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HomeProductsIntegrated Circuits (ICs)Interface - I/O ExpandersPCA9555DW
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PCA9555DW - Texas Instruments

Manufacturer Part Number
PCA9555DW
Manufacturer
Texas Instruments
Allelco Part Number
32D-PCA9555DW
Warranty
1 Year Allelco Warranty - Find out more
Stock Status:
31,553 pcs available, New & Original
Parts Description
IC XPNDR 400KHZ I2C SMBUS 24SOIC
Package
24-SOIC
Data sheet
PCA9555DW.pdf

HTML Datasheet

PCA9555.pdf
RoHs Status
ROHS3 Compliant
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Specifications

PCA9555DW Tech Specifications
Texas Instruments - PCA9555DW technical specifications, attributes, parameters and parts with similar specifications to Texas Instruments - PCA9555DW

Product Attribute Attribute Value
Manufacturer Texas Instruments
Voltage - Supply 2.3V ~ 5.5V
Supplier Device Package 24-SOIC
Series -
Package / Case 24-SOIC (0.295", 7.50mm Width)
Package Tube
Output Type Push-Pull
Operating Temperature -40°C ~ 85°C
Product Attribute Attribute Value
Number of I/O 16
Mounting Type Surface Mount
Interrupt Output Yes
Interface I²C, SMBus
Features POR
Current - Output Source/Sink 10mA, 25mA
Clock Frequency 400 kHz
Base Product Number PCA9555

Environmental & Export Classifications

ATTRIBUTE DESCRIPTION
RoHs Status ROHS3 Compliant
Moisture Sensitivity Level (MSL) 1 (Unlimited)
REACH Status REACH Unaffected
ECCN EAR99
HTSUS 8542.39.0001

Parts Introduction

PCA9555DW Image
PCA9555DW (1)

Manufacturer Part Number

PCA9555DW

Manufacturer

Texas Instruments

Introduction

The PCA9555DW is an I/O expander for the I2C bus and SMBus, providing 16 additional I/O pins.

Product Features and Performance

16 I/O ports

I2C and SMBus interface

Interrupt output with POR feature

Push-Pull output type

Source/Sink current capability of 10mA and 25mA

Product Advantages

Extended I/O capability for processors with limited I/O pins

Flexible interface accommodating both I2C and SMBus

Built-in Power-on reset improves reliability on power-up

Support for both push-pull and open-drain configurations

Key Technical Parameters

Number of I/O: 16

Interface: I2C, SMBus

Interrupt Output: Yes

Features: Power-on Reset (POR)

Output Type: Push-Pull

Current - Output Source/Sink: 10mA, 25mA

Clock Frequency: 400 kHz

Voltage - Supply: 2.3V to 5.5V

Operating Temperature: -40°C to 85°C

Mounting Type: Surface Mount

Package / Case: 24-SOIC

Quality and Safety Features

Operational across a wide temperature range

Supports hot insertion

Compatibility

Compatible with various microcontrollers and processors with I2C or SMBus interface

Application Areas

Embedded systems

Industrial control

Home automation

Server motherboards

Product Lifecycle

Obsolete status indicates it's nearing discontinuation

Alternatives or upgrades should be considered

Several Key Reasons to Choose This Product

Expands I/O port availability in space-constrained applications

Supports industry-standard I2C and SMBus for easy integration

Provides design flexibility with various output types

Facilitates reliable system operation with built-in POR

Wide operating voltage and temperature range suitable for harsh environments

Compatibility with multiple devices and applications

Accommodates future needs with alternatives due to obsolescence

Offers ease of mounting with surface mount packaging technology

Frequently Asked Questions(FAQ)

