MAX6977 19-3554 Rev 2 7/05 8-Port, 5.5V Constant-Current LED Driver with LED Fault Detection General Description Features The MAX6977 serial-interfaced LED driver provides 25Mb Industry-Standard 4-Wire Serial Interface at 5V eight open-drain, constant-current sinking LED driver 3V to 5.5V Logic Supply outputs rated at 5.5V. The MAX6977 operates from a 3V to 5.5V supply. The MAX6977 supply and the LEDs 8 Constant-Current LED Outputs Rated at 5.5V supply may power up in any order. The constant-cur- Up to 55mA Continuous Current per Output rent outputs are programmed together to up to 55mA using a single external resistor. The MAX6977 operates Output Current Programmed by Single Resistor with a 25Mb, industry-standard, 4-wire serial interface. 3% Current Matching Between Outputs The MAX6977 includes circuitry that automatically detects open-circuit LEDs. Fault status is loaded into the 6% Current Matching Between ICs serial interface shift register when LE goes high, and is Reports Open-Circuit LED Faults automatically shifted out on DOUT when the next data transmission is shifted in. -40C to +125C Temperature Range The MAX6977 uses the industry-standard shift-register- plus-latch-type serial interface. The driver accepts data shifted into an 8-bit shift register using data input DIN and clock input CLK. Input data appears at the output Ordering Information DOUT eight clock cycles later to allow cascading of multiple MAX6977s. The latch-enable input LE loads PART TEMP RANGE PIN-PACKAGE the 8 bits of shift register data into an 8-bit output latch MAX6977AUE -40C to +125C 16 TSSOP-EP* to set which LEDs are on and which are off. The output- MAX6977APE -40C to +125C 16 PDIP enable input OE gates all eight outputs on and off, and is fast enough to be used as a PWM input for LED MAX6977AAE -40C to +125C 16 SSOP intensity control. *EP = Exposed pad. For safety-related applications requiring a watchdog timer, refer to the MAX6978 data sheet that includes a fail-safe feature that blanks the display if the serial inter- face becomes inactive for more than 1s. The MAX6977 is one of a family of 12 shift-register-plus- Typical Application Circuit and Selector Guide appear at latch-type LED drivers. The family includes 8-port and end of data sheet. 16-port types, with 5.5V- or 36V-rated LED outputs, with Pin Configuration and without open-circuit LED detection and watchdog. All versions operate from a 3V to 5.5V supply, and are specified over the -40C to +125C temperature range. TOP VIEW GND 1 16 V+ Applications DIN 2 15 SET Variable Message Signs CLK 3 14 DOUT Marquee Displays LE 4 MAX6977AUE 13 OE MAX6977APE Point-of-Order Signs OUT0 5 12 OUT7 MAX6977AAE Traffic Signs OUT1 6 11 OUT6 Gaming Features OUT2 7 10 OUT5 Architectural Lighting OUT3 9 OUT4 8 TSSOP/PDIP/SSOP Maxim Integrated Products 1 For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct at 1-888-629-4642, or visit Maxims website at www.maxim-ic.com.8-Port, 5.5V Constant-Current LED Driver with LED Fault Detection ABSOLUTE MAXIMUM RATINGS Voltage (with respect to GND) Continuous Power Dissipation (T = +70C) A V+ ............................................................................-0.3V to +6V 16-Pin SSOP (derate 7.1mW/C above +70C) ............571mW OUT .......................................................................-0.3V to +6V 16-Pin PDIP (derate 10.5mW/C above +70C)............842mW DIN, CLK, LE, OE, SET ................................-0.3V to (V+ + 0.3V) 16-Pin TSSOP (derate 21.3mW/C above +70C) ......1702mW DOUT Current ..................................................................10mA Operating Temperature Range .........................-40C to +125C OUT Sink Current .............................................................60mA Junction Temperature......................................................+150C Total GND Current ...........................................................480mA Storage Temperature Range .............................-65C to +150C Lead Temperature (soldering, 10s) .................................+300C 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 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 4.5 5.6 mA + unloaded High Impedance, R = 360 ) SET Standby Current (Interface Running, All Output f = 5MHz, OE = V+, DIN and LE = V+ CLK I 4.7 6 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 10 25 mA + DOUT unloaded Active Low, R = 360 ) SET Input High Voltage V 0.7 V+ V IH DIN, CLK, LE, OE Input Low Voltage V 0.3 V+ V IL DIN, CLK, LE, OE 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+ = 4.5V to 5.5V, V = 0.8V to 2.5V, OUT Output Current OUT I 42 50 56 mA OUT R = 360 SET Output Leakage Current OUT I OE = V+, V = V+ 1 A LEAK OUT Watchdog Timeout t 1s WD 2 MAX6977