PCF8575DWR - 16-Bit I2C I/O Expander | Texas Instruments
MPN: PCF8575DWR ✓ ActivePCF8575DWR Overview
An I/O expander is an interface IC that converts serial commands from a microcontroller into parallel input or output signals. In the product hierarchy, the PCF8575 belongs to the I2C GPIO expander class, within interface ICs and broader digital semiconductor systems. It is useful when a controller needs more GPIO pins than are available directly, avoiding a redesign or the addition of a larger microcontroller package.
Key features include 16 independently latched I/O ports, a 2.5 V to 5.5 V supply range, 400 kHz fast I2C operation, and low standby-current consumption of 10 uA maximum. Three hardware address pins provide eight selectable bus addresses. The outputs can latch data for direct LED drive and include a current source to VCC for actively driving a high. An open-drain interrupt output allows a controller to react to selected input changes without continuously polling the device.
The PCF8575 implements a simple register-based interface in which the 16 ports are used for data transfer, configuration, and output control. Its quasi-bidirectional I/O structure suits many microcontroller systems, although each pin is intended primarily for ordinary digital loads rather than unrestricted capacitive or high-current loads. Power and signal behavior remain compatible with the 2.5 V to 5.5 V operating range stated by Texas Instruments.
Typical applications include industrial control modules, keypad and switch interfaces, LED status panels, relay or solenoid driver boards, building-automation equipment, and small embedded control systems. The device is particularly useful when a host controller needs 16 additional lines while retaining a compact 24-pin SOIC footprint and a two-wire connection to the main PCB.
Designers should account for the quasi-bidirectional output architecture, use appropriate pull-up arrangements for open-drain interrupt signaling, and confirm that connected loads remain within the device's output-drive limits. I2C pull-up resistance and bus capacitance should be selected for the full system, including cable length, bus speed, and the number of devices.
This page combines manufacturer specifications, distributor availability, package details, practical application guidance, and same-footprint replacement analysis to support faster component selection and PCB-level decision-making.
Drop-in alternatives for PCF8575DWR — 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 PCF8575DWR (same form factor and footprint) — differing in Interrupt Output.
PCA9555DWR
✅ Drop-InContact for price
View Datasheet →PCA9539DWR
✅ Drop-In📋 Reference alternative (not in catalog)
PCA8575D
✅ Drop-In📋 Reference alternative (not in catalog)
PCA8575D@118
✅ Drop-In📋 Reference alternative (not in catalog)
PCA9535DWR
✅ Drop-In ⚠️ Specs Unverified📋 Reference alternative (not in catalog)
PCF8575DWR Specifications
| Number of I/O Lines | 16 lines |
| Interface Type | I2C and SMBus |
| Operating Supply Voltage | 2.5 V to 5.5 V |
| Maximum I2C Bus Frequency | 400 kHz |
| Maximum Standby Current | 10 uA |
| Interrupt Output | Open drain |
| Hardware Address Inputs | 3 address pins |
| Maximum Devices per Bus | 8 devices |
| Operating Temperature | -40 C to +85 C |
| Package | 24-pin SOIC (DW) |
| Pin Count | 24 pins |
| Mounting Type | Surface mount |
| Output Port Configuration | Latched quasi-bidirectional |
| Active-High Output Mechanism | Current source to VCC |
| LED Direct Drive | Supported |
| RoHS Status | Compliant |
PCF8575DWR 24-pin soic (dw) Pin Configuration Guide
Pin configuration for PCF8575DWR (24-pin soic (dw) package). Pin numbering, functions, and connection diagrams are defined in the manufacturer datasheet. Refer to it for the exact footprint and soldering guidelines.
No detailed pinout data available for PCF8575DWR.
Refer to the datasheet for full pin configuration.
Typical Applications
PCF8575DWR is suitable for 6 applications: Industrial Control and Automation Modules, LED Status and Indicator Panels, Keypad and Human-Interface Input Expansion, Building Automation and Environmental Control, Communication and Network Interface Modules, Portable and Battery-Powered Embedded Systems.
Industrial Control and Automation Modules
The PCF8575DWR fits compact industrial controllers that need more digital lines than the host microcontroller provides. Its 16 latched quasi-bidirectional ports can monitor discrete inputs or operate relays, contactors, and status LEDs, while the 2.5 V to 5.5 V supply range supports common 3.3 V and 5 V control rails. The 400 kHz I2C interface allows the expander to share the bus with sensors and communication devices. Its -40 C to +85 C operating range covers many industrial ambient environments. Designers should use the open-drain interrupt output for change notification and verify each external load against the datasheet output-current limits before finalizing the control board.
Recommended
LED Status and Indicator Panels
The PCF8575DWR is useful when a controller must operate more LED indicators than its direct GPIO pins can support. Texas Instruments specifies latched outputs with high-current drive capability for directly driving LEDs, allowing one expander to control a bank of status indicators over I2C. The 16 available output lines reduce wiring and PCB area compared with a direct host-controller connection, while the 400 kHz bus rate supports rapid panel updates. Each LED still requires a suitable current-limiting resistor, and the total load on every port must remain within the manufacturer’s limits. A 3.3 V system can use the device within its stated 2.5 V to 5.5 V operating range.
