MAX6956ANI+_技术文档

19-2414; Rev 4; 6/10

2-Wire-Interfaced, 2.5V to 5.5V, 20-Port or

28-Port LED Display Driver and I/O Expander

MAX956

General Description

Features

o 400kbps I²C-Compatible Serial Interface

o 2.5V to 5.5V Operation

The MAX6956 compact, serial-interfaced LED display

driver/I/O expander provide microprocessors with up to

28 ports. Each port is individually user configurable to

either a logic input, logic output, or common-anode

(CA) LED constant-current segment driver. Each port

configured as an LED segment driver behaves as a

digitally controlled constant-current sink, with 16 equal

current steps from 1.5mA to 24mA. The LED drivers are

suitable for both discrete LEDs and CA numeric and

alphanumeric LED digits.

o -40°C to +125°C Temperature Range

o 20 or 28 I/O Ports, Each Configurable as

Constant-Current LED Driver

Push-Pull Logic Output

Schmitt Logic Input

Schmitt Logic Input with Internal Pullup

o 11µA (max) Shutdown Current

o 16-Step Individually Programmable Current

Each port configured as a general-purpose I/O (GPIO)

can be either a push-pull logic output capable of sink-

ing 10mA and sourcing 4.5mA, or a Schmitt logic input

with optional internal pullup. Seven ports feature config-

urable transition detection logic, which generates an

interrupt upon change of port logic level. The MAX6956

is controlled through an I²C-compatible 2-wire serial

interface, and uses four-level logic to allow 16 I²C

addresses from only 2 select pins.

Control for Each LED

o Logic Transition Detection for Seven I/O Ports

Ordering Information

PART

TEMP RANGE

-40°C to +125°C

PIN-PACKAGE

28 DIP

MAX6956ANI+

MAX6956AAI+

MAX6956AAX+

MAX6956ATL+

MAX6956AAX/V

28 SSOP

36 SSOP

The MAX6956AAX and MAX6956ATL have 28 ports

and are available in 36-pin SSOP and 40-pin thin QFN

packages, respectively. The MAX6956AAI and

MAX6956ANI have 20 ports and are available in 28-pin

SSOP and 28-pin DIP packages, respectively.

For an SPI-interfaced version, refer to the MAX6957

data sheet. For a lower cost pin-compatible port

expander without the constant-current LED drive capa-

bility, refer to the MAX7300 data sheet.

40 Thin QFN-EP*

36 SSOP

MAX6956AAX/V+T -40°C to +125°C

36 SSOP

/V denotes an automotive qualified part.

+Denotes a lead(Pb)-free/RoHS-compliant package.

T = Tape and reel.

*EP = Exposed pad.

Pin Configurations

Applications

TOP VIEW

Set-Top Boxes

Panel Meters

White Goods

Automotive

Bar Graph Displays

Industrial Controllers

System Monitoring

ISET

GND

AD0

P12

P13

P14

P15

P16

1

2

3

4

5

6

7

8

9

28 V+

27 AD1

26 SCL

25 SDA

24 P31

23 P30

22 P29

21 P28

20 P27

19 P26

18 P25

17 P24

16 P23

15 P22

MAX6956

Typical Operating Circuit appears at end of data sheet.

P17 10

P18 11

P19 12

P20 13

P21 14

SSOP/DIP

Pin Configurations continued at end of data sheet.

________________________________________________________________ Maxim Integrated Products

1

For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642,

or visit Maxim’s website at www.maxim-ic.com.

2-Wire-Interfaced, 2.5V to 5.5V, 20-Port or

28-Port LED Display Driver and I/O Expander

ABSOLUTE MAXIMUM RATINGS

Voltage (with Respect to GND)

36-Pin SSOP (derate 11.8mW/°C above T = +70°C)...941mW

A

V+.............................................................................-0.3V to +6V

SCL, SDA, AD0, AD1................................................-0.3V to +6V

All Other Pins................................................-0.3V to (V+ + 0.3V)

P4–P31 Current ................................................................ 30mA

GND Current .....................................................................800mA

Continuous Power Dissipation

40-Pin TQFN (derate 26.3mW/°C above T = +70°C) 2105mW

Operating Temperature Range

A

(T

to T

) ...............................................-40°C to +125°C

MAX

MIN

Junction Temperature......................................................+150°C

Storage Temperature Range.............................-65°C to +150°C

Soldering Temperature (reflow)

Lead(Pb)-free packages...............................................+260°C

Packages containing lead(Pb)......................................+240°C

28-Pin PDIP (derate 14.3mW/°C above T = +70°C) 1143mW

A

28-Pin SSOP (derate 9.1mW/°C above T = +70°C)...727mW

A

MAX956

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

(Typical Operating Circuit, V+ = 2.5V to 5.5V, T = T

to T

, unless otherwise noted.) (Note 1)

MAX

A

MIN

PARAMETER

SYMBOL

CONDITIONS

MIN

2.5

TYP

MAX

5.5

8

UNITS

Operating Supply Voltage

V+

V

T

A

T

A

T

A

= +25°C

5.5

All digital inputs at V+

or GND

Shutdown Supply Current

Operating Supply Current

I

µA

= -40°C to +85°C

10

11

SHDN

= T

to T

MAX

MIN

T

A

T

A

T

A

T

A

T

A

T

A

T

A

T

A

T

A

= +25°C

180

170

110

230

250

270

210

230

240

135

140

145

All ports programmed

as outputs high, no

load, all other inputs at

V+ or GND

I

= -40°C to +85°C

= T to T

GPOH

MIN

MAX

= +25°C

= -40°C to +85°C

= T to T

All ports programmed

as outputs low, no

load, all other inputs at

V+ or GND

Operating Supply Current

I

µA

GPOL

MIN

MAX

All ports programmed

as LED outputs, all LEDs

off, no load, all other

inputs at V+ or GND

= +25°C

= -40°C to +85°C

= T to T

Operating Supply Current

I

LED

MIN

MAX

INPUTS AND OUTPUTS

✕

Logic-High Input Voltage

Port Inputs

0.7

V

IH

V+

✕

Logic-Low Input Voltage

Port Inputs

0.3

V

IL

V+

GPIO inputs without pullup,

= V+ to GND

Input Leakage Current

I

, I

IH IL

-100

1

+100

nA

V

PORT

V+ = 2.5V

V+ = 5.5V

12

80

19

120

0.3

30

GPIO Input Internal Pullup to V+

Hysteresis Voltage GPIO Inputs

I

µA

V

PU

180

∆V

I

GPIO outputs, I

+85°C

= 2mA, T = -40°C to

V+ -

0.7

SOURCE

A

Output High Voltage

V

OH

GPIO outputs, I

= 1mA, T = T

to

V+ -

0.7

A

MIN

T

MAX

(Note 2)

Port Sink Current

I

V

= 0.6V

2

10

11

18

20

mA

OL

PORT

Output Short-Circuit Current

I

Port configured output low, shorted to V+

2.75

OLSC

2

_______________________________________________________________________________________

2-Wire-Interfaced, 2.5V to 5.5V, 20-Port or

28-Port LED Display Driver and I/O Expander

MAX956

ELECTRICAL CHARACTERISTICS (continued)

(Typical Operating Circuit, V+ = 2.5V to 5.5V, T = T

to T

, unless otherwise noted.) (Note 1)

MAX

A

MIN

PARAMETER

SYMBOL

CONDITIONS

MIN

TYP

MAX

UNITS

V+ = 2.5V, V

current

= 2.3V at maximum LED

= 2.4V at maximum LED

= 0.6V at maximum sink

LED

9.5

18.5

19

13.5

18

Port Drive LED Sink Current,

Port Configured as LED Driver

V+ = 3.3V, V

current (Note 2)

