PCA9554/54A/55
8- and 16-bit I2C and
SMBus I/O Port with Interrupt
The PCA9554/54A/55 were developed to enhance the Philips family
of I2C I/O expanders. The improvements include higher drive capability,
5V I/O tolerance, lower supply current, individual I/O configuration,
400 kHz clock frequency, and smaller packaging.
Philips Configuration
System Management ICs
Part Type Description
The PCA9554 and PCA9554A are 16-pin CMOS devices that provide
8 bits of General Purpose parallel Input/Output (GPIO) expansion for
I2C/SMBus applications. These I/O expanders provide a simple solu-
tion when additional I/O is needed for ACPI power switches, sensors,
pushbuttons, LEDs, fans, etc. The parts consist of an 8-bit Configura-
tion 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 PCA9555 is a 24-pin CMOS device, which
provides 16 bits of GPIO and consists of two 8-bit Configuration,
Input, Output and Polarity inversion registers.
The system master can enable the PCA9554/54A/55 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 read register can be inverted with the
Polarity Inversion Register. All registers can be read by the system mas-
ter. Although pin to pin and I2C address compatible with the PCF857X
series, software changes are required due to the enhancements and are
discussed in Application Note AN469. The PCA9554/54A/55 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. If an external hardware
reset is needed, the PCA9556/57 should be used.
Three hardware pins (A0, A1, A2) vary the fixed I2C address and allow
up to eight devices to share the same I2C/SMBus. The PCA9554A is
identical to the PCA9554 except that the fixed I2C address is different
allowing up to sixteen of these devices (eight of each) on the same
I2C/SMBus. The fixed I2C address of the PCA9555 is the same as the
PCA9554 allowing up to eight of these devices in any combination to
share the same I2C/SMBus.
PCA9554/54A/55 Features
•I
2C and SMBus compatible
• 8 or 16 programmable I/Os compatible with most processors
— Input or output
— Push-Pull or open-drain outputs
— True vs. quasi bi-directional style I/O
• Outputs can directly drive LEDs
— 25 mA max sink and 10 mA max source per bit
— Capacity of 100 mA max per 8-bit register
• Open-drain interrupt output activated when input changes state
•Low I
DDH standby current of 1.5 µA max
• 5 V tolerant I/Os
• Offered in SO Wide (D), SSOP (DB) and TSSOP (PW)
• Manufactured in high-volume CMOS process
PCA9554/54A/55 Operating Characteristics
• 2.3 V to 5.5 V operating voltage
• -40 to 85 ºC operating temperature range
• 0 to 400 kHz clock frequency