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

LED Fault Detection, and Watchdog Timer


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 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 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 multiple 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-bar, gates all 16 outputs on and off, and is fast enough to be used as a PWM input for LED intensity 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.

MAX6979: Typical Application Circuit MAX6979: Typical Application Circuit Enlarge+

Key Features

  • 25Mb Industry-Standard, 4-Wire Serial Interface at 5V
  • 3V to 5.5V Logic Supply
  • 16 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
  • Watchdog Clears Display if Interface Fails
  • Reports Open-Circuit LED Faults
  • High-Dissipation, 24-Pin Packages
  • -40°C to +125°C Temperature Range
  • Applications/Uses

    • Architectural Lighting
    • Gaming Features
    • Marquee Displays
    • Point-of-Order Signs
    • Traffic Signs
    • Variable Message Signs
    Part Number LCD or LED Digits or Char. Output Format Display Type Interface Segment Blinking VSUPPLY
    Package/Pins Budgetary
    min max See Notes
    MAX6979  LED 16-Segment Any digit type Common Anode Serial 4-Wire 25Mbit No 3 5.5
    $4.03 @1k
    See All Display Drivers (48)
    Pricing Notes:
    This pricing is BUDGETARY, for comparing similar parts. Prices are in U.S. dollars and subject to change. Quantity pricing may vary substantially and international prices may differ due to local duties, taxes, fees, and exchange rates. For volume-specific and version-specific prices and delivery, please see the price and availability page or contact an authorized distributor.

    Quality and Environmental Data

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