PCA9539DW - 16-Bit 2.3-5.5V I/O Expander | Texas Instruments
MPN: PCA9539DW ✓ Active| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $3.0813 | $3.08 |
| 10 | $0 | $0.00 |
| 100 | $0 | $0.00 |
| 500 | $0 | $0.00 |
| 1,000 | $0 | $0.00 |
PCA9539DW Overview
An I/O expander is an interface IC that converts serial bus commands into parallel input or output signals. In the product hierarchy, the PCA9539 is an I/O expander, interface controller, peripheral IC, and semiconductor. It is especially useful when a microcontroller has too few pins for buttons, LEDs, relays, logic controls, or sensor-enable signals. Its I2C/SMBus connection allows the added lines to be controlled over two shared serial wires.
The device provides 16 I/O pins, a 400 kHz bus clock, push-pull output capability, and low current consumption. According to the verified distributor data, output source and sink options include 10 mA and 25 mA configurations. The integrated interrupt output allows a connected processor to react to a change on an input without continuously polling the device, while reset and configuration registers support controlled startup and bus operation.
The PCA9539 differs from the PCA9555 because it removes the internal I/O pull-up resistors, replaces address input A2 with RESET, and uses a different address range, as stated on the official TI product page. Removing the internal pull-ups can reduce power consumption when I/O lines remain low. The separate RESET function also provides a hardware reset path, although external pull-up or pull-down requirements must be verified against the complete electrical design.
Typical uses include industrial control modules, sensor-interface boards, programmable logic controllers, remote I/O modules, instrumentation, and embedded systems requiring status LEDs, relay controls, or digital-input monitoring. The interrupt line can support efficient event-driven firmware, while the 16 parallel lines reduce the number of host-controller pins needed.
Designers should confirm the 2.3 V to 5.5 V supply range, 400 kHz bus limit, I/O voltage levels, current limits, pull-up requirements, and address configuration in the manufacturer datasheet. External pull-ups on SDA and SCL and any required I/O pull resistors should be selected for the bus voltage, capacitance, and system noise environment. The host firmware should also verify register defaults before driving attached loads.
This page combines verified manufacturer and distributor information, practical I/O-expander design guidance, and explicit data gaps for parameters not present in the supplied sources.
Drop-in alternatives for PCA9539DW — 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 PCA9539DW (same form factor and footprint) — differing in Package, Configuration Registers, I/O Voltage Tolerance, Reset Input.
Quick Comparison Tool — Select alternative parts for side-by-side comparison:
PCA9539DWR
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PCA9539PW/Q900
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View Datasheet →PCA9555D
✅ Drop-In📋 Reference alternative (not in catalog)
PCA9555DWR
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PCA9557D
✅ Drop-In✓ In Stock
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View Datasheet →PCA9539DW Specifications
| Product Type | 16-bit I/O expander |
| I/O Pin Count | 16 pins |
| Supply Voltage Range | 2.3 V to 5.5 V |
| Serial Bus Interface | I2C/SMBus |
| Maximum Bus Clock | 400 kHz |
| Output Configuration | Push-pull |
| Output Source Current | 10 mA and 25 mA options |
| Output Sink Current | 10 mA and 25 mA options |
| Interrupt | Yes |
| Reset | Yes |
| Configuration Registers | Yes |
| Power-On Reset | Yes |
| Internal I/O Pull-Up Resistors | Removed according to TI product comparison |
| Operating Temperature | -40 C to +85 C |
| Package | 24-pin SOIC (DW) |
| Mounting Type | Surface Mount |
PCA9539DW Pin Configuration
| Pin 1 | A1 — Address input or device control pin; verify exact function in the manufacturer pin description |
| Pin 2 | A0 — Address input |
| Pin 3 | RESET — Active-low reset input according to the product-family description |
| Pin 4 | INT — Interrupt output |
| Pin 5 | VSS — Ground reference |
| Pin 6 | P00 — I/O port line |
| Pin 7 | P01 — I/O port line |
| Pin 8 | P02 — I/O port line |
| Pin 9 | P03 — I/O port line |
| Pin 10 | P04 — I/O port line |
| Pin 11 | P05 — I/O port line |
| Pin 12 | P06 — I/O port line |
| Pin 13 | P07 — I/O port line |
| Pin 14 | P10 — I/O port line |
| Pin 15 | P11 — I/O port line |
| Pin 16 | P12 — I/O port line |
| Pin 17 | P13 — I/O port line |
| Pin 18 | P14 — I/O port line |
| Pin 19 | P15 — I/O port line |
| Pin 20 | SCL — I2C/SMBus serial clock |
| Pin 21 | SDA — I2C/SMBus serial data |
| Pin 22 | A2 — Address input; verify exact PCA9539 pin-function description |
| Pin 23 | NC — Not connected |
| Pin 24 | VCC — Positive supply voltage |
Typical Applications
PCA9539DW is suitable for 6 applications: Industrial Control Interface, Remote Sensor and Actuator Hub, Programmable Logic Controller Expansion, LED and Relay Control Panel, Instrumentation and Test Equipment, Embedded Accessory and Peripheral Board.
Industrial Control Interface
The PCA9539DW fits industrial control boards that need more digital lines than the host microcontroller exposes. Its 16 I/O pins can drive relay-enable signals, status indicators, valve controls, or discrete input channels while the I2C/SMBus connection keeps the serial wiring compact. The 2.3 V to 5.5 V operating range supports common industrial logic levels, while the interrupt output can notify the controller when an input changes. Because the verified comparison notes that internal I/O pull-ups are removed, the board should include any pull-ups required by the attached circuitry. Firmware can configure each port and avoid continuous polling.
