# CD74AC257M

**Texas Instruments** · Signal Switches, Multiplexers, Decoders · SOIC-16

CD74AC257M from Texas Instruments, in a SOIC-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 | Select input; routes channel I0 to output when low, channel I1 to output when high. |
| 2 | 1I0 | input | Channel 1 input 0; data input selected to 1Y output when select pin is low. |
| 3 | 1I1 | input | Channel 1 input 1; data input selected to 1Y output when select pin is high. |
| 4 | 1Y | tri_state | Channel 1 output; tri-state multiplexed output driven by selected input and controlled by output enable. |
| 5 | 2I0 | input | Channel 2 input 0; data input selected to 2Y output when select pin is low. |
| 6 | 2I1 | input | Channel 2 input 1; data input selected to 2Y output when select pin is high. |
| 7 | 2Y | tri_state | Channel 2 output; tri-state multiplexed output driven by selected input and controlled by output enable. |
| 8 | GND | power_in | Ground; reference voltage for all signal and power pins. |
| 9 | 3Y | tri_state | Channel 3 output; tri-state multiplexed output driven by selected input and controlled by output enable. |
| 10 | 3I1 | input | Channel 3 input 1; data input selected to 3Y output when select pin is high. |
| 11 | 3I0 | input | Channel 3 input 0; data input selected to 3Y output when select pin is low. |
| 12 | 4Y | tri_state | Channel 4 output; tri-state multiplexed output driven by selected input and controlled by output enable. |
| 13 | 4I1 | input | Channel 4 input 1; data input selected to 4Y output when select pin is high. |
| 14 | 4I0 | input | Channel 4 input 0; data input selected to 4Y output when select pin is low. |
| 15 | OE | input | Output enable, active low; when high forces all outputs to high impedance state regardless of inputs. |
| 16 | VCC | power_in | Positive power supply; 1.5V to 5.5V operating range for AC type, temperature range -55°C to 125°C. |

## Key specifications

| Parameter | Value |
|---|---|
| Manufacturer | Texas Instruments |
| Package | SOIC-16 |
| Category | Logic |
| Pins | 16 |

## CAD (KiCad official)

- Symbol: `CD74AC257M`
- Footprint: `Package_SO:SOIC-16_3.9x9.9mm_P1.27mm`
- 3D model: SOIC-16 (KiCad packages3D, STEP)
- 3D model files: `cd74ac257m-etched.step` / `cd74ac257m-etched.glb` carry the MPN laser-etched on the die in a toggleable `Adom.LaserEtch` group (Fusion-ready); `cd74ac257m.step` / `cd74ac257m.glb` are the bare package body.

## Provenance

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

- **Datasheet:** [Texas Instruments datasheet](https://www.ti.com/cn/lit/gpn/cd74ac257) (29 pp, sha256 `f4d61e0b521229dd`, retrieved 2026-09-27, tier: lcsc)
- **Datasheet language:** Chinese. Pin names, descriptions, and specs on this page were extracted and translated to English by ds2sf; the linked PDF is the manufacturer original.
- **Extractor:** parts-factory `2.0.0` / `extract_pins 0.2`, primary `claude-haiku-4-5-20251001` (text), consensus `claude-sonnet-4-6` (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/cd74ac257m-datasheet.pdf)