1.

General description

The PCA9538 is a 16-pin CMOS device that provides 8 bits of General Purpose parallel

I/O expanders provide a simple solution when additional I/O is needed for ACPI power

switches, sensors, push-buttons, LEDs, fans, etc.

The PCA9538 consists of an 8-bit Configuration register (input or output selection),

8-bit Input Port register, 8-bit Output Port register and an 8-bit Polarity Inversion register

(active HIGH or active LOW operation). The system master can enable the I/Os as either

inputs or outputs by writing to the I/O configuration bits. The data for each input or output

is kept in the corresponding Input Port or Output Port register. The polarity of the Input

Port register can be inverted with the Polarity Inversion register. All registers can be read

by the system master.

The PCA9538 is identical to the PCA9554 except for the removal of the internal I/O pull-up

resistor which greatly reduces power consumption when the I/Os are held LOW,

replacement of A2 with RESET and different address range.

The PCA9538 open-drain interrupt output (INT) is activated when any input state differs

from its corresponding Input Port register state and is used to indicate to the system

master that an input state has changed. The power-on reset sets the registers to their

default values and initializes the device state machine. The RESET pin causes the same

reset/initialization to occur without de-powering the device.

2.

Features

PCA9538

reset

Rev. 05 — 28 May 2009

Product data sheet