PCA9539PW/Q900,118

I/o Expanders Overview

The PCA9539PW/Q900,118 is a 24-pin CMOS device providing 16-bit general-purpose parallel input/output expansion with interrupt and reset capabilities for I2C-bus/SMBus applications. It operates within a power supply voltage range of 3.0 V to 5.5 V and supports clock frequencies up to 400 kHz. The component features an active LOW open-drain interrupt output and an active LOW reset input. It includes polarity inversion registers and internal power-on reset logic. The device is housed in a TSSOP24 package and complies with AEC-Q100 automotive standards.

I/o Expanders Feature Summary

• Provides 16-bit GPIO expansion with configurable input or output directions via configuration registers.
• Features an active LOW open-drain interrupt output that activates when any input state differs from its corresponding register state.
• Includes an active LOW reset input that initializes the SMBus/I2C-bus state machine and resets all registers to default values.
• Supports polarity inversion for input port data through dedicated polarity inversion registers.

I/o Expanders Applications

• ACPI power switches
• Sensor interfaces
• Push-button inputs
• LED control circuits
• Fan control systems

I/o Expanders Procurement Notes

Verify the specific Q900 suffix indicates AEC-Q100 qualification and extended temperature range up to +125 °C. Confirm the ordering suffix matches the required packing method and minimum order quantity specifications provided by the manufacturer. Ensure compatibility with the target system's voltage levels and interface requirements before finalizing procurement.

I/o Expanders Selection Notes

Select this component when 16-bit I/O expansion is required on an I2C bus with interrupt notification needs. Consider the PCA9539R variant if the application requires retaining I/O states during a hardware reset while only resetting the bus interface. Verify that the operating voltage range aligns with the system's VDD supply and that the TSSOP24 package fits the PCB layout constraints.

I/o Expanders Part Context

This part belongs to the PCA9539 family of low-power I/O expanders developed by NXP Semiconductors. It is functionally identical to the PCA9555 except for the removal of internal I/O pull-up resistors, replacement of the A2 address pin with a RESET pin, and a different address range. The Q900 suffix denotes automotive-grade qualification under AEC-Q100 standards.

I/o Expanders Replacement Considerations

The PCAL9539A is a pin-to-pin compatible replacement that offers additional Agile I/O features such as programmable drive strength and input latches. Note that the PCAL9539A masks all I/O interrupts at power-up by default, unlike the PCA9539 which defaults to inputs without masking.

I/o Expanders FAQ

How does the PCA9539 handle the RESET input compared to the PCA9539R?

In the PCA9539, driving the RESET pin LOW causes both the device state machine and the internal general-purpose registers to reset to their default values. In contrast, the PCA9539R RESET pin only initializes the device state machine, leaving the internal general-purpose registers unchanged to retain the last configured I/O states.

What is the default configuration of the I/O pins upon power-on reset?

At power-on reset, all 16 I/O pins are configured as inputs with high-impedance output drivers. The output port registers default to logic '1', and the configuration registers default to logic '1' (input mode).

Can the interrupt output be cleared by reading a different port?

No. Each 8-bit port is read independently. An interrupt caused by a change in Port 0 cannot be cleared by reading Port 1, and vice versa. The interrupt is deactivated only when the specific input port register causing the interrupt is read or when the input returns to its previous state.