NXP – 16-channel LED driver dims and blinks groups of RGBA LEDs

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NXP Semiconductors’ PCA9745B is a 16-channel constant-current LED driver suitable for dimming and blinking 57mA Red/Green/Blue/Amber (RGBA) LEDs in status information and displays and in amusement products.

Each LED output has its own 8-bit fixed- frequency PWM controller which operates at 31.25kHz with a duty cycle which is adjustable from 0% to 100% for precise control of the LED’s brightness.

An additional 8-bit group PWM controller has both a fixed frequency of 122Hz and an adjustable frequency between 15Hz to once every 16.8s with a duty cycle that is adjustable from 0% to 99.6%. This group PWM controller may be used to either dim or blink all LEDs at the same brightness.

Each LED output can be off on with no PWM control set at its individual PWM value or at both individual and group PWM controller values.

The PCA9745B’s sink LED outputs maintain an LED supply of up to 20V. The peak output current is adjustable with an 8-bit linear DAC from 225ΩA to 57mA.

Gradation control for all current sources is achieved via a four-wire serial bus interface. This allows the user to ramp the current automatically without the intervention of a microcontroller.

The PCA9745B has built-in open short-load and over-temperature detection circuitry. In addition a thermal shut-down feature protects the device when the internal junction temperature exceeds a set threshold.

FEATURES

  • Output current adjusted through an external resistor
  • Output current accuracy:
    - ±4% between output channels
    - ±6% between PCA9745B devices
  • 8MHz internal oscillator requires no external components
  • Internal power-on reset
  • Low stand-by current
  • ESD protection exceeds 4kV on the human body model according to JESD22-A114

APPLICATIONS

  • Amusement products
  • LED status information and displays
  • LCD backlights
  • Keypad backlights
  • Fade-in and fade-out for breathlight control

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