PCA9555DB - 16-Bit I2C GPIO Expander with Interrupt | NXP
MPN: PCA9555DB ✓ ActivePCA9555DB Overview
What is an I2C GPIO expander? An I2C GPIO expander is an interface IC that adds parallel digital input and output capability to a controller with limited pins. The PCA9555 belongs to the I/O expander, parallel I/O, interface IC, and semiconductor hierarchy. Its two 8-bit ports connect a microcontroller or processor to switches, indicators, sensors, relays, and other external circuits while keeping the host-side connection compact.
Key features include 16 configurable GPIO lines, separate input and output port registers, polarity inversion registers, 5 V tolerant I/O ports, and low standby-current consumption with a maximum of 1 uA. The 2.3 V to 5.5 V operating range supports both 3.3 V and 5 V systems. Its open-drain interrupt output allows multiple change events to be combined on a shared host interrupt line.
The device uses a two-wire I2C/SMBus interface with serial clock and serial data connections. A configurable seven-bit address supports multiple expanders on one bus, while 100 kHz and 400 kHz operating modes are identified in the provided NXP-family search data. The SSOP-24 package provides a conventional through-board surface-mount form factor with a 1.0 mm pitch.
Typical applications include industrial control panels, programmable relay boards, LED status systems, keypad interfaces, sensor aggregation, and compact embedded control systems. The PCA9555DB is especially useful when a host controller needs more GPIO than its package or board-level pin budget can provide.
Designers should confirm address selection, pull-up requirements, input thresholds, output-drive capability, and interrupt polarity against the manufacturer datasheet. Because the verified data does not include pricing or a complete pin-level table, those details remain explicitly unverified rather than inferred.
Drop-in alternatives for PCA9555DB — 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 PCA9555DB (same form factor and footprint) — differing in Interrupt Output, Package, Configuration Registers, Device Type, I/O Direction Control.
PCA9500PW
✅ Drop-InContact for price
View Datasheet →PCA9564D
✅ Drop-In📋 Reference alternative (not in catalog)
PCA9555DB
✅ Drop-InContact for price
View Datasheet →TCA9555PWR
✅ Drop-InContact for price
View Datasheet →PCA9555DB
✅ Drop-InContact for price
View Datasheet →PCA9555DB Specifications
| Device Type | 16-bit I2C/SMBus GPIO expander with interrupt |
| GPIO Count | 16 bits |
| Operating Voltage Range | 2.3 V to 5.5 V |
| I2C Maximum Frequency | 400 kHz |
| I2C/SMBus Interface | Two-wire serial interface |
| I/O Port Configuration | Input or output per bit |
| I/O Port Tolerance | 5 V tolerant |
| Interrupt Output | Active-low, open-drain |
| Standby Current | 1 uA maximum |
| Package Type | SSOP-24 |
| Package Pitch | 1.0 mm |
| Mounting Type | Surface mount |
| Device Pin Count | 24 pins |
| RoHS Status | unknown |
| REACH Status | unknown |
PCA9555DB Pin Configuration
| Pin 1 | P00 — Port 0 input/output bit 0; exact electrical direction and pin multiplexing should be confirmed in the manufacturer datasheet |
| Pin 2 | P01 — Port 0 input/output bit 1; exact electrical direction and pin multiplexing should be confirmed in the manufacturer datasheet |
| Pin 3 | P02 — Port 0 input/output bit 2; exact electrical direction and pin multiplexing should be confirmed in the manufacturer datasheet |
| Pin 4 | P03 — Port 0 input/output bit 3; exact electrical direction and pin multiplexing should be confirmed in the manufacturer datasheet |
| Pin 5 | P04 — Port 0 input/output bit 4; exact electrical direction and pin multiplexing should be confirmed in the manufacturer datasheet |
| Pin 6 | P05 — Port 0 input/output bit 5; exact electrical direction and pin multiplexing should be confirmed in the manufacturer datasheet |
| Pin 7 | P06 — Port 0 input/output bit 6; exact electrical direction and pin multiplexing should be confirmed in the manufacturer datasheet |
| Pin 8 | P07 — Port 0 input/output bit 7; exact electrical direction and pin multiplexing should be confirmed in the manufacturer datasheet |
| Pin 9 | P10 — Port 1 input/output bit 0; exact electrical direction and pin multiplexing should be confirmed in the manufacturer datasheet |
| Pin 10 | P11 — Port 1 input/output bit 1; exact electrical direction and pin multiplexing should be confirmed in the manufacturer datasheet |
| Pin 11 | P12 — Port 1 input/output bit 2; exact electrical direction and pin multiplexing should be confirmed in the manufacturer datasheet |
| Pin 12 | P13 — Port 1 input/output bit 3; exact electrical direction and pin multiplexing should be confirmed in the manufacturer datasheet |
| Pin 13 | P14 — Port 1 input/output bit 4; exact electrical direction and pin multiplexing should be confirmed in the manufacturer datasheet |
| Pin 14 | P15 — Port 1 input/output bit 5; exact electrical direction and pin multiplexing should be confirmed in the manufacturer datasheet |
| Pin 15 | P16 — Port 1 input/output bit 6; exact electrical direction and pin multiplexing should be confirmed in the manufacturer datasheet |
| Pin 16 | P17 — Port 1 input/output bit 7; exact electrical direction and pin multiplexing should be confirmed in the manufacturer datasheet |
| Pin 17 | A0 — I2C address input; exact address configuration should be confirmed in the manufacturer datasheet |
| Pin 18 | A1 — I2C address input; exact address configuration should be confirmed in the manufacturer datasheet |
| Pin 19 | A2 — I2C address input; exact address configuration should be confirmed in the manufacturer datasheet |
| Pin 20 | SCL — I2C/SMBus serial clock |
| Pin 21 | SDA — I2C/SMBus serial data |
| Pin 22 | INT — Active-low open-drain interrupt output |
| Pin 23 | VSS — Ground supply |
| Pin 24 | VDD — Positive supply voltage |
Typical Applications
PCA9555DB is suitable for 6 applications: Industrial Control Panels, Relay and Driver Interface, LED Status and Indicator Systems, Keypad and Human-Interface Control, Sensor Aggregation, Programmable Automation and Test Fixtures.
