NXP Semiconductors PCA8575BQ,118

Overview

PCA8575BQ,118 from NXP Semiconductors is a 16-bit remote I/O expander for I²C-bus with interrupt, featuring quasi-bidirectional I/O ports, 400 kHz I²C interface, 2.3 V to 5.5 V operation, and active LOW open-drain INT output. It supports LED direct drive with 25 mA sink per pin and 400 mA total package sink capability, used in industrial control and server I/O expansion.

For engineers reviewing the PCA8575BQ,118 datasheet, PCA8575BQ,118 pinout, PCA8575BQ,118 application, or PCA8575BQ,118 equivalent, key selection considerations include its DHVQFN24 package, 8 programmable slave addresses via AD0–AD2, latched output architecture, interrupt timing behavior during byte-wise read operations, and compatibility with PCF8575 software but distinct INT release timing.

Technical Context

The PCA8575BQ,118 implements a quasi-bidirectional I/O architecture where all 16 pins (P00–P07, P10–P17) operate without direction control signals; at power-up, all default to HIGH inputs via internal current sources. Its I²C interface supports Fast Mode (400 kHz), with address selection across eight values (0x20–0x27) using AD0, AD1, AD2 pins.

Interrupt generation responds to any rising or falling edge on input pins, and INT is cleared byte-wise: reading Port 0 clears P0n-associated interrupts, while reading Port 1 clears P1n-associated interrupts - differing from PCF8575's full-interrupt-clear-on-read behavior. Internal Power-On Reset initializes I/Os to logic 1 and resets I²C state machine.

Key Specifications

Pinout & Package

DHVQFN24 package: plastic dual in-line compatible thermal enhanced very thin quad flat package; no leads; 24 terminals; body 3.5 × 5.5 × 0.85 mm (SOT815-1). Exposed center pad must be soldered to PCB ground for thermal and electrical integrity.

Key Features

Applications

Equivalent & Alternatives

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

Compared with PCF8575DT,118, PCA8575BQ,118 adds critical interrupt capability for event-driven architectures; versus PCA9555PW,118, it offers simpler timing behavior and smaller DHVQFN24 package but omits polarity control and internal pull-ups.

Availability

PCA8575BQ,118 is available at Aetrix Electronics and suitable for industrial PLCs, server management subsystems, and medical equipment requiring stable component supply, extended temperature operation, and compact surface-mount packaging.

Supply support for PCA8575BQ,118 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 company headquartered in Eindhoven, Netherlands, specializing in secure connectivity solutions for automotive, industrial, and IoT applications.

The PCA8575BQ,118 belongs to NXP's I²C-compatible remote I/O expander product line, designed specifically to extend microcontroller GPIO resources in space-constrained, noise-immune industrial and computing systems.

FAQ

What is the primary function of the PCA8575BQ,118 in an embedded system?

The PCA8575BQ,118 serves as a 16-bit remote I/O expander that connects to a microcontroller via I²C bus, adding GPIO capability without consuming native MCU pins. It provides quasi-bidirectional ports, interrupt signaling via the INT pin, and direct LED drive capability. The PCA8575BQ,118 is commonly used in industrial controls, servers, and medical devices where board space and interrupt latency are critical constraints.

How does the interrupt behavior of the PCA8575BQ,118 differ from the PCF8575?

The PCA8575BQ,118 clears its INT output byte-wise: reading Port 0 (P00–P07) clears interrupts associated with those pins, while reading Port 1 (P10–P17) clears interrupts for that port. In contrast, the PCF8575 clears INT only after both bytes are read. This difference means the PCA8575BQ,118 enables finer-grained event handling but requires careful sequencing in firmware to avoid premature INT deassertion. The PCA8575BQ,118 remains software-compatible otherwise.

Can the PCA8575BQ,118 drive LEDs directly, and what are the current limits?

Yes, the PCA8575BQ,118 can drive LEDs directly with up to 25 mA sink current per I/O pin (P00–P07, P10–P17) and a total package sink limit of 400 mA. Each pin's VOL is specified at 0.5 V when sinking 25 mA at VDD = 4.5 V, ensuring sufficient voltage margin for standard LEDs. The PCA8575BQ,118 also includes transient boosted pull-up current (Itrt(pu)) for fast rising edges, improving LED turn-off response.

What package type is used for the PCA8575BQ,118, and why is the exposed pad important?

The PCA8575BQ,118 uses the DHVQFN24 package (SOT815-1), measuring 3.5 × 5.5 × 0.85 mm with 24 terminals and an exposed center pad. That pad must be soldered to a PCB thermal pad connected to ground - it serves as both a thermal conduction path (critical for dissipating heat during 400 mA sink operation) and an electrical ground reference. Omitting this connection risks thermal overload and unstable operation of the PCA8575BQ,118.

Does the PCA8575BQ,118 require external pull-up resistors on SDA and SCL lines?

Yes, the PCA8575BQ,118 requires external pull-up resistors on both SDA and SCL lines, as its I²C interface uses open-drain outputs. The datasheet specifies no internal pull-ups on these pins. Typical values range from 2.2 kΩ to 10 kΩ depending on bus capacitance and speed; for 400 kHz Fast Mode operation with ≤400 pF total bus capacitance, 4.7 kΩ is commonly used. These resistors ensure proper logic HIGH levels and meet I²C rise time specifications.