PCA8574D,518 - 8-Bit I2C I/O Expander 400kHz SO16 | NXP
Артикул: PCA8574D,518 ✗ Снят с производства| Кол-во | Цена за ед. | Итого |
|---|---|---|
| 1 | $1.15 | $1,15 |
| 10 | $1.02 | $10,20 |
| 100 | $0.88 | $88,00 |
| 500 | $0.75 | $375,00 |
| 1.000 | $0.66 | $660,00 |
PCA8574D,518 Обзор
An I2C I/O expander is an interface IC that lets a microcontroller add general-purpose input/output lines through the two-wire bidirectional serial bus (SCL, SDA). Within the system hierarchy, it sits in the interface-IC family between the MCU and peripheral loads such as LEDs, buttons, relays and sensors, offloading pin-count-limited controllers without adding parallel-bus complexity.
Key features include quasi-bidirectional I/O that can be independently assigned as input or output without direction-control registers, a 400 kHz fast-mode I2C interface, and a latched interrupt output that alerts the host to any input change. The wide 2.3 V to 5.5 V supply range lets one part serve 2.5 V, 3.3 V and 5 V designs.
Architecturally, the PCA8574D uses a pseudo-bidirectional port cell: writing a 1 to a bit lets it act as a high-impedance input; writing 0 drives a strong low with controlled sink current. The slave address is 0100 A2 A1 A0 (PCA8574 variant), and the PCA8574A sibling uses 0111, enabling up to 16 expanders (128 I/Os) on one bus.
Typical applications include keypad scanning, LED and backlight control, push-button monitoring, relay driving in industrial panels, and sensor-board GPIO expansion where MCU pins are scarce. The interrupt output enables low-power polled designs instead of continuous bus polling.
Design consideration: quasi-bidirectional outputs source limited current, so LED loads need the current-sinking wiring convention, and total package sink current must be respected per the datasheet.
This page synthesizes distributor pricing, drop-in alternatives, pinout data, and practical design notes not found in the manufacturer datasheet.
Аналоги без доработки для PCA8574D,518 — тот же корпус, pin-to-pin совместимость. Компоненты в других корпусах, требующие переработки PCB, исключены.
Инструмент быстрого сравнения — выберите альтернативные компоненты для сравнения бок о бок:
PCA8574AD,512
✅ Прямая замена📋 Справочный аналог (нет в каталоге)
PCA8574AD,118
✅ Прямая замена📋 Справочный аналог (нет в каталоге)
PCF8574D,3,512
✅ Прямая замена📋 Справочный аналог (нет в каталоге)
PCF8574DWR
✅ Прямая замена📋 Справочный аналог (нет в каталоге)
PCF8574DWG4
✅ Прямая замена📋 Справочный аналог (нет в каталоге)
PCA9674D,112
✅ Прямая замена ⚠️ Характеристики не проверены📋 Справочный аналог (нет в каталоге)
PCF8574DW
✅ Прямая замена📋 Справочный аналог (нет в каталоге)
PCA8574D,518 Характеристики
| Функция | Remote 8-bit I/O expander for I2C-bus with interrupt |
| Number of I/O | 8 (quasi-bidirectional) |
| Интерфейс | I2C (2-wire, SCL/SDA) |
| Clock Frequency | 400 kHz |
| Напряжение питания | 2.3 V to 5.5 V |
| Hardware Address Pins | 3 (A0, A1, A2) |
| Interrupt Output | Yes, open-drain active-low |
| Port Type | Quasi-bidirectional, independently assignable |
| Max Devices per Bus | 8 (16 with PCA8574A variant) |
| Корпус | 16-SOIC (SO16, 7.50 mm width) |
| Тип монтажа | Surface Mount |
| Packaging | Tape & Reel |
| Статус жизненного цикла | End of Life (per NXP product page) |
| Статус RoHS | Compliant |
Конфигурация выводов PCA8574D,518
| Контакт 1 | A0 — Hardware address input 0 |
| Контакт 2 | A1 — Hardware address input 1 |
| Контакт 3 | A2 — Hardware address input 2 |
| Контакт 4 | P0 — Quasi-bidirectional I/O port 0 |
| Контакт 5 | P1 — Quasi-bidirectional I/O port 1 |
| Контакт 6 | P2 — Quasi-bidirectional I/O port 2 |
| Контакт 7 | P3 — Quasi-bidirectional I/O port 3 |
| Контакт 8 | GND — Ground supply |
| Контакт 9 | P4 — Quasi-bidirectional I/O port 4 |
| Контакт 10 | P5 — Quasi-bidirectional I/O port 5 |
| Контакт 11 | P6 — Quasi-bidirectional I/O port 6 |
| Контакт 12 | P7 — Quasi-bidirectional I/O port 7 |
| Контакт 13 | INT — Interrupt output (open-drain, active-low) |
| Контакт 14 | SCL — I2C serial clock input |
| Контакт 15 | SDA — I2C serial data input/output |
| Контакт 16 | VDD — Supply voltage, 2.3 V to 5.5 V |
Типичное применение
PCA8574D,518 подходит для 6 применениеs: Keypad Scanning and Push-Button Monitoring, LED and Backlight Control, Industrial Panel and Relay Control, Sensor Board GPIO Expansion, Consumer Appliance and White-Goods Control, Legacy 5 V System Migration and EOL Replacement.
