PCF8574NG4 - 8-Bit I2C I/O Expander | Texas Instruments
N.º de pieza: PCF8574NG4 ✓ ActivoPCF8574NG4 Descripción general
An I/O expander is an interface IC that extends the number of general-purpose inputs and outputs available to a microcontroller or other host processor. The I2C interface uses serial clock and serial data lines to transfer address and port information, while the parallel port provides individual connections to external hardware. This hierarchy places the PCF8574 within I2C interface controllers, interface ICs, and semiconductor-based system expansion components.
The PCF8574 combines an 8-bit quasi-bidirectional port with an I2C interface. Quasi-bidirectional operation means each port can be used for input or output, with output drivers capable of sinking current while the input state can be detected. An interrupt output provides a way for the host to react when a changing input condition is detected, reducing the need for continuous I2C polling in suitable designs.
The 2.5 V to 6 V VCC range allows the device to operate with both 3.3 V and 5 V system rails. Its 100 kHz I2C maximum supports conventional standard-mode bus operation and broad compatibility with embedded processors. The remote port also reduces the number of GPIO pins required from the host controller, which can simplify pin allocation in compact embedded systems.
Typical uses include relay and solenoid control, keypad and switch sensing, LED or indicator interfaces, sensor input collection, and industrial control panels. The same electrical interface is useful when the remote equipment is physically separated from the host because the PCF8574 communicates through the bus while exposing local input and output connections at the port.
Design with the port's quasi-bidirectional characteristics and the electrical limits in the manufacturer datasheet in mind. Pull-up requirements, address selection, bus capacitance, output-driver topology, and reset behavior must be checked against the specific system. Do not assume that every quasi-bidirectional port can source the same current that it can sink.
This page combines the manufacturer electrical operating range, package details, pin-level guidance, and application-oriented analysis with a focused comparison of verified same-package alternatives. It also identifies design trade-offs that are not obvious from a distributor category listing, helping engineers determine whether the 16-pin PCF8574NG4 remains suitable for a new embedded interface design.
Alternativas directas para PCF8574NG4 — 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 PCF8574NG4 (mismo factor de forma y huella) — difiere en Interface, Package, Supply Voltage Range.
PCF8574N
✅ Sustitución directaConsulte el precio
Ver hoja de datos →PCF8574P,112
✅ Sustitución directa📋 Alternativa de referencia (no en el catálogo)
PCF8574AN
✅ Sustitución directaConsulte el precio
PCF8574AP,112
✅ Sustitución directa📋 Alternativa de referencia (no en el catálogo)
PCF8574ANG4
✅ Sustitución directa📋 Alternativa de referencia (no en el catálogo)
PCF8574NG4 Especificaciones
| Device Type | 8-bit I/O expander |
| Interfaz | I2C |
| Bus Frequency | 100 kHz |
| Supply Voltage Range | 2.5 V to 6 V |
| Number of I/O Lines | 8 lines |
| Port Type | 8-bit quasi-bidirectional |
| Bus Type | Two-line bidirectional |
| Encapsulado | 16-DIP (0.300 inch, 7.62 mm) |
| Recuento de pines | 16 pins |
| Lead Pitch | 7.62 mm |
| Tipo de montaje | Through-hole |
| Interrupt Output | 1 open-drain interrupt output |
Configuración de pines de PCF8574NG4
| Pin 1 | P0 — Quasi-bidirectional I/O port line 0 |
| Pin 2 | P1 — Quasi-bidirectional I/O port line 1 |
| Pin 3 | P2 — Quasi-bidirectional I/O port line 2 |
| Pin 4 | P3 — Quasi-bidirectional I/O port line 3 |
| Pin 5 | P4 — Quasi-bidirectional I/O port line 4 |
| Pin 6 | P5 — Quasi-bidirectional I/O port line 5 |
| Pin 7 | P6 — Quasi-bidirectional I/O port line 6 |
| Pin 8 | P7 — Quasi-bidirectional I/O port line 7 |
| Pin 9 | SCL — I2C serial clock input |
| Pin 10 | SDA — I2C serial data input and output |
| Pin 11 | INT — Interrupt output |
| Pin 12 | GND — Ground reference |
| Pin 13 | A0 — I2C address input 0 |
| Pin 14 | A1 — I2C address input 1 |
| Pin 15 | A2 — I2C address input 2 |
| Pin 16 | VCC — Power supply input |
Aplicaciones típicas
PCF8574NG4 es adecuado para 6 aplicacións: Industrial Control Panels, Relay and Solenoid Control, Keypad and Switch Sensing, LED and Indicator Interfaces, Remote Sensor Input Collection, Embedded Instrumentation Interfaces.
Industrial Control Panels
The PCF8574NG4 is well suited to industrial control panels that need more switch inputs and indicator outputs than the host controller can provide directly. Its eight quasi-bidirectional lines can monitor panel selectors and operate compatible indicators or control inputs through the I2C bus. The specified 2.5 V to 6 V VCC range supports 3.3 V and 5 V control electronics, while the 100 kHz bus limit suits slow-changing panel signals. Designers should account for the port's asymmetrical sink and source capabilities and protect external connectors against industrial transients.
