PCF8575PWR - 16-Bit I2C I/O Expander | Texas Instruments
Артикул: PCF8575PWR ✓ АктивенPCF8575PWR Обзор
An I/O expander is an interface IC that extends the number of digital input and output pins available to a microcontroller or other embedded controller. The PCF8575 sits between the host processor and external peripherals, using I2C or SMBus for command and data transfer while presenting a parallel port to connected circuitry. Its two independent eight-bit ports support both input and output operation without separate data-direction registers.
The PCF8575PWR provides 16 quasi-bidirectional I/O lines, with each line usable as an input or output. Its latched outputs have high-current drive capability for directly driving LEDs. Three hardware address pins allow up to eight devices to share the same I2C bus, while the open-drain interrupt output provides a hardware indication of input-port activity.
The interface supports operation up to 400 kHz, and standby current consumption is specified at no more than 10 microamperes. All I/O pins are high at power-on, which provides a defined reset state for the output latch. The quasi-bidirectional architecture includes a weak current source toward VCC, so engineers should account for this behavior when designing inputs, pull-ups, and output transitions.
Typical uses include expanding a limited microcontroller pin count for LEDs, switches, keypads, sensors, relay-control logic, and simple digital display interfaces. Because the device communicates over I2C or SMBus, it is particularly useful when a design needs many slow-changing digital lines but cannot allocate a dedicated parallel port on the host controller.
A key design consideration is the difference between quasi-bidirectional inputs and conventional push-pull outputs. Pull-up requirements, leakage currents, and the desired high or low state must be evaluated for every connected signal. Designers should also confirm address selection, interrupt handling, and supply levels before assigning functions to the two eight-bit ports.
This product page organizes the manufacturer specifications, pin assignments, application guidance, and same-footprint alternatives into an engineering-focused reference. It also distinguishes direct pin-compatible choices from related expanders whose input or reset behavior differs, helping simplify design validation without obscuring the trade-offs that matter on the PCB.
Аналоги без доработки для PCF8575PWR — тот же корпус, pin-to-pin совместимость. Компоненты в других корпусах, требующие переработки PCB, исключены.
Варианты в этой серии
Модели той же серии, совместимые без доработки с PCF8575PWR (тот же форм-фактор и посадочное место) — отличается по Hardware Address Inputs, Interface Type, Output Drive Capability, Package.
PCF8575PW
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PCF8575PWR Характеристики
| Number of I/O Lines | 16 |
| Number of Ports | 2 x 8-bit |
| Рабочее напряжение питания | 2.5 V to 5.5 V |
| I2C Maximum Bus Frequency | 400 kHz |
| Тип интерфейса | I2C and SMBus |
| Interrupt Output | Open-drain |
| Hardware Address Inputs | 3 |
| Maximum Devices per Bus | 8 devices |
| Standby Current | 10 microamperes maximum |
| Power-On I/O State | High |
| I/O Direction Control | Not required |
| Output Drive Capability | High-current drive for directly driving LEDs |
| Корпус | 24-pin TSSOP |
| Тип монтажа | Surface mount |
Конфигурация выводов PCF8575PWR
| Контакт 1 | P00 — Quasi-bidirectional I/O port 0, bit 0 |
| Контакт 2 | P01 — Quasi-bidirectional I/O port 0, bit 1 |
| Контакт 3 | P02 — Quasi-bidirectional I/O port 0, bit 2 |
| Контакт 4 | P03 — Quasi-bidirectional I/O port 0, bit 3 |
| Контакт 5 | P04 — Quasi-bidirectional I/O port 0, bit 4 |
| Контакт 6 | P05 — Quasi-bidirectional I/O port 0, bit 5 |
| Контакт 7 | P06 — Quasi-bidirectional I/O port 0, bit 6 |
| Контакт 8 | P07 — Quasi-bidirectional I/O port 0, bit 7 |
| Контакт 9 | INT — Open-drain interrupt output |
| Контакт 10 | A2 — Hardware address input A2 |
| Контакт 11 | A1 — Hardware address input A1 |
| Контакт 12 | A0 — Hardware address input A0 |
| Контакт 13 | SCL — Serial clock input |
