PCA9538DBR - 8-Bit I2C I/O Expander | Texas Instruments
MPN: PCA9538DBR ✗ End of LifePCA9538DBR Overview
An I/O expander is an interface IC that extends the number of digital input and output lines available to an embedded system. The PCA9538 sits between an I2C or SMBus controller and external logic, combining an 8-bit parallel port with serial control. Its hierarchy is I/O expander to interface IC to semiconductor, making it useful when a system needs more GPIO than the host controller can expose directly.
The principal features include eight independently configurable I/O lines, operation from 2.3 V to 5.5 V, and I2C communication at up to 400 kHz. Each port register can define pins as inputs or outputs, while the polarity inversion register allows input buffers to be inverted logically. The interrupt output provides a change-detection mechanism that can reduce routine polling by the controller.
The PCA9538 uses a two-wire serial interface and address pins that allow multiple expanders to share a bus. Configuration, port, polarity, and interrupt-related registers separate serial bus traffic from the parallel I/O function. This architecture supports bidirectional control of external loads and sensing of external logic states while preserving a compact serial connection to the host processor.
Typical uses include industrial control modules, programmable logic controllers, instrumentation, communications equipment, appliance control, and embedded systems requiring additional GPIO. It is especially useful for driving discrete control signals, reading switches or logic levels, and generating an interrupt when an attached external line changes state.
Designers should confirm the address configuration and reset behavior in the system power-up sequence. Pull-up requirements for SDA and SCL must follow the datasheet and the voltage level of the connected bus. The operating limits, electrical timing, and absolute maximum ratings should be reviewed before applying the device to a new design.
This product record combines verified manufacturer and distributor information, package-level guidance, compatible replacement candidates, and practical design notes. It is intended to accelerate component selection while making the limitations of lifecycle, availability, and pricing data explicit.
Drop-in alternatives for PCA9538DBR — 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 PCA9538DBR (same form factor and footprint) — differing in Package, Configuration Registers, Function, Interface, Interrupt Output.
TCA9538D
✅ Drop-In📋 Reference alternative (not in catalog)
PCA9538D,112
✅ Drop-In📋 Reference alternative (not in catalog)
PCA9538DW
✅ Drop-InContact for price
View Datasheet →PCF8574TD
✅ Drop-InContact for price
View Datasheet →PCA9554DBR
✅ Drop-InContact for price
View Datasheet →PCA9538DBR Specifications
| Number of I/O Ports | 8 ports |
| Operating Supply Voltage Range | 2.3 V to 5.5 V |
| Interface Type | I2C and SMBus |
| Maximum I2C Bus Frequency | 400 kHz |
| Interrupt Output | 1 interrupt output |
| Reset Input | 1 reset input |
| Configuration Registers | Configuration, port, and polarity control |
| Standby Current | 1 uA |
| Package | 16-pin SSOP |
| Package Family | SSOP family, surface-mount SMD |
| Mounting Type | Surface mount |
| Pin Count | 16 pins |
| I/O Configuration | Individually configurable as input or output |
| Input Polarity Control | Configurable input polarity inversion |
| Address Configuration | Hardware-configurable bus address |
PCA9538DBR Pin Configuration
| Pin 1 | A0 — Address input A0 |
| Pin 2 | A1 — Address input A1 |
| Pin 3 | A2 — Address input A2 |
| Pin 4 | P0 — I/O port 0 |
| Pin 5 | P1 — I/O port 1 |
| Pin 6 | P2 — I/O port 2 |
| Pin 7 | P3 — I/O port 3 |
| Pin 8 | VSS — Ground reference |
| Pin 9 | P4 — I/O port 4 |
| Pin 10 | P5 — I/O port 5 |
| Pin 11 | P6 — I/O port 6 |
| Pin 12 | P7 — I/O port 7 |
| Pin 13 | INT — Interrupt output |
| Pin 14 | SCL — Serial clock input |
| Pin 15 | SDA — Serial data bidirectional line |
| Pin 16 | VCC — Power supply input |
Typical Applications
PCA9538DBR is suitable for 6 applications: Industrial Control and Automation, Programmable Logic Controller Expansion, Instrumentation and Measurement Equipment, Appliance and Household Equipment Control, Communications and Network Equipment, Embedded GPIO Expansion.
Industrial Control and Automation
The PCA9538DBR fits industrial automation modules that need more digital control or sensing points than the host controller provides. Its eight configurable I/O lines can operate from 2.3 V to 5.5 V, while the 400 kHz I2C interface preserves a compact connection to the controller. The interrupt output can notify the host when an external line changes, reducing the need for continuous polling. Because a supplied distributor source classifies the device as obsolete, this application is most appropriate for repair, qualified inventory, or a design whose lifecycle plan explicitly accepts that constraint.
