PCA9538DW - 8-Bit I2C I/O Expander | Texas Instruments
Référence : PCA9538DW ✓ ActifPCA9538DW Présentation
An I2C I/O expander is a peripheral interface IC that converts a serial two-wire bus into additional parallel GPIO lines. The I2C interface belongs to the broader serial-interface hierarchy, while the PCA9538 operates at the boundary between a microcontroller and external digital I/O. By using SCL and SDA, a system can reduce direct GPIO pin requirements while retaining individually configurable input or output behavior on P0 through P7.
The PCA9538DW combines eight I/O ports, an interrupt output, a reset input, and configuration registers in one low-power device. Its 2.3 V to 5.5 V operating range covers both 3.3 V and 5 V systems. The 400 kHz I2C rate permits frequent register access, while the interrupt output allows a connected processor to respond when a configured input changes rather than polling continuously. The SOIC-16 package is a surface-mount option suitable for conventional PCB assembly.
Functionally, the device uses an 8-bit port register for each I/O line and a configuration register that selects input or output operation. According to the NXP-hosted manufacturer datasheet, the PCA9538 is a 16-pin CMOS device designed to provide eight bits of parallel GPIO expansion for I2C-bus and SMBus applications. Interrupt, reset, and configuration registers give the host a structured control interface rather than requiring individual GPIO wiring for every external line.
Typical uses include collecting digital switch states, driving discrete alarm or enable signals, expanding a host with limited GPIO, and connecting remote I/O modules over an I2C bus. The PCA9538 is particularly useful when the additional lines are distributed from the main controller or located in a panel or control module. In these arrangements, the interrupt line reduces unnecessary processor activity while the host reads the port register after a change notification.
When laying out a PCA9538DW board, route SCL and SDA as a controlled I2C bus and confirm pull-up resistor values against the bus voltage, capacitance, and clock rate. Provide a stable supply near the device and use the reset and interrupt pins according to the system’s startup and wake-up requirements. Although the 2.3 V to 5.5 V range is broad, the entire I2C system must share compatible logic levels.
This page combines verified manufacturer and distributor information, pin-level implementation guidance, application fit analysis, and candidate-replacement screening. That engineering context helps distinguish a genuine pin-compatible substitute from a device that merely performs a similar I/O-expansion function or uses a different package.
Alternatives de remplacement direct pour PCA9538DW — même boîtier, compatible broche à broche. Les références à boîtier différent nécessitant une retouche du PCB sont exclues.
Aucune alternative de remplacement direct disponible pour ce produit.
Demander des alternativesPCA9538DW Spécifications
| Number of I/O Ports | 8 ports |
| I/O Port Resolution | 8 bits |
| Supply Voltage Range | 2.3 V to 5.5 V |
| Type d'interface | I2C and SMBus |
| Maximum I2C Bus Frequency | 400 kHz |
| Interrupt Output | 1 active-low open-drain output |
| Reset Function | 1 reset input |
| Configuration Registers | 8-port input/output configuration |
| Plage de température de fonctionnement | -40 °C to +85 °C |
| Package Type | 16-pin SOIC (DW) |
| Package Body Width | 300 mil |
| Type de montage | Surface mount |
| Device Technology | CMOS |
| Statut RoHS | unknown |
Configuration des broches de PCA9538DW
| Broche 1 | A0 — Address input A0 |
| Broche 2 | A1 — Address input A1 |
| Broche 3 | A2 — Address input A2 |
| Broche 4 | P0 — Bidirectional I/O port P0 |
| Broche 5 | P1 — Bidirectional I/O port P1 |
| Broche 6 | P2 — Bidirectional I/O port P2 |
| Broche 7 | P3 — Bidirectional I/O port P3 |
| Broche 8 | GND — Ground |
| Broche 9 | P4 — Bidirectional I/O port P4 |
| Broche 10 | P5 — Bidirectional I/O port P5 |
| Broche 11 | P6 — Bidirectional I/O port P6 |
| Broche 12 | P7 — Bidirectional I/O port P7 |
| Broche 13 | INT — Interrupt output |
| Broche 14 | VCC — Power supply |
| Broche 15 | SCL — Serial clock |
| Broche 16 | SDA — Serial data |
Applications typiques
PCA9538DW convient pour 6 applications: Industrial Control Panel GPIO Expansion, Remote Sensor and Relay Interface, Communications Equipment Status Control, Test and Measurement Front Panel, Consumer Accessory and Interface Hub, Data Acquisition Front-End Control.
Industrial Control Panel GPIO Expansion
The PCA9538DW fits industrial control panels where a central controller must monitor switches, selectors, or interlock inputs and drive discrete control outputs without consuming eight direct GPIO pins. Its eight independently configurable ports operate from 2.3 V to 5.5 V, allowing deployment on either 3.3 V or 5 V logic rails. The host communicates through I2C at up to 400 kHz, while the interrupt output lets the controller respond to changed panel inputs instead of continuously polling. A 16-pin SOIC package also simplifies assembly in equipment designed around conventional surface-mount packages.
