The PCA9532 is a 16-bit I2C-bus and SMBus I/O expander
optimized for dimming LEDs in 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 set-up 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 seconds. 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 seconds the bus master
(MCU, MPU, DSP, chipset, etc.) must send repeated commands to
turn the LED on and off as is currently done when using normal I/O
Expanders like the Philips 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,
pushbuttons, 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
