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UC3845BD1G

Public Made by Adom

by adom

onsemi AC-DC Controllers & Regulators, SOIC-8. Pinout cross-checked by two models against the datasheet, KiCad symbol/footprint/3D.

componentpower management icsuc3845bd1gfactory-2.0.0extractor-text
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Contents

README

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UC3845BD1G

onsemi · AC-DC Controllers & Regulators · SOIC-8

UC3845BD1G from onsemi, in a SOIC-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 Compensation output This pin is the Error Amplifier output and is made available for loop compensation.
2 Voltage Feedback input This is the inverting input of the Error Amplifier and is normally connected to the switching power supply output through a resistor divider.
3 Current Sense input A voltage proportional to inductor current is connected to this input, and the PWM uses this information to terminate the output switch conduction.
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, and oscillator operation to 1.0 kHz is possible.
5 GND 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, with peak currents up to 1.0 A sourced and sunk by this pin.
7 VCC power_in This pin is the positive supply of the control IC.
8 Vref power_out This is the reference output, which provides charging current for capacitor CT through resistor RT.

Key specifications

Parameter Value
Manufacturer onsemi
Package SOIC-8
Category Power Management ICs
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
Bias and Driver Voltages VCC, VC 36 V Zero Series Impedance 2
Total Power Supply and Zener Current ICC + IZ 30 mA 2
Output Current, Source or Sink IO 1 A 2
Output Energy W 5 J Capacitive Load per Cycle 2
Current Sense and Voltage Feedback Inputs Vin -0.3 5.5 V 2
Error Amp Output Sink Current IO 10 mA 2
Power Dissipation SOIC-8 (D1 suffix) PD 702 mW TA = 25°C 2
Thermal Resistance Junction-to-Air SOIC-8 (D1 suffix) RJA 178 °C/W 2
Operating Junction Temperature TJ 150 °C 2
Operating Ambient Temperature TA 0 70 °C UC3844B, UC3845B 2
Storage Temperature Range Tstg -65 150 °C 2
Reference Output Voltage Vref 4.9 5 5.1 V IO = 1.0 mA, TJ = 25°C 2
Load Regulation Regload 3 25 mV IO = 1.0 mA to 20 mA 2
Line Regulation Regline 2 20 mV VCC = 12 V to 25 V 2
Total Output Variation over Line, Load, & Temperature Vref 4.82 5.18 V 2
Output Short Circuit Current ISC -30 -85 -180 mA 2
Discharge Current Idischg 7.8 8.3 8.8 mA VOSC = 2.0 V, TJ = 25°C 3
Discharge Current over TA range Idischg 7.6 8.8 mA VOSC = 2.0 V, TA = Tlow to Thigh 3
Oscillator Frequency (RT = 6.2 k, CT = 1.0 nF) fOSC 225 250 275 kHz TJ = 25°C (RT = 6.2 k, CT = 1.0 nF) 2
Frequency Change with Voltage fOSC/V 0.2 1 % VCC = 12 V to 25 V 2
Voltage Feedback Input VFB 2.42 2.5 2.58 V VO = 2.5 V 3
Input Bias Current IIB -2 0.1 µA VFB = 5.0 V 3
Open Loop Voltage Gain AVOL 65 90 dB VO = 2.0 V to 4.0 V 3
Unity Gain Bandwidth BW 0.7 1 MHz TJ = 25°C 3
Power Supply Rejection Ratio (error amp) PSRR 60 70 dB VCC = 12 V to 25 V 3
Output Current - Sink ISink 2 12 mA VO = 1.1 V, VFB = 2.7 V 3
Output Current - Source ISource -0.5 -1 mA VO = 5.0 V, VFB = 2.3 V 3
Output Voltage High State VOH 5 6.2 V RL = 15 k to ground, VFB = 2.3 V 3
Output Voltage Low State VOL 0.8 1.1 V RL = 15 k to Vref, VFB = 2.7 V 3
Current Sense Input Voltage Gain AV 2.85 3 3.15 V/V Notes 9 & 10 3
Maximum Current Sense Input Threshold Vth 0.9 1 1.1 V Note 9, latch trip point with VFB = 0 V 3
Current Sense Input Bias Current IIB -10 2 µA 3
Propagation Delay (Current Sense Input to Output) tPLH(In/Out) 150 300 ns 3
Output Voltage Low State VOL 0.1 V ISink = 20 mA 3
Output Voltage Low State VOL 1.6 V ISink = 200 mA, UC384xB 3
Output Voltage High State VOH 12.9 13.5 V ISource = 20 mA, UC384xB 3
Output Voltage with UVLO Activated VOL(UVLO) 0.1 1.1 V VCC = 6.0 V, ISink = 1.0 mA 3
Output Voltage Rise Time tr 50 150 ns CL = 1.0 nF, TJ = 25°C 3
Output Voltage Fall Time tf 50 150 ns CL = 1.0 nF, TJ = 25°C 3
Startup Threshold UCX845B Vth 7.8 8.4 9 V UCX845B 3
Minimum Operating Voltage After Turn-On UCX845B VCC(min) 7 7.6 8.2 V UCX845B 3
Power Supply Current Startup ICC 0.3 0.5 mA VCC = 6.5 V for UCX845B 4
Power Supply Current Operating ICC 12 17 mA Note 11 4
Power Supply Zener Voltage VZ 30 36 V ICC = 25 mA 4
Maximum Duty Cycle DC(max) 47 48 50 % UC384xB 4
Minimum Duty Cycle DC(min) 0 % 4

CAD (KiCad official)

  • Symbol: UC3845BD1G
  • Footprint: Package_SO:SOIC-8_3.9x4.9mm_P1.27mm
  • 3D model: SOIC-8 (KiCad packages3D, STEP)
  • 3D model files: uc3845bd1g-etched.step / uc3845bd1g-etched.glb carry the MPN laser-etched on the die in a toggleable Adom.LaserEtch group (Fusion-ready); uc3845bd1g.step / uc3845bd1g.glb are the bare package body.

Provenance

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

  • Datasheet: onsemi datasheet (22 pp, sha256 811d8a44f6a2a239, retrieved 2026-10-28, tier: manufacturer)
  • 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