Keypad Scanning and Push-Button Monitoring
The PCA8574D,518 expands an MCU with eight quasi-bidirectional lines ideal for matrix or discrete keypads in the 2.3 V to 5.5 V range. Its open-drain active-low INT output latches any input change, so the host can sleep or perform other tasks and only service the bus when a key is pressed - no continuous I2C polling is required. Ports written to 1 act as high-impedance inputs with weak pull-up, allowing switch closure to pull them low with minimal current. With three address pins, up to eight PCA8574 devices (or 16 with PCA8574A) share one 400 kHz bus, supporting large key arrays from a single controller. The trade-off: scan latency is set by bus speed, but at 400 kHz reading an 8-bit port takes microseconds.
Рекомендуется
LED and Backlight Control
The PCA8574D drives up to eight LED channels per package using the current-sinking wiring convention: the LED anode connects to VDD through a resistor and the expander output pulls low to light the LED. This suits quasi-bidirectional ports, which sink strongly but source limited current, and the datasheet total-package sink current must be respected. Typical loads include front-panel indicators, keyboard backlights and relay-module status LEDs. Writing the expander byte sets all eight channels simultaneously in one 400 kHz I2C transaction, and up to 16 expanders (128 LEDs) can share one bus using the PCA8574 plus PCA8574A address groups. Because outputs are latched, LED states persist without host intervention, reducing bus traffic in static-display applications.
Рекомендуется
Industrial Panel and Relay Control
In industrial control panels, the PCA8574D,518 provides remote GPIO for driving relay coils (via transistor drivers), reading limit-switch inputs, and controlling panel indicators over a two-wire bus that spans the cabinet with only SCL, SDA and ground. The 5.5 V maximum supply matches legacy 5 V logic, and the 2.3 V floor suits modern 3.3 V controllers. The latched interrupt output immediately flags switch-state changes, improving event response versus polling. Three hardware address pins prevent bus conflicts when several expander boards coexist. Design care items: route SCL/SDA away from relay-switching noise, use pull-ups sized for bus capacitance, and protect the quasi-bidirectional inputs from inductive transients with RC filtering or TVS devices.
Рекомендуется
Sensor Board GPIO Expansion
Compact sensor boards often exhaust MCU pins on sensor interfaces, leaving none for mode jumpers, enable lines or status signals. The PCA8574D adds eight quasi-bidirectional lines through the existing I2C bus that already connects to digital sensors, requiring no additional MCU pins. Its 2.3 V floor supports 2.5 V rail systems, and 400 kHz operation keeps configuration writes fast. Typical uses include reading configuration DIP switches, enabling sensor power rails, and generating reset pulses. The INT output can be wired to the MCU wake-up pin so board events trigger action in sleep-mode designs. Because the expander byte is latched, output states survive MCU resets, aiding recovery sequencing on multi-rail boards.
Рекомендуется
Consumer Appliance and White-Goods Control
Appliance front panels combine buttons, LEDs and small relays - exactly the mixed-input/output mix the PCA8574D quasi-bidirectional ports handle without direction registers. The wide 2.3 V to 5.5 V supply tolerates power-supply variation across appliance boards, and the SO16 7.5 mm package suits cost-driven single-sided layouts and wave-soldering-friendly designs. The interrupt output lets the main controller sleep in standby, only waking on button presses, supporting low standby-power regulatory targets. Three address pins allow separate expanders for button block and indicator block on one bus. For new appliance designs note the PCA8574D is NXP End-of-Life: qualify the PCF8574DWR or PCA8574AD as the production source before committing the layout.
