiplexer, the differen-
tial input, and the differential reference. The input multi-
plexer switches between X+, X-, Y+, Y-, AUX1, AUX2,
BAT1, BAT2, and the internal temperature sensor.
The 16-bit register inside the MAX1233/MAX1234
allows for easy control and stores results that can be
read at any time. The BUSY output indicates that a
functional operation is in progress. The PENIRQ and
KEYIRQ outputs, respectively, indicate that a screen
touch or a key press has occurred.
The time required for the T/H to acquire an input signal
is a function of how quickly its input capacitance is
charged. If the input signal’s source impedance is high,
the acquisition time lengthens, and more time must be
allowed. The acquisition time (t
) is the maximum
ACQ
TouchꢂEcreen Operation
The 4-wire touch-screen controller works by creating a
voltage gradient across the vertical or horizontal resis-
tive touch screen connected to the analog inputs of the
MAX1233/MAX1234, as shown in Figure 2. The voltage
across the touch-screen panels is applied through inter-
nal MOSFET switches that connect each resistive layer
time the device takes to acquire the input signal to 12-
bit accuracy. Configure t by writing to the ADC
ACQ
control register. See Table 1 for the maximum input sig-
nal source impedance (R
during acquisition.
) for complete settling
SOURCE
Accommodate higher source impedances by placing a
0.1µF capacitor between the analog input and GND.
to AV
and ground. For example, to measure the Y
DD
position when a pointing device presses on the touch
screen, the Y+ and Y- drivers are turned on, connecting
Input Bandwidth
The ADC’s input-tracking circuitry has a 0.5MHz small-
signal bandwidth. To avoid high-frequency signals
being aliased into the frequency band of interest, anti-
alias filtering is recommended.
one side of the vertical resistive layer to AV
and the
DD
other side to ground. The horizontal resistive layer func-
tions as a sense line. One side of this resistive layer gets
connected to the X+ input, while the other side is left
12 ______________________________________________________________________________________
1ꢀ5k ꢁEDꢂ-rotected TouchꢂEcreen
Controllers Include DAC and Keypad Controller
C1 C2 C3 C4 R1 R2
R3 R4
KEYPAD CONTROLLER
AND GPIO
OSCILLATOR
MAX1233
MAX1234
REGISTERS AND
SCAN STATE
CONTROL
TEMP
SENSOR
DOUT
SCLK
DIN
*X+
*X-
X/Y SWITCHES
SERIAL
DATA
I/O
*Y+
*Y-
MUX
CS
12-BIT
ADC
PENIRQ
KEYIRQ
*BAT1
*BAT2
BATTERY MONITOR
BATTERY MONITOR
BUSY
*AUX1
*AUX2
INTERNAL
REFERENCE
2.5V/1.0V
REF
8-BIT
DAC
DACOUT
REF
DAC
*ESD PROTECTED
Figure 1. Block Diagram
Table 1. Maximum Input Source
Impedance
+AV
DD
FORCE LINE
MAXIMUM R
COMPLETE SETTLING
DURING ACQUISITION (kΩ)
FOR
SOURCE
ACQUISITION RESOLUTION
Y+
X+
Y-
TIME (µs)
(BITS)
1.5
1.5
1.5
5.0
5.0
5.0
95
8
2.6
2.0
1.5
23
10
12
8
SENSE LINE
+REF
-REF
+IN
-IN
SENSE
LINE
10
12
8
19
15
560
470
400
FORCE LINE
95
10
12
GND
95
Figure 2. Touch-Screen Measurement
______________________________________________________________________________________ 13
1ꢀ5k ꢁEDꢂ-rotected TouchꢂEcreen
Controllers Include DAC and Keypad Controller
+AV
DD
V
REF
TEMP2
TEMP1
MAX1233
MAX1234
X+
X-
REF ON/OFF
+REF
Y+
Y-
+IN
-IN
CONVERTER
2.5V/1.0V
REFERENCE
-
REF
7.5kΩ
7.5kΩ
V
V
BAT1
BAT2
2.5kΩ
2.5kΩ
BATTERY
ON
BATTERY
ON
AUX1
AUX2
GND
Figure 3. Simplified Diagram of Analog Input Section
Analog Input Protection
to 8kV, using tꢀe Contact-Discꢀarge metꢀod and
15kV using tꢀe Air-Gap metꢀod specified in IEC-
1000-4-2.
Internal protection diodes that clamp the analog input
to AV
and GND allow the analog input pins to swing
DD
from GND - 0.3V to AV
+ 0.3V without damage.
DD
Reference for ADC
Analog inputs must not exceed AV
by more than
DD
Internal Reference
The MAX1233/MAX1234 offer an internal voltage refer-
ence for the ADC that can be set to +1.0V or +2.5V. The
MAX1233/MAX1234 typically use the internal reference
for battery monitoring, temperature measurement, and for
50mV or be lower than GND by more than 50mV for
accurate conversions. If an off-channel analog input
voltage exceeds the supplies, limit the input current to
50mA. All analog inputs are also fully ESD protected
14 ______________________________________________________________________________________
1ꢀ5k ꢁEDꢂ-rotected TouchꢂEcreen
Controllers Include DAC and Keypad Controller
ment, temperature measurement, or auxiliary input
measurement is written to the ADC control register, the
device powers on the internal reference, waits for the
internal reference to settle, completes the requested
+1.25V
BANDGAP
scan, and powers down the internal reference. The ref-
erence power delay depends upon the ADC resolution
REF PIN
3R
2R
2x
selected (see Table 8). Do not bypass REF with an
external capacitor when performing scans in auto
power-down mode.
OPTIONAL
Full-Power Mode (RES1 = 0, RES0 = 1)
In the full-power mode, the RES1 bit is set LOW and
RES0 bit is set HIGH. In this mode, the device is pow-
ered up and the internal ADC reference is always ON.
The MAX1233/MAX1234 internal reference remains fully
powered after completing a scan.
Figure 4. Block Diagram of the Internal Reference
Internal Cloc5
The MAX1233/MAX1234 operate from an internal oscil-
lator, which is accurate to within 20% of the 10MHz
specified clock rate. The internal oscillator controls the
timing of the acquisition, conversion, touch-screen set-
tling, reference power-up, and keypad debounce times.
measurement of the auxiliary inputs. Figure 4 shows the
on-chip reference circuitry of the MAX1233/MAX1234.
Set the internal reference voltage by writing to the RFV
bits in the ADC control register (see Tables 4, 5, and 12).
The MAX1233/MAX1234 can accept an external refer-
ence connected to REF for ADC conversion.
8ꢂBit DAC
The MAX1233/MAX1234 have a voltage-output, true 8-bit
monotonic DAC with less than 1LSB integral nonlinearity
error and less than 1LSB differential nonlinearity error. It
requires a supply current of only 150µA (typ) and pro-
vides a buffered voltage output. The DAC is at midscale
code at power-up and remains there until a new code is
written to the DAC register. During shutdown, the DAC’s
output is pulled to ground with a 1MΩ load.
The internal DAC can be used in various system applica-
tions such as LCD/TFT-bias control, automatic tuning
(VCO), power amplifier bias control, programmable
threshold levels, and automatic gain control (AGC).
External Reference
The MAX1233/MAX1234 can accept an external refer-
ence connected to the REF pin for ADC conversions.
The internal reference should be disabled (RES1 = 1)
when using an external reference. At a conversion rate
of 50ksps, an external reference at REF must deliver up
to 15µA of load current and have 50Ω or less output
impedance. If the external reference has high output
impedance or is noisy, bypass it close to the REF pin
with a 0.1µF capacitor.
Selecting Internal or External Reference
Set the type of reference being used by programming
the ADC control register. To select the internal refer-
ence, clock zeros into bits [A/D3:A/D0] and a zero to bit
RES1, as shown in the Control Registers section. To
change to external reference mode, clock zeros into
bits [A/D3:A/D0] and a one to bit RES1. See Table 13
for more information about selecting an internal or
external reference for the ADC.
The 8-bit DAC in the MAX1233/MAX1234 employs a
current-steering topology as shown in Figure 5. At the
core of this DAC is a reference voltage-to-current con-
verter (V/I) that generates a reference current. This cur-
rent is mirrored to 255 equally weighted current
sources. DAC switches control the outputs of these cur-
rent mirrors so that only the desired fraction of the total
current-mirror currents is steered to the DAC output.
The current is then converted to a voltage across a
resistor, and the output amplifier buffers this voltage.
Reference -ower Modes
Auto Power-Down Mode (RES1 = RES0 = 0)
The MAX1233/MAX1234 are in auto power-down mode
at initial power-up. Set the RES1 and RES0 bits to zero
to use the MAX1233/MAX1234 in the auto power-down
mode. In this mode, the internal reference is normally
off. When a command to perform a battery measure-
DAC Output Voltage
The 8-bit DAC code is binary unipolar with 1LSB =
(V
/256). The DAC has a full-scale output voltage of
REF
(0.9 × AV
- 1LSB).
DD
______________________________________________________________________________________ 15
1ꢀ5k ꢁEDꢂ-rotected TouchꢂEcreen
Controllers Include DAC and Keypad Controller
+AV
DD
V
REF
1MΩ
SW255
SW1
SW2
S1
TOUCH-SCREEN
DETECTOR
PENIRQ
TOUCH
SCREEN
OUT
X+
Y+
Figure 5. DAC Current-Steering Topology
X-
Y-
Output Buffer
The DAC voltage output is an internally buffered unity-
gain follower that slews at up to 0.4V/µs. The output
can swing from zero to full scale. With a 1/4FS to 3/4FS
output transition, the amplifier output typically settles to
1/2LSB in less than 5µs when loaded with 10kΩ in par-
allel with 50pF. The buffer amplifier is stable with any
combination of resistive loads >10kΩ and capacitive
loads <50pF.
S2
Power-On Reset
All registers of the MAX1233/MAX1234 power up at a
default zero state, except the DAC data register, which
is set to 10000000, so the output is at midscale.
Figure 6. Touch-Screen Detection Block Diagram
internally pulled to AV
through a 1MΩ resistor as
DD
shown in Figure 6. When the screen is touched, the X+
pin is pulled to GND through the touch screen and a
touch is detected.
Keypad Controller and G-IO
The keypad controller is designed to interface a matrix-
type 4 rows × 4 columns (16 keys or fewer) keypad to a
host controller. The KEY control register controls keypad
interrupt, keypad scan, and keypad debounce times.
The KeyMask and ColumnMask registers enable mask-
ing of a particular key or an entire column of the keypad
when they are not in use. The MAX1233/MAX1234 offer
two keypad data registers. KPData1 holds all keypad
scan results, including masked data, and is thus the
pending register. KPData2 holds keypad scan results of
only the unmasked keys. If 12 or fewer keys are being
monitored, one or more of the row/column pins of the
MAX1233/MAX1234 can be software programmed as
GPIO pins.
