# UC3845BM

**HGSEMI** · AC-DC Controllers And Regulators · SOP-8

UC3845BM from HGSEMI, in a SOP-8. Pinout and pin descriptions extracted from the manufacturer datasheet (extract_pins, cross-checked by a second model); symbol, footprint, and 3D from KiCad-official CAD.

## Pinout

| Pin | Name | Type | Function |
|---|---|---|---|
| 1 | COMP | output | This pin is the Error Amplifier output and is made for loop compensation, with an absolute maximum error amplifier output sink current (ISINK(E.A)) of 10 mA. |
| 2 | VFB | input | This is the inverting input of the Error Amplifier, normally connected to the switching power supply output through a resistor divider, with a specified input voltage (VI(E.A)) of 2.42 V to 2.58 V (2.5 V typ) at Vpin1 = 2.5 V. |
| 3 | ISENSE | input | A voltage proportional to inductor current is connected to this input, which the PWM uses to terminate the output switch conduction; analog inputs (pins 2, 3) are rated from -0.3 V to 5.5 V, with a maximum input signal (VI(MAX)) of 0.9 V to 1.1 V (1.0 V typ). |
| 4 | RT/CT | passive | The oscillator frequency and maximum output duty cycle are programmed by connecting resistor RT to Vref and capacitor CT to ground. |
| 5 | GROUND | power_in | This pin is the combined control circuitry and power ground. |
| 6 | OUTPUT | output | This output directly drives the gate of a power MOSFET, sourcing and sinking peak currents up to 1 A. |
| 7 | VCC | power_in | This pin is the positive supply of the integrated circuit, with an absolute maximum supply voltage of 30 V from a low impedance source. |
| 8 | Vref | power_out | This is the reference output that provides charging current for capacitor CT through resistor RT, specified at 4.9 V to 5.1 V (5.0 V typ) at TJ = 25°C and IREF = 1 mA. |

## Key specifications

| Parameter | Value |
|---|---|
| Manufacturer | HGSEMI |
| Package | SOP-8 |
| Category | Power Management (PMIC) |
| Pins | 8 |

## Electrical characteristics

Limits as printed in the datasheet (page.json `metadata.characteristics` carries them as data).

