PCA9555DW - 16-Bit I/O Expander, 2.3-5.5V | TI
MPN: PCA9555DW ✓ Active| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $0 | $0.00 |
| 10 | $0 | $0.00 |
| 100 | $0 | $0.00 |
| 500 | $0 | $0.00 |
| 1,000 | $0 | $0.00 |
PCA9555DW Overview
An I/O expander is an interface IC that translates serial I2C or SMBus commands into parallel digital input or output signals. In the signal-chain hierarchy, it sits between a microcontroller or embedded processor and external panel buttons, LEDs, relays, sensors, or other digital peripherals. The PCA9555 combines addressable input and output ports with configurable polarity and an interrupt mechanism, reducing host pin count while preserving a simple two-wire control path.
Key features include 16 configurable I/O lines, active-low open-drain interrupt output, weak pull-up configuration registers, and compatibility with both I2C and SMBus systems. Each port can be configured independently as input or output through the device registers. Input polarity inversion and output drive behavior can be programmed, allowing the same device to support active-low buttons, indicator circuits, and other digital interfaces.
The PCA9555 is controlled through a serial interface using address-select pins and command registers. This makes firmware configuration straightforward when the host already supports I2C. The 400kHz operating capability helps reduce control-loop time when multiple expander devices are present or when the system needs responsive input polling. The device is intended for systems where distributed GPIO expansion is preferable to expanding the host package.
Typical applications include industrial control panels, keypad and button interfaces, LED indication, appliance controls, instrumentation, and embedded systems requiring more GPIO than the host microcontroller provides. The 2.3V to 5.5V supply range supports both low-voltage and conventional 5V digital systems. The 24-pin SOIC package also makes the device suitable for through-hole assembly and conventional PCB layouts.
When designing around the PCA9555, account for the I2C bus pull-up requirement, correct address selection, and the electrical limits of each output. The interrupt pin should be configured with an appropriate pull-up because it is open-drain and active low. Firmware should also define startup states and port directions before external circuitry becomes active. This page summarizes the verified device identity, package, operating range, interface features, and design implications available for PCA9555DW selection.
This information distinguishes the PCA9555DW from generic 8-bit expanders by combining a 16-bit parallel interface, configurable weak pull-ups, polarity control, and interrupt support in a 2.3V to 5.5V SOIC device.
Drop-in alternatives for PCA9555DW — same package, pin-to-pin compatible. Different-package parts requiring PCB rework are excluded.
Variants in this series
Same-series models that are drop-in compatible with PCA9555DW (same form factor and footprint) — differing in Configuration Registers, Interrupt Output, Package.
Quick Comparison Tool — Select alternative parts for side-by-side comparison:
PCA9555DWR
✅ Drop-In📋 Reference alternative (not in catalog)
PCA9555D,112
✅ Drop-In📋 Reference alternative (not in catalog)
TCA9555PWR
✅ Drop-In✓ In Stock
$0.79 / Unit
View Datasheet →PCA9535DWR
✅ Drop-In📋 Reference alternative (not in catalog)
PCF8575DWR
✅ Drop-In📋 Reference alternative (not in catalog)
PCA9555DW Specifications
| Device Type | 16-bit I2C/SMBus I/O expander |
| Supply Voltage Range | 2.3 V to 5.5 V |
| I/O Port Count | 16 bits |
| Port Organization | 2 x 8-bit ports |
| Bus Interface | I2C/SMBus |
| Maximum Bus Frequency | 400 kHz |
| Interrupt Output | Active-low, open-drain |
| Weak Pull-up Registers | Configurable |
| Configuration Registers | Input/output, polarity and port configuration |
| Output Drive | Push-pull outputs |
| Operating Temperature Range | -40°C to +85°C |
| Package | 24-pin SOIC (DW) |
| Package Type | SOIC |
| Pin Count | 24 pins |
| Mounting Type | Surface mount |
| Low Standby Current | 1 µA maximum |
PCA9555DW soic Pin Configuration Guide
Pin configuration for PCA9555DW (soic 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 PCA9555DW.
Refer to the datasheet for full pin configuration.
Typical Applications
PCA9555DW is suitable for 6 applications: Industrial Control Panel, Embedded Keypad Interface, LED Status and Indicator Control, Appliance and Household Control, Instrumentation and Measurement Front Panel, Communication and Network Equipment.
Industrial Control Panel
The PCA9555DW is suitable for control panels where a controller needs to monitor many pushbuttons and drive indicators over a shared bus. Its 16-bit organization allows two 8-bit groups to be assigned to inputs and outputs, while the 2.3V to 5.5V range accommodates common industrial logic levels. The active-low open-drain interrupt can notify the host when a panel event requires service. Firmware should define input polarity, debounce behavior, and startup states before enabling external loads.