When the 1MΩ pullup resistor is first connected, the X+
pin can be floating near ground. To prevent false touch
detection in this case, the X+ pin is precharged high for
0.1µs using the 7Ω PMOS driver before touch detection
begins.
Keyꢂ-ress Detection
Key-press detection can be enabled or disabled by
writing to the keypad control register as shown in Table
17. Key-press detection is disabled at initial power-up.
Once key-press detection is enabled, the C_ pins are
internally connected to DV
and the R_ pins are inter-
DD
nally pulled to GND through a 16kΩ resistor. When a
key is pressed, the associated row pin is pulled to
DV
and the key press is detected. Figure 7 shows
DD
TouchꢂEcreen Detection
Touch-screen detection can be enabled or disabled by
writing to the ADC control register as shown in Table 4.
Touch-screen detection is disabled at initial power-up.
Once touch-screen detection is enabled, the Y- driver
is on and the Y- pin is connected to GND. The X+ pin is
the key-press detection circuitry.
Interrupts
PEN Interrupt Request (PENIRQ)
The PENIRQ output can be used to alert the host con-
troller of a screen touch. The PENIRQ output is normally
16 ______________________________________________________________________________________
1ꢀ5k ꢁEDꢂ-rotected TouchꢂEcreen
Controllers Include DAC and Keypad Controller
SIMPLIFIED KEYPAD CIRCUITRY
DRIVERS PULL HIGH
OR GO THREE-STATE
C1
C2
C3
C4
R1
R2
R3
R4
TO KEYPAD
WAKEUP AND
DEBOUNCE
LOGIC
KEYPAD
Figure 7. Key-Press Detection Circuitry
X+
X+
PENIRQ
PENIRQ
BUSY
BUSY
CS
CS
DATA
READ
DIN
DATA
READ
DOUT
TOUCH-
SCREEN
DATA
DOUT
TOUCH-
SCREEN
DATA
Figure ±a. Timing Diagram for Touch-Initiated Screen Scan
Figure ±b. Timing Diagram for Host-Initiated Screen Scan
______________________________________________________________________________________ 17
1ꢀ5k ꢁEDꢂ-rotected TouchꢂEcreen
Controllers Include DAC and Keypad Controller
high and goes low after a screen touch is detected.
PENIRQ returns high only after a touch-screen scan is
R_
completed. PENIRQ does not go low again until one of
the touch-screen data registers is read. Figures 8a and
8b show the timing diagrams for the PENIRQ pin.
KEYIRQ
Keypad Interrupt Request (KEYIRQ)
The KEYIRQ output can be used to alert the host con-
troller of a key press. The KEYIRQ output is normally
BUSY
high and goes low after a key press is detected.
KEYIRQ returns high only after a key-press scan is
completed. KEYIRQ does not go low again until one of
CS
the key-press data registers is read. Figures 9a and 9b
DATA
READ
show the timing diagrams for the KEYIRQ pin.
Busy Indicator (BUSY)
DOUT
TOUCH-
SCREEN
DATA
BUSY informs the host processor that a scan is in
progress. BUSY is normally high and goes low and
stays low during each functional operation. The host
controller should wait until BUSY is high again before
using the serial interface.
Figure 9a. Timing Diagram for Key-Press-Initiated Debounce
Scan
Digital Interface
The MAX1233/MAX1234 interface to the host controller
through a standard 3-wire serial interface at up to
10MHz. DIN and CS are the digital inputs to the
MAX1233/MAX1234. DOUT is the serial data output.
Data is clocked out at the SCLK falling edge and is high
impedance when CS is high. PENIRQ and KEYIRQ com-
municate interrupts from the touch-screen and keypad
controllers to the host processor when a screen touch or
a key press is detected. BUSY informs the host proces-
sor that a scan is in progress. In addition to these digital
I/Os, the row and column pins of the keypad controller
can be programmed as GPIO pins.
R_
KEYIRQ
BUSY
CS
DATA
READ
DIN
DOUT
Communications Protocol
The MAX1233/MAX1234 are controlled by reading from
and writing to registers through the 3-wire serial inter-
face. These registers are addressed through a 16-bit
command that is sent prior to the data. The command
is shown in Table 2.
TOUCH-
SCREEN
DATA
Figure 9b. Timing Diagram for Host-Initiated Keypad
Debounce Scan
The first 16 bits after the falling edge of CS contain the
command word. The command word begins with an
R/W bit, which specifies the direction of data flow on
the serial bus. Bits 14 through 7 are reserved for future
use. Bit 6 specifies the page of memory in which the
desired register is located. The last 6 bits specify the
address of the desired register. The next 16 bits of data
are read from or written to the address specified in the
command word. After 32 clock cycles, the interface
automatically increments its address pointer and con-
tinues reading or writing until the rising edge of CS, or
until it reaches the end of the page.
Table 2. Command Word Format
BIT15
MSB
BIT0
BIT14 BIT13 BIT12 BIT11 BIT10 BIT9
RES RES RES RES RES RES
BIT8
BIT7
BIT6
BIT5
BIT4
BIT3
BIT2
BIT1
LSB
RES PAGE ADD5 ADD4 ADD3 ADD2 ADD1 ADD0
R/W
RES
18 ______________________________________________________________________________________
1ꢀ5k ꢁEDꢂ-rotected TouchꢂEcreen
Controllers Include DAC and Keypad Controller
Table 3. Register Summary for MAX1233/MAX1234
ADDR
(HEX)
00
01
02
03
04
05
06
07
08
09
0A
0B
0C
0D
0E
0F
10
11
12
13
14
15
16
17
18
19
1A
1B
1C
1D
1E
1F
00
01
02
03
04
05
06
07
08
09
0A
0B
0C
0D
0E
REGISTER
PAGE
BIT15
BIT14
BIT13 BIT12 BIT11
BIT10
BIT9
BIT8
BIT7
BIT6
BIT5
BIT4
BIT3
BIT2
BIT1
BIT0
NAME
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
X
Y
Z1
Z2
KPD
BAT1
BAT2
AUX1
0
0
0
0
K15
0
0
0
0
0
0
0
0
0
0
GPD7
K1_15
K2_15
0
0
0
0
0
0
0
0
0
0
0
0
0
RES
0
0
0
0
K14
0
0
0
0
0
0
0
0
0
0
0
0
0
0
X11
Y11
X10
Y10
X9
Y9
X8
Y8
X7
Y7
X6
Y6
X5
Y5
X4
Y4
X3
Y3
X2
Y2
X1
Y1
X0
Y0
0
0
0
0
Z1_11 Z1_10 Z1_9
Z2_11 Z2_10 Z2_9
Z1_8 Z1_7 Z1_6 Z1_5 Z1_4 Z1_3 Z1_2 Z1_1 Z1_0
Z2_8 Z2_7 Z2_6 Z2_5 Z2_4 Z2_3 Z2_2 Z2_1 Z2_0
K8
K13
0
0
0
0
K12
0
0
0
0
K11
K10
K9
K7
K6
K5
K4
K3
K2
K1
K0
B1_11 B1_10 B1_9 B1_8 B1_7 B1_6 B1_5 B1_4 B1_3 B1_2 B1_1 B1_0
B2_11 B2_10 B2_9 B2_8 B2_7 B2_6 B2_5 B2_4 B2_3 B2_2 B2_1 B2_0
A1_11 A1_10 A1_9 A1_8 A1_7 A1_6 A1_5 A1_4 A1_3 A1_2 A1_1 A1_0
A2_11 A2_10 A2_9 A2_8 A2_7 A2_6 A2_5 A2_4 A2_3 A2_2 A2_1 A2_0
AUX2
TEMP1
TEMP2
DAC
Reserved
Reserved
Reserved
GPIO
KPData1
KPData2
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
ADC
0
0
0
0
T1_11 T1_10 T1_9
T2_11 T2_10 T2_9
T1_8 T1_7 T1_6 T1_5 T1_4 T1_3 T1_2 T1_1 T1_0
T2_8 T2_7 T2_6 T2_5 T2_4 T2_3 T2_2 T2_1 T2_0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
DA7
DA6
DA5
DA4
DA3
DA2
DA1
DA0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
GPD6
GPD5 GPD4 GPD3 GPD2 GPD1 GPD0
K1_14 K1_1 K1_1 K1_11 K1_10 K1_9 K1_8 K1_7 K1_6 K1_5 K1_4 K1_3 K1_2 K1_1 K1_0
K2_14 K2_1 K2_1 K2_11 K2_10 K2_9 K2_8 K2_7 K2_6 K2_5 K2_4 K2_3 K2_2 K2_1 K2_0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
RES
ST1
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
RES
ST0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
RES
RFV
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
RES
ADSTS
RES
RES
RES
RES
RES
RES
RES
RES
RES
RES
RES
PENSTS
A/D3 A/D2 A/D1 A/D0 RES1 RES0 AVG1 AVG2 CNR1 CNR0 ST2
KEY
DAC
KEYSTS1 KEYSTS0 DBN2 DBN1 DBN0 HLD2 HLD1 HLD0
DAPD
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
PU6
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
PU2
0
0
0
0
0
0
0
0
0
0
0
0
PU1
0
0
0
0
0
0
0
0
0
0
0
0
PU0
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
PU7
0
0
0
0
0
0
0
0
0
0
0
0
Reserved
GPIO
Pullup
0
0
0
PU5
PU4
PU3
1
1
1
0F
10
11
GPIO
GP7
KM15
CM4
GP6
KM14
CM3
GP5
GP4
GP3
GP2
GP1
GP0
KM8
0
OE7
KM7
0
OE6
KM6
0
OE5
KM5
0
OE4
KM4
0
OE3
KM3
0
OE2
KM2
0
OE1
KM1
0
OE0
KM0
0
KPKeyMask
KPColumn
Mask
KM13 KM12 KM11 KM10 KM9
CM2 CM1
0
0
0
1
1
1
1
1
1
1
1
1
1
1
1
1
1
12
13
14
15
16
17
18
19
1A
1B
1C
1D
1E
1F
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
______________________________________________________________________________________ 19
1ꢀ5k ꢁEDꢂ-rotected TouchꢂEcreen
Controllers Include DAC and Keypad Controller
In order to read the entire first page of memory, for
example, the host processor must send the
Memory Map
The MAX1233/MAX1234s’ internal memory is divided
into two pages—one for data and one for control, each
of which contains thirty-two 16-bit registers.
MAX1233/MAX1234 the command 0x8000 . The
H
MAX1233/MAX1234 then begin clocking out 16-bit data
starting with the X-data register. In order to write to the
second page of memory, the host processor sends the
Control Registers
Table 3 provides a summary of all registers and bit
locations of the MAX1233/MAX1234.
