PCF8574ADW - 8-Bit 5.5V I2C I/O Expander | Texas Instruments
料号： PCF8574ADW ✓ 量产中PCF8574ADW 概述
An I/O expander is an interface IC that extends the input/output capacity of a host such as a microcontroller or application processor. The PCF8574 belongs to the I2C I/O expander hierarchy and uses the two-wire bus for command and status transfers. Eight ports can be individually configured as inputs or outputs, while address pins allow multiple expanders to coexist on the same bus.
Key features include eight I/O lines, a 2.5 V to 5.5 V operating range, 100 kHz I2C operation, and an open-drain interrupt output. The interrupt output allows the connected processor to respond when a change occurs on an input port rather than continuously polling all eight lines. The SOIC-16 package supports conventional surface-mount assembly and is available in a -40 °C to +85 °C temperature grade.
The PCF8574A architecture uses quasi-bidirectional ports capable of both input and output operation. Each port can be driven low or released high, while an external pull-up resistor is normally required to establish the high state. The three address inputs select one of eight device addresses, allowing several PCF8574 devices to share common SCL and SDA nets. Power-on behavior depends on the external pull-up network and must be considered when defining system defaults.
Typical uses include reading control buttons and switches, driving discrete LEDs, monitoring digital status signals, and expanding the GPIO capacity of industrial controllers, test equipment, access-control panels, and compact embedded products. The interrupt line is especially useful in systems where periodic I2C polling would waste processor time or create unnecessary bus activity.
Design the interface around the device's open-drain bus architecture. Place pull-up resistors on SDA and SCL close to the bus master, confirm address-strapping levels before enabling the device, and account for the port high-current limitations when driving capacitive or LED loads. The manufacturer datasheet is the controlling reference for pinout, timing, output-current limits, and electrical characteristics.
直接替换替代料： PCF8574ADW ——相同封装，引脚兼容。需要 PCB 改动的不同封装料号已排除。
本系列中的变体
可与以下型号直接替换的同系列型号： PCF8574ADW （相同外形与封装尺寸） ——差异在于 Interface, Interrupt Output, Number of I/O Ports, Package, Product Type.
PCF8574DWR
✅ 直接替换联系询价
查看数据手册 →PCF8574DW
✅ 直接替换联系询价
查看数据手册 →PCA8574AD
✅ 直接替换📋 参考替代料（不在目录中）
PCA8574TS
✅ 直接替换📋 参考替代料（不在目录中）
PCF8574ADW 规格参数
| Product Type | 8-bit I2C/SMBus I/O expander |
| Number of I/O Ports | 8 ports |
| 接口 | I2C/SMBus |
| Maximum I2C Clock Frequency | 100 kHz |
| 工作电源电压 | 2.5 V to 5.5 V |
| Datasheet Supply Voltage Range | 2.5 V to 6 V |
| Number of Address Inputs | 3 inputs |
| Device Addressing | 8 programmable addresses |
| Interrupt Output | 1 open-drain interrupt output |
| Port Type | 8 quasi-bidirectional I/O ports |
| 封装 | 16-pin SOIC (DW) |
| 引脚数量 | 16 pins |
| 工作温度范围 | -40 °C to +85 °C |
| 安装方式 | Surface mount |
| Automotive Qualification | Not indicated as AEC-Q100 qualified |
PCF8574ADW 引脚配置
| 引脚 1 | A0 — Address input 0 |
| 引脚 2 | A1 — Address input 1 |
| 引脚 3 | A2 — Address input 2 |
| 引脚 4 | P0 — Quasi-bidirectional I/O port 0 |
| 引脚 5 | P1 — Quasi-bidirectional I/O port 1 |
| 引脚 6 | P2 — Quasi-bidirectional I/O port 2 |
| 引脚 7 | P3 — Quasi-bidirectional I/O port 3 |
| 引脚 8 | GND — Ground connection |
| 引脚 9 | P4 — Quasi-bidirectional I/O port 4 |
| 引脚 10 | P5 — Quasi-bidirectional I/O port 5 |
| 引脚 11 | P6 — Quasi-bidirectional I/O port 6 |
| 引脚 12 | P7 — Quasi-bidirectional I/O port 7 |
| 引脚 13 | INT — Interrupt output |
| 引脚 14 | SCL — Serial clock input |
| 引脚 15 | SDA — Serial data input/output |
| 引脚 16 | VCC — Power supply connection |
典型应用
PCF8574ADW 适用于 6 应用s: Industrial Control Panel, LED and Relay Status Interface, Embedded Data Acquisition Front End, Access Control and Security Equipment, Test and Measurement Equipment, Compact Consumer and IoT Controller.
Industrial Control Panel
The PCF8574ADW fits industrial control panels that need more switch inputs and indicator outputs than the host controller can provide directly. Its eight quasi-bidirectional ports can read operator inputs while driving status indicators, and the 2.5 V to 5.5 V operating range supports common industrial logic systems. Three address inputs permit multiple expanders on one I2C bus, while the interrupt output lets the controller react to a changed input without polling continuously. Because the ports are quasi-bidirectional and intended for light loading, high-current loads should use external drivers.
