8-Port, 5.5V Constant-Current LED Driver

The MAX6968 serial-interfaced LED driver provides eight open-drain, constant-current sinking LED driver outputs rated at 5.5V. The MAX6968 operates from a 3V to 5.5V supply. The MAX6968 supply and the LEDs' supply or supplies may power up in any order. The constant-current outputs are programmed together to up to 55mA using a single external resistor. The MAX6968 operates with a 25Mb, industry-standard, 4-wire serial interface.

The MAX6968 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 DOUT eight clock cycles later to allow cascading of multiple MAX6968s. The latch-enable input LE loads the 8 bits of shift register data into an 8-bit output latch to set which LEDs are on and which are off. The output-enable input active-low OE gates all eight outputs on and off, and is fast enough to be used as a PWM input for LED intensity control.

For applications requiring LED fault detection, refer to the MAX6977 data sheet that automatically detects open-circuit LEDs.

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 interface becomes inactive for more than 1s.

The MAX6968 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.

Applications

* Architectural Lighting * Gaming Features * Marquee Displays * Point-of-Order Signs * Traffic Signs * Variable Message Signs

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

* 3V to 5.5V Logic Supply

* 8 Constant-Current LED Outputs Rated at 5.5V

* Up to 55mA Continuous Current per Output

* Output Current Programmed by Single Resistor

* 3% Current Matching Between Outputs

* 6% Current Matching Between ICs

* -40°C to +125°C Temperature Range