SN74HC540 Octal Inverting Buffer

@@ -0,0 +1,68 @@+# SN74HC540++**Texas Instruments** · Buffer / Line Driver · SOIC-20++The SN74HC540 is an octal inverting buffer and line driver with 3-state outputs. Its inputs and outputs sit on opposite sides for a flow-through layout, and two active-low output-enables gate all eight buffers. Each output is the inverse of its input, useful for driving buses while inverting.++## Pinout++| Pin | Name | Type | Function |+|---|---|---|---|+| 1 | OE1 | input | Active-low output-enable 1. NORed with OE2; when either OE input is high, all Y outputs are in high-impedance state. |+| 2 | A1 | input | Data input for channel 1. CMOS logic input; drives inverted output Y1 when device is enabled. |+| 3 | A2 | input | Data input for channel 2. Drives inverted output Y2 when device is enabled. |+| 4 | A3 | input | Data input for channel 3. Drives inverted output Y3 when device is enabled. |+| 5 | A4 | input | Data input for channel 4. Drives inverted output Y4 when device is enabled. |+| 6 | A5 | input | Data input for channel 5. Drives inverted output Y5 when device is enabled. |+| 7 | A6 | input | Data input for channel 6. Drives inverted output Y6 when device is enabled. |+| 8 | A7 | input | Data input for channel 7. Drives inverted output Y7 when device is enabled. |+| 9 | A8 | input | Data input for channel 8. Drives inverted output Y8 when device is enabled. |+| 10 | GND | power_in | Ground reference (0 V). Return for VCC supply current and CMOS input/output logic levels. |+| 11 | Y8 | tri_state | 3-state inverted output for channel 8. High-current CMOS driver, ±6 mA at 5 V; drives up to 15 LSTTL loads. High-Z when either OE1 or OE2 is high. |+| 12 | Y7 | tri_state | 3-state inverted output for channel 7. High-current CMOS driver, ±6 mA at 5 V. High-Z when either OE1 or OE2 is high. |+| 13 | Y6 | tri_state | 3-state inverted output for channel 6. High-current CMOS driver, ±6 mA at 5 V. High-Z when either OE1 or OE2 is high. |+| 14 | Y5 | tri_state | 3-state inverted output for channel 5. High-current CMOS driver, ±6 mA at 5 V. High-Z when either OE1 or OE2 is high. |+| 15 | Y4 | tri_state | 3-state inverted output for channel 4. High-current CMOS driver, ±6 mA at 5 V. High-Z when either OE1 or OE2 is high. |+| 16 | Y3 | tri_state | 3-state inverted output for channel 3. High-current CMOS driver, ±6 mA at 5 V. High-Z when either OE1 or OE2 is high. |+| 17 | Y2 | tri_state | 3-state inverted output for channel 2. High-current CMOS driver, ±6 mA at 5 V. High-Z when either OE1 or OE2 is high. |+| 18 | Y1 | tri_state | 3-state inverted output for channel 1. High-current CMOS driver, ±6 mA at 5 V. High-Z when either OE1 or OE2 is high. |+| 19 | OE2 | input | Active-low output-enable 2. NORed with OE1; when either OE input is high, all Y outputs are in high-impedance state. |+| 20 | VCC | power_in | Positive supply, 2 V to 6 V recommended (absolute max 7 V). Bypass with 0.1 µF (optionally paralleled with 1 µF) placed close to the pin. |++## Key specifications++| Parameter | Value |+|---|---|+| Type | Octal inverting buffer / line driver, 3-state |+| Logic family | 74HC (CMOS) |+| Configuration | 8 inverting buffers, flow-through pinout |+| Supply voltage | 2 V to 6 V |+| Output current | +-6 mA at VCC = 4.5 V |+| Propagation delay | 14 ns typ at 5 V |+| Operating temperature | -40 C to 85 C |++## Ordering variants++- `SN74HC540DW`+- `SN74HC540N`+- `SN74HC540NS`+- `SN74HC540NSR`+- `SN74HC540PW`+- `SN74HC540J`+- `SN74HC540FK`++## CAD (KiCad official)++- Symbol: `sn74hc540.kicad_sym`+- Footprint: `sn74hc540.kicad_mod`+- 3D model: SOIC-20 wide body from KiCad `Package_SO/SOIC-20W_7.5x12.8mm_P1.27mm`.++## Provenance++Data extracted from the manufacturer datasheet, not a distributor listing:++- **Datasheet:** [Texas Instruments datasheet](https://www.ti.com/lit/ds/symlink/sn74hc540.pdf) (25 pp, sha256 `d54581bf2a2bec36`, 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/sn74hc540-datasheet.pdf)

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