1 Features
• I2C to Parallel Port Expander
• Open-Drain Active-Low Interrupt Output
• Operating Power-Supply Voltage Range of 2.3 V to
5.5 V
• 5-V Tolerant I/Os
• 400-kHz Fast I2C Bus
• Three Hardware Address Pins Allow up to Eight
Devices on the I2C/SMBus
• Input/Output Configuration Register
• Polarity Inversion Register
• Internal Power-On Reset
• Power-Up With All Channels Configured as Inputs
• No Glitch on Power Up
• Latched Outputs With High-Current Drive
Maximum Capability for Directly Driving LEDs
• Latch-Up Performance Exceeds 100 mA Per JESD
78, Class II
• ESD Protection Exceeds JESD 22
– 2000-V Human-Body Model (A114-A)
– 200-V Machine Model (A115-A)
– 1000-V Charged-Device Model (C101)

2 Description
This 8-bit I/O expander for the two-line bidirectional
bus (I2C) is designed for 2.3-V to 5.5-V VCC operation.
It provides general-purpose remote I/O expansion for
most microcontroller families via the I2C interface
[serial clock (SCL), serial data (SDA)].
The PCA9554A consists of one 8-bit Configuration
(input or output selection), Input, Output, and Polarity
Inversion (active high or active low) registers. At
power on, the I/Os are configured as inputs with a
weak pullup to VCC. However, 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.
The system master can reset the PCA9554A in the
event of a timeout or other improper operation by
utilizing the power-on reset feature, which puts the
registers in their default state and initializes the I2C/
SMBus state machine.