V+ = 5.5V, V

current

V+ = 2.5V, V

current

LED

24

25

23

24

27.5

30

I

mA

DIGIT

LED

OUT

18.5

19

28

Port Drive Logic Sink Current,

Port Configured as LED Driver

I

mA

DIGIT_SC

V+ = 5.5V, V

current

28

✕

Input High-Voltage SDA, SCL,

AD0, AD1

0.7

V

IH

V+

✕

Input Low-Voltage SDA, SCL,

AD0, AD1

0.3

V

IL

V+

Input Leakage Current SDA, SCL

Input Capacitance

Output Low-Voltage SDA

I

, I

-50

50

nA

pF

V

IH IL

(Note 2)

10

0.4

V

I

= 6mA

OL

SINK

TIMING CHARACTERISTICS (Figure 2)

(V+ = 2.5V to 5.5V, T = T

A

to T

, unless otherwise noted.) (Note 1)

MAX

MIN

PARAMETER

SYMBOL

CONDITIONS

MIN

TYP

MAX

UNITS

Serial Clock Frequency

f

400

kHz

SCL

Bus Free Time Between a STOP

and a START Condition

Hold Time (Repeated) START

Condition

Repeated START Condition

Setup Time

t

1.3

0.6

µs

BUF

t

HD, STA

t

SU, STA

STOP Condition Setup Time

Data Hold Time

Data Setup Time

SCL Clock Low Period

SCL Clock High Period

Rise Time of Both SDA and SCL

Signals, Receiving

Fall Time of Both SDA and SCL

Signals, Receiving

t

0.6

15

100

1.3

0.7

µs

ns

µs

SU, STO

t

(Note 3)

900

HD, DAT

t

SU, DAT

t

LOW

t

HIGH

20 +

t

(Notes 2, 4)

300

ns

R

0.1C

b

20 +

0.1C

t

F

b

20 +

0.1C

Fall Time of SDA Transmitting

t

(Notes 2, 5)

(Notes 2, 6)

(Note 2)

250

50

ns

pF

F,TX

b

Pulse Width of Spike Suppressed

Capacitive Load for Each Bus

Line

t

0

SP

C

400

b

Note 1: All parameters tested at T = +25°C. Specifications over temperature are guaranteed by design.

A

Note 2: Guaranteed by design.

Note 3: A master device must provide a hold time of at least 300ns for the SDA signal (referred to V of the SCL signal) in order to

IL

bridge the undefined region of SCL’s falling edge.

Note 4: C = total capacitance of one bus line in pF. t and t measured between 0.3V+ and 0.7V+.

b

R

F

Note 5: I

≤ 6mA. C = total capacitance of one bus line in pF. t and t measured between 0.3V+ and 0.7V+.

SINK

b R F

Note 6: Input filters on the SDA and SCL inputs suppress noise spikes less than 50ns.

_______________________________________________________________________________________

3

2-Wire-Interfaced, 2.5V to 5.5V, 20-Port or

28-Port LED Display Driver and I/O Expander

__________________________________________Typical Operating Characteristics

(R

= 39kΩ, T = +25°C, unless otherwise noted.)

ISET

A

OPERATING SUPPLY CURRENT

vs. TEMPERATURE

SHUTDOWN SUPPLY CURRENT

vs. TEMPERATURE

OPERATING SUPPLY CURRENT vs. V+

(NO LOADS)

0.40

0.36

0.32

0.28

0.24

0.20

0.16

0.12

0.08

0.04

0

8

100

10

V+ = 2.5V TO 5.5V

NO LOAD

ALL PORTS LED (ON)

V+ = 5.5V

7

MAX956

ALL PORTS

V+ = 3.3V

ALL PORTS

OUTPUT (0)

ALL PORTS OUTPUT (1)

ALL PORTS OUTPUT (0)

OUTPUT (1)

6

1

5

V+ = 2.5V

0.1

0.01

4

ALL PORTS LED (OFF)

3

-40.0 -12.5 15.0 42.5 70.0 97.5 125.0

2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5

V+ (V)

TEMPERATURE (°C)

GPO SINK CURRENT vs. TEMPERATURE

(OUTPUT = 0)

LED DRIVER SINK CURRENT

vs. TEMPERATURE

vs. V+

18

16

14

12

10

8

26

24

22

20

18

16

14

12

10

8

27

V

= 2.4V

V+ = 2.5V TO 5.5V, V

= 0.6V

LED

PORT

26

V+ = 5.5V

25

LED DROP = 2.4V

24

23

22

21

20

LED DROP = 1.8V

V+ = 3.3V

6

4

2

6

-40.0 -12.5 15.0 42.5 70.0 97.5 125.0

2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5

V+ (V)

-40.0 -12.5 15.0 42.5 70.0 97.5 125.0

TEMPERATURE (°C)

GPO SOURCE CURRENT vs. TEMPERATURE

(OUTPUT = 1)

GPI PULLUP CURRENT

vs. TEMPERATURE

GPO SHORT-CIRCUIT CURRENT

vs. TEMPERATURE

9

8

7

6

5

4

3

2

1000

100

10

100

V

= 1.4V

PORT

V+ = 5.5V

V+ = 3.3V

V+ = 2.5V

V+ = 5.5V

GPO = 0, PORT

SHORTED TO V+

10

V+ = 3.3V

V+ = 2.5V

GPO = 1, PORT

SHORTED TO GND

1

-40.0 -12.5 15.0 42.5 70.0 97.5 125.0

TEMPERATURE (°C)

4

_______________________________________________________________________________________

2-Wire-Interfaced, 2.5V to 5.5V, 20-Port or

28-Port LED Display Driver and I/O Expander

MAX956

Pin Description

NAME

FUNCTION

SSOP/DIP

SSOP

TQFN

36

Segment Current Setting. Connect ISET to GND through a resistor (R

the maximum segment current.

) to set

ISET

1

2, 3

4

1

2, 3

4

ISET

GND

AD0

37, 38, 39

40

Ground

Address Input 0. Sets device slave address. Connect to either GND, V+, SCL,

SDA to give four logic combinations. See Table 3.

LED Segment Drivers and GPIO. P12 to P31 can be configured as CA LED

drivers, GPIO outputs, CMOS logic inputs, or CMOS logic inputs with weak

pullup resistor.

5–24

—

P12–P31

P4–P31

1–10,

12–19,

21–30

LED Segment Drivers and GPIO. P4 to P31 can be configured as CA LED

drivers, GPIO outputs, CMOS logic inputs, or CMOS logic inputs with weak

pullup resistor.

5–32

—

25

26

—

33

34

11, 20, 31

N.C.

SDA

SCL

No Connection

32

33

I²C-Compatible Serial Data I/O

I²C-Compatible Serial Clock Input

Address Input 1. Sets device slave address. Connect to either GND, V+, SCL,

SDA to give four logic combinations. See Table 3.

27

28

—

35

36

—

34

35

—

AD1

V+

Positive Supply Voltage. Bypass V+ to GND with minimum 0.047µF capacitor.

Exposed Pad (TQFN Only). Not internally connected. Connect EP to ground

plane for maximum thermal performance.

EP

ment-plus-DP displays, with five ports left available for

GPIO (P26–P31 of U2).

Detailed Description

The MAX6956 LED driver/GPIO peripheral provides up

to 28 I/O ports, P4 to P31, controlled through an I²C-com-

patible serial interface. The ports can be configured to

any combination of constant-current LED drivers, logic

inputs and logic outputs, and default to logic inputs on

power-up. When fully configured as an LED driver, the

MAX6956 controls up to 28 LED segments with individual

16-step adjustment of the constant current through each

LED segment. A single resistor sets the maximum seg-

ment current for all segments, with a maximum of 24mA

per segment. The MAX6956 drives any combination of

discrete LEDs and CA digits, including seven-segment

and starburst alphanumeric types.

The port configuration registers set the 28 ports, P4 to

P31, individually as either LED drivers or GPIO. A pair

of bits in registers 0x09 through 0x0F sets each port’s

configuration (Tables 1 and 2).

