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MAX6979

16-Port, 5.5V Constant-Current LED Driver with LED Fault Detection and Watchdog

Maxim Integrated 

19-3703; Rev 1; 12/10

16-Port, 5.5V Constant-Current LED Driver with

LED Fault Detection and Watchdog

General Description

The MAX6979 serial-interfaced LED driver provides 16

open-drain, constant-current-sinking LED driver outputs

rated at 5.5V. The MAX6979 operates from a 3V to 5.5V

supply. The MAX6979 supply and the LEDs’ supply can

power up in any order. The constant-current outputs

are programmed together to up to 55mA using a single

external resistor. The MAX6979 operates with a 25Mb,

industry-standard, 4-wire serial interface.

The MAX6979 includes circuitry that automatically

detects open-circuit LEDs. Fault status is loaded into the

serial-interface shift register when LE goes high and is

automatically shifted out on DOUT when the next data

transmission is shifted in.

The MAX6979 includes a fail-safe feature for safety-

related applications, which blanks the display if the ser-

ial interface fails. If the serial interface becomes

inactive for more than 1s, all driver output latches are

automatically cleared. This turns off all LEDs connected

to the outputs. The shift register data is not disturbed.

The outputs remain off until the driver output latches are

updated with data turning them on, so recovery is auto-

matic if the transmission failure is temporary. The

watchdog function requires no software change to the

application driving the MAX6979.

The MAX6979 uses the industry-standard shift-register-

plus-latch-type serial interface. The driver accepts data

shifted into a 16-bit shift register using data input DIN

and clock input CLK. Input data appears at the output

DOUT 16 clock cycles later to allow cascading of multi-

ple MAX6979s. The latch-enable input, LE, loads the 16

bits of shift-register data into a 16-bit output latch to set

which LEDs are on and which are off. The output-

enable input, OE, gates all 16 outputs on and off, and is

fast enough to be used as a PWM input for LED intensi-

ty control.

The MAX6979 is one of a family of 12 shift-register-plus-

latch-type LED drivers. The family includes 8-port and

16-port types, with 5.5V- or 36V-rated LED outputs, with

and without open-circuit LED detection and watchdog.

All versions operate from a 3V to 5.5V supply, and are

specified over the -40°C to +125°C temperature range.

Variable Message Signs

Marquee Displays

Point-of-Order Signs

Traffic Signs

Gaming Features

Architectural Lighting

Applications

Features

o 25Mb Industry-Standard, 4-Wire Serial Interface at 5V

o 3V to 5.5V Logic Supply

o 16 Constant-Current LED Outputs Rated at 5.5V

o Up to 55mA Continuous Current per Output

o Output Current Programmed by Single Resistor

o 3% Current Matching Between Outputs

o 6% Current Matching Between ICs

o Watchdog Clears Display if Interface Fails

o Reports Open-Circuit LED Faults

o High-Dissipation, 24-Pin Packages

o -40°C to +125°C Temperature Range

Ordering Information

PART

TEMP RANGE

PIN-PACKAGE

MAX6979AUG+

-40°C to +125°C 24 TSSOP

MAX6979APG+

-40°C to +125°C 24 PDIP

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

Typical Application Circuit and Selector Guide appear at

end of data sheet.

Pin Configuration

TOP VIEW

+

GND 1

DIN 2

CLK 3

LE 4

OUT0 5

OUT1 6

OUT2 7

OUT3 8

MAX6979AUG

MAX6979APG

OUT4 9

OUT5 10

OUT6 11

OUT7 12

24 V+

23 SET

22 DOUT

21 OE

20 OUT15

19 OUT14

18 OUT13

17 OUT12

16 OUT11

15 OUT10

14 OUT9

13 OUT8

TSSOP/PDIP

________________________________________________________________ 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.

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