Recomendado
Relay and Solenoid Control
A PCF8574NG4 can provide a compact remote output port for relays, solenoids, and latching control loads when the attached circuits remain within the electrical limits of the quasi-bidirectional drivers. The host writes the desired output pattern over the 100 kHz I2C interface rather than consuming one GPIO pin per load. Because the port is primarily intended to sink current, relay-driver selection and flyback protection are critical. The 16-pin PDIP format also suits repairable, through-hole control boards where a socketed implementation is preferred.
Recomendado
Keypad and Switch Sensing
The PCF8574NG4 can consolidate switch or keypad scanning into eight remote port inputs while retaining a single two-wire I2C connection to the controller. With a 100 kHz maximum bus frequency, it is appropriate for human-operated inputs whose switching rates are modest compared with high-speed digital buses. Its interrupt output can indicate a changed input state so the host can read the port when needed. Firmware must account for I2C address selection, debounce timing, and the electrical behavior of the quasi-bidirectional input stage.
Recomendado
LED and Indicator Interfaces
The PCF8574NG4 can drive compatible LED indicators, status flags, or low-current display-control lines through a compact I2C-controlled port. Grouping indicators on an expander preserves microcontroller GPIO capacity for higher-bandwidth tasks and allows firmware to update several outputs with one serial transaction. Because quasi-bidirectional outputs are optimized for sinking current, the LED direction and current-limiting arrangement should be selected to match the port characteristics. The 2.5 V to 6 V operating range also permits the same expander to serve 3.3 V and 5 V indicator systems.
Recomendado
Remote Sensor Input Collection
The PCF8574NG4 can collect several digital sensor or alarm signals in a remote enclosure and report their state to a controller over I2C. This arrangement limits cable conductors to clock, data, ground, and supply while allowing the eight port inputs to interface with compatible switches, limit detectors, or digital sensors. The 100 kHz bus rate provides adequate throughput for slowly changing discrete signals. Input thresholds, leakage behavior, address assignment, and any protection network must be checked against the voltage levels used by the remote equipment.
Recomendado
Embedded Instrumentation Interfaces
The PCF8574NG4 can extend a measurement or laboratory instrument with control and status lines without requiring a large microcontroller package. Digital range-select switches, relay commands, front-panel status inputs, and alarm outputs are typical loads for its eight quasi-bidirectional lines. Its 16-pin PDIP package is particularly convenient for through-hole prototypes, educational instruments, and repairable legacy-style boards. Firmware should establish the I2C address before other devices respond, and the interrupt path should be configured to avoid false triggers from transient mechanical contacts.
Recomendado
Resumen de productos recomendados
Datos de referencia de ingeniería para PCF8574NG4 — comparación, orientación de diseño e información de cumplimiento.
Guía de selección
Comparación con alternativas
| Parámetro | Este producto | PCF8574N | PCF8574P,112 | PCF8574AN | PCF8574AP,112 | PCF8574ANG4 |
|---|---|---|---|---|---|---|
| Package | 16-DIP (0.300 inch, 7.62 mm) | 16-DIP (0.300 inch, 7.62 mm) | 16-DIP (0.300 inch, 7.62 mm) | 16-DIP (0.300 inch, 7.62 mm) | 16-DIP (0.300 inch, 7.62 mm) | 16-DIP (0.300 inch, 7.62 mm) |
| Brand | Texas Instruments | Texas Instruments | Texas Instruments | Texas Instruments | Texas Instruments | Texas Instruments |
| Number of I/O Lines | 8 | 8 | 8 | 8 | 8 | 8 |
| I2C Bus Frequency | 100 kHz | 100 kHz | 100 kHz | 100 kHz | 100 kHz | 100 kHz |
| Port Type | 8-bit quasi-bidirectional | 8-bit quasi-bidirectional | 8-bit quasi-bidirectional | 8-bit quasi-bidirectional | 8-bit quasi-bidirectional | 8-bit quasi-bidirectional |
| Interrupt Function | Yes | Yes | Yes | Yes | Yes | Yes |
Diferenciadores clave
- Direct through-hole expansion with eight I/O lines (frente a PCA9554PWR)
- Standard-mode I2C performance (frente a PCF8574AN)
- Legacy-friendly 7.62 mm lead pitch (frente a PCF8574AP,112)
Notas de diseño
The PCF8574NG4 operates across a 2.5 V to 6 V VCC range, but its I2C pins must remain compatible with the voltage used by the bus pull-ups. Do not automatically pull SDA and SCL to VCC if another device on the bus uses a lower logic level. Confirm the input and open-drain output voltage limits for every participant, and choose pull-up values from the bus capacitance and 100 kHz operating requirement in the manufacturer datasheet.
Place the expander close to the connectors or remote signals it serves to keep I2C wiring short and avoid routing vulnerable external signals through a crowded logic area. Route SDA and SCL away from relay contacts, switching-power nodes, and other sources of electrical noise. Provide solid ground return paths, decouple VCC near the device according to the manufacturer guidance, and maintain clearance appropriate to the assembly's voltage and environmental requirements.
Do not assume that an output written as logic high behaves like a fully push-pull GPIO. The PCF8574 uses quasi-bidirectional ports, so driver source and sink behavior must be checked before driving LEDs or other loads. Also assign each device a unique I2C address, account for power-up states in firmware, and use pull-ups or another defined strategy so SDA and SCL cannot remain in an indeterminate state.
Información de cumplimiento
The listed component is a Texas Instruments 16-DIP I/O expander, but no explicit RoHS, REACH, AEC-Q100, lead-free, halogen-free, or conflict-minerals declaration was identified for the exact orderable part.
