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PCU9955TW: 16-channel UFm I²C-bus 57 mA constant current LED driver

The PCU9955 is an Ultra-Fast mode (UFm) I²C-bus controlled 16-channel constant current LED driver optimized for dimming and blinking 57 mA Red/Green/Blue/Amber (RGBA) LEDs in amusement products. Each LEDn 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 99.6 % 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 LEDn 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 PCU9955 operates with a supply voltage range of 3 V to 5.5 V and the constant current sink LEDn outputs allow up to 40 V for the LED supply. The output current is adjustable with an 8-bit linear DAC from 225 µA to 57 mA.

This device has built-in open, short load and overtemperature detection circuitry. The thermal shutdown feature protects the device when internal junction temperature exceeds the limit allowed for the process.

The PCU9955 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 UFm I²C-bus slave devices operate in receive-only mode. That is, only I²C writes to PCU9955 are supported. As such, there are no status registers in PCU9955. The PCU9955 allows significantly higher data transfer rate compared to the Fast-mode Plus versions (PCA9952/55).

Software programmable LED Group and three Sub Call I²C-bus addresses allow all or defined groups of PCU9955 devices to respond to a common I²C-bus address, allowing for example, all red LEDs to be turned on or off at the same time, thus minimizing I²C-bus commands. On power-up, PCU9955 will have a unique Sub Call address to identify it as a 16-channel LED driver. This allows mixing of devices with different channel widths. Four hardware address pins on PCU9955 allow up to 16 devices on the same bus.

The Software Reset (SWRST) function allows the master to perform a reset of the PCU9955 through the I²C-bus, identical to the Power-On Reset (POR) that initializes the registers 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 same condition.

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