Overview: INTEGRATED CIRCUITS PCA9533 4-bit I2C LED dimmer
Product data sheet Supersedes data of 2003 Sep 19 2004 Oct 01 Philips Semiconductors Philips Semiconductors Product data sheet 4-bit I2C LED dimmer PCA9533 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 100 mA per package. To blink LEDs at periods greater than 1.69 second 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 PCF8574 or PCA9554. 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. Power-On Reset (POR) initializes the registers to their default state causing the bits to be set HIGH (LED off). Due to pin limitations, the PCA9533 is not featured with hardware address pins. The PCA9533/01 and the PCA9533/02 have different fixed I2C addresses allowing operation of both on the same bus.
