1.

General description

256 discrete steps for Red/Green/Blue (RGB) color mixing and back light applications.

The PCA9532 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 (> 100 Hz) 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. The open-drain outputs directly

drive the LEDs with maximum output sink current of 25 mA per bit and 200 mA per

package (100 mA per octal).

To blink LEDs at periods greater than 1.69 second the bus master (MCU, MPU, DSP,

chip set, etc.) must send repeated commands to turn the LED on and off as is currently

done when using normal I/O expanders like the NXP Semiconductors PCF8575 or

PCA9555. Any bits not used for controlling the LEDs can be used for General Purpose

parallel Input/Output (GPIO) expansion, which provides a simple solution when additional

I/O is needed for ACPI power switches, sensors, push-buttons, alarm monitoring, fans,

etc.

The active LOW hardware reset pin (RESET) and Power-On Reset (POR) initializes the

registers to their default state, all zeroes, causing the bits to be set HIGH (LED off).

Three hardware address pins on the PCA9532 allow eight devices to operate on the same

bus.

2.

Features

0.591 Hz and 152 Hz (1.69 second and 6.58 milliseconds)

PCA9532

Rev. 04 — 17 March 2009

Product data sheet