Industrial Control Panels
PCA9555DB is well suited to industrial control panels because it adds 16 configurable digital lines over a compact I2C/SMBus connection. A controller can read panel status, configure outputs, and receive change notifications through the active-low interrupt instead of polling continuously. The 2.3 V to 5.5 V range supports common control hardware, while 5 V tolerant I/O simplifies connections to logic where permitted by the complete datasheet.
Recommended
Relay and Driver Interface
PCA9555DB can provide a low-voltage command interface for relay drivers, MOSFET stages, or optocoupler inputs. Its 16 GPIO lines are useful for distributing control and status signals while keeping the host board’s direct pin count manageable. The GPIO output should drive a suitable transistor or relay-driver circuit rather than an inductive load directly, with flyback protection and a defined fail-safe state added according to the relay driver’s requirements.
Recommended
LED Status and Indicator Systems
PCA9555DB is practical for LED status and indicator systems where a compact controller needs more discrete outputs than its package provides. Each of the 16 GPIO bits can represent an operating state, alarm, channel status, or user indicator. The 400 kHz I2C/SMBus capability supports efficient updates, and the interrupt output can notify the host when an input status changes. External current limiting and, where needed, transistor drive must be sized for the indicator load.
Recommended
Keypad and Human-Interface Control
PCA9555DB can scan matrix-style keypads or collect discrete front-panel signals while preserving a small host processor footprint. Input configuration supports reading individual lines, while the interrupt output allows the controller to wake or respond only when a relevant input changes. Debounce timing, key-state mapping, and electrical rise-time behavior must be implemented in firmware and validated against the complete PCA9555DB timing and logic specifications.
Recommended
Sensor Aggregation
PCA9555DB is useful for aggregating discrete sensor outputs, interlocks, and alarm lines from a remote enclosure. Multiple digital sensors can share the expander’s 16 GPIO resources while the host communicates through the two-wire I2C/SMBus interface. The active-low open-drain interrupt provides a compact way to flag input changes, but sensor outputs must meet the input voltage and leakage limits; open-drain sensors may also require appropriate pull-ups.
Recommended
Programmable Automation and Test Fixtures
PCA9555DB can expand the control and monitoring surface of compact automation fixtures or test adapters. A host can set fixture control lines, read limit-switch states, and receive an interrupt when a sensor changes. The 2.3 V to 5.5 V range accommodates mixed embedded test electronics, while the 24-pin SSOP format supports compact boards. Production designs should verify output current, input thresholds, ESD requirements, and cable-induced transients.
Recommended
Recommended Products Summary
Engineering reference data for PCA9555DB — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | PCA9500PW | PCA9564D | PCA9555DB | TCA9555PWR |
|---|---|---|---|---|---|
| Brand | NXP Semiconductors | NXP Semiconductors | NXP Semiconductors | Texas Instruments | Texas Instruments |
| Package | SSOP-24 | SSOP-24 | SSOP-24 | SSOP-24 | TSSOP-24; footprint compatibility requires confirmation |
Key Differentiators
- 16-bit GPIO expansion with interrupt in one interface IC (vs PCA9564D)
- Verified operating range supports 3.3 V and 5 V systems (vs TCA9555PWR)
- 400 kHz serial operation (vs PCA9500PW)
- Open-drain active-low interrupt supports shared signaling (vs PCA9500PW)
Design Notes
Keep the PCA9555DB I2C traces short and route SCL and SDA away from noisy switching nodes and long motor or relay wiring. Place any required bus pull-ups near the bus master or according to the calculated distributed-bus topology, not arbitrarily at the expander. The supplied data confirms 400 kHz operation but does not provide rise-time or capacitance values, so obtain those limits from the manufacturer datasheet before finalizing trace length, pull-up resistance, or bus loading.
Do not treat the PCA9555DB as a general-purpose high-current output driver. Use the GPIO outputs for logic-level control signals, and add transistor, MOSFET, relay-driver, or buffer stages whenever the load current, voltage, inductive energy, or isolation requirement exceeds the device limits. For open-drain interrupt wiring, connect the signal to the system’s intended pull-up and account for active-low polarity in firmware.
Before firmware integration, define the I2C address from the address inputs, configure each port direction explicitly, and establish the polarity-inversion registers for external signals. The interrupt should be serviced only after the host has identified which input caused the event, and the firmware should clear or acknowledge the device’s interrupt state according to the complete register map. This sequence prevents missed transitions and avoids repeated interrupts caused by uncleared status conditions.
Compliance Information
The supplied verified data does not explicitly state RoHS, REACH, lead-free, halogen-free, conflict-minerals, or automotive qualification status. AEC-Q100 is recorded as not_applicable only because this is an interface IC and no automotive qualification evidence was provided; confirm all compliance claims with the manufacturer or authorized distributor documentation.