MAX1233/MAX1234 the command 0x0040 . The suc-
H
ceeding data is then written in 16-bit words beginning
with the ADC control register. Figures 10a and 10b show
a complete write and read operation, respectively,
between the processor and the MAX1233/MAX1234.
ADC Control Register
The ADC measures touch position, touch pressure, bat-
tery voltage, auxiliary analog inputs, and temperature.
The ADC control register determines which input is
selected and converted. Tables 4 and 5 show the for-
mat and bit descriptions for the ADC control register.
SCLK
WRITE OPERATION
CS
D0
D0
DIN
D15
D15
D15 IS READ/WRITE BIT
LOW FOR WRITE
D15–D0 COMMAND WORD
D15–D0 DATA WORD
THREE-
STATE
DOUT
THREE-
STATE
TIMING NOT TO SCALE.
Figure 10a. Timing Diagram of Write Operation
SCLK
READ OPERATION
CS
DIN
D15 D14
D0
D15–D0 COMMAND
WORD
DOUT
THREE-STATE
D0
D15
D15
D0
THREE-STATE
DATA WORD
DATA WORD
Figure 10b. Timing Diagram of Read Operation
Table 4. ADC Control Register
BIT15
BIT14 BIT13 BIT12 BIT11 BIT10 BIT9 BIT8 BIT7 BIT6 BIT5 BIT4 BIT3 BIT2 BIT1 BIT0
ST1 ST0 RFV
PENSTS ADSTS A/D3 A/D2 A/D1 A/D0 RES1 RES0 AVG1 AVG0 CNR1 CNR0 ST2
20 ______________________________________________________________________________________
1ꢀ5k ꢁEDꢂ-rotected TouchꢂEcreen
Controllers Include DAC and Keypad Controller
Bits 14-15: Pen Interrupt Status and
ADC Status Bits
Bits 6-7: Converter Averaging Control
These bits specify the number of data averages the
converter performs. Table 9 shows how to program for
the desired number of averages. When averaging is
used, ADSTS and BUSY indicate the converter is busy
until all conversions needed for the averaging finish.
These bits are identical, regardless of read or write.
These bits are used to control or monitor ADC scans.
Bits 10-13: ADC Scan Select
These bits control which input to convert and which con-
verter mode is used. The bits are identical regardless of a
read or write. See Table 7 for details about using these bits.
Bits 4-5: ADC Conversion Rate Control
These bits specify the internal conversion rate, which
the ADC uses to perform a single conversion, as shown
in Table 10. Lowering the conversion rate also reduces
power consumption. These bits are identical, regard-
less of read or write.
Bits 8-9: ADC Resolution Control
These bits specify the ADC resolution and are identical
regardless of read or write. Table 8 shows how to use
these bits to set the resolution.
Table 5. ADC Control Register Bit Descriptions
BIT
NAME
PENSTS
ADSTS
A/D3
DESCRIPTION
15 (MSB)
Read: pen interrupt status; Write: sets interrupt initiated touch-screen scans
14
Read: ADC status; Write: stops ADC
Selects ADC scan functions
13
12
A/D2
Selects ADC scan functions
11
A/D1
Selects ADC scan functions
10
A/D0
Selects ADC scan functions
9
RES1
RES0
AVG1
AVG0
CNR1
CNR0
ST2
Controls ADC resolution
8
Controls ADC resolution
7
Controls ADC result averaging
Controls ADC result averaging
Controls ADC conversion rate
Controls ADC conversion rate
Controls touch-screen settling wait time
Controls touch-screen settling wait time
Controls touch-screen settling wait time
Chooses 1.0V or 2.5V reference
6
5
4
3
2
1
ST1
ST0
0 (LSB)
RFV
Table 6. ADSTS Bit Operation
PENSTS
ADSTS
READ FUNCTION
WRITE FUNCTION
Performs one scan and waits to detect a screen touch. Upon
detection, issues an interrupt and waits until told to scan by the
host controller.
No screen touch detected;
scan or conversion in progress
0
0
Screen touch detected;
scan or conversion in progress detection, issues an interrupt and performs a scan.
Stops any ongoing scan and waits to detect a screen touch. Upon
1
0
1
0
1
1
Stops any ongoing scan and waits to detect a screen touch. Upon
detection, issues an interrupt and waits until told to scan by the
host controller.
No screen touch detected;
data available
Screen touch detected;
data available
Stops any ongoing scan and powers down the screen touch
detection circuit. No screen touches are detected in this mode.
______________________________________________________________________________________ 21
1ꢀ5k ꢁEDꢂ-rotected TouchꢂEcreen
Controllers Include DAC and Keypad Controller
Table 7. ADC Scan Select (Toucꢀ Screen, Battery, Auxiliary Cꢀannels, and Temperature)
A/D3 A/D2 A/D1 A/D0
FUNCTION
Configures the ADC reference as selected by RES [1:0] bits as shown in Table 13. No measurement
is performed.
0
0
0
0
0
0
0
0
1
0
1
0
Measures X/Y touch position and returns results to the X and Y data registers.
Measures X/Y touch position and Z1/ Z2 touch pressure and returns results to the X, Y, Z1, and Z2
data registers.
0
0
0
0
0
1
1
1
0
1
1
1
1
0
0
0
1
0
0
1
1
0
0
1
1
0
1
0
1
0
1
0
Measures X touch position and returns results to the X data register.
Measures Y touch position and returns results to the Y data register.
Measures Z1/Z2 touch pressure and returns results to the Z1 and Z2 data register.
Measures Battery Input 1 and returns results to the BAT1 data register.
Measures Battery Input 2 and returns results to the BAT2 data register.
Measures Auxiliary Input 1 and returns results to the AUX1 data register.
Measures Auxiliary Input 2 and returns results to the AUX2 data register.
Measures temperature (single ended) and returns results to the TEMP1 data register.
Measures Battery Input 1, Battery Input 2, Auxiliary Input 1, Auxiliary Input 2, and temperature
(differential), and returns results to the appropriate data registers.
1
0
1
1
1
1
1
1
1
1
1
1
0
0
1
1
0
1
0
1
Measures temperature (differential) and returns results to the TEMP1 and TEMP2 data registers.
Turns on Y+, Y- drivers. No measurement is performed.
Turns on X+, X- drivers. No measurement is performed.
Turns on Y+, X- drivers. No measurement is performed.
Table 10. ADC Conversion Rate Control
Table 8. ADC Resolution Control
CNR1 CNR0
FUNCTION
INTERNALLY TIMED
REFERENCE POWER-UP
DELAY* (µs)
ADC
RESOLUTION
RES1 RES0
3.5µs/sample
0
0
1
1
0
1
0
1
(1.5µs acquisition, 2µs conversion)
0
0
1
1
0
1
0
1
8 bit
8 bit
31
31
37
44
3.5µs/sample
(1.5µs acquisition, 2µs conversion)
10 bit
12 bit
10µs/sample
(5µs acquisition, 5µs conversion)
*Applicable only for temperature, battery, or auxiliary
measurements in auto power-up reference mode.
100µs/sample
(95µs acquisition, 5µs conversion)
Table 9. ADC Averaging Control
AVG1 AVG0
FUNCTION
No data averages (default)
4 data averages
0
0
1
1
0
1
0
1
8 data averages
16 data averages
22 ______________________________________________________________________________________
1ꢀ5k ꢁEDꢂ-rotected TouchꢂEcreen
Controllers Include DAC and Keypad Controller
Bits 1-3: Touch-Screen Settling Time Control
These bits specify the time delay from pen-touch detec-
tion to a conversion start. This allows the selection of the
appropriate settling time for the touch screen being used.
Table 11 shows how to set the settling time. These bits
are identical, regardless of read or write.
Internal ADC Reference Power-Down Control
The ADC control register controls the power setting of
the internal ADC reference. Zeros must be written to
bits A/D3–A/D0 to control internal reference power-up
followed by the appropriate logic at the RES1 and
RES0 bits. Table 13 shows the internal ADC reference
power-down control.
Bit 0: ADC Internal Reference Voltage Control
This bit selects the ADC internal reference voltage,
either +1.0V or +2.5V. This bit is identical, regardless of
read or write. The reference control bit is shown in
Table 12.
DAC Control Register
The MSB in this control register determines the power-
down control of the on-board DAC. Table 14 shows the
DAC control register. Writing a zero to bit 15 (DAPD)
powers up the DAC, while writing a 1 powers down the
DAC. Table 15 describes the DAC control register con-
tents, while Table 16 shows the DAC power-down bit.
Keypad Control Registers
The keypad control register, keypad mask register, and
keypad column mask control register control the key-
pad scanner in the MAX1233/MAX1234. The keypad
control register (Table 17) controls scanning and
debouncing, while the keypad mask register (Table 22)
and the keypad column mask control register (Table 24),
Table 11. Toucꢀ-Screen Settling Time
Control*
ST2
0
ST1
0
ST0
0
SETTLING TIME
Settling time: 0µs
0
0
1
Settling time: 100µs
Settling time: 500µs
Settling time: 1ms
Settling time: 5ms
Settling time: 10ms
Settling time: 50ms
Settling time: 100ms
0
1
0
0
1
1
Table 15. DAC Control Register
Descriptions
1
0
0
1
0
1
BIT
NAME
DAPD
0
DESCRIPTION
DAC powered down
Reserved
1
1
0
15 (MSB)
[14:0]
1
1
1
*Applicable only for X, Y, Z1, and Z2 measurements.
Table 12. ADC Reference Control Bit
Table 16. DAC Power-Down Bit
RFV
FUNCTION
+1.0V reference
+2.5V reference
DAPC
FUNCTION
0
1
0
1
DAC powered up
DAC powered down
Table 13. Internal ADC Reference Auto Power-Up Control
ADC REFERENCE
RES1
RES0
ADC REFERENCE POWER MODE
SOURCE
Power up, wait for reference to settle, and power down again for each
temperature, battery, or auxiliary scan (auto power-up mode)
0
0
Internal
0
1
1
1
0
1
Internal
External
External
Always powered up
Always powered down
Always powered down
Table 14. DAC Control Register
BIT15 BIT14 BIT13 BIT12 BIT11 BIT10 BIT9
BIT8
BIT7
BIT6
BIT5
BIT4
BIT3
BIT2
BIT1
BIT0
DAPD
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
______________________________________________________________________________________ 23
1ꢀ5k ꢁEDꢂ-rotected TouchꢂEcreen
Controllers Include DAC and Keypad Controller
Table 17. Keypad Control Register
BIT15
BIT14
BIT13 BIT12 BIT11 BIT10 BIT9 BIT8 BIT7 BIT6 BIT5 BIT4 BIT3 BIT2 BIT1 BIT0
HLD HLD
KEYSTS1 KEYSTS0 DBN2 DBN1 DBN0 HLD2
0
0
0
0
0
0
0
0
Table 18. Keypad Control Register Description
BIT
NAME
KEYSTS1
KEYSTS0
DBN2
DBN1
DBN0
HLD2
DESCRIPTION
15 (MSB)
Read: keypad interrupt status; Write: set interrupt initiated keypad scans
Read: keypad scan status; Write: stop keypad scan
Keypad debounce time control
Keypad debounce time control
Keypad debounce time control
Keypad hold time control
14
13
12
11
10
9
HLD1
Keypad hold time control
8
HLD0
Keypad hold time control
[7:0]
0
Reserved
Table 19. KEYSTS1/KEYSTS0 Functions
KEYSTS1
KEYSTS0
READ FUNCTION
WRITE FUNCTION
Scans keypad once and waits to detect a button press. Upon
detection, issues an interrupt and waits for the host’s instruction
before scanning.
