Texas Instruments PCA9538DB

Overview

PCA9538DB from Texas Instruments is an 8-bit I²C/SMBus remote I/O expander with interrupt output, active-low reset, and configurable input/output registers. It operates from 2.3 V to 5.5 V, supports 400-kHz Fast-mode I²C, features 5-V-tolerant I/Os, and delivers ≤1 μA standby current - enabling low-power sensor interface and LED control in space-constrained industrial controllers.

For engineers reviewing the PCA9538DB datasheet, PCA9538DB pinout, PCA9538DB application, or PCA9538DB equivalent, this device serves as a drop-in I/O extension solution for microcontroller systems requiring interrupt-driven port monitoring, hardware-configurable I²C addressing (via A0/A1), and robust ESD protection (2000-V HBM) without external level shifters.

Technical Context

The PCA9538DB implements an I²C slave interface with internal register mapping for configuration, polarity inversion, and input port state tracking. Its interrupt logic asserts the open-drain INT pin on any input transition, latched until the corresponding input register is read - enabling efficient event-driven polling without bus polling overhead.

It integrates power-on reset circuitry (VPORR = 1.2–1.5 V), noise-filtered SCL/SDA inputs, and push-pull I/O drivers capable of 25 mA sink per port (P0–P7) with high-current LED drive capability. All registers initialize to default states at power-up or RESET assertion, ensuring deterministic startup behavior.

Key Specifications

Pinout & Package

PCA9538DB is packaged in a 16-pin SSOP (DB) with nominal body size 6.20 mm × 5.30 mm, optimized for automated assembly and thermal performance (R_θJA = 113.2°C/W).

Key Features

Applications

Equivalent & Alternatives

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

Compared with PCA9538DB, PCA9555DB offers double I/O count and faster register access but increases layout complexity; TCA6408ADB reduces standby current by 50% but removes hardware reset - making PCA9538DB the optimal balance of interrupt reliability, reset control, and industrial-grade ESD tolerance.

Availability

PCA9538DB is available at Aetrix Electronics and suitable for industrial automation, embedded instrumentation, and LED control systems requiring stable component supply, long-term lifecycle assurance, and traceable sourcing.

Supply support for PCA9538DB 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

Texas Instruments is a global semiconductor leader specializing in analog, embedded processing, and connectivity technologies for industrial, automotive, and communications markets.

The PCA9538DB belongs to TI's I²C-compatible I/O expander product line, designed specifically for deterministic, low-power remote I/O expansion in harsh industrial environments with minimal MCU intervention.

FAQ

What is the maximum I²C clock frequency supported by the PCA9538DB?

The PCA9538DB supports Fast-mode I²C operation up to 400 kHz, as confirmed in Section 5.6 of the datasheet. This allows high-speed register reads and writes while maintaining compatibility with standard-mode (100 kHz) hosts - essential for time-critical I/O updates in motion control systems where PCA9538DB interfaces with encoder feedback or safety interlocks.

Does the PCA9538DB require external pull-up resistors on SCL and SDA lines?

Yes, the PCA9538DB requires external pull-up resistors on both SCL and SDA lines to VCC, as specified in the Pin Functions table (Section 4) and Block Diagram (Figure 7-1). The device does not integrate internal pull-ups; typical values range from 2.2 kΩ to 10 kΩ depending on bus capacitance and speed - a mandatory design requirement for reliable PCA9538DB I²C communication.

Can the PCA9538DB drive LEDs directly without external transistors?

Yes, the PCA9538DB outputs support up to 25 mA sink current per port (P0–P7) at VOL ≤ 0.5 V, enabling direct LED driving as stated in Section 5.5 Electrical Characteristics. Each port can source up to 10 mA, but sink capability is emphasized for common-anode LED configurations - a verified feature used in PCA9538DB-based status panel designs.

How does the interrupt (INT) pin behave after being asserted?

The PCA9538DB INT pin remains asserted (low) until the corresponding input port register is read - either via I²C read transaction or by reading the input port register directly. As documented in Section 7.2.4, this latching behavior ensures no edge is missed, and the interrupt clears automatically upon ACK/NACK of the read data byte - a deterministic mechanism central to PCA9538DB's role in event-driven industrial monitoring.

What is the purpose of the A0 and A1 pins on the PCA9538DB?

The A0 and A1 pins on the PCA9538DB are hardware address select inputs that set the device's 3-bit I²C slave address (bits A2–A0), allowing up to four PCA9538DB units on the same I²C bus. As defined in Table 4-1 and Section 2, these pins must be hardwired to VCC or GND before I²C communication begins - a fixed configuration enabling scalable I/O expansion without address conflicts in multi-node systems using PCA9538DB.