The 36-pin MAX6956AAX has 28 ports, P4 to P31. The

28-pin MAX6956ANI and MAX6956AAI make only 20

ports available, P12 to P31. The eight unused ports

should be configured as outputs on power-up by writ-

ing 0x55 to registers 0x09 and 0x0A. If this is not done,

the eight unused ports remain as unconnected inputs

and quiescent supply current rises, although there is no

damage to the part.

Figure 1 is the MAX6956 functional diagram. Any I/O

port can be configured as a push-pull output (sinking

10mA, sourcing 4.5mA), or a Schmitt-trigger logic input.

Each input has an individually selectable internal pullup

resistor. Additionally, transition detection allows seven

ports (P24 through P30) to be monitored in any mask-

able combination for changes in their logic status. A

detected transition is flagged through a status register

bit, as well as an interrupt pin (port P31), if desired.

Register Control of I/O Ports and LEDs

Across Multiple Drivers

The MAX6956 offers 20 or 28 I/O ports, depending on

package choice. These can be applied to a variety of

combinations of different display types, for example:

seven, 7-segment digits (Figure 7). This example

requires two MAX6956s, with one digit being driven by

both devices, half by one MAX6956, half by the other

(digit 4 in this example). The two drivers are static, and

therefore do not need to be synchronized. The

MAX6956 sees CA digits as multiple discrete LEDs. To

The Typical Operating Circuit shows two MAX6956s

working together controlling three monocolor 16-seg-

_______________________________________________________________________________________

5

2-Wire-Interfaced, 2.5V to 5.5V, 20-Port or

28-Port LED Display Driver and I/O Expander

Table 1. Port Configuration Map

REGISTER DATA

D4 D3

ADDRESS

CODE (HEX)

REGISTER

D7

D6

D5

D2

D1

D0

Port Configuration for P7, P6, P5, P4

0x09

0x0A

0x0B

0x0C

0x0D

0x0E

0x0F

P7

P6

P5

P4

Port Configuration for P11, P10, P9, P8

Port Configuration for P15, P14, P13, P12

Port Configuration for P19, P18, P17, P16

Port Configuration for P23, P22, P21, P20

Port Configuration for P27, P26, P25, P24

Port Configuration for P31, P30, P29, P28

P11

P15

P19

P23

P27

P31

P10

P14

P18

P22

P26

P30

P9

P8

P13

P17

P21

P25

P29

P12

P16

P20

P24

P28

MAX956

Table 2. Port Configuration Matrix

PORT

CONFIGURATION

BIT PAIR

PORT

REGISTER

(0x20–0x5F)

ADDRESS

CODE (HEX)

MODE

FUNCTION

PIN BEHAVIOR

UPPER

LOWER

Register bit = 0 High impedance

Open-drain current sink, with sink

Register bit = 1 current (up to 24mA) determined

Output

LED Segment Driver

GPIO Output

0x09 to 0x0F

0

by the appropriate current register

Register bit = 0 Active-low logic output

Output

Input

0x09 to 0x0F

0

1

0

1

Register bit = 1 Active-high logic output

GPIO Input

Without Pullup

Schmitt logic input

Register bit =

input logic level

Input

GPIO Input with Pullup

Schmitt logic input with pullup

Note: The logic is inverted between the two output modes; a high makes the output go low in LED segment driver mode (0x00) to

turn that segment on; in GPIO output mode (0x01), a high makes the output go high.

simplify access to displays that overlap two MAX6956s,

the MAX6956 provides four virtual ports, P0 through P3.

To update an overlapping digit, send the same code

twice as an eight-port write, once to P28 through P35 of

the first driver, and again to P0 through P7 of the sec-

ond driver. The first driver ignores the last 4 bits and

the second driver ignores the first 4 bits.

segment digit with DP can be updated in two byte-

writes, and 16-segment digits with DP can be updated

in two byte-writes plus a bit write. Also, discrete LEDs

and GPIO port bits can be lit and controlled individually

without affecting other ports.

Shutdown

When the MAX6956 is in shutdown mode, all ports are

forced to inputs (which an be read), and the pullup cur-

rent sources are turned off. Data in the port and control

registers remain unaltered, so port configuration and

output levels are restored when the MAX6956 is taken

out of shutdown. The display driver can still be pro-

grammed while in shutdown mode. For minimum sup-

ply current in shutdown mode, logic inputs should be at

GND or V+ potential. Shutdown mode is exited by set-

ting the S bit in the configuration register (Table 8).

Two addressing methods are available. Any single port

(bit) can be written (set/cleared) at once; or, any

sequence of eight ports can be written (set/cleared) in

any combination at once. There are no boundaries; it is

equally acceptable to write P0 through P7, P1 through

P8, or P31 through P38 (P32 through P38 are nonexis-

tent, so the instructions to these bits are ignored).

Using 8-bit control, a seven-segment digit with a deci-

mal point can be updated in a single byte-write, a 14-

6

_______________________________________________________________________________________

2-Wire-Interfaced, 2.5V to 5.5V, 20-Port or

28-Port LED Display Driver and I/O Expander

MAX956

INTENSITY REGISTERS

TEST REGISTER

INTENSITY

TEST

MAX6956

CONFIGURATION

PORT REGISTERS

MASK REGISTER

P4 TO P31

LED DRIVERS

OR GPIO

LED DRIVERS AND GPIO

CONFIGURATION

REGISTERS

PORT CHANGE

DETECTOR

DATA

8

CE

R/W

SEGMENT OR

GPIO DATA

R/W

8

COMMAND

REGISTER DECODE

AD0

AD1

ADDRESS

MATCHER

7

8

DATA BYTE

COMMAND BYTE

D0

D1

D2

D3

D4

D5

D6

D7

D8

D9

D10

D11

D12

D13

D14

D15

7

TO/FROM DATA REGISTERS

DATA BYTE

TO COMMAND REGISTERS

7-BIT DEVICE ADDRESS

R/W

SDA

SCL

COMMAND BYTE

SLAVE ADDRESS BYTE

Figure 1. MAX6956 Functional Diagram

Shutdown mode is temporarily overridden by the dis-

play test function.

is required on SDA. The MAX6956 SCL line operates

only as an input. A pullup resistor, typically 4.7kΩ, is

required on SCL if there are multiple masters on the 2-

wire interface, or if the master in a single-master system

has an open-drain SCL output.

Serial Interface

Serial Addressing

The MAX6956 operates as a slave that sends and

receives data through an I²C-compatible 2-wire inter-

face. The interface uses a serial data line (SDA) and a

serial clock line (SCL) to achieve bidirectional commu-

nication between master(s) and slave(s). A master (typ-

ically a microcontroller) initiates all data transfers to and

from the MAX6956, and generates the SCL clock that

synchronizes the data transfer (Figure 2).

Each transmission consists of a START condition

(Figure 3) sent by a master, followed by the MAX6956

7-bit slave address plus R/W bit (Figure 6), a register

address byte, one or more data bytes, and finally a

STOP condition (Figure 3).

Start and Stop Conditions

Both SCL and SDA remain high when the interface is

not busy. A master signals the beginning of a transmis-

sion with a START (S) condition by transitioning SDA

from high to low while SCL is high. When the master

The MAX6956 SDA line operates as both an input and

an open-drain output. A pullup resistor, typically 4.7kΩ,

_______________________________________________________________________________________________________

7

2-Wire-Interfaced, 2.5V to 5.5V, 20-Port or

28-Port LED Display Driver and I/O Expander

SDA

t

BUF

t

SU, STA

SU, DAT

t

HD, STA

t

LOW

t

SU, STO

HD, DAT

SCL

MAX956

t

HIGH

t

HD, STA

t

F

R

REPEATED START CONDITION

START CONDITION

STOP CONDITION START CONDITION

Figure 2. 2-Wire Serial Interface Timing Details

SDA

S

P

SCL

START

STOP

CONDITION

Figure 3. Standard Stop Conditions

SDA

SCL

DATA LINE STABLE;

DATA VALID

CHANGE OF DATA ALLOWED

Figure 4. Bit Transfer

has finished communicating with the slave, it issues a

STOP (P) condition by transitioning SDA from low to

high while SCL is high. The bus is then free for another

transmission (Figure 3).

