component
uc3845m
Public Unreviewedby Ray
HGSEMI AC-DC Controllers and Regulators, SOP-8. Datasheet-verified pinout, KiCad symbol/footprint/3D.
3D Model
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README
markdownUC3845M
HGSEMI · AC-DC Controllers and Regulators · SOP-8
UC3845M from HGSEMI, 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 | bidirectional | Error amplifier compensation input/output. Used to connect external feedback network (Zi/Zf) that sets the loop compensation. Pulling this pin below ~two diode drops shuts down the PWM output. |
| 2 | VFB | input | Error amplifier inverting input (voltage feedback). Internally compared against the 2.5V reference; typical feedback voltage is 2.42-2.58V. Input bias current is approximately -0.1µA (max -2µA). |
| 3 | ISENSE | input | Current-sense comparator input. Peak current is set by Ismax = 1.0V / Rs (maximum input signal 1V). Raising this pin above 1V forces shutdown; a small RC filter is recommended to suppress leading-edge switching spikes. Analog input range -0.3V to +5.5V. |
| 4 | RT/CT | bidirectional | RC oscillator timing pin. External RT (to VREF) and CT (to GND) set the oscillator frequency (up to 500kHz; typical 52kHz with RT=10kΩ, CT=3.3nF). Sawtooth amplitude ≈1.6Vpp; discharge current 7.5-8.8mA. |
| 5 | GND | power_in | Power/signal ground. Bypass capacitors should be placed close to this pin due to high peak currents associated with capacitive loads on the output. |
| 6 | OUTPUT | output | High-current totem-pole PWM output for driving N-channel power MOSFET gates directly. Sink/source up to ±1A peak, 200mA average. VOL ≈0.1V @ 20mA, VOH ≈13.5V @ 20mA; typical rise/fall times 50ns into 1nF. Low during UVLO; a pull-down resistor to GND is recommended to prevent leakage-induced turn-on of the power MOSFET. |
| 7 | VCC | power_in | Positive supply input. UVLO turn-on threshold 8.4V typ (7.8-9.0V); turn-off 7.6V typ (7-8.2V). Startup current <0.5mA, operating current ~12mA (17mA max). Absolute max 30V; internal zener clamp ~34V @ 25mA. Recommended operating range up to 28V. |
| 8 | VREF | power_out | Internally trimmed 5.0V bandgap reference output (4.90-5.10V @ 1mA, 25°C). Can source up to 20mA; short-circuit current -30 to -180mA. Typically used to bias RT and other external circuitry; requires ~0.1µF bypass capacitor to GND. |
Key specifications
| Parameter | Value |
|---|---|
| Manufacturer | HGSEMI |
| Package | SOP-8 |
| Category | PMIC |
| Pins | 8 |
Ordering variants
UC3845MM/TRUC3845MMUC3845MN
CAD (KiCad official)
- Symbol:
UC3845M - 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: HGSEMI datasheet (None pp, sha256
5f1caab1b2402b57, retrieved 2026-08-17, tier: lcsc) - Datasheet language: Chinese. Pin names, descriptions, and specs on this page were extracted and translated to English by ds2sf; the linked PDF is the manufacturer original.
- 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).
Symbol & Footprint
Schematic Symbol
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PCB Footprint
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Datasheet
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