How does the PCA9555DW’s interrupt output functionality support real-time system monitoring in I2C-based embedded designs?
The PCA9555DW provides an active-low interrupt output that asserts when any input pin changes state, enabling efficient event-driven responses without continuous polling. This reduces CPU load and improves system responsiveness in applications such as button presses or sensor state changes. By leveraging this feature, designers can implement wake-up logic from low-power modes or trigger immediate processing of asynchronous events. The interrupt is edge-sensitive and remains asserted until the host reads the input port register, ensuring reliable capture across varying I2C transaction latencies.
What are the key differences between the PCA9555DW and PCA9535D when used as GPIO expanders in 5V systems?
While both devices serve as I2C GPIO expanders, the PCA9555DW supports bidirectional I/O with configurable pull-up resistors and includes a power-on reset (POR) circuit, whereas the PCA9535D lacks built-in pull-ups and has no explicit POR mechanism. Additionally, the PCA9555DW offers higher output current per pin—up to 25mA sink—compared to the PCA9535D’s 24mA total bus capability. In 5V systems, the PCA9555DW’s wider voltage tolerance (2.3V–5.5V) and better-defined startup behavior make it more suitable for mixed-voltage environments where stable initialization is critical.
Can the PCA9555DW reliably drive LED indicators directly from a 3.3V microcontroller without additional buffering?
Yes, but only under specific conditions. The PCA9555DW can source up to 10mA per pin and sink up to 25mA, which is sufficient for standard 3mm–5mm LEDs with appropriate series resistors. When powered from 3.3V, the forward voltage drop of typical red or green LEDs (1.8V–2.2V) leaves enough margin to operate within safe limits. However, blue or white LEDs may require limiting resistors due to lower headroom, and long traces or capacitive loads could necessitate external buffers if signal integrity degrades. Always verify thermal performance under continuous load.
How does the PCA9555DW’s clock stretching capability interact with high-speed I2C masters during bus arbitration?
The PCA9555DW supports clock stretching by holding SCL low after receiving an ACK, allowing time for internal state updates before responding. This ensures reliable communication with slow peripherals but must be managed carefully alongside faster masters like those operating at 400 kHz or higher. Excessive or unpredictable stretching can delay other bus participants, potentially causing timeout errors. Designers should ensure the master implements adequate timeout thresholds and consider using dedicated interrupt-driven reads to minimize latency impact during extended stretches.
Is the PCA9555DW suitable for automotive-grade temperature monitoring using digital inputs connected to thermistors?
Indirectly, yes—but with caveats. While the PCA9555DW operates reliably from -40°C to +85°C, thermistor-based measurements require analog-to-digital conversion, which this device does not provide. Instead, thermistors would need to drive digital comparators or be sampled via an external ADC sharing the same I2C bus. The PCA9555DW’s interrupt feature could then signal when threshold crossings occur based on comparator outputs. For true temperature sensing, pairing it with a dedicated sensor IC like the TMP117 offers greater accuracy and calibration benefits.
What considerations apply when cascading multiple PCA9555DW devices on a single I2C bus?
Cascading multiple PCA9555DW units requires unique 7-bit slave addresses assigned via their hardware address pins (A0–A2), allowing up to eight devices per bus. Care must be taken to avoid address conflicts and ensure sufficient pull-up resistor values for the combined capacitance across all devices. Each additional device increases bus loading, potentially degrading rise times unless proper termination is maintained. Also, interrupt lines should be wired in parallel with open-drain configurations to prevent contention; shared interrupts simplify host handling but require software differentiation based on register reads.
How does the PCA9555DW’s output slew rate affect EMC performance in noisy industrial environments?
Although not explicitly specified in the datasheet, the push-pull outputs of the PCA9555DW exhibit moderate slew rates typical of CMOS logic at 400 kHz operation. Rapid transitions can generate electromagnetic interference (EMI), especially with long PCB traces or unterminated loads. To mitigate this, designers should use series termination resistors near the driver, minimize loop areas in ground returns, and avoid routing high-speed signals adjacent to sensitive analog paths. Shielding cables and ferrite beads on output lines further improve compliance in electrically harsh settings.
Can the PCA9555DW replace mechanical switches in human interface devices (HIDs) such as keypads?
Yes, provided debouncing and scan timing are properly addressed. The PCA9555DW captures raw input states, so software or external RC networks must handle switch bounce to avoid false triggers. With a 400 kHz I2C interface, polling intervals should exceed 50 ms to allow for debounce filtering without introducing noticeable lag. Alternatively, firmware can implement moving average or majority-vote algorithms over several samples. Given its 16-pin capacity, the PCA9555DW efficiently scales to medium-sized keypads while reducing BOM count compared to discrete solutions.