No button press detected;
scan or debounce in progress
0
0
Button press detected;
scan or debounce in progress detection, issues an interrupt and scans the keypad.
Stops any ongoing scan and waits to detect a button press. Upon
1
0
1
0
1
1
Stops any ongoing scan and waits to detect a button press. Upon
detection, issues an interrupt and waits for the host’s instruction
before scanning.
No button press detected;
data available
Button press detected;
data available
Stops any ongoing scan and powers down the button press
detection circuit. No button presses are detected in this mode.
Table 20. Keypad Debounce Time Control
DBN2 DBN1 DBN0
FUNCTION (ms)
Debounce time: 2
0
0
0
0
1
1
1
1
0
0
1
1
0
0
1
1
0
1
0
1
0
1
0
1
Debounce time: 10
Debounce time: 20
Debounce time: 50
Debounce time: 60
Debounce time: 80
Debounce time: 100
Debounce time: 120
24 ______________________________________________________________________________________
1ꢀ5k ꢁEDꢂ-rotected TouchꢂEcreen
Controllers Include DAC and Keypad Controller
allowing certain keys to be masked from detection.
Tables 18–21 show the programmable bits of the keypad
control register. Tables 23, 24, and 25 show the program-
mable bits of the keypad mask registers. The Keypad
Controller and GPIO section provides more details.
allow the keypad controller’s row and column inputs to be
configured as up to eight parallel I/O pins. Tables 26 and
27 show the GPIO control register layout and control reg-
ister descriptions. Tables 28 and 29 show the GPIO pullup
disable register and associated descriptions. For more
information, see the Applications Information section.
GPIO Control Register
The GPIO control register and the GPIO pullup register
Table 21. Keypad Hold Time Control
HLD2
HLD1
HLD0
FUNCTION
0
0
0
0
1
1
1
1
0
0
1
1
0
0
1
1
0
1
0
1
0
1
0
1
If a button is held, wait 100µs before beginning next debounce scan
If a button is held, wait 1 debounce time before beginning the next debounce scan
If a button is held, wait 2 debounce times before beginning the next debounce scan
If a button is held, wait 3 debounce times before beginning the next debounce scan
If a button is held, wait 4 debounce times before beginning the next debounce scan
If a button is held, wait 5 debounce times before beginning the next debounce scan
If a button is held, wait 6 debounce times before beginning the next debounce scan
If a button is held, wait 7 debounce times before beginning the next debounce scan
Table 22. Keypad Key Mask Control Register
BIT15 BIT14 BIT13 BIT12 BIT11 BIT10 BIT9
BIT8
BIT7
BIT6
BIT5
BIT4
BIT3
BIT2
BIT1
BIT0
KM15 KM14 KM13 KM12 KM11 KM10 KM9
KM8
KM7
KM6
KM5
KM4
KM3
KM2
KM1
KM0
Table 23. Keypad Key Mask Control Register Descriptions—Individual Mask
BIT
15
14
13
12
11
10
9
NAME
KM15
KM14
KM13
KM12
KM11
KM10
KM9
DESCRIPTION
Mask status register data update on individual key for row 4, column 4
Mask status register data update on individual key for row 3, column 4
Mask status register data update on individual key for row 2, column 4
Mask status register data update on individual key for row 1, column 4
Mask status register data update on individual key for row 4, column 3
Mask status register data update on individual key for row 3, column 3
Mask status register data update on individual key for row 2, column 3
Mask status register data update on individual key for row 1, column 3
Mask status register data update on individual key for row 4, column 2
Mask status register data update on individual key for row 3, column 2
Mask status register data update on individual key for row 2, column 2
Mask status register data update on individual key for row 1, column 2
Mask status register data update on individual key for row 4, column 1
Mask status register data update on individual key for row 3, column 1
Mask status register data update on individual key for row 2, column 1
Mask status register data update on individual key for row 1, column 1
8
KM8
7
KM7
6
KM6
5
KM5
4
KM4
3
KM3
2
KM2
1
KM1
0
KM0
Table 24. Keypad Column Mask Control Register
BIT15 BIT14 BIT13 BIT12 BIT11 BIT10 BIT9
BIT8
BIT7
BIT6
BIT5
BIT4
BIT3
BIT2
BIT1
BIT0
CM4 CM3 CM2 CM1
0
0
0
0
0
0
0
0
0
0
0
0
______________________________________________________________________________________ 25
1ꢀ5k ꢁEDꢂ-rotected TouchꢂEcreen
Controllers Include DAC and Keypad Controller
Table 25. Keypad Column Mask Control Register Descriptions
BIT
15
NAME
CM4
CM3
CM2
CM1
0
DESCRIPTION
Mask interrupt, status register, and pending register data update on all keys in column 4
Mask interrupt, status register, and pending register data update on all keys in column 3
Mask interrupt, status register, and pending register data update on all keys in column 2
Mask interrupt, status register, and pending register data update on all keys in column 1
Reserved
14
13
12
[11:0]
Table 26. GPIO Control Register
BIT15 BIT14 BIT13 BIT12 BIT11 BIT10 BIT9
BIT8
BIT7
BIT6
BIT5
BIT4
BIT3
BIT2
BIT1
BIT0
GP7
GP6
GP5
GP4
GP3
GP2
GP1
GP0
OE7
OE6
OE5
OE4
OE3
OE2
OE1
OE0
Table 27. GPIO Control Register Descriptions
DESCRIPTION
BIT
NAME
1
0
15
14
13
12
11
10
9
GP7
GP6
GP5
GP4
GP3
GP2
GP1
GP0
C4 pin becomes GPIO pin 7
C3 pin becomes GPIO pin 6
C2 pin becomes GPIO pin 5
C1 pin becomes GPIO pin 4
R4 pin becomes GPIO pin 3
R3 pin becomes GPIO pin 2
R2 pin becomes GPIO pin 1
R1 pin becomes GPIO pin 0
C4 pin remains keypad column 4
C3 pin remains keypad column 3
C2 pin remains keypad column 2
C1 pin remains keypad column 1
R4 pin remains keypad row 4
R3 pin remains keypad row 3
R2 pin remains keypad row 2
R1 pin remains keypad row 1
GPIO pin configured as an input
8
[7:0]
[OE7:OE0] GPIO pin configured as an output
Table 28. GPIO Pullup Disable Register
BIT15 BIT14 BIT13 BIT12 BIT11 BIT10 BIT9
BIT8
BIT7
BIT6
BIT5
BIT4
BIT3
BIT2
BIT1
BIT0
PU7
PU6
PU5
PU4
PU3
PU2
PU1
PU0
0
0
0
0
0
0
0
0
Analog Input Data Registers
Table 30 shows the format of the X, Y, Z , Z , BAT1,
BAT2, AUX1, AUX2, TEMP1, and TEMP2 data registers.
The data format for these registers is right justified
beginning with bit 11. Data written through the serial
interface to these registers is not stored.
Table 29. GPIO Pullup Disable Register
Descriptions
1
2
BIT
[15:8] [PU7:PU0]
[7:0]
NAME
DESCRIPTION
1: Pullup disabled. Open collector output.
2: Pullup enabled.
0
Reserved
Keypad Data Registers
Table 31 shows the formatting of the keypad data reg-
isters, while Tables 32, 33, and 34 provide individual
register bit descriptions. These registers have the same
format as the keypad mask register. Each bit repre-
sents one key on the keypad. Table 35 shows a map of
a 16-key keypad. Data written through the serial inter-
face to these registers is not stored.
Data Registers
The data results from conversions or keypad scans are
held in the data registers of the MAX1233/MAX1234.
During power-up, all of these data registers with the
exception of the DAC data register default to 0000 .
H
The DAC register defaults to 1000 .
H
26 ______________________________________________________________________________________
1ꢀ5k ꢁEDꢂ-rotected TouchꢂEcreen
Controllers Include DAC and Keypad Controller
Table 30. Analog Inputs Data Register Format
REGISTER
BIT15 BIT14 BIT13 BIT12 BIT11 BIT10 BIT9 BIT8 BIT7 BIT6 BIT5 BIT4 BIT3 BIT2 BIT1 BIT0
NAME
X
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
X11
Y11
X10
Y10
X9
Y9
X8
Y8
X7
Y7
X6
Y6
X5
Y5
X4
Y4
X3
Y3
X2
Y2
X1
Y1
X0
Y0
Y
Z1
Z1_11 Z1_10 Z1_9 Z1_8 Z1_7 Z1_6 Z1_5 Z1_4 Z1_3 Z1_2 Z1_1 Z1_0
Z2_11 Z2_10 Z2_9 Z2_8 Z2_7 Z2_6 Z2_5 Z2_4 Z2_3 Z2_2 Z2_1 Z2_0
B1_11 B1_10 B1_9 B1_8 B1_7 B1_6 B1_5 B1_4 B1_3 B1_2 B1_1 B1_0
B2_11 B2_10 B2_9 B2_8 B2_7 B2_6 B2_5 B2_4 B2_3 B2_2 B2_1 B2_0
A1_11 A1_10 A1_9 A1_8 A1_7 A1_6 A1_5 A1_4 A1_3 A1_2 A1_1 A1_0
A2_11 A2_10 A2_9 A2_8 A2_7 A2_6 A2_5 A2_4 A2_3 A2_2 A2_1 A2_0
T1_11 T1_10 T1_9 T1_8 T1_7 T1_6 T1_5 T1_4 T1_3 T1_2 T1_1 T1_0
T2_11 T2_10 T2_9 T2_8 T2_7 T2_6 T2_5 T2_4 T2_3 T2_2 T2_1 T2_0
Z2
BATT1
BATT2
AUX1
AUX2
TEMP1
TEMP2
Table 31. Keypad Data Registers
REGISTER
NAME
BIT15 BIT14 BIT13 BIT12 BIT11 BIT10 BIT9 BIT8 BIT7 BIT6 BIT5 BIT4 BIT3 BIT2 BIT1 BIT0
KBD
K15 K14 K13 K12 K11 K10 K9 K8 K7 K6 K5 K4 K3 K2 K1 K0
KPData1 K1_15 K1_14 K1_13 K1_12 K1_11 K1_10 K1_9 K1_8 K1_7 K1_6 K1_5 K1_4 K1_3 K1_2 K1_1 K1_0
KPData2 K2_15 K2_14 K2_13 K2_12 K2_11 K2_10 K2_9 K2_8 K2_7 K2_6 K2_5 K2_4 K2_3 K2_2 K2_1 K2_0
Table 32. Keypad Data Register Descriptions
BIT
15
14
13
12
11
10
9
NAME
K15
K14
K13
K12
K11
K10
K9
DESCRIPTION
Keypad scan result for row 4, column 4. Can only be masked by column mask.