推荐
LED and Relay Status Interface
The PCF8574ADW provides a practical low-speed status interface for LEDs, relay-control inputs, and other digital indicators connected to an embedded controller. Each of the eight quasi-bidirectional ports can sink an output or be read as an input, allowing one device to combine control and monitoring functions. At 100 kHz I2C operation, the interface is appropriate for ordinary panel and board-level status rather than high-rate data acquisition. External transistors or drivers should be used when an indicator or relay requires more current than the port can directly handle.
推荐
Embedded Data Acquisition Front End
The PCF8574ADW can expand a microcontroller-based acquisition system by collecting digital status from sensors, limit switches, and external equipment. Three hardware address inputs allow several devices to share the I2C bus, which is useful when a test system monitors multiple banks of equipment. The interrupt output can alert the host when an input changes, reducing unnecessary register reads. Designers should treat the quasi-bidirectional ports as light-duty digital lines and add buffering or isolation when long cables, high noise, or high-current loads are involved.
推荐
Access Control and Security Equipment
The PCF8574ADW is suitable for access-control terminals that need to read door contacts, request-to-exit buttons, or lock-status signals while driving local indicators. Eight ports reduce the GPIO burden on the system controller, and the interrupt line can signal a state change for immediate handling. The address inputs support multiple expansion groups on a shared I2C bus. In security installations, the digital logic should be isolated from external wiring as appropriate, and port drive-current limits should be checked against the load attached to every input or output.
推荐
Test and Measurement Equipment
The PCF8574ADW can add front-panel control and status lines to bench instruments, automated test systems, and programmable fixtures. A host processor can read configuration switches and remote-control indicators through the eight ports, while the interrupt output provides event-driven input handling. The 100 kHz bus rate is sufficient for control functions but is not intended for transferring large or rapidly sampled data streams. Keep sensitive analog and timing-sensitive functions on separate circuitry to prevent switching activity on the quasi-bidirectional ports from disturbing measurements.
推荐
Compact Consumer and IoT Controller
The PCF8574ADW is useful in compact IoT controllers that need a handful of extra GPIO lines for buttons, latches, indicators, or sensor-enable signals. Its 16-pin SOIC package preserves board area, while three address inputs permit expansion without dedicating multiple I2C buses. The 2.5 V to 5.5 V range supports 3.3 V and 5 V systems. Firmware must handle the open-drain interrupt correctly, including bus pull-ups, acknowledgment behavior, and the state change that occurs after the device is read.
推荐
推荐产品汇总
工程参考数据： PCF8574ADW ——对比、设计指导和合规信息。
选型指南
与替代料对比
| 参数 | 本产品 | PCF8574DWR | PCF8574DW | PCA8574AD | PCA8574TS |
|---|---|---|---|---|---|
| Package | SOIC-16 (DW) | SOIC-16 (DW) | SOIC-16 (DW) | SOIC-16 | SOIC-16 |
| Brand | Texas Instruments | Texas Instruments | Texas Instruments | NXP Semiconductors | NXP Semiconductors |
| Product Type | 8-bit I2C I/O expander | 8-bit I2C I/O expander | 8-bit I2C I/O expander | 8-bit I2C I/O expander | 8-bit I2C I/O expander |
| Number of I/O Ports | 8 ports | 8 ports | 8 ports | 8 ports | 8 ports |
| Interface | I2C/SMBus | I2C/SMBus | I2C/SMBus | I2C | I2C |
| Address Inputs | 3 inputs | 3 inputs | 3 inputs | 3 inputs | 3 inputs |
| Interrupt Output | Yes, open-drain | Yes, open-drain | Yes, open-drain | Yes | Yes |
关键差异点
- Direct same-package replacement within the Texas Instruments family （对比 PCF8574DWR)
- Cross-brand sourcing option with an 8-bit equivalent function （对比 PCA8574AD)
- Dedicated interrupt output for event-driven host control （对比 PCA8574TS)
设计说明
Place the SDA and SCL pull-up resistors near the bus master when possible, using values that satisfy the bus capacitance and rise-time requirements at the selected voltage. Address pins A0, A1, and A2 must be connected to a stable logic level before the expander is addressed. Keep the I2C route away from switching power nodes and noisy relay-driver traces, while keeping the ground return continuous beneath the device.
Do not treat the quasi-bidirectional ports as general-purpose high-current outputs. A port left high is weakly driven, so the circuit must not continuously source substantial current from an external load. Use a transistor or other driver for relays, lamps, and high fan-out loads. Firmware should also account for the port latch state, power-on pull-up behavior, and any external device that can pull an input line low.
The interrupt is an open-drain output, so it requires a pull-up and must share the interrupt node only with devices that use compatible wired-open-drain signaling. Ensure that the pull-up voltage is safe for every connected device and that the resulting rise time satisfies the host's input requirements. For long cables or noisy industrial panels, add appropriate filtering, isolation, or a dedicated interface buffer rather than extending the I2C bus directly.
合规信息
The ordering information identifies an industrial-temperature PCF8574A device, but no explicit RoHS, REACH, lead-free, halogen-free, or conflict-minerals declaration was included. The manufacturer datasheet and current product-page compliance documentation should be checked during qualification.