component

PCA9557

Public Made by Adom

by adom

TI 8-bit I2C I/O expander with reset, HVQFN-16. Eight I/O, hardware RESET, 8 addresses, 2.3-5.5 V. Datasheet-verified.

componentinterfaceio-expandergpio-expanderi2chvqfn-16texas-instruments
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Made with kicad-footprint-generator 10.0 · KiCad file format 20260206
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docs pca9557: re-etch, flat white mark read from pin 1 (service-occt 1.4.0) + chip hero · Ray
viewers pca9557: interactive cross-highlight viewers · Ray
package.json Publish 0.1.0 · Ray
page.json pca9557: component.models_3d pose record per STEP (Z-up, seated z=0, pad-centre origin, identity binding) · Ray
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pca9557-etched.glb pca9557: re-etch, flat white mark read from pin 1 (service-occt 1.4.0) + chip hero · Ray
pca9557-etched.step pca9557: re-etch, flat white mark read from pin 1 (service-occt 1.4.0) + chip hero · Ray
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README.md pca9557: laser-etched CAD + chip hero (factory 2.0.0 backfill) · Ray

PCA9557

Texas Instruments · I2C I/O expander · HVQFN-16

Adds eight general-purpose I/O pins over I2C, each set as input or output through a configuration register, with a hardware RESET input that returns the device to its power-on state on demand. A polarity-inversion register lets active-low inputs read as active-high without host logic, and three address pins put up to eight devices on one bus. It runs from 2.3 to 5.5 V. A compact, resettable I/O expander for switches, LEDs, and enable lines.

Pinout

Pin Name Type Function
1 A0 input Hardware I2C address input bit 0. Tie directly to VCC or GND to program the device's I2C slave address (up to 8 devices per bus).
2 A1 input Hardware I2C address input bit 1. Tie directly to VCC or GND.
3 A2 input Hardware I2C address input bit 2. Tie directly to VCC or GND.
4 IO0 bidirectional P-port I/O bit 0. High-impedance open-drain output structure; requires an external pullup to VCC when driven high. Configured as input at power-on.
5 IO1 bidirectional P-port I/O bit 1. Push-pull output; sinks up to 25 mA to drive LEDs directly. Input at power-on.
6 VSS power_in Ground reference for supply and I/O.
7 IO2 bidirectional P-port I/O bit 2. Push-pull output; 25 mA sink capability. Input at power-on.
8 IO3 bidirectional P-port I/O bit 3. Push-pull output; 25 mA sink capability. Input at power-on.
9 IO4 bidirectional P-port I/O bit 4. Push-pull output; 25 mA sink capability. Input at power-on.
10 IO5 bidirectional P-port I/O bit 5. Push-pull output; 25 mA sink capability. Input at power-on.
11 IO6 bidirectional P-port I/O bit 6. Push-pull output; 25 mA sink capability. Input at power-on.
12 IO7 bidirectional P-port I/O bit 7. Push-pull output; 25 mA sink capability. Input at power-on.
13 RESET input Active-low reset input. Asserting low reinitializes the registers and I2C/SMBus state machine. Tie to VCC through a pullup if unused.
14 VDD power_in Supply voltage, 2.3 V to 5.5 V. Decouple with a 0.1 µF ceramic capacitor to GND close to the pin.
15 SCL input I2C serial clock input. Requires an external pullup resistor to VCC. Supports 100 kHz standard mode and 400 kHz fast mode.
16 SDA bidirectional I2C serial data line, open-drain bidirectional. Requires an external pullup resistor to VCC.

Key specifications

Parameter Value
Type 8-bit I2C I/O expander
Interface I2C (up to 400 kHz)
I/O 8 pins (IO0-IO7)
Reset Hardware RESET input
Polarity Per-pin inversion register
Addresses 8 (A0-A2)
Supply 2.3-5.5 V
Package HVQFN-16

Ordering variants

Same part, different packaging or reel option.

  • PCA9557PW (TSSOP-16)
  • PCA9557BS (HVQFN-16)
  • PCA9557D (SOIC-16)

CAD (KiCad official)

  • Symbol: Interface_Expansion:PCA9557BS (KiCad official)
  • Footprint: Package_DFN_QFN:HVQFN-16-1EP_3x3mm_P0.5mm_EP1.5x1.5mm
  • 3D model: HVQFN-16 (KiCad packages3D, STEP)
  • 3D model files: pca9557-etched.step / pca9557-etched.glb carry the MPN laser-etched on the die in a toggleable Adom.LaserEtch group (Fusion-ready); pca9557.step / pca9557.glb are the bare package body.

Provenance

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

  • Datasheet: Texas Instruments datasheet (47 pp, sha256 d55cbe207fbcb26d, 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