Keypad scan result for row 3, column 4. Can only be masked by column mask.
Keypad scan result for row 2, column 4. Can only be masked by column mask.
Keypad scan result for row 1, column 4. Can only be masked by column mask.
Keypad scan result for row 4, column 3. Can only be masked by column mask.
Keypad scan result for row 3, column 3. Can only be masked by column mask.
Keypad scan result for row 2, column 3. Can only be masked by column mask.
Keypad scan result for row 1, column 3. Can only be masked by column mask.
Keypad scan result for row 4, column 2. Can only be masked by column mask.
Keypad scan result for row 3, column 2. Can only be masked by column mask.
Keypad scan result for row 2, column 2. Can only be masked by column mask.
Keypad scan result for row 1, column 2. Can only be masked by column mask.
Keypad scan result for row 4, column 1. Can only be masked by column mask.
Keypad scan result for row 3, column 1. Can only be masked by column mask.
Keypad scan result for row 2, column 1. Can only be masked by column mask.
Keypad scan result for row 1, column 1. Can only be masked by column mask.
8
K8
7
K7
6
K6
5
K5
4
K4
3
K3
2
K2
1
K1
0
K0
______________________________________________________________________________________ 27
1ꢀ5k ꢁEDꢂ-rotected TouchꢂEcreen
Controllers Include DAC and Keypad Controller
Table 33. Keypad Data Register 1 (Status Register) Descriptions
BIT
15
14
13
12
11
10
9
NAME
K1_15
K1_14
K1_13
K1_12
K1_11
K1_10
K1_9
DESCRIPTION
Keypad scan result for row 4, column 4. Can be masked by key mask or column mask.
Keypad scan result for row 3, column 4. Can be masked by key mask or column mask.
Keypad scan result for row 2, column 4. Can be masked by key mask or column mask.
Keypad scan result for row 1, column 4. Can be masked by key mask or column mask.
Keypad scan result for row 4, column 3. Can be masked by key mask or column mask.
Keypad scan result for row 3, column 3. Can be masked by key mask or column mask.
Keypad scan result for row 2, column 3. Can be masked by key mask or column mask.
Keypad scan result for row 1, column 3. Can be masked by key mask or column mask.
Keypad scan result for row 4, column 2. Can be masked by key mask or column mask.
Keypad scan result for row 3, column 2. Can be masked by key mask or column mask.
Keypad scan result for row 2, column 2. Can be masked by key mask or column mask.
Keypad scan result for row 1, column 2. Can be masked by key mask or column mask.
Keypad scan result for row 4, column 1. Can be masked by key mask or column mask.
Keypad scan result for row 3, column 1. Can be masked by key mask or column mask.
Keypad scan result for row 2, column 1. Can be masked by key mask or column mask.
Keypad scan result for row 1, column 1. Can be masked by key mask or column mask.
8
K1_8
7
K1_7
6
K1_6
5
K1_5
4
K1_4
3
K1_3
2
K1_2
1
K1_1
0
K1_0
Table 34. Keypad Data Register 2 (Pending Register) Descriptions
BIT
15
14
13
12
11
10
9
NAME
K2_15
K2_14
K2_13
K2_12
K2_11
K2_10
K2_9
DESCRIPTION
Keypad scan result for row 4, column 4. Can only be masked by column mask.
Keypad scan result for row 3, column 4. Can only be masked by column mask.
Keypad scan result for row 2, column 4. Can only be masked by column mask.
Keypad scan result for row 1, column 4. Can only be masked by column mask.
Keypad scan result for row 4, column 3. Can only be masked by column mask.
Keypad scan result for row 3, column 3. Can only be masked by column mask.
Keypad scan result for row 2, column 3. Can only be masked by column mask.
Keypad scan result for row 1, column 3. Can only be masked by column mask.
Keypad scan result for row 4, column 2. Can only be masked by column mask.
Keypad scan result for row 3, column 2. Can only be masked by column mask.
Keypad scan result for row 2, column 2. Can only be masked by column mask.
Keypad scan result for row 1, column 2. Can only be masked by column mask.
Keypad scan result for row 4, column 1. Can only be masked by column mask.
Keypad scan result for row 3, column 1. Can only be masked by column mask.
Keypad scan result for row 2, column 1. Can only be masked by column mask.
Keypad scan result for row 1, column 1. Can only be masked by column mask.
8
K2_8
7
K2_7
6
K2_6
5
K2_5
4
K2_4
3
K2_3
2
K2_2
1
K2_1
0
K2_0
28 ______________________________________________________________________________________
1ꢀ5k ꢁEDꢂ-rotected TouchꢂEcreen
Controllers Include DAC and Keypad Controller
DAC Data Register
The DAC data register stores data that is to be written
Applications Information
-rogrammable 8ꢂ/10ꢂ/12ꢂBit Resolution
The MAX1233/MAX1234 provide the option of three dif-
ferent resolutions for the ADC: 8, 10, or 12 bits. Lower
resolutions are practical for some measurements such
as touch pressure. Lower resolution conversions have
smaller conversion times and therefore consume less
power. Program the resolution of the MAX1233/
MAX1234 12-bit ADCs by writing to the RES1 and RES0
bits in the ADC control register. When the MAX1233/
MAX1234 power up, both bits are set to zero so the
resolution is set to 8 bits with a 31µs internally timed
reference power-up delay as indicated by the ADC res-
olution control table. As explained in the control register
section, the RES1 and RES0 bits control the reference
to the 8-bit DAC. Table 36 shows the configuration of
the DAC data register. It is right justified with bit 7–bit 0
storing the input data.
GPIO Data Register
Tables 37 and 38 show the format and descriptions for
the GPIO data register. The register is left justified with
data in bit 15–bit 8. Reading the GPIO data register
gives the state of the R_ and C_ pins. Data written to
the GPIO data register appears on those R_ and C_
pins, which are configured as general-purpose outputs.
Data written to pins not configured as general-purpose
outputs is not stored.
ADC Transfer Function
The MAX1233/MAX1234 output data is in straight bina-
ry format as shown in Figure 11. This figure shows the
ideal output code for the given input voltage and does
not include the effects of offset error, gain error, noise,
or nonlinearity.
MAX1233
MAX1234
OUTPUT CODE
11 ... 111
FULL-SCALE
TRANSITION
11 ... 110
11 ... 101
FS = V
REF
Table 35. Keypad to Key Bit Mapping
ZS = GND
COMPONENT
C1
K0
K1
K2
K3
C2
K4
K5
K6
K7
C3
K8
C4
V
REF
1LSB =
4096
R1
R2
R3
R4
K12
K13
K14
K15
00 ... 011
00 ... 010
00 ... 001
K9
K10
K11
00 ... 000
0
1
2
3
FS
FS - 3/2LSB
INPUT VOLTAGE (LSB)
Figure 11. Ideal Input ꢀoltages and Output Codes
Table 36. DAC Data Register
BIT15 BIT14 BIT13 BIT12 BIT11 BIT10 BIT9
BIT8
BIT7
BIT6
BIT5
BIT4
BIT3
BIT2
BIT1
BIT0
0
0
0
0
0
0
0
0
DA7
DA6
DA5
DA4
DA3
DA2
DA1
DA0
Table 37. GPIO Data Register
BIT15 BIT14 BIT13 BIT12 BIT11 BIT10 BIT9
BIT8
BIT7
BIT6
BIT5
BIT4
BIT3
BIT2
BIT1
BIT0
GPD7 GPD6 GPD5 GPD4 GPD3 GPD2 GPD1 GPD0
0
0
0
0
0
0
0
0
Table 38. GPIO Data Register Descriptions
BIT
15...8
7...0
NAME
GPD7...0
0
DESCRIPTION
GPIO data bits for GPIO pins 7...0
Reserved
______________________________________________________________________________________ 29
1ꢀ5k ꢁEDꢂ-rotected TouchꢂEcreen
Controllers Include DAC and Keypad Controller
nal, reference, or both may not settle into their final
+AV
DD
steady-state values before the ADC samples the inputs,
and the reference voltage may continue to change dur-
ing the conversion cycle. The MAX1233/MAX1234 can
be programmed to wait for a fixed amount of time after
a screen touch has been detected before beginning a
scan. Use the touch-screen settling control bits in the
ADC control register (Table 11) to set the settling delay
to between zero and 100ms.
FORCE LINE
Y+
The settling problem is amplified in some applications
where external filter capacitors may be required across
the touch screen to filter noise that may be generated
by the LCD panel or backlight circuitry, etc. The values
of these capacitors cause an additional settling time
requirement when the panel is touched. Any failure to
settle before conversion start may show up as a gain
error. Average the conversion result by writing to the
ADC control register, as shown in Table 10, to minimize
noise.
SENSE LINE
+REF
CONVERTER
-REF
+IN
-IN
X+
SENSE LINE
Touchꢂ-ressure Measurement
The MAX1233/MAX1234 provide two methods of mea-
surement of the pressure applied to the touch screen.
Although 8-bit resolution is typically sufficient, the follow-
ing calculations use 12-bit resolution demonstrating the
maximum precision of the MAX1233/MAX1234. Figure
13 shows the pressure measurement block diagram.
Y-
FORCE LINE
GND
Figure 12. Ratiometric Y-Coordinate Measurement
The first method performs pressure measurements
using a known X-plate resistance. After completing
three conversions, X-position, Z1-position, and Z2 posi-
power-up status when the A/D0–A/D3 bits are zero.
These values can be set initially on power-up.
