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)

Provenance

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

Datasheet: Union Semiconductor datasheet (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