# CD74HCT640M

**Texas Instruments** · Buffer/Driver/Transceiver · SOIC-20-300mil

CD74HCT640M from Texas Instruments, in a SOIC-20-300mil. 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 | DIR | input | Direction control input: selects A-to-B or B-to-A data flow; HCT input levels VIL 0.8V max, VIH 2V min. |
| 2 | A0 | bidirectional | A-bus I/O 0 (three-state); output is inverted version of B0 input when enabled. |
| 3 | A1 | bidirectional | A-bus I/O 1 (three-state); output is inverted version of B1 input when enabled. |
| 4 | A2 | bidirectional | A-bus I/O 2 (three-state); output is inverted version of B2 input when enabled. |
| 5 | A3 | bidirectional | A-bus I/O 3 (three-state); output is inverted version of B3 input when enabled. |
| 6 | A4 | bidirectional | A-bus I/O 4 (three-state); output is inverted version of B4 input when enabled. |
| 7 | A5 | bidirectional | A-bus I/O 5 (three-state); output is inverted version of B5 input when enabled. |
| 8 | A6 | bidirectional | A-bus I/O 6 (three-state); output is inverted version of B6 input when enabled. |
| 9 | A7 | bidirectional | A-bus I/O 7 (three-state); output is inverted version of B7 input when enabled. |
| 10 | GND | power_in | Ground reference (0V). |
| 11 | B7 | bidirectional | B-bus I/O 7 (three-state); output is inverted version of A7 input when enabled. |
| 12 | B6 | bidirectional | B-bus I/O 6 (three-state); output is inverted version of A6 input when enabled. |
| 13 | B5 | bidirectional | B-bus I/O 5 (three-state); output is inverted version of A5 input when enabled. |
| 14 | B4 | bidirectional | B-bus I/O 4 (three-state); output is inverted version of A4 input when enabled. |
| 15 | B3 | bidirectional | B-bus I/O 3 (three-state); output is inverted version of A3 input when enabled. |
| 16 | B2 | bidirectional | B-bus I/O 2 (three-state); output is inverted version of A2 input when enabled. |
| 17 | B1 | bidirectional | B-bus I/O 1 (three-state); output is inverted version of A1 input when enabled. |
| 18 | B0 | bidirectional | B-bus I/O 0 (three-state); output is inverted version of A0 input when enabled. |
| 19 | OE | input | Active-low output enable: low enables outputs, high puts A and B ports in high impedance. |
| 20 | VCC | power_in | Supply voltage; 4.5V to 5.5V for HCT types, with 0.1 µF bypass capacitor recommended. |

## Key specifications

| Parameter | Value |
|---|---|
| Manufacturer | Texas Instruments |
| Package | SOIC-20-300mil |
| Category | Logic ICs |
| Pins | 20 |

## CAD (KiCad official)

- Symbol: `CD74HCT640M`
- Footprint: `Package_SO:SOIC-20W_7.5x12.8mm_P1.27mm`
- 3D model: SOIC-20-300mil (KiCad packages3D, STEP)
- 3D model files: `cd74hct640m-etched.step` / `cd74hct640m-etched.glb` carry the MPN laser-etched on the die in a toggleable `Adom.LaserEtch` group (Fusion-ready); `cd74hct640m.step` / `cd74hct640m.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/cd74hct640) (19 pp, sha256 `21ee67f9e5d6228b`, retrieved 2026-10-08, 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 0.3`, 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/cd74hct640m-datasheet.pdf)