Acknowledge

The acknowledge bit is a clocked 9th bit, which the

recipient uses to handshake receipt of each byte of

data (Figure 5). Thus, each byte transferred effectively

requires 9 bits. The master generates the 9th clock

pulse, and the recipient pulls down SDA during the

acknowledge clock pulse, such that the SDA line is sta-

ble low during the high period of the clock pulse. When

the master is transmitting to the MAX6956, the

MAX6956 generates the acknowledge bit because the

Bit Transfer

One data bit is transferred during each clock pulse.

The data on SDA must remain stable while SCL is high

(Figure 4).

8

_______________________________________________________________________________________

2-Wire-Interfaced, 2.5V to 5.5V, 20-Port or

28-Port LED Display Driver and I/O Expander

MAX956

START CONDITION

CLOCK PULSE FOR ACKNOWLEDGMENT

SCL

1

2

8

9

SDA

BY TRANSMITTER

S

SDA

BY RECEIVER

Figure 5. Acknowledge

SDA

1

MSB

0

A3

A2

A1

A0

LSB

R/W

ACK

SCL

Figure 6. Slave Address

MAX6956 is the recipient. When the MAX6956 is trans-

mitting to the master, the master generates the

acknowledge bit because the master is the recipient.

byte of information is the command byte. The com-

mand byte determines which register of the MAX6956

is to be written by the next byte, if received. If a STOP

condition is detected after the command byte is

received, then the MAX6956 takes no further action

(Figure 8) beyond storing the command byte.

Slave Address

The MAX6956 has a 7-bit-long slave address (Figure 6).

The eighth bit following the 7-bit slave address is the

R/W bit. It is low for a write command, high for a read

command.

Any bytes received after the command byte are data

bytes. The first data byte goes into the internal register of

the MAX6956 selected by the command byte (Figure 9). If

multiple data bytes are transmitted before a STOP condi-

tion is detected, these bytes are generally stored in subse-

quent MAX6956 internal registers because the command

byte address generally autoincrements (Table 4).

The first 3 bits (MSBs) of the MAX6956 slave address

are always 100. Slave address bits A3, A2, A1, and A0

are selected by address inputs, AD1 and AD0. These

two input pins may be connected to GND, V+, SDA, or

SCL. The MAX6956 has 16 possible slave addresses

(Table 3) and therefore, a maximum of 16 MAX6956

devices may share the same interface.

Message Format for Reading

The MAX6956 is read using the MAX6956’s internally

stored command byte as address pointer, the same

way the stored command byte is used as address

pointer for a write. The pointer generally autoincre-

ments after each data byte is read using the same rules

as for a write (Table 4). Thus, a read is initiated by first

configuring the MAX6956’s command byte by perform-

Message Format for Writing

the MAX6956

A write to the MAX6956 comprises the transmission of

the MAX6956’s slave address with the R/W bit set to

zero, followed by at least 1 byte of information. The first

_______________________________________________________________________________________

9

2-Wire-Interfaced, 2.5V to 5.5V, 20-Port or

28-Port LED Display Driver and I/O Expander

V+

7-SEGMENT DIGIT 1

7-SEGMENT DIGIT 2

7-SEGMENT DIGIT 3

7-SEGMENT DIGIT 4

MAX956

VIRTUAL SEGMENTS

P0 P1 P2 P3 P4 P5 P6 P7 P8 P9 P10 P11 P12 P13 P14 P15 P16 P17 P18 P19 P20 P21 P22 P23 P24 P25 P26 P27 P28 P29 P30 P31

V+

7-SEGMENT DIGIT 5

7-SEGMENT DIGIT 6

7-SEGMENT DIGIT 7

VIRTUAL SEGMENTS

P0 P1 P2 P3 P4 P5 P6 P7 P8 P9 P10 P11 P12 P13 P14 P15 P16 P17 P18 P19 P20 P21 P22 P23 P24 P25 P26 P27 P28 P29 P30 P31

Figure 7. Two MAX6956s Controlling Seven 7-Segment Displays

D15 D14 D13 D12 D11 D10 D9 D8

COMMAND BYTE IS STORED ON RECEIPT OF STOP CONDITION

ACKNOWLEDGE FROM MAX6956

SLAVE ADDRESS

COMMAND BYTE RECEIVED

S

0

A

COMMAND BYTE

A

P

ACKNOWLEDGE FROM MAX6956

R/W

Figure 8. Command Byte Received

ACKNOWLEDGE FROM MAX6956

HOW COMMAND BYTE AND DATA BYTE MAP INTO MAX6956's REGISTER

ACKNOWLEDGE FROM MAX6956

D15 D14 D13 D12 D11 D10 D9 D8

D7 D6 D5 D4 D3 D2 D1 D0

S

SLAVE ADDRESS

0

A

DATA BYTE

1 BYTE

A

P

COMMAND BYTE

R/W

Figure 9. Command and Single Data Byte Received

10 ______________________________________________________________________________________

2-Wire-Interfaced, 2.5V to 5.5V, 20-Port or

28-Port LED Display Driver and I/O Expander

MAX956

ACKNOWLEDGE FROM MAX6956

HOW COMMAND BYTE AND DATA BYTE MAP INTO MAX6956's REGISTER

ACKNOWLEDGE FROM MAX6956

D15 D14 D13 D12 D11 D10 D9 D8

D7 D6 D5 D4 D3 D2 D1 D0

SLAVE ADDRESS

COMMAND BYTE

DATA BYTE

S

0

A

P

n BYTES

R/W

AUTOINCREMENT MEMORY WORD ADDRESS

Figure 10. n Data Bytes Received

Table 3. MAX6956 Address Map

DEVICE ADDRESS

CONNECTION

AD1

GND

V+

AD0

GND

V+

A6

1

A5

0

A4

0

A3

0

1

A2

0

1

0

1

A1

0

1

0

1

0

1

0

1

A0

0

1

0

1

0

1

0

1

0

1

0

1

0

1

0

1

SDA

SCL

GND

V+

SDA

SCL

GND

V+

SDA

SCL

SDA

SCL

GND

V+

SDA

SCL

Table 4. Autoincrement Rules

COMMAND BYTE ADDRESS RANGE

x0000000 to x1111110

x1111111

AUTOINCREMENT BEHAVIOR

Command address autoincrements after byte read or written

Command address remains at x1111111 after byte written or read

ing a write (Figure 8). The master can now read n con-

secutive bytes from the MAX6956, with the first data

byte being read from the register addressed by the ini-

tialized command byte. When performing read-after-

write verification, remember to reset the command

byte’s address because the stored control byte

address generally has been autoincremented after the

write (Table 4). Table 5 is the register address map.

