NXP Semiconductors PCA9539APW,118

Overview

PCA9539APW,118 from NXP Semiconductors is a 16-bit I²C-bus GPIO expander with interrupt and active-low reset, operating from 1.65 V to 5.5 V. It provides two 8-bit configurable I/O ports (P0 and P1), supports 400 kHz Fast-mode I²C, features 25 mA sink capability per output, and includes polarity inversion and configuration registers for flexible input/output control. It is used in ACPI power switches, sensor interfaces, LED drivers, and push-button monitoring systems.

For engineers reviewing the PCA9539APW,118 datasheet, PCA9539APW,118 pinout, PCA9539APW,118 application, or PCA9539APW,118 equivalent, key selection considerations include its 1.65–5.5 V supply range, open-drain INT output with Schmitt-trigger inputs, 5 V tolerant I/Os, TSSOP24 package, and compatibility with legacy PCA9539 designs.

Technical Context

The PCA9539APW,118 implements a dual-port I²C slave architecture with four register pairs (Input/Output/Polarity Inversion/Configuration) mapped across two 8-bit ports. Its internal state machine initializes on power-on or RESET assertion, setting all I/Os as high-impedance inputs and loading default register values (e.g., Configuration = 0xFF, Output = 0xFF).

Interrupt generation is edge-sensitive and tied exclusively to input-state changes on pins configured as inputs; outputs cannot trigger INT. The open-drain INT output requires an external pull-up to VDD and asserts low when any input differs from its corresponding Input Port register value.

Key Specifications

Pinout & Package

TSSOP24 package (SOT355-1), 4.4 mm body width, 0.65 mm lead pitch, surface-mount compatible.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar GPIO expander applications.

Compared with PCA9539AHF,128 and PCAL9539A, the PCA9539APW,118 delivers proven TSSOP24 reliability, lowest bill-of-materials cost, and seamless legacy compatibility - making it ideal for volume production where pinout stability and manufacturing simplicity are prioritized.

Availability

PCA9539APW,118 is available at Aetrix Electronics and suitable for ACPI power management, sensor interface hubs, LED status panel control, and keypad scan interface applications requiring stable component supply across industrial and embedded product lifecycles.

Supply support for PCA9539APW,118 includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.

Manufacturer

NXP Semiconductors is a global semiconductor leader focused on secure connectivity solutions for automotive, industrial, and IoT applications.

The PCA9539A product line delivers scalable, low-power I²C GPIO expansion for resource-constrained embedded systems - designed specifically to reduce MCU pin count while maintaining interrupt-driven responsiveness and wide voltage interoperability.

FAQ

What is the maximum I²C clock frequency supported by the PCA9539APW,118?

The PCA9539APW,118 supports Fast-mode I²C operation up to 400 kHz. This is confirmed in the official NXP datasheet Rev. 2 (August 2013), Section 2 "Features and benefits". The device meets standard Fast-mode timing requirements including t_LOW, t_HIGH, and t_SU;STA, enabling reliable communication with modern microcontrollers without requiring slower standard-mode clocks. PCA9539APW,118 does not support High-speed mode (3.4 MHz).

Does the PCA9539APW,118 require external pull-up resistors on SCL and SDA lines?

Yes, the PCA9539APW,118 requires external pull-up resistors on both SCL and SDA lines to VDD, as stated in Section 5.2 "Pin description" of the datasheet. Its I²C interface uses open-drain outputs, so pull-ups are mandatory for proper bus operation. Typical values range from 2.2 kΩ to 10 kΩ depending on bus capacitance and speed; 4.7 kΩ is commonly used for 400 kHz operation. PCA9539APW,118 itself does not integrate internal pull-ups.

Can the PCA9539APW,118 drive LEDs directly, and what is the maximum current per pin?

Yes, the PCA9539APW,118 can drive LEDs directly with up to 25 mA sink current per I/O pin, as specified in Section 1 "General description" and Section 2 "Features and benefits". This applies to all 16 I/Os (P0_0–P0_7 and P1_0–P1_7) when configured as outputs. The device maintains this rating across its full 1.65–5.5 V supply range. PCA9539APW,118 does not support source current - LEDs must be connected anode-to-VDD, cathode-to-I/O.

How does the RESET pin function on the PCA9539APW,118, and is a pull-up resistor required?

The RESET pin on the PCA9539APW,118 is active-low and causes immediate register and I²C state machine reset to power-on defaults without de-powering VDD. As documented in Section 5.2 and Section 6.5, it requires an external pull-up resistor to VDD if no active driver is connected - otherwise the device may fail to initialize correctly. The minimum pulse width for reset assertion is t_w(rst), specified in timing tables. PCA9539APW,118 relies on this external pull-up for reliable startup behavior.

Is the PCA9539APW,118 pin-compatible with the original PCA9539?

Yes, the PCA9539APW,118 is explicitly documented as a pin-to-pin replacement for the PCA9539 in Section 1 "General description": "The PCA9539A is a pin-to-pin replacement to the PCA9539". Electrical characteristics, register map, pin functions, and timing are identical. No PCB or firmware changes are needed when upgrading from PCA9539 to PCA9539APW,118 - making it a seamless drop-in solution for existing designs.