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PCF8575 16-Bit I2C I/O Expander

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by Ray

16-bit quasi-bidirectional I/O expander over I2C with an interrupt output.

gpio-expanderi2cio-expander16-bitinterrupttissop-24
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PCF8575

Texas Instruments · I/O Expander · SSOP-24

The PCF8575 is a 16-bit quasi-bidirectional I/O expander controlled over I2C. Its two 8-bit ports act as inputs or open-drain outputs with weak pull-ups, and an interrupt output flags a change on any input. Three hardware address pins let up to eight devices share a bus. It is the 16-bit sibling of the 8-bit PCF8574.

Pinout

Pin Name Type Function
1 INT output Interrupt output (active-low, open-drain). Connect to VCC through a pull-up resistor. Asserts when any P-port input changes state.
2 A1 input I2C hardware address input 1. Connect directly to VCC or ground; pull-up resistors are not needed. Combined with A0/A2 to give up to eight unique bus addresses.
3 A2 input I2C hardware address input 2. Connect directly to VCC or ground; pull-up resistors are not needed.
4 P00 bidirectional P-port 0, bit 0. Quasi-bidirectional I/O with push-pull design structure; latched outputs with high-current drive for LEDs. IOL up to 25 mA, IOH transient pullup ~-10 mA.
5 P01 bidirectional P-port 0, bit 1. Quasi-bidirectional I/O with push-pull design structure.
6 P02 bidirectional P-port 0, bit 2. Quasi-bidirectional I/O with push-pull design structure.
7 P03 bidirectional P-port 0, bit 3. Quasi-bidirectional I/O with push-pull design structure.
8 P04 bidirectional P-port 0, bit 4. Quasi-bidirectional I/O with push-pull design structure.
9 P05 bidirectional P-port 0, bit 5. Quasi-bidirectional I/O with push-pull design structure.
10 P06 bidirectional P-port 0, bit 6. Quasi-bidirectional I/O with push-pull design structure.
11 P07 bidirectional P-port 0, bit 7. Quasi-bidirectional I/O with push-pull design structure.
12 GND power_in Ground reference for the device.
13 P10 bidirectional P-port 1, bit 0. Quasi-bidirectional I/O with push-pull design structure.
14 P11 bidirectional P-port 1, bit 1. Quasi-bidirectional I/O with push-pull design structure.
15 P12 bidirectional P-port 1, bit 2. Quasi-bidirectional I/O with push-pull design structure.
16 P13 bidirectional P-port 1, bit 3. Quasi-bidirectional I/O with push-pull design structure.
17 P14 bidirectional P-port 1, bit 4. Quasi-bidirectional I/O with push-pull design structure.
18 P15 bidirectional P-port 1, bit 5. Quasi-bidirectional I/O with push-pull design structure.
19 P16 bidirectional P-port 1, bit 6. Quasi-bidirectional I/O with push-pull design structure.
20 P17 bidirectional P-port 1, bit 7. Quasi-bidirectional I/O with push-pull design structure.
21 A0 input I2C hardware address input 0. Connect directly to VCC or ground; pull-up resistors are not needed.
22 SCL input I2C serial clock line. Connect to VCC through a pull-up resistor. Supports up to 400 kHz (Fast-mode I2C).
23 SDA bidirectional I2C serial data line (open-drain). Connect to VCC through a pull-up resistor.
24 VCC power_in Supply voltage input. Recommended operating range 2.5 V to 5.5 V (absolute max 6.5 V). Bypass with a decoupling capacitor to GND.

Key specifications

Parameter Value
Type 16-bit I2C I/O expander
I/O 16, quasi-bidirectional (2 ports)
Interface I2C (up to 400 kHz)
Interrupt Open-drain, on input change
Addressing 3 hardware address pins (up to 8)
Supply voltage 2.5 V to 5.5 V
Operating temperature -40 C to 85 C

Ordering variants

Same part, different packaging or reel option.

  • PCF8575DB
  • PCF8575DBR
  • PCF8575DBQ
  • PCF8575DBQR
  • PCF8575DGV
  • PCF8575DGVR
  • PCF8575DW
  • PCF8575DWR
  • PCF8575PW
  • PCF8575PWR
  • PCF8575RGE
  • PCF8575RGER
  • PCF8575RGET

CAD (KiCad official)

  • Symbol: pcf8575.kicad_sym
  • Footprint: pcf8575.kicad_mod
  • 3D model: SSOP-24 body from KiCad Package_SO/SSOP-24_3.9x8.7mm_P0.635mm.

Provenance

Data extracted from the manufacturer datasheet, not a distributor listing:

  • Datasheet: Texas Instruments datasheet (44 pp, sha256 c9a02501bf10ed80, retrieved 2026-08-17, tier: manufacturer)
  • Extractor: ds2sf (Claude). Every pin and dimension is cited to a datasheet page; it refuses to fabricate.
  • CAD: KiCad official libraries (CC-BY-SA 4.0).

Datasheet PDF