(Subsequently A/D0–A/D3 bits are not zero, and any
other value of these bits is exclusive to ADC resolution
programming.)
tion, use the following equation to calculate R
:
TOUCH
X
Z
2
POSITION
4096
−1
R
= R
×
×
TOUCH
XPLATE
Differential Ratiometric Touchꢂ-osition
Measurement
Z
1
The MAX1233/MAX1234 provide differential conver-
sions. Figure 12 shows the switching matrix configura-
tion for Y coordinate measurement. The +REF and -REF
inputs are connected directly to Y+ and Y-. The conver-
sion result is a percentage of the external resistances,
and is unaffected by variation in the total touch-screen
resistance or the on-resistance of the internal switching
matrix. The touch screen remains powered during the
acquisition and conversion process.
The second method requires knowing both the X-plate
and Y-plate resistance. Three touch-screen conver-
sions are required in this method as well for measure-
ment of the X-position, Y-position, and Z- position of the
touch screen. Use the following equation to calculate
R
:
TOUCH
R
X
4096
XPLATE
POSITION
4096
−1
R
=
×
×
TOUCH
Z
1
Z
1
TouchꢂEcreen Eettling
There are two mechanisms that affect the voltage level
at the point where the touch panel is pressed. One is
electrical ringing due to parasitic capacitance between
the top and bottom layers of the touch screen and the
other is the mechanical bouncing caused by vibration
of the top layer of the touch screen. Thus, the input sig-
Y
POSITION
4096
− R
×
YPLATE
30 ______________________________________________________________________________________
1ꢀ5k ꢁEDꢂ-rotected TouchꢂEcreen
Controllers Include DAC and Keypad Controller
FORCE LINE
SENSE LINE
MEASURE X-POSITION
HOST WRITES
ADC
X+
Y+
BATTERY INPUT 1 OR
BATTERY INPUT 2
CONTROL REGISTER
TOUCH
START CLOCK
V
X-POSITION
SET BUSY
LOW
X-
Y-
OPEN CIRCUIT
FORCE LINE
SENSE LINE
FORCE LINE
Y+
MEASURE Z1-RESISTANCE
IS ADC
REFERENCE IN
AUTO POWER-DOWN
MODE?
X+
NO
TOUCH
V
YES
Z1-RESISTANCE
POWER UP REFERENCE
X-
Y-
FORCE LINE
OPEN CIRCUIT
POWER UP
ADC
FORCE LINE
POWER DOWN
ADC
OPEN CIRCUIT
X+
Y+
CONVERT
BATTERY INPUT 1 OR 2
TOUCH
POWER DOWN REFERENCE
V
Z2-RESISTANCE
SET BUSY HIGH
X-
Y-
FORCE LINE
SENSE LINE
NO
IS DATA
AVERAGING DONE?
MEASURE Z2-RESISTANCE
TURN OFF CLOCK
Figure 13. Pressure Measurement Block Diagram
YES
DONE
2.7V
DC/DC
CONVERTER
STORE BATTERY INPUT 1 OR 2 IN
BAT1 OR BAT2 REGISTER
BATTERY
0.5V TO
6.0V
AV
DD
V
BAT
7.5kΩ
Figure 15. Battery ꢀoltage-Reading Flowchart
Batteryꢂkoltage Monitors
Two dedicated analog inputs (BAT1 and BAT2) allow the
MAX1233/MAX1234 to monitor the battery voltages prior
to the DC/DC converter. Figure 14 shows the battery volt-
age monitoring circuitry. The MAX1233/ MAX1234 direct-
ly monitor battery voltages from 0.5V to 6V. An internal
resistor network divides down BAT1 and BAT2 by 4 so
that a 6V battery voltage results in a 1.5V input to the
ADC. To minimize power consumption, the divider is only
enabled during the sampling of BAT1 and BAT2. Figure
15 illustrates the process of battery input reading.
0.125V TO 1.5V
CONVERTER
2.5kΩ
Figure 14. Battery Measurement Block Diagram
______________________________________________________________________________________ 31
1ꢀ5k ꢁEDꢂ-rotected TouchꢂEcreen
Controllers Include DAC and Keypad Controller
Auxiliary Analog Inputs
Two auxiliary analog inputs (AUX1 and AUX2) allow the
HOST WRITES
AUXILIARY INPUT 1 OR
AUXILIARY INPUT 2
ADC
MAX1233/MAX1234 to monitor analog input voltages
CONTROL REGISTER
from zero to V
. Figure 16 illustrates the process of
REF
auxiliary input reading.
START CLOCK
Temperature Measurements
The MAX1233/MAX1234 provide two temperature mea-
surement options: a single-ended conversion method
and a differential conversion method. Both temperature
measurement techniques rely on the semiconductor
junction’s operational characteristics at a fixed current
SET BUSY
LOW
level. The forward diode voltage (V ) vs. temperature
BE
IS ADC
REFERENCE IN
AUTO POWER-DOWN
MODE?
is a well-defined characteristic. The ambient tempera-
ture can be predicted in applications by knowing the
value of the V voltage at a fixed temperature and then
BE
NO
monitoring the delta of that voltage as the temperature
changes. Figure 17 illustrates the functional block of the
internal temperature sensor.
YES
POWER UP REFERENCE
The single conversion method requires calibration at a
known temperature, but only requires a single reading
to predict the ambient temperature. First, the internal
diode forward bias voltage is measured by the ADC at a
known temperature. Subsequent diode measurements
provide an estimate of the ambient temperature through
extrapolation. This assumes a temperature coefficient of
-2.1mV/°C. The single conversion method results in a
resolution of 0.29°C/LSB (2.5V reference) and
0.12°C/LSB (1.0V reference) with a typical accuracy of
2°C. Figure 18 shows the flowchart for the single tem-
perature measurement.
POWER UP
ADC
POWER DOWN
ADC
CONVERT
AUXILIARY INPUT 1 OR 2
POWER DOWN REFERENCE
SET BUSY HIGH
NO
IS DATA
AVERAGING DONE?
The differential conversion method uses two measure-
ment points. The first measurement is performed with a
fixed bias current into the internal diode. The second
measurement is performed with a fixed multiple of the
original bias current. The voltage difference between the
first and second conversion is proportional to the
absolute temperature and is expressed by the following
formula:
TURN OFF CLOCK
YES
DONE
STORE AUXILIARY INPUT 1 OR 2 IN
AUX1 OR AUX2 REGISTER
∆V = (kT/q) ✕ ln(N)
BE
Figure 16. Auxiliary Input Flowchart
where:
∆V = difference in diode voltage
N = current ratio of the second measurement to the first
measurement
BE
A/D
CONVERTER
MUX
k = Boltzmann’s constant (1.38 × 10-23 eV/°Kelvin)
q = electron charge (1.60 × 10-19 C)
T = temperature in °Kelvin
The resultant equation solving for °K is:
T(°K) = q x ∆V / (k × ln(N))
TEMP1
TEMP2
Figure 17. Internal Block Diagram of Temperature Sensor
32 ______________________________________________________________________________________
1ꢀ5k ꢁEDꢂ-rotected TouchꢂEcreen
Controllers Include DAC and Keypad Controller
HOST WRITES
ADC
CONTROL REGISTER
HOST WRITES
ADC
CONTROL REGISTER
TEMPERATURE INPUT 1
TEMPERATURE INPUT 1
AND TEMPERATURE INPUT 2
START CLOCK
START CLOCK
SET BUSY
LOW
SET BUSY
LOW
CONVERT
TEMPERATURE INPUT 2
IS ADC
REFERENCE IN
AUTO POWER-DOWN
MODE?
IS ADC
REFERENCE IN
AUTO POWER-DOWN
MODE?
NO
NO
NO
IS DATA
AVERAGING DONE?
YES
YES
YES
POWER UP REFERENCE
POWER UP REFERENCE
STORE TEMPERATURE INPUT 2 IN
TEMP2 REGISTER
POWER UP
ADC
POWER UP
ADC
POWER DOWN
ADC
POWER DOWN
ADC
CONVERT
TEMPERATURE INPUT 1
CONVERT
TEMPERATURE INPUT 1
POWER DOWN REFERENCE
POWER DOWN REFERENCE
SET BUSY HIGH
SET BUSY HIGH
NO
IS DATA
AVERAGING DONE?
NO
IS DATA
AVERAGING DONE?
TURN OFF CLOCK
TURN OFF CLOCK
YES
YES
DONE
DONE
STORE TEMPERATURE INPUT 1 IN
TEMP1 REGISTER
STORE TEMPERATURE INPUT 1 IN
TEMP1 REGISTER
Figure 19. Differential Temperature Measurement Process
Figure 1±. Single Temperature Measurement Process
where:
is 1.6°C/LSB (2.5V reference) and 0.65°C/LSB (1V ref-
erence) with a typical accuracy of 3°C. Figure 19
shows the differential temperature measurement-
process.
∆V = V (I N) - V (I1) (in mV)
T(°K) = 2.68(°K/mV) × ∆V(mV)
T(°C) = [2.68(°K/mV) × ∆V(mV) - 273°K]°C/ °K
This differential conversion method does not require a
test temperature calibration and can provide much
improved absolute temperature measurement. In the
differential conversion method, however, the resolution
Note: The bias current for each diode temperature
measurement is only turned ON during the acquisition
and, therefore, does not noticeably increase power
consumption.
______________________________________________________________________________________ 33
1ꢀ5k ꢁEDꢂ-rotected TouchꢂEcreen
Controllers Include DAC and Keypad Controller
The keys scanned by the keypad row and column pins
are debounced for a period of time (debounce period)
as determined by bits [DBN2:DBN0] of the keypad
control register.
Battery koltage, Auxiliary Input, and
Temperature Input Ecan
Use this scan to make periodic measurements of both
battery inputs, both auxiliary inputs, and both tempera-
ture inputs. The respective data registers have the lat-
est results at the end of each cycle. Thus, a single write
by the host to the MAX1233/MAX1234 ADC control reg-
ister results in six different measurements being made.
Figure 20 shows this scan operation.
The keypad controller continues scanning until the keypad
stays in the same state for an entire debounce period.
Keypad Data
Keypad data can be read out of either the keypad data
status register (maskable), or the keypad data pending
register (not maskable). The keypad mask register is
used to mask individual keys in the keypad data status
register.
TouchꢂInitiated Ecreen Ecans
(-ꢁNETE = 1; ADETE = 0)
In the touch-initiated screen-scan mode, the
MAX1233/MAX1234 automatically perform a touch-
screen scan upon detecting a screen touch. The touch-
screen scans performed are determined by the
[A/D3:A/D0] written to the ADC control register. Figure
21 shows the flowchart for a complete touch-initiated X-
and Y- coordinate scan. Selection of resolution, conver-
sion rate, averaging, and touch-screen settling time
determine the overall conversion time.
GPIO Control
Write to bits [GP7:GP0] of the GPIO control register to
configure one or more of the R_/C_pins as a GPIO pin.