Recommended
Programmable Logic Controller Expansion
The PCA9538DBR can expand the I/O capacity of a programmable logic controller or embedded controller without allocating eight direct host pins. Each of the eight port lines can be configured for input or output, allowing the same device to read limit switches and drive discrete control signals. Operating across 2.3 V to 5.5 V supports common industrial logic levels, and the interrupt output offers a practical change-detection path. Engineers should verify the controller's bus voltage, pull-up arrangement, address allocation, and available expansion ports before incorporating this obsolete part into new machinery.
Recommended
Instrumentation and Measurement Equipment
The PCA9538DBR is useful in instrumentation when front-panel indicators, mode controls, and discrete status inputs exceed the available GPIO of a measurement controller. Its eight configurable lines reduce parallel wiring to an I2C bus running at up to 400 kHz, while interrupt support can report asynchronous input changes. The 2.3 V to 5.5 V operating range accommodates multiple logic systems found in test and measurement products. For new professional instruments, engineers should normally select an active equivalent and confirm accuracy requirements, input thresholds, isolation, noise, and operating-temperature requirements from the full datasheet.
Recommended
Appliance and Household Equipment Control
The PCA9538DBR can concentrate appliance controls such as buttons, indicators, relays, and discrete sensor connections behind a single serial interface. Eight configurable I/O lines support mixed input and output use, while 400 kHz I2C communication provides sufficient control bandwidth for non-timing-critical appliance functions. Its 2.3 V to 5.5 V range is compatible with common embedded logic voltages. The device's obsolete classification means it is best viewed as a repair or continuity option for an existing appliance design rather than the default choice for a new product launch.
Recommended
Communications and Network Equipment
The PCA9538DBR can provide housekeeping I/O in communications equipment where status LEDs, hardware reset controls, presence detectors, or relay signals would otherwise consume valuable controller pins. The serial bus connection preserves routing flexibility, and the 400 kHz operating rate supports ordinary supervisory control traffic rather than high-bandwidth data transfer. Interrupt output can alert the communications processor when monitored external state changes. For network infrastructure requiring long product availability, an active replacement should be selected and tested for address compatibility, bus capacitance, level translation, and system-level EMC requirements.
Recommended
Embedded GPIO Expansion
The PCA9538DBR is well suited to embedded systems whose host controller has insufficient exposed GPIO for switches, LEDs, latches, or peripheral control lines. Eight independently configurable ports allow the same expander to handle both sensed states and driven outputs, while the 2.3 V to 5.5 V supply range supports several embedded platforms. The two-wire bus reduces pin and routing requirements, and the interrupt output can provide event-driven control. Firmware must initialize the configuration, port-direction, and polarity registers, and production designers should verify lifecycle availability before committing to the obsolete device.
Recommended
Recommended Products Summary
Engineering reference data for PCA9538DBR — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | TCA9538D | PCA9538D,112 | PCA9538DW | PCF8574TD | PCA9554DBR |
|---|---|---|---|---|---|---|
| Package | SSOP-16 | SSOP-16 | SSOP-16 | SSOP-16 | SSOP-16 | SSOP-16 |
| Brand | Texas Instruments | Texas Instruments | Texas Instruments | Texas Instruments | NXP Semiconductors | Texas Instruments |
| I/O Port Count | 8 | 8 | 8 | 8 | 8 | 4 |
Key Differentiators
- Manufacturer-supported upgraded replacement (vs TCA9538D)
- Exact PCA9538 family continuity (vs PCA9538D,112)
- More I/O than a reduced-port companion (vs PCA9554DBR)
- Interrupt and reset feature set (vs PCF8574TD)
Design Notes
Operate the PCA9538DBR only within its documented 2.3 V to 5.5 V supply range. The device can remain connected to a powered I2C bus while its own supply is off, so verify the host system's sequencing and bus-isolation requirements before hot-plugging or field replacement. Confirm that SDA and SCL pull-ups are referenced to the correct active bus voltage and do not back-feed the expander during power transitions.
Place the PCA9538DBR close to the connector or controlled circuitry that uses its eight I/O lines, while keeping the I2C route away from noisy switching nodes. Route SDA and SCL as a compact differential-capacitance pair, minimize stubs, and place pull-up resistors at the physically appropriate end of the bus. Review the address pins and the INT trace to prevent unintended bus loading or false interrupt events.
A replacement is not automatically a drop-in solution merely because both devices have 16 pins. Before substituting TCA9538, a PCA9538 ordering variant, PCF8574, or PCA9554, compare package drawings, address pins, reset polarity, interrupt behavior, register addresses, input thresholds, output-driver topology, and supply limits. Update host firmware for any changed register map or device identity, and perform production tests across voltage, temperature, bus loading, and output-state transitions.
Initialize the PCA9538 registers in a controlled sequence after reset. Set port directions before writing outputs so that an unintended output level is not driven onto external circuitry, and apply the required polarity and configuration values before enabling interrupts. The verified snippets do not provide complete timing values, so use the manufacturer datasheet for reset timing, register initialization order, and bus timing.
Compliance Information
The supplied verified snippets do not state RoHS, REACH, AEC-Q100, lead-free, halogen-free, or conflict-minerals status. These fields remain unknown rather than being inferred from the manufacturer or package.