| Контакт 14 | SDA — Serial data input and output |
| Контакт 15 | P10 — Quasi-bidirectional I/O port 1, bit 0 |
| Контакт 16 | P11 — Quasi-bidirectional I/O port 1, bit 1 |
| Контакт 17 | P12 — Quasi-bidirectional I/O port 1, bit 2 |
| Контакт 18 | P13 — Quasi-bidirectional I/O port 1, bit 3 |
| Контакт 19 | P14 — Quasi-bidirectional I/O port 1, bit 4 |
| Контакт 20 | P15 — Quasi-bidirectional I/O port 1, bit 5 |
| Контакт 21 | P16 — Quasi-bidirectional I/O port 1, bit 6 |
| Контакт 22 | P17 — Quasi-bidirectional I/O port 1, bit 7 |
| Контакт 23 | VDD — Positive supply voltage |
| Контакт 24 | VSS — Ground reference |
Типичное применение
PCF8575PWR подходит для 6 применениеs: LED Status and Indicator Expansion, Keypad and Human Interface Expansion, Industrial Sensor and Discrete Signal Interface, Relay and Discrete Control Interface, Battery-Powered Embedded Peripheral Interface, Data Acquisition and Test Equipment Control.
LED Status and Indicator Expansion
The PCF8575PWR fits LED and indicator designs that need more output lines than the host controller can provide directly. Its two eight-bit quasi-bidirectional ports can latch LED states while commands travel over the shared I2C bus at up to 400 kHz. This arrangement reduces pin usage without occupying a dedicated parallel peripheral. According to the Texas Instruments manufacturer datasheet, the latched outputs have high-current drive capability for directly driving LEDs. Engineers should still verify the available output current for each supply voltage and LED color. A common bank-resistor design also limits simultaneous current and makes it easier to manage heat, brightness variation, and connector current limits across the board.
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Keypad and Human Interface Expansion
The PCF8575PWR is useful when a keypad, switch panel, or similar human interface requires more digital lines than remain on the host microcontroller. The 16 quasi-bidirectional lines can be divided between row and column scanning, read switch states, or drive interface-control signals. Because the device operates from 2.5 V to 5.5 V, it can support low-voltage embedded systems as well as 5 V logic designs. The interrupt output offers a way to report input activity without continuous polling. In practice, debounce and matrix ghosting remain application-level concerns, so the firmware and pull-up network should be designed alongside the expander connection rather than treated as automatic functions of the IC.
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Industrial Sensor and Discrete Signal Interface
The PCF8575PWR can serve as the digital interface between an embedded controller and multiple discrete sensors, selectors, or monitoring inputs. Its 16 quasi-bidirectional lines provide more parallel status channels than a small microcontroller normally exposes, while the I2C/SMBus connection keeps the host-side wiring compact. The open-drain interrupt is particularly useful when a change must prompt immediate processing rather than routine polling. Since the ports are quasi-bidirectional, external sensors and switches must be checked for leakage, pull-up strength, and voltage compatibility. The 400 kHz bus rate is more than adequate for slow-changing industrial status signals, provided the bus is correctly terminated and routed.
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Relay and Discrete Control Interface
The PCF8575PWR can provide the low-speed control layer for relays, latches, and other discrete actuators controlled by a microcontroller with limited output pins. Its latched outputs retain commanded states between serial updates, allowing the host to change multiple control lines in one transaction. The open-drain interrupt is not needed for every relay function, but it can support feedback or status inputs elsewhere in the same interface module. Because quasi-bidirectional outputs include a pull-up path toward VCC, the design must account for off-state current and the current drawn while switching an attached device. Relay drivers, flyback protection, and any required isolation remain separate external circuit requirements.
