MAX6978

19-3578; Rev 1; 3/05 8-Port, 5.5V Constant-Current LED Driver with LED Fault Detection and Watchdog General Description The MAX6978 serial-interfaced LED driver provides eight open-drain, constant-current sinking LED driver outputs rated at 5.5V. The MAX6978 operates from a 3V to 5.5V supply. The MAX6978 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 MAX6978 operates with a 25Mb, industry-standard, 4-wire serial interface. The MAX6978 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 MAX6978 includes a fail-safe feature for safetyrelated applications, which blanks the display if the serial 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 automatic if the transmission failure is temporary. The www.DataSheet4U.com watchdog function requires no software change to the application driving the MAX6978. The MAX6978 uses the industry-standard shift-registerplus-latch-type serial interface. The driver accepts da...