Operation with Multiple Masters

If the MAX6956 is operated on a 2-wire interface with

multiple masters, a master reading the MAX6956

should use a repeated start between the write, which

sets the MAX6956’s address pointer, and the read(s)

that takes the data from the location(s). This is because

it is possible for master 2 to take over the bus after

master 1 has set up the MAX6956’s address pointer but

before master 1 has read the data. If master 2 subse-

______________________________________________________________________________________ 11

2-Wire-Interfaced, 2.5V to 5.5V, 20-Port or

28-Port LED Display Driver and I/O Expander

Table 5. Register Address Map

COMMAND ADDRESS

REGISTER

HEX

CODE

D15

X

D14

0

D13

0

D12

0

D11

0

D10

0

D9

0

D8

0

No-Op

0x00

0x02

0x04

0x06

0x07

0x09

0x0A

0x0B

0x0C

0x0D

0x0E

Global Current

X

0

1

0

Configuration

X

0

1

0

Transition Detect Mask

Display Test

X

0

1

0

MAX956

X

0

1

Port Configuration P7, P6, P5, P4

Port Configuration P11, P10, P9, P8

Port Configuration P15, P14, P13, P12

Port Configuration P19, P18, P17, P16

Port Configuration P23, P22, P21, P20

Port Configuration P27, P26, P25, P24

Port Configuration P31, P30, P29, P28

Current054

X

0

1

0

1

X

0

1

0

1

0

X

0

1

0

1

X

0

1

0

X

0

1

0

1

X

0

1

0

X

0

1

0

1

0

1

0

1

0x0F

0x12

0x13

Current076

Current098

X

0

1

0

1

0

1

0

1

0

1

0

1

0

1

0

1

0

1

0

1

0

1

0

1

0

1

0

1

0

1

0

1

0

1

0

1

0

1

0

1

0

1

0

1

0

0x14

0x15

0x16

0x17

0x18

0x19

0x1A

0x1B

0x1C

0x1D

0x1E

0x1F

0x20

0x21

0x22

0x23

0x24

0x25

0x26

0x27

0x28

0x29

0x2A

Current0BA

Current0DC

Current0FE

Current110

Current132

Current154

Current176

Current198

Current1BA

Current1DC

Current1FE

Port 0 only (virtual port, no action)

Port 1 only (virtual port, no action)

Port 2 only (virtual port, no action)

Port 3 only (virtual port, no action)

Port 4 only (data bit D0; D7–D1 read as 0)

Port 5 only (data bit D0; D7–D1 read as 0)

Port 6 only (data bit D0; D7–D1 read as 0)

Port 7 only (data bit D0; D7–D1 read as 0)

Port 8 only (data bit D0; D7–D1 read as 0)

Port 9 only (data bit D0; D7–D1 read as 0)

Port 10 only (data bit D0; D7–D1 read as 0)

12 ______________________________________________________________________________________

2-Wire-Interfaced, 2.5V to 5.5V, 20-Port or

28-Port LED Display Driver and I/O Expander

MAX956

Table 5. Register Address Map (continued)

COMMAND ADDRESS

HEX

CODE

REGISTER

D15

X

D14

0

1

D13

1

0

D12

0

1

0

D11

1

0

1

0

1

D10

0

1

0

1

0

1

0

1

0

1

D9

1

0

1

0

1

0

1

0

1

0

1

0

1

0

1

0

1

0

1

D8

1

0

1

0

1

0

1

0

1

0

1

0

1

0

1

0

1

0

1

0

1

0

1

0

1

0

1

0

1

0

1

0

1

0

1

0

1

Port 11 only (data bit D0; D7–D1 read as 0)

Port 12 only (data bit D0; D7–D1 read as 0)

Port 13 only (data bit D0; D7–D1 read as 0)

Port 14 only (data bit D0; D7–D1 read as 0)

Port 15 only (data bit D0; D7–D1 read as 0)

Port 16 only (data bit D0; D7–D1 read as 0)

Port 17 only (data bit D0; D7–D1 read as 0)

Port 18 only (data bit D0; D7–D1 read as 0)

Port 19 only (data bit D0; D7–D1 read as 0)

Port 20 only (data bit D0; D7–D1 read as 0)

Port 21 only (data bit D0; D7–D1 read as 0)

Port 22 only (data bit D0; D7–D1 read as 0)

Port 23 only (data bit D0; D7–D1 read as 0)

Port 24 only (data bit D0; D7–D1 read as 0)

Port 25 only (data bit D0; D7–D1 read as 0)

Port 26 only (data bit D0; D7–D1 read as 0)

Port 27 only (data bit D0; D7–D1 read as 0)

Port 28 only (data bit D0; D7–D1 read as 0)

Port 29 only (data bit D0; D7–D1 read as 0)

Port 30 only (data bit D0; D7–D1 read as 0)

Port 31 only (data bit D0; D7–D1 read as 0)

4 ports 4–7 (data bits D0–D3; D4–D7 read as 0)

5 ports 4–8 (data bits D0–D4; D5–D7 read as 0)

6 ports 4–9 (data bits D0–D5; D6–D7 read as 0)

7 ports 4–10 (data bits D0–D6; D7 reads as 0)

8 ports 4–11 (data bits D0–D7)

0x2B

0x2C

0x2D

0x2E

0x2F

0x30

0x31

0x32

0x33

0x34

0x35

0x36

0x37

0x38

0x39

0x3A

0x3B

0x3C

0x3D

0x3E

0x3F

0x40

0x41

0x42

0x43

0x44

0x45

0x46

0x47

0x48

0x49

0x4A

0x4B

0x4C

0x4D

0x4E

0x4F

8 ports 5–12 (data bits D0–D7)

8 ports 6–13 (data bits D0–D7)

8 ports 7–14 (data bits D0–D7)

8 ports 8–15 (data bits D0–D7)

8 ports 9–16 (data bits D0–D7)

8 ports 10–17 (data bits D0–D7)

8 ports 11–18 (data bits D0–D7)

8 ports 12–19 (data bits D0–D7)

8 ports 13–20 (data bits D0–D7)

8 ports 14–21 (data bits D0–D7)

8 ports 15–22 (data bits D0–D7)

______________________________________________________________________________________ 13

2-Wire-Interfaced, 2.5V to 5.5V, 20-Port or

28-Port LED Display Driver and I/O Expander

Table 5. Register Address Map (continued)

COMMAND ADDRESS

REGISTER

HEX

CODE

D15

X

D14

1

D13

0

D12

1

D11

0

D10

0

D9

0

1

0

1

0

1

0

1

D8

0

1

0

1

0

1

0

1

0

1

0

1

0

1

0

1

8 ports 16–23 (data bits D0–D7)

0x50

0x51

0x52

0x53

0x54

0x55

0x56

0x57

0x58

0x59

0x5A

0x5B

0x5C

0x5D

0x5E

0x5F

8 ports 17–24 (data bits D0–D7)

X

1

0

1

0

8 ports 18–25 (data bits D0–D7)

X

1

0

1

0

8 ports 19–26 (data bits D0–D7)

X

1

0

1

0

MAX956

8 ports 20–27 (data bits D0–D7)

X

1

0

1

0

1

8 ports 21–28 (data bits D0–D7)

X

1

0

1

0

1

8 ports 22–29 (data bits D0–D7)

X

1

0

1

0

1

8 ports 23–30 (data bits D0–D7)

X

1

0

1

0

1

8 ports 24–31 (data bits D0–D7)

X

1

0

1

0

7 ports 25–31 (data bits D0–D6; D7 reads as 0)

6 ports 26–31 (data bits D0–D5; D6–D7 read as 0)

5 ports 27–31 (data bits D0–D4; D5–D7 read as 0)

4 ports 28–31 (data bits D0–D3; D4–D7 read as 0)

3 ports 29–31 (data bits D0–D2; D3–D7 read as 0)

2 ports 30–31 (data bits D0–D1; D2–D7 read as 0)

1 port 31 only (data bit D0; D1–D7 read as 0)

X

1

0

1

0

X

1

0

1

0

X

1

0

1

0

X

1

0

1

X

1

0

1

X

1

0

1

X

1

0

1

Note: Unused bits read as 0.

quently changes, the MAX6956’s address pointer, then

master 1’s delayed read may be from an unexpected

location.

drive of each LED segment driver. Individual/global

brightness control is selected by setting the configura-

tion register I bit (Table 9). The global current register

(0x02) data are then ignored, and segment currents are

set using register addresses 0x12 through 0x1F (Tables

12, 13, and 14). Each segment is controlled by a nibble

of one of the 16 current registers.

