PCA9531

Features:

• Eight LED drivers (on, off, flashing at a programmable rate)
• Two selectable, fully programmable blink rates (frequency andduty cycle) between 0.625 and 160 Hz (1.6 and 6.25 milliseconds)
• 256 brightness steps
• Input/outputs not used as LED drivers can be used as regular GPIOs
• Internal oscillator requires no external components
• I2C interface logic compatible with SMBus
• Internal power-on reset
• Noise filter on SCL/SDA inputs
• Active low reset input
• Eight open drain outputs directly drive LEDs to 25 mA
• Edge rate control on outputs
• No glitch on power-up
• Supports hot insertion
• Low stand-by current
• Operating power supply voltage range of 2.3 V to 5.5 V
• 0 to 400 kHz clock frequency
• ESD protection exceeds 2000 V HBM per JESD22-A114,150 V MM per JESD22-A115 and 1000 V CDM per JESD22-C101
• Latch-up testing is done to JEDEC Standard JESD78 which exceeds 100 mA
• Package offer: SO16, TSSOP16, HVQFN16


Pinout




Specifications

SYMBOL	PARAMETER	CONDITIONS	MIN	MAX	UNIT
VDD	Supply voltage		-0.5	6.0	V
VI/O	DC input current on an I/O		VSS - 0.5	5.5	V
II/O	DC output current on an I/O		-	± 55	mA
ISS	Supply current		-	200	mA
Ptot	Total power dissipation		-	400	mW
Tstg	Storage temperature range		-65	+150
Tamb	Operating ambient temperature		-40	+85

Description

The PCA9531 is an 8-bit I²C & SMBus I/O expander optimized for dimming LEDs in 256 discrete steps for Red/Green/Blue (RGB) color mixing and back light applications.

The PCA9531 contains an internal oscillator with two userprogrammable 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 can not be seen and then using the duty cycle to vary the amount of time the LED is on and thus theaverage current through the LED.

The initial setup sequence programs of PCA9531 the two blink rates/duty cyclesfor each individual PWM. From then on, only one command from thebus master is required to turn individual LEDs ON, OFF, BLINKRATE 1 or BLINK RATE 2. Based on the programmed frequencyand duty cycle, BLINK RATE 1 and BLINK RATE 2  of PCA9531 will cause theLEDs to appear at a different brightness or blink at periods up to 1.6second. 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 1.6 second the bus master(MCU, MPU, DSP, chipset, etc.) PCA9531 must send repeated commands to turn the LED of PCA9531 on and off as is currently done when using normal I/OExpanders like the Philips PCF8574 or PCA9554. Any bits not usedfor controlling the LEDs can be used for General Purpose ParallelInput/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 PCA9531 to their default statecausing the bits to be set high (LED off).

Three hardware address pins on the PCA9531 allow eight devicesto operate on the same bus.