Recommandé
Remote Sensor and Relay Interface
The PCA9538DW can connect a microcontroller to remote discrete sensors, alarm signals, and relay-enable lines over the two-wire I2C bus. The eight P0-P7 lines provide the parallel interface needed where individual signals are physically separated, while the 2.3 V to 5.5 V supply range supports common industrial logic levels. Up to 400 kHz communication speed is suitable for periodic status collection, and interrupt signaling can reduce processor activity when an input state changes. System designers should confirm pull-up values and logic compatibility across the complete bus.
Recommandé
Communications Equipment Status Control
In communications equipment, the PCA9538DW can expand a baseband or supervisory processor into additional control and status lines distributed around a chassis. Its I2C and SMBus capability operates up to 400 kHz, allowing register-based access through SCL and SDA rather than a large parallel bus. The device supports 2.3 V to 5.5 V operation for compatibility with common logic systems, and the interrupt output can report a changed input without continuous polling. Its SOIC-16 package is practical for boards requiring conventional surface-mount assembly and traceable manufacturing processes.
Recommandé
Test and Measurement Front Panel
The PCA9538DW is useful in test and measurement front panels where rotary switches, pushbuttons, status LEDs, and range-select lines exceed the available GPIO of an instrument controller. Eight configurable ports can read operator inputs and drive panel indicators, while the 400 kHz I2C interface keeps the controller-to-panel connection compact. The 2.3 V to 5.5 V operating range supports integration into mixed-voltage laboratory equipment after logic-level verification. The interrupt output can identify an operator action quickly, and the 16-pin SOIC package is straightforward for production PCB assembly.
Recommandé
Consumer Accessory and Interface Hub
The PCA9538DW can expand a compact embedded controller in a consumer accessory, smart-home controller, or configuration hub that needs multiple discrete control lines. Its eight I/O ports avoid dedicating eight controller pins to buttons, LEDs, relay drives, or status indicators. The 2.3 V minimum supply voltage supports 3.3 V systems, and the 5.5 V maximum supports 5 V designs. At up to 400 kHz, I2C access is fast enough for routine register changes, while the interrupt output supports event-driven button or switch handling with lower polling overhead.
Recommandé
Data Acquisition Front-End Control
The PCA9538DW can provide control and status lines for a data-acquisition front end when range selection, trigger enables, channel enables, or alarm indicators would otherwise overload the acquisition controller. The eight ports are accessible through I2C at up to 400 kHz, allowing configuration commands and status reads to share two bus conductors with other peripherals. Its 2.3 V to 5.5 V supply range accommodates common acquisition-system logic rails. The interrupt output can flag a changed external state, while reset and configuration registers support deterministic startup and port-direction setup.
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Récapitulatif des produits recommandés
Données de référence d'ingénierie pour PCA9538DW — comparaison, recommandations de conception et informations de conformité.
Guide de sélection
Comparaison avec les alternatives
| Paramètre | Ce produit |
|---|---|
| Package | 16-pin SOIC (DW) |
| Brand | Texas Instruments |
| Number of I/O Ports | 8 ports |
| I/O Port Resolution | 8 bits |
| Supply Voltage Range | 2.3 V to 5.5 V |
| Interface | I2C and SMBus |
| Maximum Bus Frequency | 400 kHz |
| Operating Temperature | -40 °C to +85 °C |
| Interrupt Output | Yes |
| Reset Input | Yes |
| Configuration Registers | Yes |
Principaux différenciateurs
- Eight I/O lines with integrated interrupt and control registers (vs PCF8574DWE4)
- Wide 2.3 V to 5.5 V operating range (vs PCF8574DWE4)
- Well-supported manufacturer and distributor sourcing (vs PCA9538PWG4)
Notes de conception
Do not treat a similarly functional I2C expander as a drop-in replacement without verifying the physical footprint, address pins, port register behavior, reset polarity, and interrupt polarity. The NXP PCA9538APW is described as pin-to-pin compatible with the PCA9538, but the supplied evidence does not establish that its package option matches the PCA9538DW’s 16-pin SOIC footprint. Confirm the package drawing and complete register behavior before substitution.
Place the device so SCL and SDA follow the system’s I2C layout rules and remain away from noisy switching paths. The verified excerpts do not provide the manufacturer’s recommended pull-up values, so resistor selection must be based on the actual bus voltage, total capacitance, number of devices, and the 400 kHz operating target. Preserve a common ground path between the expander and controller, and decouple VCC locally according to the complete datasheet guidance.
Although the PCA9538DW supports 2.3 V to 5.5 V, this range applies to the device and its supported I/O logic, not automatically to every peripheral on the bus. Pull SDA and SCL high only to a rail that all connected devices can tolerate. For systems combining 5 V and 3.3 V devices, use an appropriate bus translator or level-shifting arrangement instead of assuming the PCA9538’s broad supply range solves the mismatch.
Use the interrupt output as an event signal rather than relying on continuous polling when the application permits it. Ensure the host handles the interrupt source, reads the relevant port state, and clears the device’s interrupt condition in the sequence required by the manufacturer datasheet. The verified excerpts identify the interrupt output but do not provide detailed edge and polarity information, so those details must be taken from the complete datasheet.
Informations de conformité
The supplied verified excerpts do not state RoHS, REACH, AEC-Q100, lead-free, halogen-free, or conflict-minerals status for PCA9538DW. No compliance claim was inferred from the distributor listings.