Command Address Autoincrementing

Address autoincrementing allows the MAX6956 to be

configured with the shortest number of transmissions

by minimizing the number of times the command

address needs to be sent. The command address

stored in the MAX6956 generally increments after each

data byte is written or read (Table 4).

Transition (Port Data Change) Detection

Port transition detection allows any combination of the

seven ports P24–P30 to be continuously monitored for

changes in their logic status (Figure 11). A detected

change is flagged on the transition detection mask reg-

ister INT status bit, D7 (Table 15). If port P31 is config-

ured as an output (Tables 1 and 2), then P31 also

automatically becomes an active-high interrupt output

(INT), which follows the condition of the INT status bit.

Port P31 is set as output by writing bit D7 = 0 and bit

D6 = 1 to the port configuration register (Table 1). Note

that the MAX6956 does not identify which specific

port(s) caused the interrupt, but provides an alert that

one or more port levels have changed.

Initial Power-Up

On initial power-up, all control registers are reset, the

current registers are set to minimum value, and the

MAX6956 enters shutdown mode (Table 6).

LED Current Control

LED segment drive current can be set either globally or

individually. Global control simplifies the operation

when all LEDs are set to the same current level,

because writing just the global current register sets the

current for all ports configured as LED segment drivers.

It is also possible to individually control the current

14 ______________________________________________________________________________________

2-Wire-Interfaced, 2.5V to 5.5V, 20-Port or

28-Port LED Display Driver and I/O Expander

MAX956

Table 6. Power-Up Configuration

ADDRESS

CODE

(HEX)

REGISTER DATA

REGISTER

FUNCTION

POWER-UP CONDITION

D7 D6

D5 D4

D3

D2 D1

D0

Port Register

Bits 4 to 31

0x24 to

0x3F

LED Off; GPIO Output Low

1/16 (minimum on)

X

0

X

0

Global

Current

0x02

0

X

0

Shutdown Enabled

Current Control = Global

Transition Detection Disabled

Configuration

Register

0x04

0

X

Input Mask

Register

All Clear (Masked Off)

Normal Operation

0x06

0x07

0x09

X

1

0

X

0

X

1

0

X

0

X

1

0

X

0

X

1

0

Display Test

Port

Configuration

P7, P6, P5, P4: GPIO Inputs Without Pullup

Port

Configuration

P11, P10, P9, P8: GPIO Inputs Without Pullup

P15, P14, P13, P12: GPIO Inputs Without Pullup

P19, P18, P17, P16: GPIO Inputs Without Pullup

P23, P22, P21, P20: GPIO Inputs Without Pullup

P27, P26, P25, P24: GPIO Inputs Without Pullup

P31, P30, P29, P28: GPIO Inputs Without Pullup

0x0A

0x0B

0x0C

0x0D

0x0E

0x0F

1

0

1

0

1

0

1

0

Port

Configuration

Port

Configuration

Port

Configuration

Port

Configuration

Port

Configuration

Current054

Current076

Current098

Current0BA

Current0DC

Current0FE

Current110

Current132

Current154

Current176

Current198

Current1BA

Current1DC

Current1FE

1/16 (minimum on)

0x12

0x13

0x14

0x15

0x16

0x17

0x18

0x19

0x1A

0x1B

0x1C

0x1D

0x1E

0x1F

0

X = unused bits; if read, zero results.

______________________________________________________________________________________ 15

2-Wire-Interfaced, 2.5V to 5.5V, 20-Port or

28-Port LED Display Driver and I/O Expander

Table 7. Configuration Register Format

REGISTER DATA

ADDRESS CODE

(HEX)

FUNCTION

D7

D6

D5

D4

D3

D2

D1

D0

Configuration Register

0x04

M

I

X

S

Table 8. Shutdown Control (S Data Bit D0) Format

MAX956

REGISTER DATA

ADDRESS CODE

FUNCTION

(HEX)

D7

M

D6

D5

X

D4

X

D3

X

D2

X

D1

X

D0

0

Shutdown

0x04

I

Normal Operation

M

X

1

Table 9. Global Current Control (I Data Bit D6) Format

REGISTER DATA

ADDRESS

CODE (HEX)

FUNCTION

D7

D6

D5

D4

D3

D2

D1

D0

Global

Constant-current limits for all digits are

controlled by one setting in the Global Current

register, 0x02

0x04

M

0

1

X

S

Individual Segment

Constant-current limit for each digit is

individually controlled by the settings in the

Current054 through Current1FE registers

M

X

Table 10. Transition Detection Control (M-Data Bit D7) Format

REGISTER DATA

ADDRESS CODE

(HEX)

FUNCTION

D7

0

D6

D5

X

D4

X

D3

X

D2

X

D1

X

D0

S

Disabled

Enabled

0x04

I

1

X

S

The mask register contains 7 mask bits, which select

which of the seven ports P24–P30 are to be monitored

(Table 15). Set the appropriate mask bit to enable that

port for transition detect. Clear the mask bit if transitions

on that port are to be ignored. Transition detection

works regardless of whether the port being monitored is

set to input or output, but generally, it is not particularly

useful to enable transition detection for outputs.

M bit in the configuration register (Table 10). Whenever

the configuration register is written with the M bit set,

the MAX6956 updates an internal 7-bit snapshot regis-

ter, which holds the comparison copy of the logic states

of ports P24 through P30. The update action occurs

regardless of the previous state of the M bit, so that it is

not necessary to clear the M bit and then set it again to

update the snapshot register.

To use transition detection, first set up the mask register

and configure port P31 as an output, as described

above. Then enable transition detection by setting the

When the configuration register is written with the M bit

set, transition detection is enabled and remains

enabled until either the configuration register is written

16 ______________________________________________________________________________________

2-Wire-Interfaced, 2.5V to 5.5V, 20-Port or

28-Port LED Display Driver and I/O Expander

MAX956

Table 11. Global Segment Current Register Format

LED DRIVE

FRACTION

TYPICAL SEGMENT

CURRENT (mA)

ADDRESS

CODE (HEX)

D7

D6

D5

D4

D3

D2

D1

D0

HEX CODE

1/16

2/16

1.5

3

0x02

X

0

1

0

1

0

1

0

1

0

1

0

1

0

1

0

1

0

1

0

1

0

1

0

1

0

1

0

1

0

1

0xX0

0xX1

0xX2

0xX3

0xX4

0xX5

0xX6

0xX7

0xX8

0xX9

0xXA

0xXB

0xXC

0xXD

0xXE

0xXF

3/16

4.5

6

4/16

5/16

7.5

9

6/16

7/16

10.5

12

8/16

9/16

13.5

15

10/16

11/16

12/16

13/16

14/16

15/16

16/16

16.5

18

19.5

21

22.5

24

X = Don’t care bit.

with the M bit clear, or a transition is detected. The INT

status bit (transition detection mask register bit D7)

goes low. Port P31 (if enabled as INT output) also goes

low, if it was not already low.

M bit set, to take a new snapshot of the seven ports

P24 to P30.

Display Test Register

Display test mode turns on all ports configured as LED

drivers by overriding, but not altering, all controls and

port registers, except the port configuration register

(Table 16). Only ports configured as LED drivers are

affected. Ports configured as GPIO push-pull outputs

do not change state. In display test mode, each port’s

current is temporarily set to 1/2 the maximum current

Once transition detection is enabled, the MAX6956

continuously compares the snapshot register against

the changing states of P24 through P31. If a change on

any of the monitored ports is detected, even for a short

time (like a pulse), the INT status bit (transition detec-

tion mask register bit D7) is set. Port P31 (if enabled as

INT output) also goes high. The INT output and INT sta-

tus bit are not cleared if more changes occur or if the

data pattern returns to its original snapshot condition.

The only way to clear INT is to access (read or write)

the transition detection mask register (Table 15). So if

the transition detection mask register is read twice in

succession after a transition event, the first time reads

with bit D7 set (identifying the event), and the second

time reads with bit D7 clear.

limit as controlled by R

.

