PCA9922 - Constant Current LED Driver for Video Walls

The NXP PCA9922 is a single-chip solution for LED display driving that is optimized for LED video walls, video billboards, and digital signage.

 

The PCA9922 integrates a shift register, accompanying data latches, eight NPN constant-current sink drivers, and an LED output error detection circuit. The shift register and latches allow direct interfacing with microprocessor-based systems. With a 5 V logic supply, typical serial data-input rates can reach up to 25 MHz. A serial data output permits cascading between multiple devices in applications requiring additional drive lines. Open LED connections can be detected and signaled back to the host microprocessor through the SERIAL DATA OUT pin.

 

The brightness of an LED sign is proportional to the current flowing through the LEDs. The PCA9922 is designed specifically to address the variables that affect the brightness consistency of an LED sign. Selection of the Rext (current setting resistor) value determines the maximum current to be maintained by the outputs.

Features

  • 8 LED driver outputs with low-side, constant-current control
  • 25 MHz serial interface
  • Maximum current from 15 to 60 mA for all 8 output channels (set by external resistor)
  • Constant current matching at 25 °C, VDD = 5.0 V :
    • Bit-to-bit: ±6 %
    • Chip-to-chip: ±10 %
  • Gradual turn-on/turn-off output to limit EMI
  • Error detection mode for line open, output short to ground, LED open, and LED short
  • Operating voltage: 3.3...5.5 V
  • ESD protection exceeds 2000 V HBM and 1000 V CDM
  • Package options: DIP16, TSSOP16 and HVQFN20

Key Applications

  • Full-color, multi-color, and monochrome LED signs
  • LED billboard displays
  • Colorful LED video walls
  • Traffic display signs
  • Transportation and commercial LED signs
  • Scrolling message boards

Typical Multi-Device Architecture

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