Recommended
Embedded Keypad Interface
Use the PCA9555DW to connect keypad or switch matrices to a microcontroller without consuming dedicated GPIO pins. Sixteen I/O lines provide enough parallel signals for compact keypad scanning, status keys, or configuration switches, while the serial host interface reduces wiring complexity. Configure the required lines as inputs and use the interrupt to report state changes efficiently. Check the external switch voltage levels and account for scan timing in the host firmware.
Recommended
LED Status and Indicator Control
The PCA9555DW can drive grouped LED status indicators when the host must preserve package pins for higher-speed or mixed-signal functions. Two programmable 8-bit ports allow firmware to update display status in parallel while keeping the physical interface compact. The verified 2.3V to 5.5V operating range supports common logic systems, but LED current, polarity, and series resistance must be designed for the chosen supply. The interrupt output is less central in a continuously refreshed indicator application.
Recommended
Appliance and Household Control
The PCA9555DW can expand a small appliance controller to handle door switches, mode buttons, relays, and status lamps through one I2C/SMBus connection. The 16 I/O lines allow a compact controller to separate input sensing from output control, while configurable polarity helps match active-low switch networks. The device should be placed where its 2.3V to 5.5V supply range matches the logic system. Firmware should initialize port directions and output states before enabling connected actuators.
Recommended
Instrumentation and Measurement Front Panel
The PCA9555DW is useful in instrumentation front panels where range selectors, mode buttons, alarm inputs, and indicator outputs must be connected to a controller. Its two 8-bit ports provide organized grouping for input sensing and output control, and the interrupt line can signal a changed front-panel state without continuous host polling. The 400kHz interface capability helps support timely updates when several controls are managed by the host. Verify logic thresholds and protection requirements for external equipment.
Recommended
Communication and Network Equipment
The PCA9555DW can add local status, configuration, and alarm I/O to a communication module whose main processor has insufficient package pins. The serial bus keeps the expansion wiring compact, and the active-low interrupt allows a host to respond to external events. In network-oriented equipment, isolate or protect external lines according to the enclosure and electromagnetic environment; the expander itself does not provide surge protection. Confirm the system voltage and ensure that all connected signals remain within the verified operating limits.
Recommended
Recommended Products Summary
Engineering reference data for PCA9555DW — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | PCA9555DWR | PCA9555D,112 | TCA9555PWR | PCA9535DWR | PCF8575DWR |
|---|---|---|---|---|---|---|
| Package | 24-pin SOIC (DW) | 24-pin SOIC (DW) | 24-pin SOIC (DW) | 24-pin SOIC (PW) | 24-pin SOIC (D) | 24-pin SOIC (D) |
| Brand | Texas Instruments | Texas Instruments | Texas Instruments | Texas Instruments | Texas Instruments | Texas Instruments |
Key Differentiators
- 16-bit expansion in a single device (vs PCF8575DWR)
- Programmable weak pull-ups and polarity control (vs PCA9535DWR)
- Broad 2.3V to 5.5V supply range (vs TCA9555PWR)
- Active-low open-drain interrupt output (vs PCA9555DWR)
Design Notes
The verified PCA9555DW operating range is 2.3V to 5.5V, so the supply must remain within that interval during startup, normal operation, and shutdown. Confirm the logic levels of every connected peripheral and select I2C pull-ups for the actual bus voltage and capacitance. The verified low-standby-current specification is 1 µA maximum, but total system consumption also includes enabled ports, pull-ups, and connected devices.
Place the device close to the connector or controlled peripheral group and keep the I2C traces short and continuous. Provide the required bus pull-ups at a location consistent with the system’s I2C topology, and route the interrupt trace away from noisy switching nodes where practical. Because the interrupt output is active-low and open-drain, use a suitable pull-up and do not add a push-pull driver to that signal.
Initialize port direction, polarity, and output latch values before enabling connected loads; otherwise an external device may see an unintended startup state. Do not assume that a same-package comparison part has the same register map or address behavior. Review the exact manufacturer pinout, device address configuration, electrical limits, and firmware sequence before substituting PCA9555DW-family candidates.
Treat the I2C lines as a shared bus with pull-up-defined high levels. Check rise time against the bus capacitance and the host timing budget at the selected 400kHz operating point. If several expanders or long routes are present, measure the bus rather than relying only on nominal component values. Configure the interrupt mask and polarity in firmware to avoid unnecessary wakeups and false event handling.
Compliance Information
The supplied verified data confirms the Texas Instruments product, electrical operating range, interface features, package, and temperature range, but it does not provide compliance-status evidence. No RoHS, REACH, AEC-Q100, lead-free, halogen-free, or conflict-minerals claim is inferred.
