74HC257D

@@ -0,0 +1,58 @@+# 74HC257D++**Nexperia** · Signal Switches / Encoders & Decoders / Multiplexers · SOIC-16++74HC257D from Nexperia, in a SOIC-16. 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 | S | input | Common data select input. Selects between the nI0 inputs (S=LOW) and nI1 inputs (S=HIGH) routed to the nY outputs. |+| 2 | 1I0 | input | Data input from source 0 for multiplexer channel 1. Routed to 1Y when S=LOW and OE=LOW. |+| 3 | 1I1 | input | Data input from source 1 for multiplexer channel 1. Routed to 1Y when S=HIGH and OE=LOW. |+| 4 | 1Y | tri_state | 3-state multiplexer output for channel 1. High-impedance when OE=HIGH. |+| 5 | 2I0 | input | Data input from source 0 for multiplexer channel 2. Routed to 2Y when S=LOW and OE=LOW. |+| 6 | 2I1 | input | Data input from source 1 for multiplexer channel 2. Routed to 2Y when S=HIGH and OE=LOW. |+| 7 | 2Y | tri_state | 3-state multiplexer output for channel 2. High-impedance when OE=HIGH. |+| 8 | GND | power_in | Ground (0 V) reference. |+| 9 | 3Y | tri_state | 3-state multiplexer output for channel 3. High-impedance when OE=HIGH. |+| 10 | 3I1 | input | Data input from source 1 for multiplexer channel 3. Routed to 3Y when S=HIGH and OE=LOW. |+| 11 | 3I0 | input | Data input from source 0 for multiplexer channel 3. Routed to 3Y when S=LOW and OE=LOW. |+| 12 | 4Y | tri_state | 3-state multiplexer output for channel 4. High-impedance when OE=HIGH. |+| 13 | 4I1 | input | Data input from source 1 for multiplexer channel 4. Routed to 4Y when S=HIGH and OE=LOW. |+| 14 | 4I0 | input | Data input from source 0 for multiplexer channel 4. Routed to 4Y when S=LOW and OE=LOW. |+| 15 | OE | input | 3-state output enable input, active LOW. When OE=HIGH, all nY outputs are in the high-impedance OFF-state. |+| 16 | VCC | power_in | Supply voltage. 2.0 V to 6.0 V for 74HC257; 4.5 V to 5.5 V for 74HCT257. |++## Key specifications++| Parameter | Value |+|---|---|+| Manufacturer | Nexperia |+| Package | SOIC-16 |+| Category | Logic |+| Pins | 16 |++## Ordering variants++Same part, different packaging or reel option.++- `74HC257DD`+- `74HC257DPW`++## CAD (KiCad official)++- Symbol: `74HC257D`+- Footprint: `Package_SO:SOIC-16_3.9x9.9mm_P1.27mm`+- 3D model: SOIC-16 (KiCad packages3D, STEP)++## Provenance++Data extracted from the manufacturer datasheet, not a distributor listing:++- **Datasheet:** [Nexperia datasheet](https://assets.nexperia.com/documents/data-sheet/74HC257D.pdf) (15 pp, sha256 `9a5ab16a50053e88`, 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](docs/74hc257d-datasheet.pdf)

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