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Battery-Powered Embedded Peripheral Interface
The PCF8575PWR is appropriate for battery-powered embedded products that need additional digital lines without adding a large parallel port. Its standby current is specified at no more than 10 microamperes, while its 2.5 V minimum operating voltage covers low-voltage embedded rails. The two-wire interface reduces host pin count and wiring complexity in compact products. For energy-sensitive designs, the interrupt output can help the controller avoid frequent bus polling, although the wake-up strategy and pull-up leakage still need to be included in the power budget. The 400 kHz I2C rate is suitable for configuration and status traffic rather than high-throughput data transfer.
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Data Acquisition and Test Equipment Control
The PCF8575PWR can extend measurement and test systems by handling digital control lines, range selections, relay commands, and status inputs. Its 16-bit port makes it convenient for fixtures where the host controller must coordinate several instrument-control signals while preserving an I2C or SMBus connection. The open-drain interrupt allows input changes to be reported to the controller, reducing unnecessary register reads. Electrical compatibility with the test system must be checked because the ports are quasi-bidirectional and operate within a 2.5 V to 5.5 V supply range. High-current outputs, external relays, and protection networks should be assessed against the complete load rather than the nominal logic voltage alone.
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Справочные инженерные данные для PCF8575PWR — сравнение, рекомендации по проектированию и информация о соответствии.
Руководство по выбору
Сравнение с аналогами
| Параметр | Этот товар | PCF8575PW | PCF8575CPWR |
|---|---|---|---|
| Brand | Texas Instruments | Texas Instruments | Texas Instruments |
| Package | 24-pin TSSOP | 24-pin TSSOP - same | 24-pin TSSOP - same |
| Number of I/O Lines | 16 | 16 | 16 |
| Operating Supply Voltage | 2.5 V to 5.5 V | 2.5 V to 5.5 V | 2.5 V to 5.5 V |
| Maximum Bus Frequency | 400 kHz | 400 kHz | 400 kHz |
| Serial Interface | I2C and SMBus | I2C and SMBus | I2C and SMBus |
| Interrupt Output | Open-drain | Open-drain | Open-drain |
| Hardware Address Inputs | 3 | 3 | 3 |
| Maximum Devices per Bus | 8 devices | 8 devices | 8 devices |
| Power-On I/O State | High | High | High |
| Standby Current | 10 microamperes maximum | 10 microamperes maximum | 10 microamperes maximum |
Ключевые отличия
- Exact 16-bit functionality in the established 24-pin TSSOP footprint (против PCF8575PW)
- Pin-compatible same-family option with matching bus and interrupt features (против PCF8575CPWR)
- Three hardware address inputs expand bus capacity (против PCF8575PW)
Заметки по проектированию
Place the device close to the I2C controller and place SDA and SCL pull-up resistors near the bus master or according to the system-level I2C implementation guidance. Keep the SDA and SCL traces short, route them away from switching nodes and noisy analog inputs, and maintain continuous ground references. The three A0, A1, and A2 address pins must be connected to defined logic levels before the device begins communicating on the shared bus.
Treat every PCF8575 port as quasi-bidirectional rather than as a conventional push-pull GPIO. The internal current source toward VCC can influence a pin when an external circuit drives it weakly, so external pull-ups, pull-downs, leakage, and bus-driver strength must be evaluated together. When a connected device actively drives a pin, verify that its voltage and current remain within the electrical limits stated in the manufacturer datasheet.
Do not assume all PCF8575-compatible expanders have identical reset behavior. The Texas Instruments manufacturer datasheet states that the PCF8575 I/O pins power up high, while other expanders may power up as inputs or provide individually configurable directions. For safety-sensitive loads, add suitable external reset or isolation so that an unexpected high output state cannot create an undesirable system condition.
Decouple the PCF8575 supply with a local ceramic capacitor and route it directly to the device ground and supply pins. Include pull-up current, output leakage, and the attached peripheral load in the supply budget; a 2.5 V to 5.5 V operating range does not guarantee that every connected signal or LED arrangement is valid at both extremes.
Информация о соответствии
Target-device compliance details require confirmation from the manufacturer product documentation. The PCF8575PWR is a general-purpose interface IC, but that classification alone does not establish AEC-Q100 qualification.