# BL8851

**BL(Shanghai Belling)** · AC-DC Controllers & Regulators · SOT-23-6

BL8851 from BL(Shanghai Belling), in a SOT-23-6. 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 | GND | power_in | Ground reference for the controller. |
| 2 | FB | input | Feedback input whose voltage level, together with the current-sense signal at pin 4, sets the PWM duty cycle; open-loop voltage 3.9 to 4.2 V and absolute maximum -0.3 to 7 V. |
| 3 | RT | input | Dual-function pin connected through an NTC resistor to ground for over-temperature shutdown/latch control, or through a Zener to VDD for adjustable over-voltage protection; absolute maximum -0.3 to 7 V. |
| 4 | CS | input | Current sense input with 220 ns leading edge blanking and 0.75 V internal current limit threshold; absolute maximum -0.3 to 7 V. |
| 5 | VDD | power_in | Power supply input, recommended 10 to 30 V, absolute maximum 40 V DC, with UVLO on at 9 V typ and off at 15.3 V typ. |
| 6 | GATE | output | Totem-pole gate driver output for the external power MOSFET, clamped at 15 V. |

## Key specifications

| Parameter | Value |
|---|---|
| Manufacturer | BL(Shanghai Belling) |
| Package | SOT-23-6 |
| Category | Power Management ICs |
| Pins | 6 |

## Electrical characteristics

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

| Parameter | Symbol | Min | Typ | Max | Unit | Conditions | Page |
|---|---|---|---|---|---|---|---|
| VDD DC Supply Voltage | VDD |  |  | 40 | V |  | 3 |
| VDD DC Clamp Current |  |  |  | 10 | mA |  | 3 |
| FB Input Voltage |  | -0.3 |  | 7 | V |  | 3 |
| Sense Input Voltage |  | -0.3 |  | 7 | V |  | 3 |
| RT Input Voltage |  | -0.3 |  | 7 | V |  | 3 |
| Operating Junction Temperature | TJ | -20 |  | 150 | °C | Min/Max | 3 |
| Storage Temperature | Tstg | -55 |  | 160 | °C |  | 3 |
| VDD Supply Voltage | VDD | 10 |  | 30 | V |  | 3 |
| Operating Ambient Temperature | TA | -20 |  | 85 | °C |  | 3 |
| VDD Start up Current | Istartup |  | 5 | 20 | uA | VDD=11V, measure leakage current into VDD | 4 |
| Operation Current | I_VDD_Operation |  | 2 |  | mA | VFB=3V | 4 |
| VDD Under Voltage Lockout Enter | UVLO(ON) | 8 | 9 | 10 | V | Enter | 4 |
| VDD Under Voltage Lockout Exit | UVLO(OFF) | 14.3 | 15.3 | 16.3 | V | Exit (Recovery) | 4 |
| Pull-up PMOS active | Vpull-up |  | 13 |  | V |  | 4 |
| VDD clamp voltage | Vdd_clamp | 30 | 32 | 34 | V | Ivdd=10mA | 4 |
| Over voltage protection voltage | OVP(ON) | 24 | 26 | 28 | V | CS=0V,FB=3V, Ramp up VDD until gate clock is off | 4 |
| Latch release voltage | Vlatch_release |  | 5 |  | V |  | 4 |
| VFB Open Loop Voltage | VFB_Open |  | 3.9 | 4.2 | V |  | 4 |
| PWM input gain | Avcs |  | 2 |  | V/V | ΔVFB/ΔVCS | 4 |
| Maximum duty cycle |  | 75 | 80 | 85 | % | VDD=14V,VFB=3V,VCS=0V | 4 |
| Threshold enter green mode | Vref_green |  | 2 |  | V |  | 4 |
| Threshold exit burst mode | Vref_burst_H |  | 1.275 |  | V |  | 4 |
| Threshold enter burst mode | Vref_burst_L |  | 1.175 |  | V |  | 4 |
| FB pin short circuit current | IFB_Short |  | 0.4 |  | mA | Short FB pin to GND and measure current | 4 |
| Power Limiting FB Threshold Voltage | VTH_PL |  | 3.7 |  | V |  | 4 |
| Power limiting Debounce Time | TD_PL | 80 | 88 | 96 | mSec |  | 4 |
| FB Input Impedance | ZFB_IN |  | 4 |  | Kohm |  | 4 |
| Soft start time |  |  | 4 |  | ms |  | 4 |
| Leading edge blanking time | T_blanking |  | 220 |  | ns |  | 4 |
| Sense Input Impedance | ZSENSE_IN |  | 40 |  | Kohm |  | 4 |
| Over Current Detection and Control Delay | TD_OC |  | 120 |  | nSec | From Over Current Occurs till the Gatedrive output start to turn off | 4 |
| Internal Current Limiting Threshold Voltage | VTH_OC |  | 0.75 |  | V | FB=3.3V | 4 |
| CS voltage clamper | Vocp_clamper |  | 0.9 |  | V |  | 4 |
| Normal Oscillation Frequency | FOSC | 60 | 65 | 70 | KHZ | VDD=14V, FB=3V, CS=0V | 4 |
| Frequency jittering | △f_OSC | -4 |  | 4 | % |  | 4 |
| Shuffling frequency | F_shuffling |  | 32 |  | Hz |  | 4 |
| Frequency Temperature Stability | △f_Temp |  | 1 |  | % |  | 4 |
| Frequency Voltage Stability | f_VDD |  | 1 |  | % |  | 5 |
| Burst Mode Base Frequency | F_Burst |  | 22 |  | KHZ |  | 5 |
| Output low level | VOL |  |  | 1 | V | VDD=14V, Io=5mA | 5 |
| Output high level | VOH | 6 |  |  | V | VDD=14V, Io=20mA | 5 |
| Output clamp voltage | V_clamp |  | 15 |  | V |  | 5 |
| Output rising time | T_r |  | 175 |  | nS | 1V ~ 12V @ CL=1000pF | 5 |
| Output falling time | T_f |  | 85 |  | nS | 12V ~ 1V @ CL=500pF | 5 |
| Output current of RT pin | IRT | 95 | 100 | 105 | uA |  | 5 |
| Threshold voltage for OTP | VOTP | 0.95 | 1 | 1.05 | V |  | 5 |
| OTP debounce time | Td_OTP |  | 32 |  | Cycle |  | 5 |
| Float voltage at RT pin | VRT_FL |  | 2.3 |  | V |  | 5 |
| External OVP threshold voltage | Vth_OVP |  | 4 |  | V |  | 5 |

## CAD (KiCad official)

- Symbol: `BL8851`
- Footprint: `Package_TO_SOT_SMD:SOT-23-6`
- 3D model: SOT-23-6 (KiCad packages3D, STEP)
- 3D model files: `bl8851-etched.step` / `bl8851-etched.glb` carry the MPN laser-etched on the die in a toggleable `Adom.LaserEtch` group (Fusion-ready); `bl8851.step` / `bl8851.glb` are the bare package body.

## Provenance

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

- **Datasheet:** [BL(Shanghai Belling) datasheet](docs/bl8851-datasheet.pdf) (7 pp, sha256 `0553dcea6b39e677`, retrieved 2026-10-22, tier: lcsc)
- **Extractor:** parts-factory `2.0.0` / `extract_pins 0.3`, primary `claude-sonnet-5-5` (text+vision), consensus `claude-opus-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/bl8851-datasheet.pdf)