# CD40257BM

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

CD40257BM 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 | INPUT SELECT | input | Select input: low passes the A inputs to the outputs, high passes the B inputs. |
| 2 | A1 | input | Channel 1 data input A, routed to D1 when select is low. |
| 3 | B1 | input | Channel 1 data input B, routed to D1 when select is high. |
| 4 | D1 | tri_state | Channel 1 three-state output, high impedance when output disable is high. |
| 5 | A2 | input | Channel 2 data input A, routed to D2 when select is low. |
| 6 | B2 | input | Channel 2 data input B, routed to D2 when select is high. |
| 7 | D2 | tri_state | Channel 2 three-state output, high impedance when output disable is high. |
| 8 | VSS | power_in | Ground (negative supply) reference terminal for all voltages. |
| 9 | D3 | tri_state | Channel 3 three-state output, high impedance when output disable is high. |
| 10 | B3 | input | Channel 3 data input B, routed to D3 when select is high. |
| 11 | A3 | input | Channel 3 data input A, routed to D3 when select is low. |
| 12 | D4 | tri_state | Channel 4 three-state output, high impedance when output disable is high. |
| 13 | B4 | input | Channel 4 data input B, routed to D4 when select is high. |
| 14 | A4 | input | Channel 4 data input A, routed to D4 when select is low. |
| 15 | OUTPUT DISABLE | input | 3-state output disable: high puts all outputs in high impedance, low enables them. |
| 16 | VDD | power_in | Positive supply, recommended 3 V to 18 V, absolute maximum -0.5 V to +20 V. |

## Key specifications

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

## CAD (KiCad official)

- Symbol: `CD40257BM`
- Footprint: `Package_SO:SOIC-16_3.9x9.9mm_P1.27mm`
- 3D model: SOIC-16 (KiCad packages3D, STEP)
- 3D model files: `cd40257bm-etched.step` / `cd40257bm-etched.glb` carry the MPN laser-etched on the die in a toggleable `Adom.LaserEtch` group (Fusion-ready); `cd40257bm.step` / `cd40257bm.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/cd40257b) (10 pp, sha256 `d9965b2fa9121640`, retrieved 2026-10-05, 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/cd40257bm-datasheet.pdf)