PCA9531D,112

The PCA9531D,112 is a 8-bit I?C-bus and SMBus I/O Expander optimized for dimming LEDs in 256 discrete steps for red/green/blue (RGB) colour mixing and back light applications. The PCA9531 contains an internal oscillator with two user programmable blink rates and duty cycles coupled to the output PWM. The LED brightness is controlled by setting the blink rate high enough (>100Hz) that the blinking cannot be seen and then using the duty cycle to vary the amount of time the LED is on and thus the average current through the LED. The initial setup sequence programs the two blink rates/duty cycles for each individual PWM. From then on, only one command from the bus master is required to turn individual LEDs on, off, blink rate 1 or blink rate 2. Based on the programmed frequency and duty cycle, blink rate 1 and blink rate 2 will cause the LEDs to appear at a different brightness or blink at periods up to 1.69 second.