# 74LCX257MTCX

**onsemi** · Signal Switches, Multiplexers, Decoders · TSSOP-16

74LCX257MTCX from onsemi, in a TSSOP-16. Pinout and pin descriptions extracted from the manufacturer datasheet (extract_pins, cross-checked by a second model); symbol, footprint, and 3D from KiCad-official CAD.

## Pinout

| Pin | Name | Type | Function |
|---|---|---|---|
| 1 | S | input | Common Data Select input: LOW selects the I0x inputs and HIGH selects the I1x inputs. |
| 2 | I0a | input | Data input from Source 0 for channel a, selected when S is LOW. |
| 3 | I1a | input | Data input from Source 1 for channel a, selected when S is HIGH. |
| 4 | Za | tri_state | 3-STATE multiplexer output for channel a, high impedance when OE is HIGH. |
| 5 | I0b | input | Data input from Source 0 for channel b, selected when S is LOW. |
| 6 | I1b | input | Data input from Source 1 for channel b, selected when S is HIGH. |
| 7 | Zb | tri_state | 3-STATE multiplexer output for channel b, high impedance when OE is HIGH. |
| 8 | GND | power_in | Ground pin. |
| 9 | Zd | tri_state | 3-STATE multiplexer output for channel d, high impedance when OE is HIGH. |
| 10 | I1d | input | Data input from Source 1 for channel d, selected when S is HIGH. |
| 11 | I0d | input | Data input from Source 0 for channel d, selected when S is LOW. |
| 12 | Zc | tri_state | 3-STATE multiplexer output for channel c, high impedance when OE is HIGH. |
| 13 | I1c | input | Data input from Source 1 for channel c, selected when S is HIGH. |
| 14 | I0c | input | Data input from Source 0 for channel c, selected when S is LOW. |
| 15 | OE | input | Active-low 3-STATE output enable input: a HIGH level forces the outputs to high impedance. |
| 16 | VCC | power_in | Supply voltage pin, operating range 2.0 V to 3.6 V. |

## Key specifications

| Parameter | Value |
|---|---|
| Manufacturer | onsemi |
| Package | TSSOP-16 |
| Category | Logic |
| Pins | 16 |

## CAD (KiCad official)

- Symbol: `74LCX257MTCX`
- Footprint: `Package_SO:TSSOP-16_4.4x5mm_P0.65mm`
- 3D model: TSSOP-16 (KiCad packages3D, STEP)
- 3D model files: `74lcx257mtcx-etched.step` / `74lcx257mtcx-etched.glb` carry the MPN laser-etched on the die in a toggleable `Adom.LaserEtch` group (Fusion-ready); `74lcx257mtcx.step` / `74lcx257mtcx.glb` are the bare package body.

## Provenance

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

- **Datasheet:** [onsemi datasheet](https://www.onsemi.com/pdf/datasheet/74lcx257mtcx-d.pdf) (11 pp, sha256 `f4ca62b37784aeca`, retrieved 2026-10-27, tier: manufacturer)
- **Extractor:** parts-factory `2.0.0` / `extract_pins 0.3`, primary `claude-sonnet-5-5` (vision), consensus `claude-opus-5-5` (agreed), guards: pin_guards 0.1: passed. Pins are checked against the footprint pad set and their cited datasheet pages before publish.
- **CAD:** KiCad official libraries (CC-BY-SA 4.0).

[Datasheet PDF](docs/74lcx257mtcx-datasheet.pdf)