# UM823RS

**Union Semiconductor** · Supervisor and Reset ICs · SOT-23-5

UM823RS from Union Semiconductor, in a SOT-23-5. 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 | RESET | output | Active-low reset output. Pulses low for 200 ms (typ) when triggered and remains low whenever VCC is below the 2.63 V (typ) reset threshold or when MR is a logic low. Guaranteed valid down to VCC = 1 V. Push-pull output sinks/sources current (VOL ≤ 0.3 V @ 4 mA, VOH ≥ 0.8·VCC @ 1 mA). |
| 2 | GND | power_in | Ground reference for all signals. |
| 3 | MR | input | Active-low manual-reset input. Triggers a reset pulse when pulled below 0.3·VCC. Has an internal 52 kΩ (35-75 kΩ) pull-up to VCC; may be driven from TTL/CMOS logic, shorted to GND with a switch, or left open. Connect to VCC if unused. |
| 4 | WDI | input | Watchdog input. If WDI remains high or low longer than the 1.6 s (typ) watchdog timeout period, the internal watchdog timer expires and a reset is triggered. The watchdog timer clears on any rising or falling edge (min 50 ns pulse) or whenever RESET is asserted. Leaving WDI unconnected or three-stated disables the watchdog function. |
| 5 | VCC | power_in | Supply voltage input. Operating range 1.0 V to 7 V (absolute max 8 V). Typical supply current 3 µA (R/S/T/Y/Z threshold options) with MR and WDI unconnected. |

## Key specifications

| Parameter | Value |
|---|---|
| Manufacturer | Union Semiconductor |
| Package | SOT-23-5 |
| Category | PMIC |
| Pins | 5 |

## Ordering variants

Same part, different packaging or reel option.

- `UM823RS`
- `UM823RP`

## CAD (KiCad official)

- Symbol: `UM823RS`
- Footprint: `Package_TO_SOT_SMD:SOT-23-5`
- 3D model: SOT-23-5 (KiCad packages3D, STEP)
- 3D model files: `um823rs-etched.step` / `um823rs-etched.glb` carry the MPN laser-etched on the die in a toggleable `Adom.LaserEtch` group (Fusion-ready); `um823rs.step` / `um823rs.glb` are the bare package body.

## Provenance

Data extracted from the manufacturer datasheet, not a distributor listing:

- **Datasheet:** [Union Semiconductor datasheet](docs/um823rs-datasheet.pdf) (11 pp, sha256 `9413e8dcc1f62525`, retrieved 2026-08-17, tier: lcsc)
- **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/um823rs-datasheet.pdf)