CAT24C128WI-GT3 from onsemi, in a SOIC-8. Pinout and pin descriptions extracted from the manufacturer datasheet by ds2sf; symbol, footprint, and 3D from KiCad-official CAD.

Pinout

Pin	Name	Type	Function
1	A0	input	Device address input bit 0. Combined with A1 and A2 to select one of up to 8 devices on the same I2C bus; must match the corresponding bit in the slave address byte. Internally pulled LOW when left undriven.
2	A1	input	Device address input bit 1. Combined with A0 and A2 to select one of up to 8 devices on the same I2C bus. Internally pulled LOW when left undriven.
3	A2	input	Device address input bit 2. Combined with A0 and A1 to select one of up to 8 devices on the same I2C bus. Internally pulled LOW when left undriven.
4	VSS	power_in	Ground reference for the device. Connect directly to the system ground plane.
5	SDA	bidirectional	I2C serial data input/output. Open-drain output; requires an external pull-up resistor to VCC. Data is latched on the rising edge of SCL and driven on the falling edge.
6	SCL	input	I2C serial clock input driven by the bus master. Supports Standard (100 kHz), Fast (400 kHz) and Fast-Plus (1 MHz, Rev C) modes.
7	WP	input	Write Protect input. When held HIGH, all write operations to the EEPROM array are inhibited; tie LOW (or leave undriven - pin is internally pulled LOW) to allow writes. Strong internal pull-down; external driver must source the pull-down current when driving HIGH.
8	VCC	power_in	Positive supply input, 1.8 V to 5.5 V. Bypass locally with a 0.1 uF capacitor to VSS. Typical operating currents: 1 mA read, 3 mA write; standby current ~1-5 uA.

Key specifications

Parameter	Value
Manufacturer	onsemi
Package	SOIC-8
Category	Memory
Pins	8

Ordering variants

Same part, different packaging or reel option.

CAT24C128WI-GT3W
CAT24C128WI-GT3
CAT24C128WI-GT3L
CAT24C128WI-GT3Y
CAT24C128WI-GT3Z
CAT24C128WI-GT3HU4
CAT24C128WI-GT3HU3

CAD (KiCad official)

Symbol: CAT24C128WI-GT3
Footprint: Package_SO:SOIC-8_3.9x4.9mm_P1.27mm
3D model: SOIC-8 (KiCad packages3D, STEP)

3D model downloads

Two STEP files. Same geometry, different body top:

File	Size	Use it when
`cat24c128wi-gt3.step`	122 KB	You want the bare part, or you mark your own boards.
`cat24c128wi-gt3-etched.step`	2.7 MB	You want the part with `CAT24C128WI-GT3` already on it.

The marking in the etched file is real recessed geometry cut into the solid, not a texture or a decal: 664 faces against 147 in the bare model. It survives export, section views, and rendering in any CAD tool, and it drops straight into KiCad or Fusion with no extra setup.

Provenance

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

Datasheet: onsemi datasheet (16 pp, sha256 287d5c87d3fe9a4a, 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