ISET

Selecting External Component R

ISET

to Set Maximum Segment Current

The MAX6956 uses an external resistor R to set the

ISET

maximum segment current. The recommended value,

39kΩ, sets the maximum current to 24mA, which makes

the segment current adjustable from 1.5mA to 24mA in

1.5mA steps.

Transition detection is a one-shot event. When INT has

been cleared after responding to a transition event,

transition detection is automatically disabled, even

though the M bit in the configuration register remains

set (unless cleared by the user). Reenable transition

detection by writing the configuration register with the

To set a different segment current, use the formula:

R

ISET

= 936kΩ / I

SEG

where I

is the desired maximum segment current.

SEG

______________________________________________________________________________________ 17

2-Wire-Interfaced, 2.5V to 5.5V, 20-Port or

28-Port LED Display Driver and I/O Expander

Table 12. Individual Segment Current Registers

REGISTER

FUNCTION

ADDRESS

CODE (HEX)

D7

D6

D5

D4

D3

D2

D1

D0

Current054 register

Current076 register

Current098 register

Current0BA register

Current0DC register

Current0FE register

Current110 register

Current132 register

Current154 register

Current176 register

Current198 register

Current1BA register

Current1DC register

Current1FE register

0x12

0x13

0x14

0x15

0x16

0x17

0x18

0x19

0x1A

0x1B

0x1C

0x1D

0x1E

0x1F

Segment 5

Segment 4

Segment 7

Segment 9

Segment 6

Segment 8

Segment 11

Segment 13

Segment 15

Segment 17

Segment 19

Segment 21

Segment 23

Segment 25

Segment 27

Segment 29

Segment 31

Segment 10

Segment 12

Segment 14

Segment 16

Segment 18

Segment 20

Segment 22

Segment 24

Segment 26

Segment 28

Segment 30

MAX956

Table 13. Even Individual Segment Current Format

SEGMENT

LED DRIVE

FRACTION

CONSTANT

CURRENT WITH

ADDRESS

CODE (HEX)

D7

D6

D5

D4

D3

D2

D1

D0

HEX CODE

R

= 39kΩ (mA)

ISET

1/16

2/16

1.5

3

0x12 to 0x1F

0

1

0

1

0

1

0

1

0

1

0

1

0

1

0

1

0

1

0

1

0

1

0

1

0

1

0

1

0

1

0xX0

0xX1

0xX2

0xX3

0xX4

0xX5

0xX6

0xX7

0xX8

0xX9

0xXA

0xXB

0xXC

0xXD

0xXE

0xXF

3/16

4.5

6

4/16

5/16

7.5

9

6/16

7/16

10.5

12

See Table 14.

8/16

9/16

13.5

15

10/16

11/16

12/16

13/16

14/16

15/16

16/16

16.5

18

19.5

21

22.5

24

18 ______________________________________________________________________________________

2-Wire-Interfaced, 2.5V to 5.5V, 20-Port or

28-Port LED Display Driver and I/O Expander

MAX956

Table 14. Odd Individual Segment Current Format

SEGMENT

LED

ADDRESS

CODE (HEX)

CONSTANT

DRIVE

FRACTION

D7

D6

D5

D4

D3

D2

D1

D0

HEX CODE

CURRENT WITH

R

= 39kΩ (mA)

ISET

1/16

2/16

1.5

3

0x12 to 0x1F

0

1

0

1

0

1

0

1

0

1

0

1

0

1

0

1

0

1

0

1

0

1

0

1

0

1

0

1

0

1

0x0X

0x1X

0x2X

0x3X

0x4X

0x5X

0x6X

0x7X

0x8X

0x9X

0xAX

0xBX

0xCX

0xDX

0xEX

0xFX

3/16

4.5

6

4/16

5/16

7.5

9

6/16

7/16

10.5

12

See Table 13.

8/16

9/16

13.5

15

10/16

11/16

12/16

13/16

14/16

15/16

16/16

16.5

18

19.5

21

22.5

24

The recommended value of R

is 39kΩ.

ISET

Applications Information

The recommended value of R

allowed value, since it sets the display driver to the

maximum allowed segment current. R can be a

higher value to set the segment current to a lower maxi-

mum value where desired. The user must also ensure

that the maximum current specifications of the LEDs

connected to the driver are not exceeded.

is the minimum

ISET

Driving Bicolor and Tricolor LEDs

Bicolor digits group a red and a green die together for

each display element, so that the element can be lit

red, green (or orange), depending on which die (or

both) is lit. The MAX6956 allows each segment’s cur-

rent to be set individually from 1/16th (minimum current

and LED intensity) to 16/16th (maximum current and

LED intensity), as well as off (zero current). Thus, a

bicolor (red-green) segment pair can be set to 289

color/intensity combinations. A discrete or CA tricolor

(red-green-yellow or red-green-blue) segment triad can

be set to 4913 color/intensity combinations.

ISET

The drive current for each segment can be controlled

through programming either the Global Current register

(Table 11) or Individual Segment Current registers

(Tables 12, 13, and 14), according to the setting of the

Current Control bit of the Configuration register (Table 9).

These registers select the LED’s constant-current drive

from 16 equal fractions of the maximum segment cur-

rent. The current difference between successive current

Power Dissipation Issues

Each MAX6956 port can sink a current of 24mA into an

LED with a 2.4V forward-voltage drop when operated

from a supply voltage of at least 3.0V. The minimum

voltage drop across the internal LED drivers is there-

fore (3.0V - 2.4V) = 0.6V. The MAX6956 can sink 28 x

24mA = 672mA when all outputs are operating as LED

steps, I , is therefore determined by the formula:

STEP

I

= I

/ 16

STEP

SEG

If I

= 24mA, then I

= 24mA / 16 = 1.5mA.

SEG

STEP

______________________________________________________________________________________ 19

2-Wire-Interfaced, 2.5V to 5.5V, 20-Port or

28-Port LED Display Driver and I/O Expander

GPIO INPUT

GPIO IN

CONDITIONING

GPIO/PORT

GPIO/PORT OUT

OUTPUT LATCH

INT STATUS STORED AS MSB OF MASK REGISTER

P31

MAX956

CLOCK PULSE AFTER EACH READ ACCESS TO MASK REGISTER

R

S

INT

OUTPUT LATCH

CONFIGURATION REGISTER M BIT = 1

GPIO IN

GPIO INPUT

D

Q

CONDITIONING

P30

P29

GPIO/PORT OUT

MASK REGISTER BIT 6

MASK REGISTER BIT 5

GPIO/PORT OUTPUT LATCH

GPIO IN

GPIO INPUT

CONDITIONING

GPIO/PORT OUT

GPIO/PORT OUTPUT LATCH

GPIO IN

GPIO INPUT

CONDITIONING

D

Q

P28

P27

GPIO/PORT OUT

MASK REGISTER BIT 4

GPIO/PORT OUTPUT LATCH

GPIO IN

GPIO INPUT

CONDITIONING

OR

MASK REGISTER BIT 3

GPIO/PORT OUT

GPIO/PORT OUTPUT LATCH

GPIO IN

GPIO INPUT

CONDITIONING

D

Q

P26

P25

GPIO/PORT OUT

MASK REGISTER BIT 2

MASK REGISTER BIT 1

GPIO/PORT OUTPUT LATCH

GPIO IN

GPIO INPUT

CONDITIONING

GPIO/PORT OUT

GPIO/PORT OUTPUT LATCH

GPIO IN

GPIO INPUT

CONDITIONING

D

Q

P24

GPIO/PORT OUT

MASK REGISTER LSB

GPIO/PORT OUTPUT LATCH

CLOCK PULSE WHEN WRITING CONFIGURATION REGISTER WITH M BIT SET

Figure 11. Maskable GPIO Ports P24 Through P31

20 ______________________________________________________________________________________

2-Wire-Interfaced, 2.5V to 5.5V, 20-Port or

28-Port LED Display Driver and I/O Expander

MAX956

Table 15. Transition Detection Mask Register

REGISTER

ADDRESS

(HEX)

REGISTER DATA

READ/

WRITE

FUNCTION

D7

D6

D5

D4

D3

D2

D1

D0

Port

30

mask

Port

29

mask

Port

28

mask

Port

27

mask

Port

26

mask

Port

25

mask

Port

24

mask

Read

Write

INT Status*

Unchanged

Mask

Register

0x06

*INT is automatically cleared after it is read.

