PCF8574DW - 8-Bit 100kHz I2C I/O Expander | Texas Instruments
N.º de pieza: PCF8574DW ✓ Activo| Cant. | Precio unitario | Total |
|---|---|---|
| 1 | $1.0956 | $1,10 |
| 10 | $1.0956 | $10,96 |
| 100 | $1.0956 | $109,56 |
| 500 | $1.0956 | $547,80 |
| 1.000 | $1.0956 | $1.095,60 |
PCF8574DW Descripción general
An I/O expander is an interface IC that translates serial I2C commands into parallel digital inputs or outputs. The PCF8574 belongs to the parallel-port expansion and I2C interface hierarchy. It uses two bus lines, SCL and SDA, to receive configuration and port-state data from a microcontroller, then presents P0 through P7 as individually controlled digital ports. Its interrupt output allows a host to react when an input condition changes without continuously polling the bus.
The principal features include eight I/O ports, a maximum I2C clock frequency of 100 kHz, a 2.5 V to 6 V VCC operating range stated in the datasheet, and low standby-current consumption with a listed maximum standby current of 10 µA. The open-drain interrupt output is compatible with common microcontroller interrupt inputs. The 16-SOIC package is a surface-mount SOIC-16 footprint, and the DWR tape-and-reel ordering code must not be confused with the DW tube ordering code.
The quasi-bidirectional port architecture makes the PCF8574 useful for simple control and status signals. A port can be written as an output or sampled as an input, but the electrical behavior and pull-up implementation require care when driving external loads. The interrupt pin provides an event-oriented alternative to periodic reads when one or more input lines change state. Firmware must also verify the device address and bus pull-up arrangement when multiple expanders share the same two-wire bus.
Typical applications include keypad and control-panel scanning, relay or solenoid control, LED indication, sensor and switch input aggregation, industrial control modules, and general embedded systems where a microcontroller has too few GPIO pins. The expander is particularly useful when the required signals are simple logic levels and the bus is already present. It is less suitable when high-speed edge-sensitive inputs, high-current output drive, or strong isolation requirements are present.
Designers should verify pull-up resistors on SDA and SCL, ensure that all connected devices use compatible voltage levels, and account for total bus capacitance. Port pins intended as inputs should not be forced into incompatible logic states, while output loads should remain within verified current and voltage limits. This page combines the supplied manufacturer and distributor data with practical design guidance, comparison parameters, and sourcing information.
Alternativas directas para PCF8574DW — mismo encapsulado, compatible pin a pin. Se excluyen las piezas de otro encapsulado que requieren retrabajo de la PCB.
Variantes de esta serie
Modelos de la misma serie compatibles directamente con PCF8574DW (mismo factor de forma y huella) — difiere en Interface, Package, Interrupt Output, RoHS Status, Hardware Address Pins.
Herramienta de comparación rápida — seleccione piezas alternativas para compararlas lado a lado:
PCF8574DWR
✅ Sustitución directa📋 Alternativa de referencia (no en el catálogo)
PCF8574ADW
✅ Sustitución directa📋 Alternativa de referencia (no en el catálogo)
PCA9557D
✅ Sustitución directa✓ En stock
$0.71 / unidad
Ver hoja de datos →PCF8574ATD-T
✅ Sustitución directa📋 Alternativa de referencia (no en el catálogo)
PCA8574AD,512
✅ Sustitución directa📋 Alternativa de referencia (no en el catálogo)
PCF8574DW Especificaciones
| Product Type | 8-bit I2C I/O expander |
| Number of I/O Ports | 8 |
| I2C Maximum Clock Frequency | 100 kHz |
| Operating Supply Range | 2.5 V to 6 V VCC |
| Product-Page Supply Range | 2.5 V to 5.5 V |
| Interfaz | I2C two-line bidirectional bus |
| Port Architecture | Quasi-bidirectional I/O |
| Interrupt Output | Open-drain |
| Standby Current | 10 µA maximum |
| Encapsulado | 16-SOIC |
| Recuento de pines | 16 pins |
| Tipo de montaje | Surface mount |
| Application Category | I/O expander |
| Bus | I2C/SMBus |
| Port Names | P0 through P7 |
| Manufacturer | Texas Instruments |
Configuración de pines de PCF8574DW
| Pin 1 | A0 — Address input A0 |
| Pin 2 | A1 — Address input A1 |
| Pin 3 | A2 — Address input A2 |
| Pin 4 | P0 — Port P0 I/O |
| Pin 5 | P1 — Port P1 I/O |
| Pin 6 | P2 — Port P2 I/O |
| Pin 7 | P3 — Port P3 I/O |
| Pin 8 | GND — Ground |
| Pin 9 | P4 — Port P4 I/O |
| Pin 10 | P5 — Port P5 I/O |
| Pin 11 | P6 — Port P6 I/O |
| Pin 12 | P7 — Port P7 I/O |
| Pin 13 | INT — Open-drain interrupt output |
| Pin 14 | SDA — Serial data input/output |
| Pin 15 | SCL — Serial clock input |
| Pin 16 | VCC — Power supply |
Aplicaciones típicas
PCF8574DW es adecuado para 7 aplicacións: Microcontroller GPIO Expansion, Keypad and Control Panel, LED and Indicator Control, Industrial Switch and Sensor Aggregation, Relay and Solenoid Control Interface, Embedded Instrument and Test Module, General I2C Peripheral Sharing.
Microcontroller GPIO Expansion
The PCF8574DW fits a design where a microcontroller needs eight additional simple digital lines without dedicating eight GPIO pins. It connects to the host through the two-wire I2C interface at up to 100 kHz and presents P0 through P7 as parallel ports. This arrangement is useful for compact embedded controllers, provided the added signals operate within the device's verified electrical limits and the firmware assigns each port explicitly.
