PCA9957 Constant Current LED Driver

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            PCA9957 Constant Current LED Driver
                    NXP's flexible SPI LED controller is optimized for full-color RGB status and fun light displays
    

Image of NXP's PCA9957 Constant Current LED Driver NXP's PCA9957 is a daisy-chain, SPI-compatible, four-wire, serial bus controlled, twenty-four-channel, constant current LED driver that is optimized for dimming and blinking 32 mA red/green/blue/amber (RGBA) LEDs.

Each LED output has an 8-bit resolution (256 steps), fixed-frequency, individual PWM controller that operates at 31.25 kHz with a duty cycle that is adjustable from 0% to 100% to allow the LED to be set to a specific brightness value. An additional 8-bit resolution (256 steps) group PWM controller has both a fixed frequency of 122 Hz and an adjustable frequency between 15 Hz to once every 16.8 seconds with a duty cycle that is adjustable from 0% to 99.6% that is used to either dim or blink the LEDs with the same value.

Each LED output can be OFF, ON (no PWM control), set at its individual PWM controller value, or set at both individual and group PWM controller values. The PCA9957 operates with a supply voltage range of 2.7 V to 5.5 V and the constant current sink LED outputs allow up to 5 V for the LED supply. The output peak current is adjustable with an 8-bit linear DAC from 125 μA to 31.875 mA with REXT = 2 kΩ.

Features

Gradation control for all channels
- Each channel can be assigned to one of six gradation control groups
- Programmable gradation time and rate for ramp-up and/or ramp-down operations
- Programmable step time (6-bit) from 0.5 ms (minimum) to 512 ms (maximum)
- Programmable hold-on time after ramp-up and hold-off time after ramp-down (3-bit) from 0 s to 6 s
- Programmable final ramp-up and hold-on current
- Programmable brightness current output adjustment with either linear or exponential curve
24 constant current output channels can sink up to 32 mA, and tolerate up to 5.5 V when OFF
Output current accuracy
- ±6.5% absolute accuracy with 30 mA output current
- Maximum of ±4% channel-to-channel variation
- Maximum of ±6 % device-to-device variation
Open/short-load/overtemperature detection mode to detect individual LED errors
Four-wire serial bus interface with 10 MHz data clock rate
256-step (8-bit) linear programmable brightness per LED output varying from fully OFF (default) to fully ON (maximum brightness) using a 31.25 kHz PWM signal
256-step group brightness control allows general dimming (using a 122 Hz PWM signal) from fully OFF to maximum brightness (default)
256-step group blinking with frequency programmable from 15 Hz to 16.8 s and duty cycle from 0% to 99.6%

Twenty-four LED drivers, each output programmable at the following:
- OFF
- ON
- 8-bits programmable LED brightness
- 8-bits programmable group dimming/blinking mixed with individual LED brightness
- Programmable LED output delay to reduce EMI and surge currents
Active LOW output-enable (OE) input pin allows for hardware blinking and dimming of the LEDs
8 MHz internal oscillator requires no external components
Internal power-on reset
No glitch on LED outputs on power-up
Low standby current
Operating power supply voltage (V_DD) range of 2.7 V to 5.5 V
5.5 V tolerant inputs on non-LED pins
-40°C to +85°C operation
Latch-up performance exceeds 100 mA per JESD 78, Class II
ESD protection exceeds the following:
- 2 kV human-body model (A114-A)
- 1 kV charged-device model (C101)
Offered in HVQFN40 package

Applications

Fade-in and fade-out for breath-light controls
LCD backlights
LED displays

LED status information
RGB or RGBA LED drivers