描述 Description

The PCU9956A is an Ultra Fast-mode (UFm) I2C-bus controlled 24-channel constantcurrent LED driver optimized for dimming and blinking 57 mA Red/Green/Blue/Amber(RGBA) LEDs in amusement products. Each LED output has its own 8-bit resolution(256 steps) fixed frequency individual PWM controller that operates at 31.25 kHz with aduty cycle that is adjustable from 0 % to 99.6 % to allow the LED to be set to a specificbrightness value. An additional 8-bit resolution (256 steps) group PWM controller has botha fixed frequency of 122 Hz and an adjustable frequency between 15 Hz to once every16.8 seconds with a duty cycle that is adjustable from 0 % to 99.6 % that is used to eitherdim or blink all LEDs with the same value.
Each LED output can be off, on (no PWM control), set at its individual PWM controllervalue or at both individual and group PWM controller values. The PCU9956A operateswith a supply voltage range of 3 V to 5.5 V and the constant current sink LED outputsallow up to 20 V for the LED supply. The output peak current is adjustable with an 8-bitlinear DAC from 225 μA to 57 mA.
A thermal shutdown feature protects the device when internal junction temperatureexceeds the limit allowed for the process.
The PCU9956A device is the first LED controller device in a new Ultra Fast-mode (UFm)I2C-bus family. UFm I2C-bus devices offer higher frequency (up to 5 MHz). the UFmI2C-bus slave devices operate in receive-only mode. That is, only I2C writes to PCU9956Aare supported. As such, there are no status registers in PCU9956A. The PCU9956Aallows significantly higher data transfer rate compared to the Fast-mode Plus version(PCA9956A).
The active LOW output enable input pin (OE) blinks all the LED outputs and can be usedto externally PWM the outputs, which is useful when multiple devices need to be dimmedor blinked together without using software control.
Software programmable LED Group and three Sub Call I2C-bus addresses allow all ordefined groups of PCU9956A devices to respond to a common I2C-bus address, allowingfor example, all red LEDs to be turned on or off at the same time or marquee chasingeffect, thus minimizing I2C-bus commands. On power-up, PCU9956A will have a uniqueSub Call address to identify it as a 24-channel LED driver. This allows mixing of deviceswith different channel widths. Three hardware address pins on PCU9956A allow up to125 devices on the same bus.
The Software Reset (SWRST) function allows the master to perform a reset of thePCU9956A through the I2C-bus, identical to the Power-On Reset (POR) that initializes theregisters to their default state causing the output current switches to be OFF (LED off).This allows an easy and quick way to reconfigure all device registers to the samecondition.

特性 Features

24 LED drivers. Each output programmable at:Off
On
Programmable LED brightness
Programmable group dimming/blinking mixed with individual LED brightness
Programmable LED output delay to reduce EMI and surge currents

24 constant current output channels can sink up to 57 mA, tolerate up to 20 V whenOFF
Output current adjusted through an external resistor (REXT input)
Output current accuracy±4 % between output channels
±6 % between PCU9956A devices

Thermal shut-down for overtemperature
5 MHz Ultra Fast-mode I2C-bus interface
256-step (8-bit) linear programmable brightness per LED output varying from fully off(default) to maximum brightness using a 31.25 kHz PWM signal
256-step group brightness control allows general dimming (using a 122 Hz PWMsignal) from fully off to maximum brightness (default)
256-step group blinking with frequency programmable from 15 Hz to 16.8 s and dutycycle from 0 % to 99.6 %
Output state change programmable on the Acknowledge (bit 9, this bit is always setto 1 by I2C-bus master) or the STOP Command to update outputs byte-by-byte or all atthe same time (default to ‘Change on STOP’).
Active LOW Output Enable (OE) input pin allows for hardware blinking and dimming ofthe LEDs
Three quinary hardware address pins allow 125 PCU9956A devices to be connectedto the same I2C-bus and to be individually programmed
4 software programmable I2C-bus addresses (one LED Group Call address and threeLED Sub Call addresses) allow groups of devices to be addressed at the same time inany combination (for example, one register used for ‘All Call’ so that all thePCU9956As on the I2C-bus can be addressed at the same time and the secondregister used for three different addresses so that 1?3 of all devices on the bus can beaddressed at the same time in a group). Software enable and disable for eachprogrammable I2C-bus address.
Unique power-up default Sub Call address allows mixing of devices with differentchannel widths
Software Reset feature (SWRST Call) allows the device to be reset through theI2C-bus
8 MHz internal oscillator requires no external components
Internal power-on reset
Noise filter on USDA/USCL inputs
No glitch on LED outputs on power-up
Low standby current
Operating power supply voltage (VDD) range of 3 V to 5.5 V
5.5 V tolerant inputs on non-LED pins
?40 °C to +85 °C operation
ESD protection exceeds 3000 V HBM per JESD22-A114
Latch-up testing is done to JEDEC Standard JESD78 which exceeds 100 mA
Packages offered: HTSSOP38

應(yīng)用 Application

Amusement products
RGB or RGBA LED drivers
LED status information
LED displays
LCD backlights
Keypad backlights for cellular phones or handheld devices