PCA9554DW - 8-Bit I/O Expander | Texas Instruments
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PCA9554DW Overview
An I/O expander is an interface IC that converts a serial bus into parallel digital input or output lines. In the product hierarchy, PCA9554DW belongs to I/O expander controllers within interface ICs and broader semiconductor devices. The PCA9554 includes one 8-bit configuration register, input register, output register, and polarity-inversion register. At power-on, its I/O ports are inputs with weak pull-ups, and the system master can subsequently configure each line as input or output.
Three hardware address pins, A0, A1, and A2, program the fixed I2C address and allow up to eight devices to share one I2C bus or SMBus. The open-drain active-low interrupt output provides a change notification from the remote I/O ports. According to the Texas Instruments product page, PCA9554 is pin-to-pin and I2C-address compatible with the PCF8574, although software changes are required because PCA9554 adds configuration-register functionality.
The PCA9554DW is useful for low-cost control of LEDs, relays, sensors, keys, and other digital peripherals where the host has insufficient GPIO pins. It can reduce MCU package size and pin count, while the interrupt line lets the processor sleep until an input event occurs. Inputs can also be configured with polarity inversion to simplify active-high or active-low system logic.
Design attention should focus on bus pull-ups, address selection, output transition timing, and the electrical limits of each remote port. Weak pull-ups are intended primarily for power-up defaults, not as a replacement for strong external pull-ups on a heavily loaded I2C bus. Confirm external-device logic levels and avoid driving a port in a way that conflicts with its alternate input or output function.
This page combines verified manufacturer and distributor information with package, application, comparison, and design guidance. It distinguishes confirmed replacements from unverified substitutions and preserves missing electrical values rather than estimating them. The result helps engineers identify whether PCA9554DW fits a new design or whether a documented same-package alternative requires additional validation.
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| Device Type | 8-bit I2C/SMBus I/O expander |
| Number of I/O Lines | 8 |
| Operating Supply Voltage Range | 2.3 V to 5.5 V |
| I2C Clock Frequency | 400 kHz |
| Interface | I2C/SMBus |
| Power-On I/O Configuration | Inputs |
| Power-On Pull-Up | Weak pull-up to VCC |
| Configuration Registers | One 8-bit configuration register |
| Input Register | One 8-bit input register |
| Output Register | One 8-bit output register |
| Polarity Inversion Register | One 8-bit active-high or active-low polarity register |
| Interrupt Output | Open-drain active-low interrupt output |
| Address Selection Pins | A0, A1, A2 |
| Maximum Devices per Bus | 8 |
| Package | 16-SOIC |
| Package Width | 7.50 mm |
| Operating Temperature | -40 °C to +85 °C |
PCA9554DW 7.50 mm Pin Configuration Guide
Pin configuration for PCA9554DW (7.50 mm package). Pin numbering, functions, and connection diagrams are defined in the manufacturer datasheet. Refer to it for the exact footprint and soldering guidelines.
No detailed pinout data available for PCA9554DW.
Refer to the datasheet for full pin configuration.
Typical Applications
PCA9554DW is suitable for 6 applications: Remote Control and GPIO Expansion, LED and Human-Interface Control, Sensor and Alarm Input Consolidation, Power and Appliance Control, Battery-Powered IoT Node, Server and Network Peripherals.
Remote Control and GPIO Expansion
PCA9554DW fits host-controller designs that need eight additional digital I/O lines without enlarging the MCU package. Connect it to the I2C bus, assign one of eight A0-A2 address combinations, and configure the ports through the serial interface. Its eight configurable lines can reduce GPIO pressure on an STM32, MSP430, or similar controller. The open-drain active-low interrupt also allows the firmware to sleep until an input changes. Exact port drive limits must be taken from the manufacturer datasheet before the design is finalized.
Recommended
LED and Human-Interface Control
PCA9554DW can centralize LEDs, pushbuttons, selectors, and other human-interface signals behind a compact serial interface. Its power-on default is inputs with weak pull-ups, which helps avoid accidental LED activation during startup. Firmware can change port direction through the configuration register and invert input polarity for active-low buttons or indicators. Use suitable current-limiting components and verify each output's electrical limits from the official datasheet before laying out the board.
Recommended
Sensor and Alarm Input Consolidation
PCA9554DW is useful when several digital sensors, interlocks, or alarm lines must be gathered at a distance from the main controller. Eight input ports share a two-wire I2C/SMBus connection, while the active-low open-drain interrupt provides a hardware indication of a port-state change. Configure each line for input and use the polarity-inversion register when the external signal is active-high. The verified operating range of -40 °C to +85 °C supports many industrial and embedded environments.
Recommended
Power and Appliance Control
PCA9554DW can provide a compact control interface for appliances or power accessories that require multiple enable, mode, or status signals. The host writes output values over I2C and reads back input states through the same interface, simplifying control-state monitoring. If an output must drive a relay, MOSFET, or high-current lamp, place a suitable driver stage between the expander and load. Exact output-drive and absolute-maximum ratings are not present in the supplied excerpts and must be verified before implementation.
Recommended
Battery-Powered IoT Node
PCA9554DW can reduce the GPIO burden of a compact IoT controller while retaining a simple 2.3 V to 5.5 V interface range. A microcontroller can control the eight ports and use the interrupt line to avoid continuous polling, which may help reduce active processing time in a battery-powered design. Power consumption is not supplied in the verified excerpts, so battery-life calculations require the manufacturer datasheet and representative firmware workload rather than assumptions.
Recommended
Server and Network Peripherals
PCA9554DW can add discrete control and status signals in server, network, or storage equipment without consuming eight dedicated MCU GPIO pins. The eight ports may represent module enables, fault flags, presence detection, or other slow-changing signals, while the interrupt output alerts the controller when an input changes. Because the verified 400 kHz clock limit is appropriate for control rather than high-speed data, use a dedicated interface for bandwidth-intensive peripherals. Keep I2C routing away from noisy sources and confirm address uniqueness.
Recommended
Recommended Products Summary
Engineering reference data for PCA9554DW — comparison, design guidance, and compliance information.
Selection Guide
Design Notes
Decouple PCA9554DW VCC close to the device with local bypass capacitance selected against the manufacturer's recommended network. Route the supply from the appropriate system rail and keep switching-current paths away from the I2C and interrupt traces. Exact capacitor values and port-drive limits are not present in the supplied excerpts, so use the official datasheet rather than generic values before release.
Treat the weak port pull-ups as power-up defaults, not as the primary I2C pull-up network. Size external SDA and SCL pull-ups from bus voltage, total capacitance, sink-current limits, and the intended 400 kHz rate. Keep both bus traces short, route them away from switching nodes, and verify rise time with the complete bus loading rather than an isolated expander.
Do not assume PCF8574 firmware will operate unchanged on PCA9554. Texas Instruments states that the devices are pin-to-pin and I2C-address compatible but that software changes are required because PCA9554 adds enhanced register behavior. Review startup defaults, port-direction control, polarity handling, and interrupt servicing. Also assign A0-A2 before routing the PCB so no address conflicts occur on a shared bus.
Compliance Information
The supplied verified excerpts do not explicitly state RoHS, REACH, AEC-Q100, lead-free, halogen-free, or conflict-minerals status. No compliance claim is inferred from the manufacturer or distributor listing.