# SN74LS257BN

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

SN74LS257BN from Texas Instruments, in a PDIP-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 | A/B | input | Select input that chooses the A data inputs when low or the B data inputs when high for all four multiplexers. |
| 2 | 1A | input | Data input A of multiplexer 1, passed to 1Y when A/B is low. |
| 3 | 1B | input | Data input B of multiplexer 1, passed to 1Y when A/B is high. |
| 4 | 1Y | tri_state | 3-state output of multiplexer 1, high impedance when G is high. |
| 5 | 2A | input | Data input A of multiplexer 2, passed to 2Y when A/B is low. |
| 6 | 2B | input | Data input B of multiplexer 2, passed to 2Y when A/B is high. |
| 7 | 2Y | tri_state | 3-state output of multiplexer 2, high impedance when G is high. |
| 8 | GND | power_in | Ground. |
| 9 | 3Y | tri_state | 3-state output of multiplexer 3, high impedance when G is high. |
| 10 | 3B | input | Data input B of multiplexer 3, passed to 3Y when A/B is high. |
| 11 | 3A | input | Data input A of multiplexer 3, passed to 3Y when A/B is low. |
| 12 | 4Y | tri_state | 3-state output of multiplexer 4, high impedance when G is high. |
| 13 | 4B | input | Data input B of multiplexer 4, passed to 4Y when A/B is high. |
| 14 | 4A | input | Data input A of multiplexer 4, passed to 4Y when A/B is low. |
| 15 | G | input | Active-low output control; a high level puts all four outputs in the high-impedance state. |
| 16 | VCC | power_in | Positive supply voltage. |

## Key specifications

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

## CAD (KiCad official)

- Symbol: `SN74LS257BN`
- Footprint: `Package_DIP:DIP-16_W7.62mm`
- 3D model: PDIP-16 (KiCad packages3D, STEP)
- 3D model files: `sn74ls257bn-etched.step` / `sn74ls257bn-etched.glb` carry the MPN laser-etched on the die in a toggleable `Adom.LaserEtch` group (Fusion-ready); `sn74ls257bn.step` / `sn74ls257bn.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/sn74ls257b) (24 pp, sha256 `e97f63b00f996504`, retrieved 2026-10-16, tier: lcsc)
- **Extractor:** parts-factory `2.0.0` / `extract_pins 0.3`, primary `claude-sonnet-5-5` (text+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/sn74ls257bn-datasheet.pdf)