Write to bits [OE7:OE0] of the GPIO control register to
configure the pins as an input or an output. GPIO data
can be read from or written to the GPIO data register. A
read returns the logic state of the GPIO pin. A write sets
the logic state of a GPIO output pin. Writing to a GPIO
input pin has no effect.
Figure 22 shows the complete flowchart for a touch-
initiated X, Y, and Z scan.
Table 38 shows ADSTS Bit Operation.
GPIO Pullup Disable Register
When programmed as GPIO output, by default, the
GPIO pins are active CMOS outputs. Write a 1 to the
pullup disable register to configure the GPIO output as
an open-drain output.
HostꢂInitiated Ecreen Ecans
(-ꢁNETE = ADETE = 0)
In this mode, the host processor decides when a touch-
screen scan begins. The MAX1233/MAX1234 detect a
screen touch and drive PENIRQ LOW. The host recog-
nizes the interrupt request and can choose to write to
the ADC control register to select a touch-screen scan
function (PENSTS = ADSTS = 0). Figures 23 and 24
show the process of a host-initiated screen scan.
Using the 8ꢂBit DAC for LCD/TFT
Contrast Control
Design Example:
The 8-bit DAC offers the ability to control biasing of
LCD/TFT screens. In the circuit of Figure 27, it is
desired to have the MAX1677 DC-DC converter’s V
OUT
Key-Press Initiated Debounce Scan
(KEYSTS1 = 1, KEYSTS0 =0)
to be adjustable.
In the key-press initiated debounce mode, the
MAX1233/MAX1234 automatically perform a debounce
upon detecting a key press. Key scanning begins once
a key press has been detected and ends when a key
press has been debounced (Figures 25 and 9a).
The minimum and maximum DAC voltages (V
DAC(LOW)
Characteristics table.
DAC(HIGH)
) can be found in the Electrical
and V
The output voltage of the MAX1677 (V
) can be cal-
OUT
culated by noting the following equations:
Host-Initiated Debounce Scan
In this mode, the host processor decides when a
debounce scan begins. The MAX1233/MAX1234 detect
a key press and drive KEYIRQ low. The host processor
recognizes the interrupt request and can choose to
write to the keypad control register to initiate a
debounce scan (Figures 26 and 9b).
V
= V
+ i R1
[Equation 1]
[Equation 2]
[Equation 3]
[Equation 4]
OUT
REFDAC
1
i = i + i
1 3
2
i = V
2
/ R2
REFDAC
i = (V
3
- V
) / R3
DAC
REFDAC
Substituting equations 2, 3, and 4 into equation 1
yields:
Keypad Debouncing
Keys are debounced either when (1) a key press has
been detected, or (2) when commanded by the host MPU.
V
= V
REFDAC
+ (R1 / R2) V + (R1 / R3)
REF
OUT
(V
REFDAC
- V
)
[Equation 5]
DAC
34 ______________________________________________________________________________________
1ꢀ5k ꢁEDꢂ-rotected TouchꢂEcreen
Controllers Include DAC and Keypad Controller
BATTERY VOLTAGE, AUXILIARY INPUT, AND TEMPERATURE INPUT SCAN ([A/D3:A/D0] = 1011)
HOST WRITES
ADC
CONTROL REGISTER
CONVERT
BATTERY INPUT 2
CONVERT
TEMPERATURE INPUT 1
START CLOCK
NO
IS DATA
AVERAGING DONE?
NO
IS DATA
AVERAGING DONE?
SET BUSY
LOW
YES
YES
IS ADC
REFERENCE IN
AUTO POWER-DOWN
MODE?
NO
STORE BATTERY INPUT 2 IN
BAT2 REGISTER
STORE TEMPERATURE INPUT 1 IN
TEMP1 REGISTER
YES
CONVERT
AUXILIARY INPUT 1
CONVERT
TEMPERATURE INPUT 2
POWER UP REFERENCE
POWER UP
ADC
NO
IS DATA
AVERAGING DONE?
NO
IS DATA
AVERAGING DONE?
CONVERT
BATTERY INPUT 1
YES
YES
STORE AUXILIARY INPUT 1 IN
AUX1 REGISTER
STORE TEMPERATURE INPUT 2 IN
TEMP2 REGISTER
NO
IS DATA
AVERAGING DONE?
POWER DOWN
ADC
CONVERT
AUXILIARY INPUT 2
YES
POWER DOWN REFERENCE
SET BUSY HIGH
STORE BATTERY INPUT 1 IN
BAT1 REGISTER
NO
IS DATA
AVERAGING DONE?
YES
TURN OFF CLOCK
DONE
STORE AUXILIARY INPUT 2 IN
AUX2 REGISTER
Figure 20. Scan Mode Flowchart
______________________________________________________________________________________ 35
1ꢀ5k ꢁEDꢂ-rotected TouchꢂEcreen
Controllers Include DAC and Keypad Controller
PENIRQ-INITIATED
X- AND Y- SCREEN SCAN
SCREEN
TOUCH
POWER DOWN ADC
TURN ON DRIVERS: X+. X-
ARE THERE
UNREAD SCAN
RESULTS?
YES
NO
NO
IS TOUCH-SCREEN
SETTLING DONE?
SET
PENIRQ LOW
YES
POWER UP ADC
GO TO
HOST-INITIATED
SCAN
NO
IS PENSTS
BIT = 1?
(FIGURE 23)
CONVERT Y- COORDINATES
YES
START CLOCK
IS DATA
AVERAGING DONE?
NO
SET BUSY LOW
YES
STORE Y- COORDINATES IN
Y- REGISTER
TURN ON DRIVERS: Y+, Y-
POWER DOWN
ADC
NO
IS TOUCH-SCREEN
SETTLING DONE?
SET BUSY HIGH
TURN OFF CLOCK
RESET PENIRQ HIGH
YES
POWER UP ADC
CONVERT X- COORDINATES
DONE
IS DATA
AVERAGING DONE?
NO
YES
STORE X- COORDINATES
IN X- REGISTER
Figure 21. Touch-Initiated X- and Y- Coordinate Screen Scan
36 ______________________________________________________________________________________
1ꢀ5k ꢁEDꢂ-rotected TouchꢂEcreen
Controllers Include DAC and Keypad Controller
PENIRQ-INITIATED
X, Y, AND Z SCREEN SCAN
SCREEN
TOUCH
STORE X- COORDINATES
CONVERT Z - COORDINATES
1
IN X- REGISTER
ARE THERE
UNREAD SCAN
RESULTS?
YES
POWER DOWN ADC
NO
IS DATA
AVERAGING DONE?
TURN ON DRIVERS: X+, X-
NO
YES
SET
PENIRQ LOW
STORE Z - COORDINATES
1
1
IN Z - REGISTER
NO
IS TOUCH-SCREEN
SETTLING DONE?
GO TO
HOST-INITIATED
SCAN
IS PENSTS
BIT = 1?
CONVERT Z COORDINATES
2
YES
(FIGURE 24)
POWER UP ADC
YES
NO
IS DATA
AVERAGING DONE?
START CLOCK
CONVERT Y- COORDINATES
YES
SET BUSY LOW
STORE Z - COORDINATES
2
IN Z - REGISTER
2
NO
IS DATA
AVERAGING DONE?
TURN ON DRIVERS: Y+, Y-
POWER UP ADC
SET BUSY HIGH
TURN OFF CLOCK
YES
STORE Y- COORDINATES IN
Y- REGISTER
NO
IS TOUCH-SCREEN
SETTLING DONE?
POWER DOWN ADC
YES
POWER UP ADC
TURN ON DRIVERS: Y+, X-
RESET PENIRQ HIGH
DONE
CONVERT X- COORDINATES
NO
IS TOUCH-SCREEN
SETTLING DONE?
NO
IS DATA
AVERAGING DONE?
YES
POWER UP ADC
Figure 22. Touch-Initiated X- , Y-, and Z- Coordinate Screen Scan
______________________________________________________________________________________ 37
1ꢀ5k ꢁEDꢂ-rotected TouchꢂEcreen
Controllers Include DAC and Keypad Controller
HOST-INITIATED
X- AND Y- SCREEN SCAN
SCREEN
TOUCH
STORE X- COORDINATES
IN X- REGISTER
POWER DOWN ADC
ARE THERE
UNREAD SCAN
RESULTS?
YES
TURN ON DRIVERS: X+, X-
NO
SET
PENIRQ LOW
NO
IS TOUCH-SCREEN
SETTLING DONE?
GO TO
TOUCH-INITIATED
SCAN
YES
IS PENSTS
BIT = 1?
YES
(FIGURE 21)
POWER UP ADC
NO
HOST WRITES
ADC CONTROL REGISTER
(PENSTS = ADSTS = 0)
CONVERT Y- COORDINATES
SET BUSY LOW
START CLOCK
NO
IS DATA
AVERAGING DONE?
YES
STORE Y- COORDINATES IN
Y- REGISTER
TURN ON DRIVERS: Y+, Y-
POWER DOWN ADC
SET BUSY HIGH
NO
IS TOUCH-SCREEN
SETTLING DONE?
YES
TURN OFF CLOCK
POWER UP ADC
RESET PENIRQ HIGH
DONE
CONVERT X- COORDINATES
NO
IS DATA
AVERAGING DONE?
YES
Figure 23. Host-Initiated X- and Y- Coordinate Screen Scan
38 ______________________________________________________________________________________
1ꢀ5k ꢁEDꢂ-rotected TouchꢂEcreen
Controllers Include DAC and Keypad Controller
HOST-INITIATED
X-, Y-, AND Z- SCREEN SCAN
TURN ON DRIVERS: Y+, X-
SCREEN
TOUCH
NO
IS TOUCH-SCREEN
SETTLING DONE?
ARE THERE
UNREAD SCAN
RESULTS?
YES
TURN ON DRIVERS: X+, X-
YES
POWER UP ADC
NO
SET
PENIRQ LOW
NO
IS TOUCH-SCREEN
SETTLING DONE?
CONVERT Z - COORDINATES
1
GO TO
TOUCH-INITIATED
SCAN
YES
IS PENSTS
BIT = 1?
YES
(FIGURE 22)
NO
IS DATA
POWER UP ADC
AVERAGING DONE?
NO
HOST WRITES
ADC
CONTROL REGISTER
YES
CONVERT Y- COORDINATES
STORE Z - COORDINATES
1
IN Z - REGISTER
1
START CLOCK
SET BUSY LOW
NO
IS DATA
AVERAGING DONE?
CONVERT Z - COORDINATES
2
YES
NO
IS DATA
AVERAGING DONE?
STORE Y- COORDINATES IN
Y- REGISTER
TURN ON DRIVERS: Y+, Y-
YES
POWER DOWN ADC
STORE Z - COORDINATES
2
NO
IS TOUCH-SCREEN
SETTLING DONE?