| Parameter | Symbol | Min | Typ | Max | Unit | Conditions | Page |
|---|---|---|---|---|---|---|---|
| Reference Output Voltage | VREF | 4.9 | 5 | 5.1 | V | TJ = 25°C, IREF = 1 mA | 3 |
| Line Regulation | ΔVREF |  | 6 | 20 | mV | 12V ≤ VCC ≤ 25 V | 3 |
| Load Regulation | ΔVREF |  | 6 | 25 |  | 1 mA ≤ IREF ≤ 20mA | 3 |
| Short Circuit Output Current | ISC |  | -100 | -180 | mA | TA = 25°C | 3 |
| Oscillation Frequency | f | 47 | 52 | 57 | KHz | TJ = 25°C | 3 |
| Frequency Change with Voltage | Δf/ΔVCC |  | 0.05 | 1 | % | 12V ≤ VCC ≤ 25 V | 3 |
| Error Amplifier Input Bias Current | IBIAS |  | -0.1 | -2 | µA | VFB=3V | 3 |
| Error Amplifier Input Voltage | VI(E.A) | 2.42 | 2.5 | 2.58 | V | Vpin1 = 2.5V | 3 |
| Open Loop Voltage Gain | AVOL |  | 65 | 90 | dB | 2V ≤ V0 ≤ 4V | 3 |
| Unity Gain Bandwidth | UGBW |  | 0.5 | 0.6 | MHz | Tj=25°C, Note 3 | 3 |
| Power Supply Rejection Ratio | PSRR |  | 60 | 70 | dB | 12V ≤ VCC ≤ 25 V | 3 |
| Output Sink Current | ISINK |  | 2 | 7 | mA | Vpin2 = 2.7V, Vpin1 = 1.1V | 3 |
| Output Source Current | ISOURCE |  | -0.5 | -1 | mA | Vpin2 = 2.3V, Vpin1 = 5V | 3 |
| Error Amplifier High Output Voltage | VOH |  | 5 | 6 | V | Vpin2 = 2.3V, RL = 15KΩ to GND | 3 |
| Error Amplifier Low Output Voltage | VOL |  | 0.8 | 1.1 | V | Vpin2 = 2.7V, RL = 15KΩ to PIN 8 | 3 |
| Current Sense Gain | GV | 2.85 | 3 | 3.15 | V/V | Note 1 & 2 | 3 |
| Maximum Input Signal | VI(MAX) | 0.9 | 1 | 1.1 | V | Vpin1 = 5V (Note 1) | 3 |
| Current Sense Input Bias Current | IBIAS |  | -3 | -10 | µA | Vpin3 = 3V | 3 |
| Output Low Voltage | VOL |  | 0.08 | 0.4 | V | ISINK = 20 mA | 3 |
| Output Low Voltage | VOL |  | 1.4 | 2.2 | V | ISINK = 200 mA | 3 |
| Output High Voltage | VOH |  | 13 | 13.5 | V | ISINK = 20 mA | 3 |
| Output High Voltage | VOH |  | 12 | 13 | V | ISINK = 200 mA | 3 |
| Rise Time | tR |  | 45 | 150 | nS | TJ = 25°C, CL = 1nF (Note 3) | 3 |
| Fall Time | tF |  | 35 | 150 | nS | TJ = 25°C, CL = 1nF (Note 3) | 3 |
| Start Threshold Voltage | VTH(ST) | 7.8 | 8.4 | 9 | V | UC3843B,UC3845B | 3 |
| Minimum Operating Voltage (After Turn On) | VOPR(min) | 7 | 7.6 | 8.2 | V | UC3843B,UC3845B | 3 |
| Maximum Duty Cycle | D(MAX) | 47 | 48 | 50 | % | UC3844B,UC3845B | 3 |
| Minimum Duty Cycle |  | 0 |  |  |  |  | 3 |
| Start-Up Current | IST |  | 0.17 | 0.3 | mA | UC3842B/43B/44B/45B | 3 |
| Operating Supply Current | ICC (OPR) |  | 13 | 17 | mA | Vpin3 = Vpin2 = 0V | 3 |
| Zener Voltage | VZ |  | 30 | 38 | V | ICC=25 mA | 3 |
| Supply Voltage (low impedance source) | VCC |  |  | 30 | V |  | 2 |
| Output Current | IO | -1 |  | 1 | A |  | 2 |
| Input Voltage (Analog Inputs pins 2,3) | VI | -0.3 |  | 5.5 | V |  | 2 |
| Error Amp Output Sink Current | ISINK (E.A) |  |  | 10 | mA |  | 2 |
| Power Dissipation | PO |  |  | 1 | W | TA=25°C | 2 |
| Storage Temperature Range | Tstg | -65 |  | 150 | °C |  | 2 |
| Lead Temperature | TL |  |  | 260 | °C | soldering 5 sec. | 2 |
| Operating Ambient Temperature | TA | -40 |  | 85 | °C | characterized for operation | 1 |

## CAD (KiCad official)

- Symbol: `UC3845BM`
- Footprint: `Package_SO:SOIC-8_3.9x4.9mm_P1.27mm`
- 3D model: SOP-8 (KiCad packages3D, STEP)
- 3D model files: `uc3845bm-etched.step` / `uc3845bm-etched.glb` carry the MPN laser-etched on the die in a toggleable `Adom.LaserEtch` group (Fusion-ready); `uc3845bm.step` / `uc3845bm.glb` are the bare package body.

## Provenance

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

- **Datasheet:** [HGSEMI datasheet](https://jlcpcb.com/api/file/downloadByFileSystemAccessId/8590456093773099008) (11 pp, sha256 `27376c62601f1c47`, retrieved 2026-10-18, tier: lcsc)
- **Extractor:** parts-factory `2.0.0` / `extract_pins 0.3`, primary `claude-haiku-5-5` (text), consensus `claude-sonnet-5-5` (agreed), guards: pin_guards 0.1: passed. Pins are checked against the footprint pad set and their cited datasheet pages before publish.
- **CAD:** KiCad official libraries (CC-BY-SA 4.0).

[Datasheet PDF](docs/uc3845bm-datasheet.pdf)