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 PCA9538 consists of one 8-bit Configuration (input or output selection), Input Port, Output Port, and Polarity Inversion (active high or active low) registers. At power on, the I/Os are configured as inputs. 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 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 system master can reset the PCA9538 in the event of a timeout or other improper operation by asserting a low in the RESET input. The power-on reset puts the registers in their default state and initializes the I2C/SMBus state machine. The RESET pin causes the same reset/initialization to occur without powering down the part.

The PCA9538 open-drain interrupt (INT) 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.

INT can be connected to the interrupt input of a microcontroller. By sending an interrupt signal on this line, the remote I/O can inform the microcontroller if there is incoming data on its ports without having to communicate via the I2C bus. Thus, the PCA9538 can remain a simple slave device.

The device outputs (latched) have high-current drive capability for directly driving LEDs. It has low current consumption.

Two hardware pins (A0 and A1) are used to program and vary the fixed I2C address and allow up to four devices to share the same I2C bus or SMBus.

• Low Standby Current Consumption of 1μAMax
• I2C to Parallel Port Expander
• Open-Drain Active-Low Interrupt Output
• Active-Low Reset Input
• Operating Power-Supply Voltage Range of 2.3V to 5.5V
• 5-V Tolerant I/O Ports
• 400-kHz Fast I2C Bus
• Two Hardware Address Pins Allow up to Four Devices on the I2C/SMBus
• Input/Output Configuration Register
• Polarity Inversion Register
• Power-Up With All Channels Configured as Inputs
• No Glitch on Power Up
• Noise Filter on SCL/SDA Inputs
• 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)