Texas Instruments PCA9539DBQR

Overview

PCA9539DBQR from Texas Instruments is a 16-bit I²C/SMBus remote I/O expander with interrupt, reset, and configuration registers, operating from 2.3 V to 5.5 V. It provides two 8-bit configurable I/O ports (P00–P07, P10–P17), open-drain active-low INT output, active-low RESET input, and polarity inversion register - enabling real-time input change detection in industrial control panels and embedded sensor hubs.

For engineers reviewing the PCA9539DBQR datasheet, PCA9539DBQR pinout, PCA9539DBQR application, or PCA9539DBQR equivalent, this device supports fast-mode I²C (400 kHz), 5-V-tolerant I/Os, low standby current (≤1 μA), and hardware address selection via A0/A1 pins for multi-device bus sharing.

Technical Context

The PCA9539DBQR implements dual 8-bit register banks - Configuration, Input Port, Output Port, and Polarity Inversion - all accessible over I²C. At power-on, all I/Os default to high-impedance inputs, and the internal power-on reset (VPORR = 1.2 V) initializes register states without requiring external de-powering.

Its interrupt logic triggers on any input state change versus stored Input Port register value, with INT asserted within 4 μs and cleared only upon reading the corresponding port register. The RESET pin forces full register and state-machine reset synchronously, independent of I²C activity.

Key Specifications

Pinout & Package

PCA9539DBQR is packaged in a 24-pin SSOP (DBQ) with body size 8.20 mm × 5.30 mm, optimized for space-constrained PCB layouts while maintaining hand-solderability and thermal performance (θ_JA = 61 °C/W).

Key Features

Applications

Equivalent & Alternatives

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

Compared with PCA9539DBQR, PCA9555DBQR trades lower power for built-in pullups, while TCA6424ARGJR offers enhanced interrupt control at the cost of voltage flexibility and reset functionality - making PCA9539DBQR optimal for mixed-voltage, reset-critical, ultra-low-power industrial I/O expansion.

Availability

PCA9539DBQR is available at Aetrix Electronics and suitable for industrial control panels, embedded sensor hubs, automotive body controllers, and IoT edge gateways requiring stable component supply and long-term production support.

Supply support for PCA9539DBQR 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 delivering analog and embedded processing solutions, with decades of expertise in interface ICs, power management, and industrial-grade reliability.

The PCA9539 belongs to TI's I²C/SMBus I/O expander product line, designed specifically for remote GPIO expansion in resource-constrained embedded systems where low power, interrupt capability, and robust bus operation are essential.

FAQ

What is the maximum I²C clock frequency supported by the PCA9539DBQR?

The PCA9539DBQR supports Fast-mode I²C operation up to 400 kHz. This is confirmed in Section 6.6 of the datasheet, which specifies fscl(max) = 400 kHz under recommended operating conditions. The timing parameters - including tSCH (clock high time ≥0.6 μs) and tSCL (clock low time ≥1.3 μs) - are fully characterized for reliable communication at this rate. PCA9539DBQR maintains signal integrity across temperature and voltage ranges without requiring external clock stretching.

Does the PCA9539DBQR require external pullup resistors on SDA and SCL lines?

Yes, the PCA9539DBQR requires external pullup resistors on both SDA and SCL lines because it uses open-drain I²C interface architecture. Section 5 of the datasheet explicitly states that SDA and SCL must be connected to VCC through pullup resistors. 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. PCA9539DBQR does not integrate internal pullups on these lines.

Can the PCA9539DBQR drive LEDs directly without external transistors?

Yes, the PCA9539DBQR can drive LEDs directly: each I/O pin supports up to 25 mA sink current, and each 8-bit port (P00–P07 or P10–P17) supports up to 100 mA total. Section 6.5 Electrical Characteristics confirms IOL = 25 mA per pin at VOL = 0.5 V. PCA9539DBQR's latched outputs and push-pull structure eliminate the need for external current-limiting transistors when driving standard indicator LEDs with appropriate series resistors.

How does the interrupt (INT) pin of the PCA9539DBQR behave after a state change is detected?

The INT pin of the PCA9539DBQR is an open-drain, active-low output that asserts within 4 μs (tIV) of any input state change relative to its stored Input Port register value. It remains asserted until the corresponding port register is read - either Port 0 or Port 1 - at which point the interrupt is cleared during the ACK/NACK phase of the I²C read transaction. PCA9539DBQR does not auto-clear; reading the correct port is mandatory to de-assert INT.

Is the PCA9539DBQR compatible with 5-V microcontrollers when powered from a 3.3-V supply?

Yes, the PCA9539DBQR supports 5-V-tolerant I/Os across its full operating range (2.3 V to 5.5 V VCC). Section 1 Features and Section 6.3 confirm that I/O pins tolerate up to 5.5 V regardless of VCC level - meaning PCA9539DBQR can safely interface with 5 V logic signals (e.g., switches, sensors, or MCUs) even when powered from 3.3 V, eliminating the need for external level shifters.