Table 16. Display Test Register

REGISTER DATA

ADDRESS CODE

(HEX)

MODE

D7

X

D6

X

D5

X

D4

X

D3

X

D2

X

D1

X

D0

0

Normal Operation

Display Test Mode

0x07

X

1

X = Don’t care bit

segment drivers at full current. On a 3.3V supply, a

MAX6956 dissipates (3.3V - 2.4V) ^ꢀ672mA = 0.6W

when driving 28 of these 2.4V forward-voltage drop

LEDs at full current. This dissipation is within the ratings

of the 36-pin SSOP package with an ambient tempera-

ture up to +98°C. If a higher supply voltage is used or

the LEDs used have a lower forward-voltage drop than

2.4V, the MAX6956 absorbs a higher voltage, and the

MAX6956’s power dissipation increases.

Low-Voltage Operation

The MAX6956 operates down to 2V supply voltage

(although the sourcing and sinking currents are not guar-

anteed), providing that the MAX6956 is powered up ini-

tially to at least 2.5V to trigger the device’s internal reset.

Serial Interface Latency

When a MAX6956 register is written through the I²C inter-

face, the register is updated on the rising edge of SCL

during the data byte’s acknowledge bit (Figure 5). The

delay from the rising edge of SCL to the internal register

being updated can range from 50ns to 350ns.

If the application requires high drive current and high

supply voltage, consider adding a series resistor to

each LED to drop excessive drive voltage off-chip. For

example, consider the requirement that the MAX6956

must drive LEDs with a 2.0V to 2.4V specified forward-

voltage drop, from an input supply range is 5V 5ꢀ

with a maximum LED current of 20mA. Minimum input

supply voltage is 4.75V. Maximum LED series resistor

value is (4.75V - 2.4V - 0.6V)/0.020A = 87.5Ω. We

choose 82Ω 2ꢀ. Worst-case resistor dissipation is at

maximum toleranced resistance, i.e., (0.020A)²^ꢀ(82Ω

^ꢀ1.02) = 34mW. The maximum MAX6956 dissipation

per LED is at maximum input supply voltage, minimum

toleranced resistance, minimum toleranced LED for-

ward-voltage drop, i.e., 0.020 x (5.25V - 2.0V - (0.020A

^ꢀ82Ω x 0.98)) = 32.86mW. Worst-case MAX6956 dissi-

pation is 920mW driving all 28 LEDs at 20mA full cur-

rent at once, which meets the 941mW dissipation

ratings of the 36-pin SSOP package.

PC Board Layout Considerations

Ensure that all of the MAX6956 GND connections are

used. A ground plane is not necessary, but may be useful

to reduce supply impedance if the MAX6956 outputs are

to be heavily loaded. Keep the track length from the ISET

resistor as short as possible, and take the

GND end of the resistor either to the ground plane or

directly to the GND pins.

pin to the R

ISET

Power-Supply Considerations

The MAX6956 operates with power-supply voltages of

2.5V to 5.5V. Bypass the power supply to GND with a

0.047µF capacitor as close to the device as possible.

Add a 1µF capacitor if the MAX6956 is far away from

the board’s input bulk decoupling capacitor.

______________________________________________________________________________________ 21

2-Wire-Interfaced, 2.5V to 5.5V, 20-Port or

28-Port LED Display Driver and I/O Expander

Typical Operating Circuit

3V

36

32

30

28

26

5

V+

P4

P5

a1

a2

b

LED1

U1

47nF

3

2

1

GND

ISET

P6

MAX6956AAX

P7

c

P8

d1

d2

e

7

39kΩ

P9

MAX956

9

P10

P11

P12

P13

P14

P15

P16

P17

P18

P19

P20

P21

P22

P23

35

4

11

6

AD1

AD0

SDA

SCL

f

g1

g2

h

33

34

8

DATA

10

12

13

14

15

16

17

18

19

20

CLOCK

i

31

29

27

25

24

23

22

21

P31

P30

P29

P28

P27

P26

P25

P24

j

k

l

m

dp

ca

a1

a2

b

LED2

c

d1

d2

e

f

g1

g2

h

i

3V

j

k

32

30

36

P4

P5

V+

l

U2

47nF

m

dp

ca

28

26

5

3

2

1

P6

GND

ISET

MAX6956AAX

P7

P8

7

39kΩ

P9

9

P10

P11

P12

P13

P14

P15

P16

P17

P18

P19

P20

P21

P22

P23

a1

a2

b

LED3

35

4

11

6

AD1

AD0

SDA

SCL

33

34

8

c

10

12

13

14

15

16

17

18

19

20

d1

d2

e

31

29

27

25

24

23

22

21

P31

P30

P29

P28

P27

P26

P25

P24

IRQ OUT

f

g1

g2

h

i

1

2

j

k

l

m

dp

ca

SW1 SW2

SW3

22 ______________________________________________________________________________________

2-Wire-Interfaced, 2.5V to 5.5V, 20-Port or

28-Port LED Display Driver and I/O Expander

MAX956

Pin Configurations (continued)

TOP VIEW

ISET

GND

AD0

P8

1

2

3

4

5

6

7

8

9

36 V+

35 AD1

34 SCL

33 SDA

32 P4

MAX6956

P8

P12

P9

1

2

30

29

28

27

26

25

24

23

22

21

P4

P12

P9

31 P31

30 P5

P31

P5

3

P13

P10

P30

29

P13

P10

P14

P11

P15

P16

P17

4

P30

P6

5

28 P6

MAX6956

6

P29

P7

P14 10

P11 11

P15 12

P16 13

P17 14

P18 15

P19 16

P20 17

P21 18

27 P29

26 P7

7

P28

P27

P26

8

25 P28

24 P27

23 P26

22 P25

21 P24

20 P23

19 P22

9

10

TQFN

SSOP

Package Information

Chip Information

For the latest package outline information and land patterns, go

to www.maxim-ic.com/packages. Note that a “+”, “#”, or “-” in

the package code indicates RoHS status only. Package draw-

ings may show a different suffix character, but the drawing per-

tains to the package regardless of RoHS status.

PROCESS: CMOS

PACKAGE

TYPE

PACKAGE

CODE

OUTLINE

NO.

LAND

PATTERN NO.

28 DIP

28 SSOP

N28+2

A28+1

21-0043

21-0056

21-0040

21-0141

—

90-0095

90-0098

90-0055

36 SSOP

A36+4

40 Thin QFN-EP

T4066+5

______________________________________________________________________________________ 23

2-Wire-Interfaced, 2.5V to 5.5V, 20-Port or

28-Port LED Display Driver and I/O Expander

Revision History

REVISION

NUMBER

REVISION

DATE

PAGES

CHANGED

DESCRIPTION

2

3

4

11/03

3/09

6/10

—

1, 2, 5, 23

1

Added exposed pad information and updated packaging information

Added lead-free and automotive qualified parts to Ordering Information

MAX956

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.

24 ____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600

Maxim is a registered trademark of Maxim Integrated Products, Inc.


型号：	MAX6956ANI+
厂家：	MAXIM INTEGRATED PRODUCTS
描述：	Interface Circuit, CMOS, PDIP28, ROHS COMPLIANT, PLASTIC, DIP-28 光电二极管
文件：	总24页 (文件大小：249K)
中文：	中文翻译
下载：	下载PDF数据表文档文件

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