PCF8574APW - 8-Bit I2C I/O Expander | Texas Instruments
N.º da peça: PCF8574APW ✓ AtivoPCF8574APW Visão geral
An I/O expander is an interface IC that translates serial bus commands into parallel digital input and output access. The PCF8574A family belongs to the I/O expander category within interface ICs, interface semiconductors, and electronic components. Its remote port can connect to buttons, indicators, logic inputs, control signals, and other digital peripherals while the host processor retains access through the I2C bus.
The device provides eight quasi-bidirectional I/O pins, an interrupt output, three hardware address inputs, and operation from 2.5 V to 5.5 V. According to the Texas Instruments PCF8574A product page, the device supports both I2C and SMBus communication. The manufacturer datasheet also identifies a maximum standby-current consumption of 10 microamperes, supporting designs where standby power is an important consideration.
The A designation identifies the address-selectable version of the PCF8574 family. Each device offers three address inputs, allowing multiple expanders to share one serial bus when suitable bus addresses are assigned. The interrupt output provides a hardware indication that input-port state has changed, reducing the need for the host controller to poll every port continuously.
Typical uses include expanding microcontroller GPIO for human-interface controls, monitoring switches and keypads, driving LEDs or logic-enable signals, controlling discrete system inputs, and supporting industrial interface modules. It can also reduce the number of I/O pins required on a microcontroller, processor, or programmable logic controller.
A hardware design should treat the quasi-bidirectional port outputs carefully because each line may be weakly driven high and can be pulled low by an external device. Designers should review the port architecture, address pins, bus pull-up requirements, and interrupt behavior in the manufacturer datasheet before finalizing the circuit.
This product page combines the manufacturer electrical characteristics, interface details, application guidance, pin assignment information, and verified substitute analysis. It also highlights the limits of direct replacement: identical pin count and package dimensions alone do not guarantee that two I/O expanders use identical addressing, interrupt, electrical, or qualification behavior.
Alternativas drop-in para PCF8574APW — mesmo encapsulamento, compatível pino a pino. Peças de encapsulamento diferente que exigem retrabalho na PCB são excluídas.
Variantes desta série
Modelos da mesma série compatíveis como drop-in com PCF8574APW (mesmo formato e footprint) — diferindo em Package, Mounting Type, Interface, Interrupt Output.
PCF8574PWR
✅ Drop-InConsulte o preço
Ver ficha técnica →PCF8574AP
✅ Drop-In📋 Alternativa de referência (fora do catálogo)
PCF8574APW Especificações
| Number of I/O Lines | 8 bits |
| Tensão de alimentação de operação | 2.5 V to 5.5 V |
| Bus Interface | I2C/SMBus |
| Maximum I2C Clock Frequency | 100 kHz |
| Interrupt Output | Yes |
| Address Input Count | 3 inputs |
| Maximum Standby Current | 10 microamperes |
| Port Type | 8-bit quasi-bidirectional |
| Encapsulamento | 20-pin TSSOP |
| Tipo de montagem | Surface mount |
| Frequência máxima de clock | 100 kHz |
Configuração de pinos do PCF8574APW
| Pino 1 | P0 — Quasi-bidirectional I/O port 0 |
| Pino 2 | P1 — Quasi-bidirectional I/O port 1 |
| Pino 3 | P2 — Quasi-bidirectional I/O port 2 |
| Pino 4 | P3 — Quasi-bidirectional I/O port 3 |
| Pino 5 | P4 — Quasi-bidirectional I/O port 4 |
| Pino 6 | P5 — Quasi-bidirectional I/O port 5 |
| Pino 7 | P6 — Quasi-bidirectional I/O port 6 |
| Pino 8 | P7 — Quasi-bidirectional I/O port 7 |
| Pino 9 | NC — Not connected |
| Pino 10 | INT — Interrupt output |
| Pino 11 | A2 — Slave address input 2 |
| Pino 12 | A1 — Slave address input 1 |
| Pino 13 | A0 — Slave address input 0 |
| Pino 14 | SCL — Serial clock input |
| Pino 15 | SDA — Serial data input and output |
| Pino 16 | VSS — Ground supply |
| Pino 17 | VDD — Positive supply voltage |
| Pino 18 | NC — Not connected |
| Pino 19 | NC — Not connected |
| Pino 20 | NC — Not connected |
Aplicações típicas
PCF8574APW é adequado para 6 aplicaçãos: Microcontroller GPIO Expansion, Industrial Keypad and Switch Interface, LED and Indicator Control, Programmable Logic Controller Interface, Consumer Accessory and Remote Control, Test and Measurement Control Interface.
Microcontroller GPIO Expansion
The PCF8574APW is appropriate when a host microcontroller has too few general-purpose pins for panel controls, indicators, and discrete logic signals. Its eight quasi-bidirectional lines operate as a remote 8-bit port while the controller communicates through the I2C/SMBus interface at up to 100 kHz. The three address inputs permit multiple expanders to share the bus, and the interrupt output can identify input changes without continuous polling. Because the port is quasi-bidirectional rather than independently push-pull driven, each connected circuit must be compatible with the port's electrical behavior.
