PCA9550D datasheet(7/26 Pages) NXP

7 / 26 page

PCA9550_5

Product data sheet

Rev. 05 — 13 October 2008

7 of 26

NXP Semiconductors

PCA9550

2-bit I2C-bus LED driver with programmable blink rates

6.4 Pins used as GPIOs

LED pins not used to control LEDs can be used as General Purpose Input/Outputs

(GPIOs).

For use as input, set LEDn to high-impedance (01) and then read the pin state via the

Input register.

For use as output, connect external pull-up resistor to the pin and size it according to the

DC recommended operating characteristics. LEDn output pin is HIGH when the output is

programmed as high-impedance, and LOW when the output is programmed LOW through

the LED selector register (LS0). The output can be pulse-width controlled when PWM0 or

PWM1 are used.

6.5 Power-on reset

When power is applied to VDD, an internal Power-On Reset (POR) holds the PCA9550 in

a reset condition until VDD has reached VPOR. At that point, the reset condition is released

and the PCA9550 registers are initialized to their default states, all the outputs in the

OFF state. Thereafter, VDD must be lowered below 0.2 V to reset the device.

6.6 External RESET

A reset can be accomplished by holding the RESET pin LOW for a minimum of tw(rst). The

PCA9550 registers and I2C-bus state machine will be held in their default states until the

RESET input is once again HIGH.

This input requires a pull-up resistor to VDD if no active connection is used.

PCA9550D Datasheet(PDF) 7 Page - NXP Semiconductors