Recomendado
Keypad and Control Panel
The PCF8574DW can reduce the number of host GPIO pins required by a keypad, switch bank, or simple control panel. Eight ports can represent scanned inputs or panel-control signals while SCL and SDA carry commands from the host. The 16-SOIC package is suitable for a compact PCB, but switch debouncing, port polarity, pull resistors, and the device's quasi-bidirectional input behavior should be verified in firmware and hardware.
Recomendado
LED and Indicator Control
The PCF8574DW is useful when an embedded board needs more indicator outputs than the host controller can provide directly. P0 through P7 can operate LED or logic-level indicator signals through suitable current-limiting and drive circuitry. The 100 kHz I2C rate is adequate for ordinary status updates, while the application must avoid exceeding verified port current and voltage limits and should account for common-anode versus common-cathode wiring.
Recomendado
Industrial Switch and Sensor Aggregation
The PCF8574DW can aggregate digital limit switches, alarm inputs, or simple sensor-enable signals in an industrial control module. The interrupt output provides an event-oriented path for notifying the host when an input condition changes, reducing unnecessary bus polling if the system is designed correctly. Industrial implementations must verify voltage levels, isolation strategy, grounding, surge protection, and the interrupt polarity against the manufacturer datasheet.
Recomendado
Relay and Solenoid Control Interface
The PCF8574DW can provide logic-level control signals to relay drivers, transistor stages, or solenoid interface circuits when the load is not connected directly to an expander port. Its eight ports allow multiple control channels to share the I2C bus, while external transistors or drivers provide the required current and voltage capability. The supplied data does not verify direct high-current port ratings, so the application should use staged drive and consult the official datasheet.
Recomendado
Embedded Instrument and Test Module
The PCF8574DW is a practical choice for a compact test or measurement module that needs digital configuration lines for relays, range-select switches, front-panel indicators, or instrument enables. I2C allows the measurement controller to configure several auxiliary signals without consuming a large number of direct GPIO pins. The 100 kHz bus is suitable for ordinary configuration traffic, but safety-critical isolation, calibration state, and fault handling must be designed independently of the expander.
Recomendado
General I2C Peripheral Sharing
The PCF8574DW can be added to a board that already uses I2C sensors, memory, or other peripherals when the system needs another eight digital ports. Address planning is essential because multiple devices share SCL and SDA, and the host must avoid address conflicts. Use pull-ups appropriate for the complete bus, account for capacitance and level compatibility, and validate the assembled board with the intended peripherals rather than testing the expander in isolation.
Recomendado
Resumen de productos recomendados
Datos de referencia de ingeniería para PCF8574DW — comparación, orientación de diseño e información de cumplimiento.
Guía de selección
Comparación con alternativas
| Parámetro | Este producto | PCF8574DWR | PCF8574ADW | PCA9557D | PCF8574ATD-T | PCA8574AD,512 |
|---|---|---|---|---|---|---|
| Brand | Texas Instruments | Texas Instruments | Texas Instruments | Texas Instruments | NXP Semiconductors | NXP Semiconductors |
| Product Type | 8-bit I2C I/O expander | 8-bit I/O expander | Related PCF8574 variant | I2C I/O expander | I2C GPIO expander candidate | I2C GPIO expander |
| Functional Compatibility | PCF8574 reference function | Closest listed replacement | Related variant | Related TI expander | Cross-brand comparison candidate | Cross-brand I2C GPIO candidate |
Diferenciadores clave
- Directly matches the requested 8-bit PCF8574 function and 100 kHz I2C class (frente a PCA8574AD,512)
- Same-brand 16-SOIC replacement path with verified related ordering data (frente a PCF8574DWR)
- Open-drain interrupt supports event-driven host response (frente a PCA9557D)
- Cross-brand alternatives require more validation (frente a PCF8574ATD-T)
Notas de diseño
Keep SDA and SCL traces short, route them away from noisy switching nodes, and place the associated bus pull-ups close to the master or according to the complete-bus capacitance calculation. The verified operating class is a 100 kHz I2C device, so trace length and pull-up selection should be validated with the actual peripheral population rather than with the PCF8574DW alone. Do not omit address-strapping components if multiple expanders may be installed.
The PCF8574 ports are quasi-bidirectional, so an output port can be influenced by external pull-up or pull-down circuitry. Avoid using a port simultaneously as a strong output and an externally driven input unless the manufacturer electrical limits support that arrangement. For switches and sensors, define the inactive state in hardware and software, verify input levels, and use the datasheet's port behavior rather than treating every pin as a modern push-pull GPIO.
For actuator or relay-control boards, keep the PCF8574DW away from inductive paths and route switched-current wiring separately from SDA, SCL, and port traces. Use a suitable transistor or driver stage when the load exceeds verified port capability, and provide local decoupling at the IC power pin. This is especially important when the same board contains motors, solenoids, or high-current LED drivers that can introduce ground bounce and supply transients.
Confirm the system logic voltage before connecting SDA, SCL, address pins, interrupt, and port signals to the PCF8574DW. The supplied manufacturer product page lists 2.5 V to 5.5 V operation, while the datasheet search result lists 2.5 V to 6 V VCC. Treat these as source-specific statements and use the latest manufacturer datasheet for design limits. The PCF8574DW does not perform automatic level shifting between incompatible voltage domains.
Información de cumplimiento
The supplied verified data does not explicitly state RoHS, REACH, AEC-Q100, lead-free, halogen-free, or conflict-mineral status for PCF8574DW. These fields remain unknown pending confirmation from the current Texas Instruments product documentation.