1 Features
• Low standby-current consumption of 1 μA max
• I2C to Parallel port expander
• Open-drain active-low interrupt output
• Active-low reset input
• 5-V Tolerant I/O ports
• Compatible with most microcontrollers
• 400-kHz Fast I2C Bus
• Polarity inversion register
• Address by two hardware address pins for use of
up to four devices
• Latched outputs with high-current drive 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)
– 1000-V Charged-device model (C101)

2 Description
This 16-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 PCA9539 consists of two 8-bit Configuration
(input or output selection), Input Port, Output Port,
and Polarity Inversion (active-high or active-low
operation) registers. At power-on, the I/Os are
configured as inputs. 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.