What role does the PCA9555DW’s power-on reset (POR) circuit play in preventing undefined states during brownout conditions?
The integrated POR circuit ensures all registers default to known states upon initial power-up or supply droop below ~2.0V. This prevents spurious interrupts or incorrect output levels during startup transients common in battery-powered or unstable power supplies. In brownout scenarios where VCC drops momentarily, the device resets cleanly once voltage recovers above the threshold, avoiding partial state corruption that could lead to erratic behavior. This enhances system reliability in cost-sensitive applications where dedicated reset ICs are omitted.
How does the PCA9555DW compare to the MAX7311AWG+ in terms of output configuration flexibility?
The MAX7311AWG+ offers individually configurable open-drain or push-pull outputs per channel, while the PCA9555DW uses a global configuration for all ports. This makes the MAX7311 more flexible for mixed-voltage interfacing (e.g., driving 5V logic from a 3.3V MCU), whereas the PCA9555DW simplifies control at the expense of uniformity. Additionally, the MAX7311 supports higher clock speeds (up to 1 MHz), but the PCA9555DW’s 400 kHz operation aligns well with standard SMBus implementations. Choice depends on whether per-pin direction control or simpler addressing is prioritized.
Are there any layout constraints for minimizing crosstalk between PCA9555DW input pins in dense PCBs?
Yes. Adjacent input pins should maintain minimum clearance of 0.2 mm (8 mil) to reduce capacitive coupling, especially in high-impedance sensing applications. Guard rings around sensitive traces and placing ground planes beneath unused routing layers help isolate signals. Avoid running digital return currents under input pins; instead, route them along edges or separate layers. These practices preserve noise margins and prevent false triggering caused by crosstalk, particularly important when inputs monitor slow-changing analog-derived digital signals.
Does the PCA9555DW support hot-swapping of peripheral modules connected to its I/O ports?
Not natively. Hot-swapping introduces risk of latch-up or ESD damage during insertion/removal. While the device itself is protected against electrostatic discharge per JESD22 standards, dynamic connection/disconnection without isolation circuitry can violate absolute maximum ratings. Implementing series current-limiting resistors, TVS diodes, and optocouplers or MOSFETs for isolation is recommended. The PCA9555DW lacks built-in protection for hot-plug events, so external safeguards are necessary for robust hot-swap compatibility.
How does the PCA9555DW’s Moisture Sensitivity Level (MSL) of 1 influence storage and assembly processes?
With an MSL rating of 1, the PCA9555DW has unlimited floor life at <30°C and <60% relative humidity, simplifying inventory management. It does not require bake-out before reflow soldering, even after extended exposure, making it ideal for rapid prototyping and small-batch production. However, operators should still follow standard ESD precautions during handling due to its CMOS construction. This low sensitivity reduces manufacturing overhead and supports just-in-time assembly workflows without special environmental controls.
What limitations exist when using the PCA9555DW to drive relay coils directly?
Relay coils typically require 50–100 mA of inrush current, exceeding the PCA9555DW’s 25mA sink limit per pin. Driving them directly risks damaging the IC. Instead, use a transistor (e.g., NPN BJT or N-channel MOSFET) as a switch controlled by one of the PCA9555DW’s output pins. The expander then provides logic-level control while offloading power delivery to the external driver. Flyback diodes across the coil protect the transistor from inductive kickback, and snubber circuits may be needed for high-frequency switching applications.
How does the PCA9555DW’s voltage supply range impact compatibility with legacy 5V systems?
The PCA9555DW accepts 2.3V to 5.5V on VCC, making it backward compatible with 5V-tolerant microcontrollers like older ARM7 or PIC18 families. Its I2C interface remains functional down to 3.0V, preserving communication even as supply voltages decline. Input thresholds are defined relative to VCC, so 5V logic signals are safely interpreted when VCC is at 5V. However, when interfacing with 3.3V-only devices, ensure pull-up resistors on SDA/SCL are sized appropriately for the lower supply rails to meet rise-time requirements per I2C specifications.
Can the PCA9555DW be used to emulate UART-to-I2C bridging in legacy serial systems?
Partially, but with functional constraints. The PCA9555DW cannot decode UART frames automatically; it only exposes general-purpose I/O. To bridge UART data, an MCU or dedicated protocol converter must read UART bytes and write them to the PCA9555DW’s memory-mapped registers. The receiving end would then poll or respond to interrupts based on these writes. This approach adds latency and complexity versus purpose-built bridges, but works for simple command passing or status reporting where full duplex isn’t required.

