1. General description
The PCA9534 is a 16-pin CMOS device that provide 8 bits of General Purpose parallel
Input/Output (GPIO) expansion for I
2
C-bus/SMBus applications and was developed to
enhance the NXP Semiconductors family of I
2
C-bus I/O expanders. The improvements
include higher drive capability, 5 V I/O tolerance, lower supply current, individual I/O
configuration, 400 kHz clock frequency, and smaller packaging. I/O expanders provide a
simple solution when additional I/O is needed for ACPI power switches, sensors,
push buttons, LEDs, fans, etc.
The PCA9534 consists of an 8-bit Configuration register (Input or Output selection); 8-bit
Input register, 8-bit Output 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 or Output 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. Although pin-to-pin and I
2
C-bus address compatible with the PCF8574 series,
software changes are required due to the enhancements and are discussed in Application
Note AN469.
The PCA9534 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.
The PCA9534 open-drain interrupt output 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.
Three hardware pins (A0, A1, A2) vary the fixed I
2
C-bus address and allow up to eight
devices to share the same I
2
C-bus/SMBus.
2. Features and benefits
8-bit I
2
C-bus GPIO
Operating power supply voltage range of 2.3 V to 5.5 V
5 V tolerant I/Os
Polarity Inversion register
Active LOW interrupt output
Low standby current
Noise filter on SCL/SDA inputs
No glitch on power-up
Internal power-on reset
PCA9534
8-bit I
2
C-bus and SMBus low power I/O port with interrupt
Rev. 4 — 7 November 2017 Product data sheet