IIN Z - REGISTER
2
YES
POWER DOWN ADC
SET BUSY HIGH
POWER UP ADC
CONVERT X- COORDINATES
TURN OFF CLOCK
NO
IS DATA
AVERAGING DONE?
RESET PENIRQ HIGH
DONE
YES
STORE X- COORDINATES
IN X- REGISTER
POWER DOWN ADC
Figure 24. Host-Initiated X-, Y-, and Z- Coordinate Screen Scan
______________________________________________________________________________________ 39
1ꢀ5k ꢁEDꢂ-rotected TouchꢂEcreen
Controllers Include DAC and Keypad Controller
HOST-INITIATED DEBOUNCE SCAN
KEY-PRESS-INITIATED DEBOUNCE SCAN
KEYPAD
TOUCH
KEYPAD
TOUCH
ARE THERE
UNREAD DEBOUNCE
RESULTS?
YES
ARE THERE
YES
UNREAD DEBOUNCE
RESULTS?
NO
SET
KEYIRQ LOW
NO
SET
KEYIRQ LOW
YES
GO TO KEY-PRESS-INITIATED
DEBOUNCE SCAN
IS KEYSTS1 = 1?
NO
NO
GO TO HOST-INITIATED
DEBOUNCE SCAN
IS KEYSTS1 = 1?
HOST WRITES
ADC
YES
CONTROL REGISTER
START CLOCK
START CLOCK
SET BUSY LOW
SET BUSY LOW
SCAN AND DEBOUNCE KEYS
SCAN AND DEBOUNCE KEYS
STORE KEYPAD SCAN
RESULTS IN REGISTER
STORE KEYPAD SCAN
RESULTS IN REGISTER
SET BUSY HIGH
RESET KEYIRQ HIGH
DONE
SET BUSY HIGH
RESET KEYIRQ HIGH
DONE
Figure 25. Key-Press-Initiated Debounce Scan
Figure 26. Host-Initiated Debounce Scan
40 ______________________________________________________________________________________
1ꢀ5k ꢁEDꢂ-rotected TouchꢂEcreen
Controllers Include DAC and Keypad Controller
V
BATT
MAX1233
MAX1234
FEEDBACK
RESISTORS
SIMPLIFIED DC/DC CONVERTER
AV
DD
DACOUT
R3
ERROR AMP
R1
R2
i
i
1
DAC
CONTROL
V
REF
i
3
2
V
OUT
(LCD BIAS)
1.25V
MAX1677
Figure 27. LCD Contrast Control Circuit
CS
SCK
CS
CS
SCK
CS
DCLK
DOUT
DCLK
DOUT
MISO
MISO
SPI
MICROWIRE
MAX1233
MAX1234
MAX1233
MAX1234
V
DD
MOSI
DIN
MOSI
DIN
BUSY
PENIRQ
KEYIRQ
BUSY
PENIRQ
KEYIRQ
SS
Figure 2±a. SPI Interface
Figure 2±b. MICROWIRE Interface
Equation 5 shows that the maximum output voltage occurs
for the minimum DAC voltage, and that the minimum
output voltage occurs for the maximum DAC voltage.
Calculate V
using the following equation:
OUTMIN
V
= V
/ R3
+ (R1
REFMIN
/ R2
)V
+
OUTMIN
REFMIN
MIN
- V
MAX REFMIN
)
DACMAX
(R1
) (V
MIN
MAX
To ensure that the desired output swing is achieved,
choose appropriate values of R1, R2, and R3.
[Equation 7]
is too low for desired operation, avoid the DAC
If V
OUTMIN
Calculate V
using the following equation:
OUTMAX
codes, which cause the output voltage to go too low.
V
= V
+ (R1
REFMAX
/ R2 )V
MIN REFMAX
OUTMAX
REFMAX
MAX
- V
Connection to Etandard Interface
+ (R1
/ R3
) (V
)
DACMIN
MAX
MIN
SPI and MICROWIRE Interfaces
When using an SPI interface (Figure 28a) or
MICROWIRE (Figure 28b), set the CPOL = CPHA = 0.
At least four 8-bit operations are necessary to read or
write data to/from the MAX1233/MAX1234. DOUT data
transitions on the serial clock’s falling edge and is
clocked into the µP on the DCLK’s rising edge. The first
[Equation 6]
exceeds the maximum ratings of the
LCD/TFT display, the DAC codes that cause the output
voltage to go too high must be avoided.
If V
OUTMAX
______________________________________________________________________________________ 41
1ꢀ5k ꢁEDꢂ-rotected TouchꢂEcreen
Controllers Include DAC and Keypad Controller
connections. Establish a single-point analog ground
CS
SCK
CS
(star ground point) at GND. Connect all analog grounds
to the star ground. Connect the digital system ground
to the star ground at this point only. For lowest noise oper-
ation, the ground return to the star ground’s power supply
should be low impedance and as short as possible.
DCLK
DOUT
MISO
QSPI
MAX1233
MAX1234
High-frequency noise in the power supply may affect
the high-speed comparator in the ADC. Bypass the
supply to the star ground with a 0.1µF capacitor as
close to pins 1 and 2 of the MAX1233/MAX1234 as
possible. Minimize capacitor lead lengths for best sup-
ply-noise rejection. If the power supply is very noisy, a
10Ω resistor can be connected as a lowpass filter.
V
DD
MOSI
DIN
BUSY
PENIRQ
KEYIRQ
SS
Figure 29. QSPI Interface
While using the MAX1233/MAX1234 with a resistive
touch screen, the interconnection between the convert-
er and the touch screen should be as short and robust
as possible. Since resistive touch screens have a low
resistance, longer or loose connections are a source of
error. Noise can also be a major source of error in
touch-screen applications (e.g., applications that
require a backlight LCD panel). This EMI noise can be
coupled through the LCD panel to the touch screen
and cause “flickering” of the converted data. Utilizing a
touch screen with a bottom-side metal layer connected
to ground couples the majority of noise to ground. In
addition, the filter capacitors from Y+, Y-, X+, and X-
inputs to ground also help reduce the noise further.
Caution should be observed for settling time of the
touch screen.
SUPPLIES
GND
+3V/+5V
+3V/+5V
R* = 10Ω
AV
GND
DV
DD
V
DD
DGND
DD
DIGITAL
CIRCUITRY
MAX1233
MAX1234
*OPTIONAL
Definitions
Integral Nonlinearity
Integral nonlinearity (INL) is the deviation of the values
on an actual transfer function from a straight line. This
straight line can be either a best-straight-line fit or a line
drawn between the end points of the transfer function,
once offset and gain errors have been nullified. The
static linearity parameters for the MAX1233/MAX1234
are measured using the end-point method.
Figure 30. Power-Supply Grounding Connection
two 8-bit data streams write the command word into the
MAX1233/MAX1234. The next two 8-bit data streams
can contain either the input or output data.
QSPI Interface
Using the high-speed QSPI interface (Figure 29) with
CPOL = 0 and CPHA = 0, the MAX1233/MAX1234 sup-
Differential Nonlinearity
Differential nonlinearity (DNL) is the difference between
an actual step width and the ideal value of 1LSB. A
DNL error specification of less than 1LSB guarantees
no missing codes and a monotonic transfer function.
port a maximum f
of 10MHz. DOUT data transi-
SCLK
tions on the serial clock’s falling edge and is clocked
into the µP on the DCLK’s rising edge.
Layout, Grounding, and Bypassing
Aperture Jitter
For best performance, use printed circuit boards with
good layouts; do not use wire-wrap boards even for
prototyping. Ensure that digital and analog signal lines
are separated from each other. Do not run analog and
digital (especially clock) lines parallel to one another, or
digital lines underneath the ADC package.
Aperture jitter (t ) is the sample-to-sample variation in
AJ
the time between the samples.
Aperture Delay
Aperture delay (t ) is the time defined between the
AD
falling edge of the sampling clock and the instant when
an actual sample is taken.
Figure 30 shows the recommended system ground
42 ______________________________________________________________________________________
1ꢀ5k ꢁEDꢂ-rotected TouchꢂEcreen
Controllers Include DAC and Keypad Controller
EignalꢂtoꢂNoise Ratio
For a waveform perfectly reconstructed from digital sam-
ples, signal-to-noise ratio (SNR) is the ratio of full-scale
analog input (RMS value) to the RMS quantization error
(residual error). The ideal, theoretical minimum analog-
to-digital noise is caused by quantization error only and
results directly from the ADC’s resolution (N bits):
Total Harmonic Distortion
Total harmonic distortion (THD) is the ratio of the RMS
sum of the first five harmonics of the input signal to the
fundamental itself. This is expressed as:
2
2
2
2
V
+ V + V + V
3 4 5
2
THD = 20 × log
2
SNR = (6.02 ✕ N + 1.76) dB
V
1
In reality, there are other noise sources besides quanti-
zation noise: thermal noise, reference noise, clock jitter,
etc. SNR is computed by taking the ratio of the RMS
signal to the RMS noise, which includes all spectral
components minus the fundamental, the first five har-
monics, and the DC offset.
where V is the fundamental amplitude, and V through
1
2
V
are the amplitudes of the 2nd- through 5th-order
harmonics, respectively.
5
EpuriousꢂFree Dynamic Range
Spurious-free dynamic range (SFDR) is the ratio of RMS
amplitude of the fundamental (maximum signal compo-
nent) to the RMS value of the next-largest distortion
component.
EignalꢂtoꢂNoise -lus Distortion
Signal-to-noise plus distortion (SINAD) is the ratio of the
fundamental input frequency’s RMS amplitude to the
RMS equivalent of all other ADC output signals:
SINAD (dB) = 20 ✕ log (Signal
/ Noise
)
RMS
RMS
ꢁffective Number of Bits
Effective number of bits (ENOB) indicates the global
accuracy of an ADC at a specific input frequency and
sampling rate. An ideal ADC’s error consists of
quantization noise only. With an input range equal to
the full-scale range of the ADC, calculate the effective
number of bits as follows:
Chip Information
TRANSISTOR COUNT: 28,629
ENOB = (SINAD - 1.76) / 6.02
______________________________________________________________________________________ 43
1ꢀ5k ꢁEDꢂ-rotected TouchꢂEcreen
Controllers Include DAC and Keypad Controller
-ac5age Information
(The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information,
go to www.maxim-ic.com/packages.)
Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are
implied. Maxim reserves the right to change the circuitry and specifications without notice at any time.
44 ____________________Maxim Integrated -roducts, 120 Ean Gabriel Drive, Eunnyvale, CA 94086 408ꢂ737ꢂ7600
© 2002 Maxim Integrated Products
Printed USA
is a registered trademark of Maxim Integrated Products.
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