PCF8575DB - 16-Bit I2C I/O Expander | Texas Instruments
Артикул: PCF8575DB ✓ АктивенPCF8575DB Обзор
An I/O expander is an interface IC that extends the number of digital input and output lines available to a microcontroller or other host processor. The PCF8575 belongs to the I2C interface IC hierarchy and uses a serial command-and-data bus to transfer port state over two wires. Its 16 quasi-bidirectional lines can reduce the number of GPIO pins required by a host while remaining suitable for common logic-level inputs, relay-control signals, status indicators, and LED loads.
Each quasi-bidirectional I/O has latched output capability and high-current drive for directly driving LEDs. The same line can be read as an input without changing the output latch, although the electrical behavior differs from a conventional push-pull output. At power-on, all I/O ports are high. The three address pins provide hardware-selectable device addresses for a maximum of eight PCF8575 devices on one bus, while the open-drain interrupt output provides a hardware indication of input-port state changes.
The interface supports both I2C and SMBus operation, and the verified product information identifies operation up to 400 kHz. Low standby-current consumption is specified at a maximum of 10 µA. These characteristics make the device useful in embedded systems where bus wiring, connector pin count, standby power, or host GPIO availability constrain the design. The 24-pin SSOP, identified by distributor records as SSOP-24 with a 5.30 mm width and 0.209 inch lead spacing, supports compact surface-mount assembly.
Typical uses include reading switches and keypads, driving LED indicators, monitoring digital control signals, controlling discrete transistors or relays, and expanding I/O in industrial controllers, appliance controllers, test equipment, and microcontroller boards. Because the interrupt output is open-drain, multiple interrupt-capable devices can share a common signal when the system supports wired-AND behavior. Firmware must also account for the I2C address, port polarity, and quasi-bidirectional input current requirements.
The primary design consideration is choosing the pull-up voltage and ensuring that the bus capacitance and wiring permit reliable operation at 400 kHz. I2C pull-up resistors should be placed on the host side of long or branched wiring, and software should acknowledge only the interrupt source determined by the device address. The available verified material does not provide a complete pin table, explicit price values, or detailed absolute-maximum ratings.
This product page consolidates the verified manufacturer description, distributor package identification, I2C features, interrupt behavior, power-on state, and available substitute references. It also adds application guidance, engineering caveats, and a transparent distinction between verified specifications and parameters that still require confirmation from the complete manufacturer datasheet.
Аналоги без доработки для PCF8575DB — тот же корпус, pin-to-pin совместимость. Компоненты в других корпусах, требующие переработки PCB, исключены.
PCF8575DBRE4
✅ Прямая замена📋 Справочный аналог (нет в каталоге)
PCF8575TSDB
✅ Прямая замена📋 Справочный аналог (нет в каталоге)
PCF8575DB Характеристики
| Product Type | Remote 16-bit I/O expander with interrupt output |
| Number of I/O Lines | 16 lines |
| Port Configuration | Two 8-bit quasi-bidirectional ports, P07-P00 and P17-P10 |
| Supply Voltage Range | 2.5 V to 5.5 V |
| Интерфейс | I2C and SMBus |
| Maximum I2C Bus Speed | 400 kHz |
| Interrupt Output | Open-drain |
| Hardware Address Inputs | 3 address pins |
| Maximum Devices Per Bus | 8 devices |
| Output Port Structure | Latched quasi-bidirectional outputs |
| Output Drive Capability | High-current drive capability for directly driving LEDs |
| Power-On Port State | All I/O pins high |
| Standby Current | 10 µA maximum |
| Корпус | 24-pin SSOP |
| Package Width | 5.30 mm |
| Package Lead Spacing | 0.209 inch |
| Тип монтажа | Surface mount |
Руководство по цоколевке PCF8575DB в корпусе 0.209 inch
Цоколевка для PCF8575DB (корпус 0.209 inch). Нумерация выводов, функции и схемы подключения определены в техническом описании производителя. Обратитесь к нему для точного посадочного места и рекомендаций по пайке.
Нет подробных данных о распиновке для PCF8575DB.
Обратитесь к даташиту для полной конфигурации выводов.
Типичное применение
PCF8575DB подходит для 6 применениеs: Microcontroller GPIO Expansion, LED and Indicator Control, Keypad and Switch Reading, Industrial Relay and Discrete Control, Appliance and Home-Control Interface, Test and Measurement Control.
Microcontroller GPIO Expansion
The PCF8575DB adds 16 digital lines to a microcontroller without consuming 16 dedicated GPIO pins. Its P07–P00 and P17–P10 ports can be configured individually as inputs or outputs, and the I2C interface operates as fast as 400 kHz. This is useful in compact embedded controllers where connector count is constrained but logic-level switches, indicators, and discrete control signals must be accessible. Three hardware address pins allow up to eight devices on one bus, although the host must still decode the address-specific interrupt source. Firmware should initialize the outputs after reset because the verified datasheet states that all I/O pins power up high.
Рекомендуется
LED and Indicator Control
The PCF8575DB can directly drive LED loads because its latched quasi-bidirectional outputs include the high-current drive capability identified by Texas Instruments. Sixteen outputs can support display segments, status lamps, or board indicators while reducing the number of host connections. Because the port lines are quasi-bidirectional rather than conventional push-pull outputs, the designer should confirm that the LED current and polarity remain within the device limits. The power-on state is high, so a low-active indicator will illuminate briefly during startup unless firmware, reset logic, or external transistor gating prevents it.
