Texas Instruments TCA9539RTWR

Overview

TCA9539RTWR from Texas Instruments is a 16-bit I²C/SMBus I/O expander IC providing parallel GPIO expansion for microcontrollers in low-voltage systems. It operates from 1.65 V to 5.5 V, supports 400-kHz Fast-mode I²C, features active-low interrupt (INT) and reset (RESET) pins, and delivers latched push-pull outputs capable of directly driving LEDs - used in server rack management and telecom switching equipment.

For engineers reviewing the TCA9539RTWR datasheet, TCA9539RTWR pinout, TCA9539RTWR application, or TCA9539RTWR equivalent, key selection criteria include its 5-V-tolerant I/Os, hardware addressability via A0/A1 pins (up to four devices on one bus), internal power-on reset, noise-filtered SCL/SDA inputs, and configurable input/output polarity per port.

Technical Context

The TCA9539RTWR implements two independent 8-bit I/O ports (P00–P07 and P10–P17), each with dedicated configuration, input, output, and polarity inversion registers. All registers are accessible via standard I²C read/write operations using a 7-bit slave address determined by A0 and A1 logic levels.

Its interrupt generation is edge-triggered on input state change and latched until cleared by host read; the active-low RESET pin forces register initialization without power cycling. The device uses push-pull output drivers with ±10 mA high-level and 25 mA low-level sink capability at VCC ≥ 2.3 V, enabling direct LED drive without external transistors.

Key Specifications

Pinout & Package

Package: 24-pin WQFN (RTW), 4.00 mm × 4.00 mm, exposed thermal pad - optimized for space-constrained PCB layouts and thermal performance in dense server modules.

Key Features

Applications

Equivalent & Alternatives

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

Compared with PCA9539PW and MAX7329ATL+, the TCA9539RTWR provides optimal thermal performance in space-constrained designs due to its exposed-pad WQFN, lowest standby current across 1.65–5.5 V range, and seamless compatibility with existing TI I²C ecosystem tools and reference firmware.

Availability

TCA9539RTWR is available at Aetrix Electronics and suitable for server rack management, telecom switching equipment, and industrial PLC I/O expansion requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for TCA9539RTWR 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 focused on analog and embedded processing technologies, serving industrial, automotive, and communications markets with high-reliability components.

The TCA9539RTWR belongs to TI's I²C peripheral portfolio designed specifically for remote GPIO expansion in resource-constrained embedded systems - emphasizing low power, voltage flexibility, and interrupt-driven efficiency.

FAQ

What is the maximum I²C clock frequency supported by the TCA9539RTWR?

The TCA9539RTWR supports I²C Standard-mode up to 100 kHz and Fast-mode up to 400 kHz. Its timing parameters - including tSCH (0.6 µs min), tSCL (1.3 µs min), and tVD(DATA) (0.9 µs max) - are fully compliant with Fast-mode specifications across the full 1.65–5.5 V VCC range, enabling high-speed GPIO polling in time-critical applications.

Does the TCA9539RTWR require external pull-up resistors on SCL and SDA lines?

Yes, the TCA9539RTWR requires external pull-up resistors on both SCL and SDA lines to establish valid logic-high levels. The datasheet specifies typical values of 1 kΩ to 10 kΩ depending on bus capacitance and speed; for 400 kHz operation with ≤400 pF total bus load, 4.7 kΩ is commonly used. The INT and RESET pins also require pull-ups.

Can the TCA9539RTWR drive LEDs directly without current-limiting resistors?

No - while the TCA9539RTWR has high-current sink capability (25 mA per pin at Tj ≤65°C), an external current-limiting resistor is mandatory for LED drive to prevent damage from overcurrent and thermal runaway. The resistor value must be selected based on forward voltage, desired LED current, and VCC to ensure IOL remains within absolute maximum ratings.

How does the interrupt (INT) pin behave after being asserted on the TCA9539RTWR?

The INT pin on the TCA9539RTWR is latched active-low and remains asserted until the host reads the corresponding input port register (P0 or P1). This latch mechanism ensures no interrupt event is missed during I²C transaction latency. Reading either input register clears the interrupt condition and releases INT, provided no new input change occurs during the read cycle.

Is the TCA9539RTWR pin-compatible with other members of the TCA9539 family?

Yes - the TCA9539RTWR shares identical pinout and register mapping with all TCA9539 variants (e.g., TCA9539PW, TCA9539RGE), differing only in package type (WQFN vs TSSOP vs VQFN) and thermal characteristics. Firmware, layout, and schematic designs are fully interchangeable across these variants, enabling drop-in replacement for thermal or assembly optimization.