Recommended
Keypad and Human-Interface Input Expansion
The PCF8575DWR can extend a microcontroller-based control panel with additional switch, keypad, and interlock inputs. Sixteen latched ports provide enough parallel lines for matrix-style keypad scanning or multiple discrete switch inputs, while the I2C transfer reduces the number of host-controller pins required. The three hardware address pins allow as many as eight expanders to share one bus according to the Texas Instruments product page. The open-drain interrupt output can notify the controller of selected input changes instead of requiring continuous polling. Firmware must debounce mechanical contacts and account for the quasi-bidirectional input/output characteristics of the ports.
Recommended
Building Automation and Environmental Control
The PCF8575DWR can add local digital control points to building-automation controllers, including occupancy inputs, alarm outputs, status indicators, and simple alarm relays. Its 2.5 V to 5.5 V range supports low-voltage controllers, while 16 ports provide enough parallel channels for a distributed room or equipment module. The 400 kHz I2C link allows the controller to poll or update the expander efficiently, and the open-drain interrupt supports event-driven handling of relevant input changes. Because building equipment can impose inductive loads, engineers must add suitable protection and drive circuitry and should not treat the quasi-bidirectional outputs as unrestricted relay drivers.
Recommended
Communication and Network Interface Modules
The PCF8575DWR is appropriate for small communication modules that require configuration inputs, link-state indicators, or control outputs beyond the available host pins. Its two-wire interface is especially useful in space-constrained equipment where parallel control wiring would increase connector count and PCB complexity. The device can operate at 400 kHz, while its three address pins allow several peripheral nodes on a shared bus. In a network-facing module, the interrupt line can signal a local status change without continuous register polling, reducing host-controller workload. The I2C bus must remain electrically isolated from noisy power converters, and pull-up values must be selected from total capacitance and operating voltage rather than copied without calculation.
Recommended
Portable and Battery-Powered Embedded Systems
The PCF8575DWR can expand a portable device’s limited GPIO resources without adding a larger controller package. Its maximum standby-current consumption of 10 uA is useful in battery-operated equipment, and its 16 latched ports can control indicators, user-interface inputs, and low-power accessories. The device supports 2.5 V to 5.5 V operation, allowing use with common low-energy rails. When power consumption is critical, the host firmware should avoid unnecessary polling, use the interrupt input where practical, and disable external loads during sleep periods. The selected I2C pull-up network must also be checked for its effect on standby current because resistor values trade bus rise time against continuous leakage.
Recommended
Recommended Products Summary
Engineering reference data for PCF8575DWR — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | PCA9555DWR | PCA9539DWR | PCA8575D | PCA8575D@118 | PCA9535DWR |
|---|---|---|---|---|---|---|
| Package | 24-pin SOIC (DW) | 24-pin SOIC (DW) | 24-pin SOIC (DW) | 24-pin SOIC | 24-pin SOIC tape and reel | 24-pin SOIC (DW) |
| Brand | Texas Instruments | Texas Instruments | Texas Instruments | NXP Semiconductors | NXP Semiconductors | Texas Instruments |
| I/O Count | 16 lines | 16 lines | 16 lines | 16 lines | 16 lines | 16 lines |
| Interface | I2C and SMBus | I2C and SMBus | I2C and SMBus | I2C/SMBus | I2C/SMBus | I2C |
Key Differentiators
- Provides a verified open-drain interrupt alongside 16 latched ports (vs PCA9539DWR)
- Supports eight device addresses through three hardware pins (vs PCA8575D)
- Lower minimum supply requirement than PCA9539DWR (vs PCA9539DWR)
- Combines 400 kHz operation with low standby consumption (vs PCA8575D)
Design Notes
Decouple the PCF8575DWR VCC pin with local high-frequency and bulk capacitance, and route the return path directly to the device ground. The verified data does not specify recommended capacitor values or output-current limits, so those values must be taken from the manufacturer datasheet rather than estimated. Because the I2C pull-up network can also draw continuous current, calculate its effect on standby power using the actual pull-up voltage and resistance before selecting low-power system values.
Place the device close to the I2C host and keep the SCL and SDA routes short, continuous, and away from switching nodes or high-current return paths. Series damping resistors may be evaluated for edge-rate control after checking the bus capacitance and the host-controller timing. The three address pins must be tied to defined logic levels before the part starts; floating address inputs could cause an unintended bus address and unreliable peripheral selection.
Do not assume that every 16-bit I2C expander is register-compatible with the PCF8575DWR. PCA9555, PCA9539, PCA8575, and PCA9535 devices can have different input thresholds, output behavior, address schemes, and interrupt polarity. Validate the complete startup sequence, power-on port state, input polarity, and output-drive conditions in the target system. For the open-drain interrupt path, use an appropriate pull-up and account for every device that can pull the shared line low.
The PCF8575 ports are quasi-bidirectional and are intended for ordinary digital loads, not for unrestricted capacitive, inductive, or high-current operation. When driving relays, solenoids, lamps, or long cables, use suitable transistors, flyback protection, and interface logic. Verify the maximum drive current for both a single port and the combined ports, since thermal and absolute-maximum ratings are distinct from the recommended operating limits.
Compliance Information
The verified DigChip specifications explicitly identify the device as RoHS compliant and describe a green plastic package. The supplied data does not establish REACH, AEC-Q100, lead-free, halogen-free, or conflict-minerals status.
