SN74HC157

@@ -0,0 +1,60 @@+# SN74HC157++**Texas Instruments** · Quad 2-to-1 multiplexer · SOIC-16++Four 2-to-1 digital multiplexers sharing one select line, in high-speed CMOS, SOIC-16. A single A/B select routes either the four A inputs or the four B inputs to the four Y outputs, and an active-low enable forces the outputs low. That makes it the easy way to switch a 4-bit bus between two sources: two data words into one, an address between two counters, or a display between two values. Cascade or stack them for wider buses. Runs 2-6 V.++## Pinout++| Pin | Name | Type | Function |+|---|---|---|---|+| 1 | A/B | input | Address select input (A/B, active-low means low selects A, high selects B). Standard CMOS input; when G is low, Y follows selected A or B input for all four channels. |+| 2 | 1A | input | Channel 1 data input A. Routed to 1Y when A/B is low and G is low. |+| 3 | 1B | input | Channel 1 data input B. Routed to 1Y when A/B is high and G is low. |+| 4 | 1Y | output | Channel 1 data output. Drives the selected A or B input; forced low when G is high. ±6mA drive at 5V. |+| 5 | 2A | input | Channel 2 data input A. Routed to 2Y when A/B is low and G is low. |+| 6 | 2B | input | Channel 2 data input B. Routed to 2Y when A/B is high and G is low. |+| 7 | 2Y | output | Channel 2 data output. Drives the selected A or B input; forced low when G is high. |+| 8 | GND | power_in | Ground reference, 0V. Continuous current through VCC or GND is limited to ±70mA (absolute max). |+| 9 | 3Y | output | Channel 3 data output. Drives the selected A or B input; forced low when G is high. |+| 10 | 3B | input | Channel 3 data input B. Routed to 3Y when A/B is high and G is low. |+| 11 | 3A | input | Channel 3 data input A. Routed to 3Y when A/B is low and G is low. |+| 12 | 4Y | output | Channel 4 data output. Drives the selected A or B input; forced low when G is high. |+| 13 | 4B | input | Channel 4 data input B. Routed to 4Y when A/B is high and G is low. |+| 14 | 4A | input | Channel 4 data input A. Routed to 4Y when A/B is low and G is low. |+| 15 | G | input | Output strobe, active low. When G is high, all four Y outputs are forced low regardless of A/B or data inputs; when G is low the mux operates normally. |+| 16 | VCC | power_in | Positive supply, 2V to 6V recommended (5V nominal). Absolute max 7V. Decouple with 0.1uF close to the pin. |++## Key specifications++| Parameter | Value |+|---|---|+| Type | Quad 2-to-1 multiplexer |+| Channels | 4 bits (2:1 each) |+| Select | one shared A/B line |+| Enable | active-low (forces Y low) |+| Outputs | true (non-inverting) |+| Logic family | HC (high-speed CMOS) |+| Supply voltage | 2-6 V |+| Package | SOIC-16 |++## Ordering variants++- `SN74HC157D (SOIC-16, tube)`+- `SN74HC157DR (SOIC-16, tape & reel)`++## CAD (KiCad official)++- Symbol: `74xx:74LS157 (pin-compatible with 74HC157)`+- Footprint: `Package_SO:SOIC-16_3.9x9.9mm_P1.27mm`+- 3D model: SOIC-16 (KiCad packages3D)++## Provenance++Data extracted from the manufacturer datasheet, not a distributor listing:++- **Datasheet:** [Texas Instruments datasheet](https://www.ti.com/lit/ds/symlink/sn74hc157.pdf) (37 pp, sha256 `4dcd9386eac88c0e`, 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/sn74hc157-datasheet.pdf)

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