1. General description
The PCA9538 is a 16-pin CMOS device that provides 8 bits of General Purpose parallel
Input/Output (GPIO) expansion with interrupt and reset for I
2
C-bus/SMBus applications
and was developed to enhance the NXP Semiconductors family of I
2
C-bus I/O expanders.
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.
Two hardware pins (A0 and A1) vary the fixed I
2
C-bus address and allow up to four
devices to share the same I
2
C-bus/SMBus.
2. Features and benefits
8-bit I
2
C-bus GPIO with interrupt and reset
Operating power supply voltage range of 2.3 V to 5.5 V (3.0 V to 5.5 V
for PCA9538PW/Q900)
5 V tolerant I/Os
Polarity Inversion register
Active LOW interrupt output
Active LOW reset input
Low standby current
Noise filter on SCL/SDA inputs
No glitch on power-up
PCA9538
8-bit I
2
C-bus and SMBus low power I/O port with interrupt and
reset
Rev. 8 — 8 November 2017 Product data sheet