Рекомендуется
Legacy 5 V System Migration and EOL Replacement
Because NXP has issued a discontinuance notice for the PCA8574D, many legacy 5 V designs need a sourcing strategy. The NXP datasheet explicitly lists the PCA8574AD as a drop-in replacement, and FindIC cross-references confirm the TI PCF8574DWR SOIC-16 is terminal- and package-compatible, requiring no PCB modification. Firmware written for the PCA8574D address 0100 A2A1A0 must account for the PCF8574 fixed address portion and its 100 kHz maximum I2C speed; designs running at 100 kHz are timing-compatible. This application context matters for medical, industrial and transportation boards with long service lives where last-time-buy quantities and second-source qualification are standard practice.
Рекомендуется
Сводка рекомендуемых товаров
Справочные инженерные данные для PCA8574D,518 — сравнение, рекомендации по проектированию и информация о соответствии.
Руководство по выбору
Сравнение с аналогами
| Параметр | Этот товар | PCA8574AD,512 | PCA8574AD,118 | PCF8574DWR | PCF8574DWG4 | PCA9674D,112 |
|---|---|---|---|---|---|---|
| Package | SO16 (16-SOIC, 7.50 mm) | SO16 - same | SO16 - same | SOIC-16 (7.50 mm) - same | SOIC-16 (7.50 mm) - same | SO16 - same |
| Brand | NXP Semiconductors | NXP Semiconductors | NXP Semiconductors | Texas Instruments | Texas Instruments | NXP Semiconductors |
| I/O Count | 8 quasi-bidirectional | 8 quasi-bidirectional | 8 quasi-bidirectional | 8 quasi-bidirectional | 8 quasi-bidirectional | |
| I2C Maximum Speed | 400 kHz | 400 kHz | 100 kHz | 100 kHz | 400 kHz (up to 1 MHz capable) | |
| Supply Voltage Range | 2.3 V to 5.5 V | 2.3 V to 5.5 V | 2.3 V to 5.5 V | 2.3 V to 5.5 V | 2.3 V to 5.5 V | |
| Interrupt Output | Yes (open-drain, active-low) | Yes | Yes | Yes | Yes | |
| Slave Address Fixed Portion | 0100 (A2 A1 A0 selectable) | 0111 (A2 A1 A0 selectable) | 0100 (matches PCA8574D) | 0100 (matches PCA8574D) | 1110 (differs from PCA8574D) |
Ключевые отличия
- 400 kHz fast-mode I2C (против PCF8574DWR)
- Direct NXP drop-in successor available (против PCF8574DWG4)
- Doublable address space within same footprint (против PCF8574DWR)
Заметки по проектированию
The PCA8574D supply range is 2.3 V to 5.5 V, and its I/O and SDA/SCL pins are referenced to VDD. Never pull the I2C bus up above the expander supply: in mixed 3.3 V/5 V systems, either run pull-ups to the expander's VDD rail or insert a bus buffer/level translator. Decouple VDD with a 100 nF ceramic capacitor placed within a few millimeters of pin 16, and verify the quiescent and port sink current budget against the datasheet limits when driving multiple outputs low simultaneously.
Keep SCL and SDA traces short and route them away from switching loads such as relays and LED backlights driven from the same board. Size I2C pull-up resistors for the total bus capacitance: at 400 kHz fast mode, typical values are 2.2k to 4.7k ohm for short buses; increase resistance for low-power standby or decrease it as bus length grows. The open-drain INT output also needs a pull-up to VDD and should be routed to an MCU interrupt-capable pin rather than polled.
Three pitfalls recur with the PCA8574D. First, quasi-bidirectional ports source limited current - drive LEDs by sinking current (anode to VDD), never by sourcing. Second, at power-up all ports default high (inputs), so ensure external loads tolerate this state. Third, the PCA8574D and PCA8574A use different fixed slave-address groups (0100 vs 0111) and the PCF8574 differs in I2C speed (100 kHz) - firmware written for 400 kHz must be checked before drop-in migration. Finally, this part is NXP End-of-Life; secure stock or qualify PCA8574AD/PCF8574DWR before new production.
Информация о соответствии
NXP product page lists the PCA8574D under Environmental Quality with RoHS compliance; REACH and halogen-free status not stated in provided data.