Рекомендуется
Keypad and Switch Reading
A PCF8575DB can acquire up to 16 switch or keypad signals over I2C without dedicating a GPIO pin to every contact. The open-drain interrupt output provides a hardware indication that an input line has changed, allowing the host to remain responsive while polling is reduced. Each line must have a defined inactive level because the quasi-bidirectional port uses a pull-up-style current source when read as an input. Firmware should scan the port, apply debouncing appropriate to the mechanical switch, and distinguish the interrupting address when more than one expander is present.
Рекомендуется
Industrial Relay and Discrete Control
The PCF8575DB can provide the logic layer for relay drivers, solenoids, or discrete transistor controls when each external stage is designed for the required voltage and current. Its 16 latched output lines reduce wiring complexity in PLC-like remote I/O modules, while the 2.5 V to 5.5 V supply range supports multiple embedded logic levels. Quasi-bidirectional outputs are not ideal substitutes for a dedicated power MOSFET or relay driver, so flyback protection, drive-current margins, and inductive isolation must be handled externally. The common interrupt output can summarize changes across multiple addressed modules.
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Appliance and Home-Control Interface
The PCF8575DB is useful in appliance controllers that must connect buttons, door sensors, display indicators, and small electromechanical controls to a limited-pin microcontroller. Two serial bus wires replace many parallel GPIO routes, while the interrupt output allows the host to react to state changes instead of continuously polling. The verified 10 µA maximum standby current supports low-power designs when the host disables unused downstream loads. Firmware should account for the high power-on state and use safe defaults in external circuitry for motors, heaters, and door-lock mechanisms.
Рекомендуется
Test and Measurement Control
A PCF8575DB can expand a test fixture or instrument controller with 16 digital control and monitoring lines while retaining a compact 24-pin SSOP footprint. The I2C interface is appropriate for communicating with front-panel buttons, relay-control signals, and equipment status inputs, and its hardware address inputs permit several distributed I/O blocks. Designers should avoid using the quasi-bidirectional port for high-speed signals and should validate rise and fall times on external buses. Open-drain interrupt wiring can support a shared summary signal, provided every attached node can safely tolerate the wired-AND behavior.
Рекомендуется
Сводка рекомендуемых товаров
Справочные инженерные данные для PCF8575DB — сравнение, рекомендации по проектированию и информация о соответствии.
Руководство по выбору
Сравнение с аналогами
| Параметр | Этот товар | PCF8575DBRE4 | PCF8575TSDB |
|---|---|---|---|
| Brand | Texas Instruments | Texas Instruments | Texas Instruments |
| Package | 24-SSOP (DB) | 24-SSOP (DB) | 24-SSOP (TSDB) |
| I/O Count | 16 bits | 16 bits | 16 bits |
| Supply Voltage Range | 2.5 V to 5.5 V | 2.5 V to 5.5 V | 2.5 V to 5.5 V |
| Bus Interface | I2C and SMBus | I2C and SMBus | I2C and SMBus |
Ключевые отличия
- Sixteen quasi-bidirectional lines with independent input or output use (против PCF8575TSDB)
- Eight devices can share one I2C bus (против PCF8575DBRE4)
- Compact 24-pin surface-mount implementation (против PCF8575TSDB)
- Interrupt-driven remote I/O monitoring (против PCF8575DBRE4)
Заметки по проектированию
Route SDA and SCL as a compact, continuous bus and place the pull-up resistors near the host side of the PCB rather than beside every peripheral. The verified device supports 400 kHz, so long branches, excessive capacitance, and weakly sized pull-ups can create timing failures even when the bus frequency is correctly configured. Review rise time against the slowest attached device and keep pull-up voltage consistent with the 2.5 V to 5.5 V operating range.
Do not treat the quasi-bidirectional P00–P07 and P10–P17 lines as ordinary push-pull GPIOs. The manufacturer states that the ports can be used as inputs or outputs, but input reading depends on the active current-source behavior. External switches and pull resistors must establish a valid inactive level. Also account for the documented power-on condition in which every I/O pin is high, especially when a connected actuator could be energized during startup.
Use the open-drain interrupt output with a pull-up to the host's active logic voltage, and do not assume it can source current. If several PCF8575 devices share one interrupt line, firmware must identify the source by reading the addressed devices. The verified standby-current limit is 10 µA maximum, which is useful for low-power systems, but the total system demand also includes pull-up current and any LED or external-driver load connected to the I/O pins.
Before releasing PCB artwork, compare the selected DB package drawing against the complete Texas Instruments pin configuration. The verified excerpts identify a 24-pin SSOP with a 5.30 mm width and 0.209 inch lead spacing, but they do not enumerate every pin number. Verify power, ground, address, interrupt, SDA, and SCL assignments directly from the official PDF rather than copying a similarly named expander's pinout.
Информация о соответствии
The supplied verified excerpts do not state RoHS, REACH, AEC-Q100, lead-free, halogen-free, or conflict-minerals status. These fields must be checked against the current manufacturer product page or declaration before procurement.