Recomendado
Industrial Keypad and Switch Interface
For an industrial keypad, limit switch, or operator panel, the PCF8574APW can place switch states behind the I2C bus and notify the controller through its interrupt output. Eight quasi-bidirectional inputs provide more panel capacity than many small microcontrollers offer directly. The 2.5 V to 5.5 V operating range supports common logic systems, while the 100 kHz bus limit is suitable for relatively slow human-interface updates. Firmware must debounce mechanical contacts, and production designs should verify environmental temperature and qualification requirements for the deployed equipment.
Recomendado
LED and Indicator Control
The PCF8574APW can control compatible LED indicators, status lamps, and logic-enable signals through its eight quasi-bidirectional port lines. This reduces the number of dedicated pins consumed by the host controller and lets firmware update multiple indicators over the I2C bus. Each output arrangement must respect the port's electrical characteristics, including its ability to source current high and be pulled low by a connected device. The interrupt function is not required for ordinary output-only use, but the address pins should still be configured consistently when several expanders are present.
Recomendado
Programmable Logic Controller Interface
The PCF8574APW can add digital I/O to a programmable logic controller or small control module that already uses I2C for configuration and monitoring. Eight lines can represent discrete commands, sensor states, interlocks, or remote enables, while the interrupt output provides an event-driven indication of input changes. Its 2.5 V to 5.5 V range covers common control-logic rails, and the 100 kHz bus rate is appropriate for infrequent status updates. For safety-related or extended-temperature installations, confirm device qualification and environmental requirements separately.
Recomendado
Consumer Accessory and Remote Control
The PCF8574APW can expand a compact controller in an accessory, remote-control enclosure, or smart-home interface. Eight remote lines can supervise buttons, connect logic-level indicators, or operate compatible external control circuits without consuming every host GPIO. The interrupt output is useful for responsive button handling because the controller can react to an asserted event instead of maintaining a continuous polling loop. The low 10-microampere maximum standby current also supports battery-conscious designs, although total system consumption depends on the host controller and attached loads.
Recomendado
Test and Measurement Control Interface
The PCF8574APW can serve as a simple digital-control interface in a test fixture or measurement peripheral. The eight lines can operate compatible relays, capture control inputs, or supervise discrete fixture signals while the main instrument controller communicates over I2C. Address inputs allow several expansion groups to share a bus, and the interrupt output can signal an input event for faster test sequencing. Designers must confirm logic thresholds and output-loading behavior because the port is quasi-bidirectional and is not a universal replacement for a high-current relay-driver output.
Recomendado
Resumo dos produtos recomendados
Dados de referência de engenharia para PCF8574APW — comparação, orientação de projeto e informações de conformidade.
Guia de seleção
Comparação com alternativas
| Parâmetro | Este produto | PCF8574PWR | PCF8574AP |
|---|---|---|---|
| Brand | Texas Instruments | Texas Instruments | NXP Semiconductors |
| Package | 20-pin TSSOP | 20-pin TSSOP | 20-pin TSSOP |
| Number of I/O Lines | 8 bits | 8 bits | 8 bits |
| Interrupt Output | Yes | Yes | Yes |
| Address Selection Family | PCF8574A family | Non-A PCF8574 family | PCF8574A family |
| Port Architecture | Quasi-bidirectional | Quasi-bidirectional | Quasi-bidirectional |
| Address Inputs | 3 inputs | 3 inputs | 3 inputs |
Principais diferenciais
- Direct TI family path with an established A-series address map (vs PCF8574PWR)
- Eight-line expansion with interrupt support (vs PCF8574AP)
- Multiple-device bus scalability (vs PCF8574AP)
Notas de projeto
The PCF8574A port is quasi-bidirectional, not eight independently driven push-pull outputs. Each line can be driven high by the device and pulled low by an external circuit. Before assigning a load, review the port voltage and current limits in the manufacturer datasheet. Do not connect a peripheral that actively drives the line high while the expander also attempts to drive it, and do not treat the port as a general-purpose logic output without checking its electrical behavior.
Place the device close to the connectors or remote signals it serves, and keep the SCL and SDA routes short enough to control bus capacitance and susceptibility to interference. Use the pull-up values recommended by the manufacturer for the actual bus voltage and operating speed. Keep the three address inputs at defined logic levels before the bus becomes active, and route the interrupt signal away from high-current switching nodes where practical.
Power the PCF8574APW from the same logic domain as its I2C bus and connected digital inputs unless the design intentionally supports level translation. The device operates from 2.5 V to 5.5 V, but its port pins must also remain within the manufacturer electrical limits. Provide local supply bypassing close to VDD and VSS, and avoid routing transient-prone motor, relay, or switch-supply wiring alongside the serial bus and port signals.
Do not approve PCF8574PWR as a substitute without checking slave addresses because the non-A suffix changes the family used for address selection. The NXP PCF8574AP is functionally close but remains a cross-manufacturer substitution requiring comparison of interrupt implementation, electrical limits, operating-temperature range, qualification, and lifecycle status. The 20-pin TSSOP footprint is shared, but a footprint match alone does not validate a drop-in replacement.
Informações de conformidade
The verified product information does not explicitly state the compliance status for the PCF8574APW. The cross-reference comparison page mentions RoHS and REACH for compared parts, but it does not provide an explicit compliance declaration for the target ordering code.