SN74HC123 Dual Monostable

@@ -0,0 +1,65 @@+# SN74HC123++**Texas Instruments** · Monostable Multivibrator · SOIC-16++The SN74HC123 contains two retriggerable monostable multivibrators (one-shots). A trigger edge starts an output pulse whose width is set by an external resistor and capacitor, and a new trigger during the pulse retriggers (extends) it. Each has an active-low clear to end the pulse early. It is used for pulse generation, edge-to-pulse conversion, and timing.++## Pinout++| Pin | Name | Type | Function |+|---|---|---|---|+| 1 | 1A | input | Monostable 1 trailing-edge trigger input (active-low, Schmitt trigger). A high-to-low transition on 1A triggers the one-shot when 1B = H and 1R = H. |+| 2 | 1B | input | Monostable 1 leading-edge trigger input (active-high, Schmitt trigger). A low-to-high transition on 1B triggers the one-shot when 1A = L and 1R = H. |+| 3 | 1R | input | Monostable 1 reset input (active-low). Driving 1R low terminates the output pulse and holds 1Q = L, 1Q_bar = H. Must be tied high when unused. |+| 4 | 1Q_bar | output | Monostable 1 inverted (complementary) buffered output. Drives 10 LSTTL loads (15 LSTTL as a bus driver) over the -55 to 125 C range. |+| 5 | 2Q | output | Monostable 2 non-inverted buffered output. Pulse width tW = 0.45 * 2Rx * 2Cx at VCC = 5V. |+| 6 | 2Cx | passive | Monostable 2 external timing capacitor terminal. Connect Cx from this pin to 2RxCx (pin 7); the capacitor sets the output pulse width together with 2Rx. |+| 7 | 2RxCx | passive | Monostable 2 external Rx/Cx common node. Connect the external timing resistor from VCC to this pin and the timing capacitor between 2Cx (pin 6) and this pin. Minimum Rx ~5 kOhm, minimum Cx = 0 pF. |+| 8 | GND | power_in | Device ground reference (0 V). |+| 9 | 2A | input | Monostable 2 trailing-edge trigger input (active-low, Schmitt trigger). A high-to-low transition on 2A triggers the one-shot when 2B = H and 2R = H. |+| 10 | 2B | input | Monostable 2 leading-edge trigger input (active-high, Schmitt trigger). A low-to-high transition on 2B triggers the one-shot when 2A = L and 2R = H. |+| 11 | 2R | input | Monostable 2 reset input (active-low). Driving 2R low terminates the output pulse and holds 2Q = L, 2Q_bar = H. Must be tied high when unused. |+| 12 | 2Q_bar | output | Monostable 2 inverted (complementary) buffered output. |+| 13 | 1Q | output | Monostable 1 non-inverted buffered output. Pulse width tW = 0.45 * 1Rx * 1Cx at VCC = 5V. |+| 14 | 1Cx | passive | Monostable 1 external timing capacitor terminal. Connect Cx from this pin to 1RxCx (pin 15). |+| 15 | 1RxCx | passive | Monostable 1 external Rx/Cx common node. Connect the external timing resistor from VCC to this pin and the timing capacitor between 1Cx (pin 14) and this pin. |+| 16 | VCC | power_in | Positive supply. HC types: 2 V to 6 V. HCT types: 4.5 V to 5.5 V. Absolute max 7 V. |++## Key specifications++| Parameter | Value |+|---|---|+| Type | Dual retriggerable monostable (one-shot) |+| Logic family | 74HC (CMOS) |+| Timing | External R and C set pulse width |+| Retriggerable | Yes, with clear input |+| Supply voltage | 2 V to 6 V |+| Operating temperature | -40 C to 85 C |++## Ordering variants++- `SN74HC123E`+- `SN74HC123M`+- `SN74HC123MT`+- `SN74HC123M96`+- `SN74HC123NSR`+- `SN74HC123PW`+- `SN74HC123PWR`+- `SN74HC123PWT`+- `SN74HC123F3A`++## CAD (KiCad official)++- Symbol: `sn74hc123.kicad_sym`+- Footprint: `sn74hc123.kicad_mod`+- 3D model: SOIC-16 body from KiCad `Package_SO/SOIC-16_3.9x9.9mm_P1.27mm`.++## Provenance++Data extracted from the manufacturer datasheet, not a distributor listing:++- **Datasheet:** [Texas Instruments datasheet](https://www.ti.com/lit/ds/symlink/cd74hc123.pdf) (24 pp, sha256 `1ae45a9eac40347d`, 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/sn74hc123-datasheet.pdf)

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