Parts with Similar Specifications

The three parts on the right have similar specifications to Texas Instruments PCA9555DW

Product Attribute PCA9555DWRG4 PCA9555DWG4 PCA9555DWR PCA9555DGVR
Part Number PCA9555DWRG4 PCA9555DWG4 PCA9555DWR PCA9555DGVR
Manufacturer Texas Instruments Luminary Micro / Texas Instruments Texas Instruments Texas Instruments
Features - - - Simultaneous Sampling
Base Product Number - DAC34H84 MAX500 ADS62P42
Series - - - -
Voltage - Supply - - - -
Output Type - Current - Unbuffered Voltage - Buffered -
Package / Case - 196-LFBGA 16-DIP (0.300', 7.62mm) 64-VFQFN Exposed Pad
Package - Tape & Reel (TR) Tube Tape & Reel (TR)
Interface - - - -
Mounting Type - Surface Mount Through Hole Surface Mount
Interrupt Output - - - -
Number of I/O - - - -
Current - Output Source/Sink - - - -
Operating Temperature - -40°C ~ 85°C 0°C ~ 70°C -40°C ~ 85°C
Clock Frequency - - - -
Supplier Device Package - 196-NFBGA (12x12) 16-PDIP 64-VQFN (9x9)

PCA9555DW Datasheet PDF

Download PCA9555DW pdf datasheets and Texas Instruments documentation for PCA9555DW - Texas Instruments.

PCN Design/Specification
Design 25/Feb/2022.pdf PCA9555 04/Sep/2018.pdf
HTML Datasheet
PCA9555.pdf

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Customer Reviews

Evaluation: 10 Articles

  • Nath***rooks
    Jun 11, 2026

    Installed this power component in a converter board. Output remained stable under different load conditions and thermal performance was better than expected.

  • Dani***alkerTech
    Jun 1, 2026

    Product works, but setup took more effort than expected. Once configured the MCU ran reliably, although documentation support felt older compared with newer platforms. Fine for maintenance projects.

  • Yuki***aka88
    May 26, 2026

    信号通信プロジェクトでこのRS-485トランシーバーを使用しました。設置は簡単で、長距離ケーブルでも通信は安定していました。消費電力も、以前使用していたものより低くなっています。

  • Stev***aker
    May 20, 2026

    Solid diode for power rectification. Works well in switching circuits.

  • Bran***Lewis
    May 11, 2026

    Compact FPGA with good performance. Suitable for basic signal processing tasks.

  • Oliv***arris
    May 7, 2026

    Reliable I/O expander. Works well in embedded control applications.

  • Jess***Jones
    Apr 17, 2026

    It offers good value for the price, and the specifications match the description. I’ve been using it for two days with no issues, and I’ll definitely buy it again if I need it in the future.

  • Mich***Smith
    Apr 17, 2026

    Shipping was on time, the component pins are neatly aligned, and I tested 10 of them with a multimeter—all readings were within the specified range. Highly recommended.

  • Aman***arris
    Apr 3, 2026

    It was great—the entire process, from placing the order to receiving the package, went very smoothly. The components were consistent, the price was fair, and I had a very pleasant shopping experience.

  • Mike***nch
    Apr 3, 2026

    Better than expected! The resistance and capacitance readings were spot-on, and it passed the test on the first try. The service was reliable, and the packaging was thoughtful—I highly recommend it.

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PCA9555DW Image

PCA9555DW

Texas Instruments
32D-PCA9555DW

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