NXP Semiconductors PCF8574TS/3,112

Overview

PCF8574TS/3,112 from NXP Semiconductors is an 8-bit quasi-bidirectional I²C-bus I/O expander with active-LOW open-drain interrupt output, operating from 2.5 V to 6 V, supporting up to 100 kHz I²C communication, and featuring 8 latched I/O ports that default to inputs with 100 µA internal pull-up at power-on - used in LED signage, keypad monitoring, and industrial control systems.

For engineers reviewing the PCF8574TS/3,112 datasheet, PCF8574TS/3,112 pinout, PCF8574TS/3,112 application, or PCF8574TS/3,112 equivalent, this device delivers remote parallel I/O expansion with interrupt-driven change detection, low standby current (2.5 µA typical), and SSOP20 packaging for space-constrained embedded designs requiring stable I²C peripheral extension.

Technical Context

The PCF8574TS/3,112 implements a single-register quasi-bidirectional I/O architecture where each of the eight ports (P0–P7) functions as input or output without direction register overhead; port states are read/written via one 8-bit data byte over Standard-mode I²C (100 kHz max).

Its interrupt logic asserts INT (active LOW) on any input state transition relative to the last-read register value, enabling event-driven microcontroller wake-up; internal Power-On Reset initializes all I/Os as inputs with 100 µA weak pull-up to VDD, eliminating external reset circuitry.

Key Specifications

Pinout & Package

PCF8574TS/3,112 is housed in a 20-pin plastic shrink small outline package (SSOP20), 4.4 mm body width, with 0.65 mm lead pitch and surface-mount footprint optimized for high-density PCB layouts.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar I²C I/O expander applications.

Compared with PCA8574TS/3,118 and PCA9674BS,118, the PCF8574TS/3,112 offers proven 100 kHz interoperability with legacy controllers and wider 2.5–6.0 V operation - ideal for cost-sensitive industrial and battery-powered applications where upgrade headroom is not required.

Availability

PCF8574TS/3,112 is available at Aetrix Electronics and suitable for LED signage control, keypad matrix monitoring, and industrial PLC I/O expansion requiring stable component supply across long production lifecycles.

Supply support for PCF8574TS/3,112 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 broad analog, digital, and mixed-signal portfolio expertise.

The PCF8574 series belongs to NXP's legacy I²C peripheral family designed specifically for low-cost, low-power remote I/O expansion in resource-constrained embedded systems - emphasizing simplicity, robustness, and wide-voltage compatibility.

FAQ

What is the I²C address configuration method for PCF8574TS/3,112?

The PCF8574TS/3,112 uses three hardware address pins (A0, A1, A2) to configure one of eight possible 7-bit slave addresses. These pins must be externally tied HIGH or LOW - no internal pull-ups exist. For the PCF8574 variant, the fixed address prefix is 0100b, so with A2–A0 = 000b, the write address is 0x40 and read address is 0x41. All address combinations are documented in the datasheet Table 4.

Does PCF8574TS/3,112 support true bidirectional I/O without external components?

Yes - PCF8574TS/3,112 implements quasi-bidirectional I/O on P0–P7, meaning each pin functions as input or output without a direction register. At power-on, all ports default to inputs with 100 µA internal pull-up to VDD. Writing '1' configures as input; writing '0' activates strong pull-down for output LOW. No external direction logic or resistors are needed for basic operation.

How does the interrupt (INT) pin of PCF8574TS/3,112 behave during I²C read/write cycles?

The INT pin of PCF8574TS/3,112 is automatically de-asserted (goes HIGH) on the rising edge of the acknowledge bit after a read or write operation. It remains HIGH until any input port state differs from its corresponding register value. During rapid successive reads/writes, brief glitches may occur, but the interrupt reliably signals first-change events - not edge counts or debounced transitions.

Can PCF8574TS/3,112 drive LEDs directly, and what are the current limits?

Yes - PCF8574TS/3,112 can directly drive LEDs with its 10 mA sink capability per port (P0–P7) and 80 mA total package limit. Each output uses an internal N-channel transistor; connect LED anode to VDD and cathode to port pin with appropriate current-limiting resistor. Do not exceed 10 mA per pin or 80 mA total to avoid thermal stress or latch-up.

What is the power-on reset behavior of PCF8574TS/3,112, and how does it affect initial I/O state?

PCF8574TS/3,112 includes an internal Power-On Reset (POR) circuit that holds the device in reset until VDD reaches VPOR (~1.3–2.4 V). Upon release, all I/O ports initialize as inputs with 100 µA weak pull-up to VDD - resulting in logic HIGH at each pin unless externally pulled LOW. This ensures safe, predictable startup without external reset components or firmware initialization delays.