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8-Port, 5.5V Constant-Current LED Driver with LED Fault Detection

Product Details

Key Features

Simplified Block Diagram

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Key Features

  • 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
  • Reports Open-Circuit LED Faults
  • -40°C to +125°C Temperature Range
  • Applications/Uses

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

    Description

    The MAX6977 serial-interfaced LED driver provides eight open-drain, constant-current sinking LED driver outputs rated at 5.5V. The MAX6977 operates from a 3V to 5.5V supply. The MAX6977 supply and the LEDs' supply may power up in any order. The constant-current outputs are programmed together to up to 55mA using a single external resistor. The MAX6977 operates with a 25Mb, industry-standard, 4-wire serial interface.

    The MAX6977 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 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 DOUT eight clock cycles later to allow cascading of multiple MAX6977s. 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 outputenable input OE-bar gates all eight outputs on and off, and is fast enough to be used as a PWM input for LED intensity control.

    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 MAX6977 is one of a family of 12 shift-register-pluslatch- 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.

    Simplified Block Diagram

    MAX6977: Typical Application Circuit MAX6977: Typical Application Circuit Zoom icon

    Technical Docs

    Support & Training

    Search our knowledge base for answers to your technical questions.

    Filtered Search

    Our dedicated team of Applications Engineers are also available to answer your technical questions. Visit our support portal .

    Sampling:
    Selecting the Sample button above will redirect to the third-party ADI Sample Site. The part selected will carry over to your cart on this site once logged in. Please create a new account there if you have never used the site before. Contact SampleSupport@analog.com with any questions regarding this Sample Site.