Recommended
Remote Sensor and Actuator Hub
The PCA9539DW is useful when a remote sensor or actuator board needs several low-speed digital control and status lines connected to a central processor. Sixteen ports can represent sensor enables, alarm outputs, relay drive requests, or equipment-state inputs, while the 400 kHz serial bus provides sufficient rate for typical supervisory control traffic. The interrupt line supports event-driven operation when an input changes, reducing unnecessary bus transactions. The 2.3 V to 5.5 V range allows deployment in both 3.3 V and 5 V systems, subject to correct pull-up and logic-level design.
Recommended
Programmable Logic Controller Expansion
The PCA9539DW can add compact parallel I/O to a programmable logic controller or embedded automation controller without consuming a large number of host pins. The 16-bit architecture can support discrete input modules, output groups, panel indicators, and actuator-enable signals. Its interrupt capability allows the controller to respond to external events through one dedicated signal rather than repeatedly reading every port. The 400 kHz I2C/SMBus limit is suitable for supervisory and configuration traffic, not high-speed parallel data transfer. System designers should verify address selection, reset behavior, and external pull-up requirements against the TI documentation.
Recommended
LED and Relay Control Panel
The PCA9539DW can centralize indicator and relay-control lines in a compact control panel. Its 16 push-pull I/O ports are suitable for logic-level control tasks when the attached loads remain within the device's specified current and voltage limits. The interrupt input can also monitor panel switches or fault signals and alert the host controller. Using one serial bus for multiple panel functions reduces wiring complexity and frees microcontroller pins. The engineer must add suitable current-limiting, driver, or transistor circuitry for LEDs and relays rather than assuming the I/O pins can drive every load directly.
Recommended
Instrumentation and Test Equipment
The PCA9539DW can expand front-panel controls and status signals in instrumentation systems where the primary controller handles measurement functions and needs additional discrete I/O. Typical assignments include range-select control, relay enable, trigger status, alarm indication, and user-panel monitoring. The 16-bit structure provides a convenient split between two 8-bit ports, while the interrupt line supports efficient event notification. Its 2.3 V to 5.5 V range permits use with common laboratory and embedded control voltage rails. Exact timing, output-drive, and electrical limits should be taken from the manufacturer datasheet before driving external loads.
Recommended
Embedded Accessory and Peripheral Board
The PCA9539DW is suitable for accessory boards connected to an embedded platform through I2C/SMBus, including keypad interfaces, display-control boards, storage-card enable logic, and peripheral configuration. Sixteen ports can expose controls that would otherwise occupy several host pins, and the interrupt output can report button or status events. The 400 kHz bus rate is appropriate for configuration traffic and slow digital controls. The PCA9539's lack of internal I/O pull-ups means that the board designer should determine whether external pull-ups or pull-downs are required on connected lines. Firmware should also account for the separate RESET behavior and address range.
Recommended
Recommended Products Summary
Engineering reference data for PCA9539DW — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | PCA9539DWR | PCA9539PW | PCA9555D | PCA9555DWR | PCA9557D |
|---|---|---|---|---|---|---|
| Package | 24-SOIC (DW) | 24-SOIC (DW) - same | TSSOP - not same footprint | 24-SOIC (DW) - same | 24-SOIC (DW) - same | 24-SOIC (DW) - same |
| Brand | Texas Instruments | Texas Instruments | Texas Instruments | Texas Instruments | Texas Instruments | Texas Instruments |
Key Differentiators
- Dedicated RESET and different address arrangement (vs PCA9555D)
- Lower-power design when I/O lines are held low (vs PCA9555D)
- Verified 16-bit 400 kHz I/O expansion (vs PCA9557D)
Design Notes
Do not assume PCA9539DW has the same internal I/O pull-ups as PCA9555. The official TI comparison states that PCA9539 removes those pull-ups and replaces A2 with RESET. Confirm the intended pin functions and address range in the current datasheet, then add only the external resistors required by the attached circuitry and bus topology. This is especially important when adapting an existing PCA9555 board.
Route SDA and SCL as short, controlled-impedance communication traces away from noisy switching nodes and keep pull-up placement close to the bus devices. The verified data gives a 400 kHz bus limit but does not specify PCB trace length or pull-up values. Derive those values from bus capacitance, rise-time requirements, voltage level, and the host-controller characteristics rather than using an unsupported fixed resistor value.
Check the VCC range of 2.3 V to 5.5 V against the regulator output and every connected peripheral. If the expander controls LEDs, relays, or other inductive loads, use suitable driver stages and protection instead of relying on the I/O pins to absorb load transients. The verified listing mentions 10 mA and 25 mA source/sink options, but the exact applicable conditions must be confirmed in the manufacturer electrical tables.
Treat the interrupt line as a shared signal that requires correct polarity and rise/fall behavior in the receiving firmware. Debounce or qualify mechanical switch inputs in hardware or software, and account for the PCA9539 configuration registers before interpreting an interrupt. The device's interrupt feature can reduce polling, but incorrect configuration may cause missed events or repeated interrupts.
Compliance Information
The supplied verified data does not provide specific RoHS, REACH, AEC-Q100, lead-free, halogen-free, or conflict-minerals statements. AEC-Q100 is marked not applicable because the supplied information does not identify this part as an automotive-qualified device.
