NXP Semiconductors PCAL9539AHF,128

Overview

PCAL9539AHF,128 from NXP Semiconductors is a 16-bit I²C-bus/SMBus 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_0–P0_7, P1_0–P1_7), supports 400 kHz Fast-mode I²C, delivers 25 mA sink per output for direct LED driving, and powers up with all I/Os as high-impedance inputs and interrupts masked - enabling glitch-free board bring-up in ACPI power switches, sensor interfaces, and fan control systems.

For engineers reviewing the PCAL9539AHF,128 datasheet, PCAL9539AHF,128 pinout, PCAL9539AHF,128 application, or PCAL9539AHF,128 equivalent, key selection considerations include its Agile I/O features (programmable drive strength, input latching, per-pin pull-up/pull-down enable/selection, interrupt masking/status), 5 V tolerant I/Os, Schmitt-trigger inputs for noise immunity, and HWQFN24 thermal-enhanced package with exposed pad.

Technical Context

The PCAL9539AHF,128 implements a dual-bank 16-bit parallel I/O architecture controlled via I²C, with separate Configuration, Input, Output, and Polarity Inversion registers per port plus extended Agile I/O registers (output drive strength, input latch, pull-up/pull-down enable/selection, interrupt mask/status, output port configuration). Its interrupt logic monitors input state changes against the Input Port register and asserts open-drain INT only when unmasked pins transition - with status readable via dedicated 8-bit interrupt status registers (4Ch, 4Dh).

Power management includes internal power-on reset and external active-low RESET pin that reinitializes registers and I²C state machine without de-powering VDD; both reset paths enforce default I/O input configuration and masked interrupts. The device supports bank-selectable push-pull or open-drain output stages via register 4Fh, and all I/Os are 5 V tolerant regardless of VDD level (1.65–5.5 V).

Key Specifications

Pinout & Package

PCAL9539AHF,128 uses the HWQFN24 (SOT994-1) package: 4 mm × 4 mm × 0.75 mm body with 24 terminals and an exposed thermal pad requiring solder connection to PCB ground for optimal thermal and electrical performance.

Key Features

Applications

Equivalent & Alternatives

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

Compared with PCA9539APW,118 and TCA6424ARGJR, PCAL9539AHF,128 uniquely combines wide VDD range (1.65–5.5 V), 5 V tolerant I/Os, per-pin Agile I/O configurability, and interrupt source identification - making it optimal for industrial, computing, and mixed-voltage embedded systems requiring reliability and debuggability.

Availability

PCAL9539AHF,128 is available at Aetrix Electronics and suitable for ACPI power management, sensor interface, fan control, LED indication, and industrial I/O expansion requiring stable component supply and long-term production continuity.

Supply support for PCAL9539AHF,128 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, with deep expertise in interface, power management, and embedded processing technologies.

The PCAL9539AHF,128 belongs to NXP's Agile I/O GPIO expander family, designed specifically to simplify system-level I/O expansion while delivering advanced signal integrity, power efficiency, and diagnostic capabilities in space-constrained embedded designs.

FAQ

What is the default I/O configuration at power-up for PCAL9539AHF,128?

At power-up, PCAL9539AHF,128 initializes all 16 I/O pins (P0_0–P0_7, P1_0–P1_7) as high-impedance inputs, sets all Configuration registers (06h, 07h) to 0xFF, masks all interrupts (Interrupt Mask registers 4Ah, 4Bh = 0xFF), and clears all Output registers (02h, 03h = 0xFF). This ensures no unintended output states or spurious interrupts during system startup.

Does PCAL9539AHF,128 support 5 V logic levels on its I/O pins?

Yes, PCAL9539AHF,128 features 5 V tolerant I/Os - meaning all GPIO pins (P0_0–P0_7, P1_0–P1_7) can safely accept input voltages up to 5.5 V regardless of the VDD supply voltage (1.65–5.5 V). This enables direct interfacing with 5 V peripherals without external level shifters.

How does the interrupt mechanism work in PCAL9539AHF,128?

PCAL9539AHF,128 asserts its open-drain INT pin when any unmasked input pin changes state relative to its Input Port register value. The Interrupt Status registers (4Ch, 4Dh) identify exactly which pin(s) caused the interrupt. Reading the corresponding Input Port register clears the interrupt - unless input latching is enabled, in which case the interrupt persists until the latched value is read.

What package type and thermal requirements apply to PCAL9539AHF,128?

PCAL9539AHF,128 uses the HWQFN24 (SOT994-1) package: 4 mm × 4 mm × 0.75 mm with 24 terminals and an exposed thermal pad. For proper operation, the VSS pin (9) and exposed pad must both be connected to PCB ground; thermal vias under the pad are recommended to enhance heat dissipation and electrical stability.

Can PCAL9539AHF,128 drive LEDs directly, and what is its maximum output current?

Yes, PCAL9539AHF,128 can directly drive LEDs with up to 25 mA sink current per I/O pin - sufficient for standard indicator LEDs. Its programmable output drive strength (four levels) allows fine-tuning of rise/fall times and power consumption, while the 5 V tolerant I/Os support common-anode LED configurations across mixed-voltage systems.