NXP Semiconductors PCAL9538ABS,128

Overview

PCAL9538ABS,128 from NXP Semiconductors is an 8-bit I²C-bus/SMBus GPIO expander with interrupt, reset, and Agile I/O features, operating from 1.65 V to 5.5 V. It provides 8 programmable I/Os with 25 mA sink capability, maskable interrupts, latched inputs, and per-pin pull-up/pull-down control. It is used in ACPI power switches, LED/fan control, sensor interfaces, and push-button monitoring in embedded industrial and consumer systems.

For engineers reviewing the PCAL9538ABS,128 datasheet, PCAL9538ABS,128 pinout, PCAL9538ABS,128 application, or PCAL9538ABS,128 equivalent, key selection considerations include its HVQFN16 package, 400 kHz Fast-mode I²C support, 5 V tolerant I/Os, power-up interrupt masking, and Agile I/O register set (output drive strength, input latch, interrupt status, pull-up/down enable/selection).

Technical Context

The PCAL9538ABS,128 implements a dual-register I²C interface with standard PCA9538A-compatible registers (Input/Output/Polarity/Configuration) plus extended Agile I/O registers at addresses 40h–4Fh. Its interrupt logic uses edge-triggered detection on input pins and supports both latched and non-latched modes, with an interrupt status register (46h) enabling source identification.

It integrates programmable output drive strength (four levels per pin), per-pin pull-up/pull-down enable (43h) and selection (44h, 100 kΩ), and bank-selectable push-pull/open-drain output configuration (4Fh). The RESET pin performs a full register and state-machine reset without power cycling, and the INT output is open-drain with internal logic asserting on any unmasked input state change.

Key Specifications

Pinout & Package

HVQFN16 package (3 mm × 3 mm × 0.85 mm, SOT758-1), thermally enhanced with exposed center pad requiring PCB thermal vias and solder connection to VSS for proper operation and reliability.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar I/O expansion applications.

Compared with PCA9538APW,118 and TCA6408APWR, the PCAL9538ABS,128 delivers deterministic interrupt source identification, hardware-assisted input debouncing via latching, and per-pin biasing control - reducing host CPU load and simplifying layout in space-constrained, interrupt-driven systems.

Availability

PCAL9538ABS,128 is available at Aetrix Electronics and suitable for industrial HMIs, IoT sensor nodes, and embedded power management systems requiring stable component supply, long-term lifecycle assurance, and RoHS-compliant sourcing.

Supply support for PCAL9538ABS,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, and security ICs.

The PCAL9538ABS,128 belongs to NXP's Agile I/O family, designed specifically to extend microcontroller I/O capabilities in resource-constrained embedded systems while delivering field-programmable flexibility for dynamic signal conditioning and interrupt management.

FAQ

What is the default I/O configuration of the PCAL9538ABS,128 at power-up?

At power-up or RESET assertion, all eight I/O pins (P0–P7) of the PCAL9538ABS,128 are configured as high-impedance inputs, and all interrupt mask bits (register 45h) are set to 1, disabling interrupts by default. This prevents spurious INT assertions during system initialization and ensures predictable startup behavior without requiring initial I²C writes.

Does the PCAL9538ABS,128 support 5 V logic levels on its I/O pins?

Yes, the PCAL9538ABS,128 features 5 V tolerant I/Os, meaning P0–P7 can safely accept input voltages up to 5.5 V regardless of VDD level (1.65 V to 5.5 V). This allows direct interfacing with 5 V peripherals such as legacy sensors or comparators without level-shifting circuitry, simplifying design and improving signal integrity.

How does the interrupt status register (address 46h) function in the PCAL9538ABS,128?

The interrupt status register (46h) in the PCAL9538ABS,128 is a read-only register where each bit corresponds to one I/O pin (S0–S7). A logic 1 indicates that the associated pin generated the most recent unmasked interrupt event. Reading this register does not clear the interrupt - only reading the Input Port register (00h) clears the INT output and resets the status bits for latched inputs.

Can the PCAL9538ABS,128 drive LEDs directly, and what is its maximum sink current?

Yes, the PCAL9538ABS,128 can drive LEDs directly with up to 25 mA sink current per I/O pin (P0–P7) when configured as outputs. This eliminates the need for external driver transistors in low-power indicator applications. For optimal efficiency and thermal performance, use the programmable output drive strength registers (40h/41h) to match current to LED forward voltage and desired brightness.

What package type and thermal requirements apply to the PCAL9538ABS,128?

The PCAL9538ABS,128 uses the HVQFN16 package (SOT758-1), measuring 3 mm × 3 mm × 0.85 mm with an exposed thermal pad. The pad must be soldered to a PCB copper area connected to VSS, and thermal vias should be placed beneath it to ensure reliable heat dissipation and long-term solder joint integrity under continuous 25 mA loading.