MAX6979 19-3703 Rev 1 12/10 16-Port, 5.5V Constant-Current LED Driver with LED Fault Detection and Watchdog General Description Features 25Mb Industry-Standard, 4-Wire Serial Interface at 5V The MAX6979 serial-interfaced LED driver provides 16 open-drain, constant-current-sinking LED driver outputs 3V to 5.5V Logic Supply rated at 5.5V. The MAX6979 operates from a 3V to 5.5V 16 Constant-Current LED Outputs Rated at 5.5V supply. The MAX6979 supply and the LEDs supply can Up to 55mA Continuous Current per Output power up in any order. The constant-current outputs are programmed together to up to 55mA using a single Output Current Programmed by Single Resistor external resistor. The MAX6979 operates with a 25Mb, 3% Current Matching Between Outputs industry-standard, 4-wire serial interface. 6% Current Matching Between ICs The MAX6979 includes circuitry that automatically Watchdog Clears Display if Interface Fails detects open-circuit LEDs. Fault status is loaded into the Reports Open-Circuit LED Faults serial-interface shift register when LE goes high and is automatically shifted out on DOUT when the next data High-Dissipation, 24-Pin Packages transmission is shifted in. -40C to +125C Temperature Range 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 Ordering Information inactive for more than 1s, all driver output latches are automatically cleared. This turns off all LEDs connected PART TEMP RANGE PIN-PACKAGE to the outputs. The shift register data is not disturbed. MAX6979AUG+ -40C to +125C 24 TSSOP The outputs remain off until the driver output latches are MAX6979APG+ -40C to +125C 24 PDIP updated with data turning them on, so recovery is auto- matic if the transmission failure is temporary. The +Denotes a lead(Pb)-free/RoHS-compliant package. watchdog function requires no software change to the application driving the MAX6979. Typical Application Circuit and Selector Guide appear at The MAX6979 uses the industry-standard shift-register- end of data sheet. 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 Pin Configuration 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 TOP VIEW which LEDs are on and which are off. The output- + enable input, OE, gates all 16 outputs on and off, and is GND 1 24 V+ fast enough to be used as a PWM input for LED intensi- DIN 2 23 SET ty control. CLK 3 22 DOUT The MAX6979 is one of a family of 12 shift-register-plus- latch-type LED drivers. The family includes 8-port and LE 4 21 OE 16-port types, with 5.5V- or 36V-rated LED outputs, with OUT0 5 20 OUT15 and without open-circuit LED detection and watchdog. OUT1 6 19 OUT14 All versions operate from a 3V to 5.5V supply, and are MAX6979AUG specified over the -40C to +125C temperature range. OUT2 7 18 OUT13 MAX6979APG OUT3 8 17 OUT12 Applications OUT4 9 16 OUT11 Variable Message Signs OUT5 10 15 OUT10 Marquee Displays OUT6 11 14 OUT9 Point-of-Order Signs OUT7 12 13 OUT8 Traffic Signs Gaming Features TSSOP/PDIP Architectural Lighting Maxim Integrated Products 1 For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642, or visit Maxims website at www.maxim-ic.com.16-Port, 5.5V Constant-Current LED Driver with LED Fault Detection and Watchdog ABSOLUTE MAXIMUM RATINGS Voltage (with respect to GND) Operating Temperature Range .........................-40C to +125C V+.............................................................................-0.3V to +6V Junction Temperature......................................................+150C OUT ........................................................................-0.3V to +6V Storage Temperature Range .............................-65C to +150C DIN, CLK, LE, OE, SE ..................................-0.3V to (V+ + 0.3V) Lead Temperature (soldering, 10s) .................................+300C DOUT Current.................................................................10mA Soldering Temperature (reflow) OUT Sink Current ..............................................................60mA Lead(Pb)-free packages..............................................+260C Total GND Current ............................................................960mA Packages containing lead(Pb).....................................+240C Continuous Power Dissipation (T = +70C) A 24-Pin PDIP (derate 13.3mW/C over +70C)............1067mW 24-Pin TSSOP (derate 12.2mW/C over +70C) .........975mW 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+ = 3V to 5.5V, T = T to T , unless otherwise noted. Typical values are at V+ = 5V, T = +25C.) A MIN MAX A (Note 1) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS Operating Supply Voltage V+ 3.0 5.5 V Output Voltage V 5.5 V OUT Standby Current All logic inputs at V+ or GND, DOUT (Interface Idle, All Output Ports I 5.7 8 mA + unloaded High Impedance, R = 360 ) SET Standby Current (Interface Running, All Output f = 5MHz, OE = V+, DIN and LE = V+ CLK I 6 8.5 mA + Ports High Impedance, or GND, DOUT unloaded R = 360 ) SET Supply Current All logic inputs at V+ or GND, (Interface Idle, All Output Ports I 18 25 mA + DOUT unloaded Active Low, R = 360 ) SET Input High Voltage 0.7 x V V IH DIN, CLK, LE, OE V+ Input Low Voltage 0.3 x V V IL DIN, CLK, LE, OE V+ Hysteresis Voltage V 0.8 V I DIN, CLK, LE, OE Input Leakage Current I , I -1 +1 A IH IL DIN, CLK, LE, OE V + Output High Voltage DOUT V I = 4mA V OH SOURCE - 0.5V Output Low Voltage V I = 4mA 0.5 V OL SINK V+ = 3V to 5.5V, V = 0.5V to 2.5V, OUT Output Current OUT I 37 50 61 mA OUT R = 360 SET Output Leakage Current OUT I OE = V+, V = V+ 1 A LEAK OUT Watchdog Timeout t 0.1 1 2.5 s WD 2 MAX6979