PCA9957 24-channel SPI serial bus 32 mA/5.5 V constant current LED driver Rev. 2.1 22 October 2021 Product data sheet 1 General description The PCA9957 is a daisy-chain SPI-compatible 4-wire serial bus controlled 24-channel constant current LED driver optimized for dimming and blinking 32 mA Red/Green/Blue/ Amber (RGBA) LEDs. Each LED output has its own 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 all LEDs with the same value. Each LED output can be off, on (no PWM control), set at its individual PWM controller value or 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 A to 31.875 mA with REXT = 2 k. Gradation control for all current sources is achieved via the 4-wire serial bus interface and allows user to ramp current automatically without MCU intervention. 8-bit DACs are available to adjust brightness levels for each LED current source. There are six selectable gradation control groups and each group has four independent registers to control ramp-up and ramp-down rate, step time, hold ON/OFF time and final hold ON output current. Two gradation operation modes are available for each group: single shot mode (output pattern once) and continuous mode (output pattern repeat). Each channel can be set to either gradation mode or normal mode and assigned to any one of these six gradation control groups. This device has built-in open, short load and overtemperature detection circuitry. The error information from the corresponding register can be read via the 4-wire serial bus. Additionally, a thermal shutdown feature protects the device when internal junction temperature exceeds the limit allowed for the process. The PCA9957 device is designed to use 4-wire read/write serial bus with higher data clock frequency (up to 10 MHz). The active LOW output enable input pin (OE) blinks all the LED outputs and can be used to externally PWM the outputs, which is useful when multiple devices need to be dimmed or blinked together without using software control.NXP Semiconductors PCA9957 24-channel SPI serial bus 32 mA/5.5 V constant current LED driver 2 Features and benefits 24 LED drivers. Each output programmable at: 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 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, 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 adjusted through an external resistor (REXT input) Output current accuracy 6.5 % absolute accuracy with 30 mA output current Maximum 4 % channel to channel variation Maximum 6 % device to device variation Open/short load/overtemperature detection mode to detect individual LED errors 4-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 maximum brightness fully ON 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 % 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 LEDn outputs on power-up Low standby current Operating power supply voltage (V ) range of 2.7 V to 5.5 V DD 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 per JESD22: 2 kV Human-Body Model (A114-A) 1 kV Charged-Device Model (C101) Package offered: HVQFN40 PCA9957 All information provided in this document is subject to legal disclaimers. NXP B.V. 2021. All rights reserved. Product data sheet Rev. 2.1 22 October 2021 2 / 56