UC3845B

@@ -0,0 +1,47 @@+# UC3845B++**UMW** · AC-DC Controllers and Regulators · SOP-8++UC3845B from UMW, in a SOP-8. 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 | COMP | output | Error Amplifier output pin, used for external loop compensation. Typical high output voltage 5-6 V, low output 0.8-1.1 V (with 15 kΩ load). |+| 2 | VFB | input | Inverting input of the Error Amplifier. Normally connected to the switching power supply output through a resistor divider; internal reference at 2.5 V (typ). Input bias current -0.1 µA typ. |+| 3 | ISENSE | input | Current sense input. A voltage proportional to the inductor current (up to ~1 V max) is applied here; the PWM comparator uses this to terminate output switch conduction each cycle. Input voltage range -0.3 to 5.5 V max. |+| 4 | RT/CT | passive | Oscillator timing pin. Oscillator frequency and maximum output duty cycle are set by connecting a timing resistor RT from VREF to this pin and a timing capacitor CT from this pin to ground. Operating frequency up to 500 kHz. |+| 5 | GND | power_in | Combined control circuitry and power ground return for the IC. |+| 6 | OUT | output | Totem-pole gate drive output for an external power MOSFET. Sources/sinks peak currents up to 1 A. VOH ≈ 13-13.5 V, VOL ≈ 0.08-1.4 V depending on load; rise/fall time ~35-45 ns into 1 nF. |+| 7 | VCC | power_in | Positive supply for the IC. UVLO start threshold 8.4 V typ (7.8-9 V), min operating 7.6 V typ (7-8.2 V) after turn-on. Absolute max 30 V; zener clamp ≈ 30-38 V at 25 mA. Operating supply current 13 mA typ; start-up current 0.5 mA typ. |+| 8 | VREF | power_out | Internal 5 V reference output (4.9-5.1 V), used to charge timing capacitor CT through timing resistor RT and to bias external circuitry. Short-circuit current typically -100 mA (limited to -180 mA max). Load current 1-20 mA. |++## Key specifications++| Parameter | Value |+|---|---|+| Manufacturer | UMW |+| Package | SOP-8 |+| Category | PMIC |+| Pins | 8 |++## Ordering variants++- `UC3845B`++## CAD (KiCad official)++- Symbol: `UC3845B`+- Footprint: `Package_SO:SOIC-8_3.9x4.9mm_P1.27mm`+- 3D model: SOP-8 (KiCad packages3D, STEP)++## Provenance++Data extracted from the manufacturer datasheet, not a distributor listing:++- **Datasheet:** [UMW datasheet](docs/uc3845b-datasheet.pdf) (13 pp, sha256 `562bc6cb07a3fb91`, 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/uc3845b-datasheet.pdf)

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