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UC3845G-S08-R

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

componentpower management (pmic)uc3845g-s08-rfactory-2.0.0extractor-text
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Contents

README

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UC3845G-S08-R

UTC Unisonic Tech · AC-DC Controllers And Regulators · SOIC-8

UC3845G-S08-R from UTC Unisonic Tech, 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 Error amplifier output, made available for loop compensation.
2 VFB input Voltage feedback input, the inverting input of the error amplifier, normally connected to the switching supply output through a resistor divider.
3 ISENSE input Input for a voltage proportional to inductor current, used by the PWM to terminate output switch conduction (current sense input threshold 1.0 V typ., 0.9 V min., 1.1 V max.).
4 RT/CT passive Oscillator timing pin: resistor RT connects to Vref and capacitor CT to ground to set oscillator frequency and maximum duty cycle; operation to 1 MHz is possible.
5 GND power_in Power ground.
6 Output output Directly drives the gate of a power MOSFET, sourcing and sinking peak currents up to 1 A; the output switches at one-half the oscillator frequency.
7 VCC power_in Positive supply input (UC3845 undervoltage lockout: startup threshold 8.4 V typ., minimum operating voltage 7.6 V typ. after turn-on).
8 VREF power_out Reference output providing 5.0 V typ. (4.82 V to 5.18 V total variation) and charging current for timing capacitor CT through resistor RT.

Key specifications

Parameter Value
Manufacturer UTC Unisonic Tech
Package SOIC-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 IOUT=1.0mA, TJ=25°C 4
Line Regulation ΔVOUT 2 20 mV VCC=12V ~ 25V 4
Load Regulation ΔVOUT 3 25 mV IOUT=1.0mA ~ 20mA 4
Total Output Variation over Line, Load, Temperature VREF 4.82 5.18 V Over line, load, temperature 4
Output Short Circuit Current ISC -30 -85 -180 mA 4
Frequency fOSC 47 52 57 kHz TJ=25°C 4
Frequency fOSC 46 60 kHz 0°C ≤ TA ≤ 70°C 4
Frequency Change with Voltage fOSC/V 0.2 1 % VCC=12V ~ 25V 4
Voltage Feedback Input VFB 2.42 2.5 2.58 V VOUT=2.5V 4
Output Voltage Swing High VOH 5 6.2 V RL=15k to ground, VFB=2.3V 4
Output Voltage Swing Low VOL 0.8 1.1 V RL=15k to VREF, VFB=2.7V 4
Output Current Sink ISINK 2 12 mA VOUT=1.1V, VFB=2.7V 4
Output Current Source ISOURCE -0.5 -1 mA VOUT=5.0V, VFB=2.3V 4
Error Amplifier Input Bias Current II(BIAS) -0.1 -2 μA VFB=2.7V 4
Open Loop Voltage Gain GVO 65 90 dB VOUT=2.0V ~ 4.0V 4
Power Supply Rejection Ratio (error amplifier) PSRR 60 70 dB VCC=12V ~ 25V 4
Unity Gain Bandwidth GBW 0.7 1 MHz TJ=25°C 4
Current Sense Input Voltage Gain GV 2.85 3 3.15 V/V (Note 2, 3) 5
Maximum Current Sense Input Threshold VI(THR) 0.9 1 1.1 V (Note 2) 5
Current Sense Input Bias Current II(BIAS) -2 -10 μA 5
Propagation Delay tPLH(IN/OUT) 150 300 ns 5
Output Voltage Low VOL 0.1 0.4 V ISINK=20mA 5
Output Voltage Low VOL 1.6 2.2 V ISINK=200mA 5
Output Voltage High VOH 13 13.5 V ISINK=20mA 5
Output Voltage High VOH 12 13.4 V ISINK=200mA 5
Output Voltage with UVLO Activated VOL(UVLO) 0.1 1.1 V VCC=6.0V, ISINK=1.0mA 5
Output Voltage Rise Time tR 50 150 ns CL=1.0nF, TJ=25°C 5
Output Voltage Fall Time tF 50 150 ns CL=1.0nF, TJ=25°C 5
Startup Threshold (UC3844) VTHR 14.5 16 17.5 V UC3844 column 5
Minimum Operating Voltage After Turn-On (UC3844) VCC(MIN) 8.5 10 11.5 V UC3844 column 5
Maximum Duty Cycle DCMAX 47 48 50 % 5
Minimum Duty Cycle DCMIN 0 % 5
Power Supply Zener Voltage VZ 30 36 V ICC=25mA 5
Power Supply Current (UC3844) ICC 12 17 mA VCC=14V, UC3844 column 5
Startup Current ISTART-UP 0.3 0.5 mA VCC=14V, UVLO Active 5
Current Sense and Voltage Feedback Inputs Voltage VIN -0.3 5.5 V 4
Total Power Supply and Zener Current ICC+IZ 30 mA 4
Error Amp Output Sink Current ISINK 10 mA 4
Output Current, Source or Sink IOUT 1 A Note 2 4
Output Energy (Capacitive Load per cycle) W 5 μJ Capacitive load per cycle 4
Power Dissipation (SOP-8) PD 800 mW SOP-8 4
Junction Temperature TJ 150 °C 4
Storage Temperature TSTG -65 150 °C 4
Operation Temperature TOPR 0 70 °C 4
Junction to Ambient (SOP-8) θJA 156 °C/W SOP-8 4

CAD (KiCad official)

  • Symbol: UC3845G-S08-R
  • Footprint: Package_SO:SOIC-8_3.9x4.9mm_P1.27mm
  • 3D model: SOIC-8 (KiCad packages3D, STEP)
  • 3D model files: uc3845g-s08-r-etched.step / uc3845g-s08-r-etched.glb carry the MPN laser-etched on the die in a toggleable Adom.LaserEtch group (Fusion-ready); uc3845g-s08-r.step / uc3845g-s08-r.glb are the bare package body.

Provenance

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

  • Datasheet: UTC Unisonic Tech datasheet (7 pp, sha256 43d85764f509307f, 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