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UC3845D8G4

UC3845D8G4 PWM Controller, 48% Duty Cycle, 500 kHz, SOIC-8

MPNUC3845D8G4
End of Life

Texas Instruments UC3845D8G4 current-mode PWM controller, 48% max duty cycle, up to 500 kHz switching, 12 V to 28 V supply, 8-SOIC package, commercial temperature range.

Texas Instruments UC3845D8G4 datasheet (PDF)
Independent supplier — new & surplus stockAuthenticity-screened · ESD-safe packingListing updated Jul 2026

Specifications

UC3845D8G4 specifications
ParameterValue
Output typeTransistor Driver
MountingSurface Mount
Voltage - supply (Vcc (Vdd))12V ~ 28V
Frequency - switchingUp to 500kHz
I/O channels1
Output phases1
Duty cycle48%
Operating temperature0°C~70°C(TA)
PackageTube
FunctionStep-Up, Step-Down, Step-Up/Step-Down
TopologyBoost, Buck, Buck-Boost, Flyback, Forward
Clock syncNo
Case8-SOIC (0.154\", 3.90mm Width)
Control featuresFrequency Control
Output configurationPositive, Isolation Capable
Synchronous rectifierNo

Product details

What the 48% duty cycle means for your converter

The UC3845D8G4 is a current-mode PWM controller from TI's UC3845 family, built for step-up, step-down, and step-up/step-down topologies including boost, buck, buck-boost, flyback, and forward converters. Its 48% maximum duty cycle is the headline limit — it caps the on-time per switching cycle, which directly sets the transformer turns ratio in a flyback or the voltage step-down ratio in a buck. If your design needs more than 48% on-time, this is not the part; step up to the UC3844 (50%) or UC3843 (100%) siblings.

Switching frequency and supply rails

Switching frequency goes up to 500 kHz, which lets you shrink the magnetics and output capacitors compared to a 100 kHz design — good for board-space-constrained supplies. The Vcc range of 12 V to 28 V matches the bias rail from an auxiliary winding or a linear regulator off the bulk DC bus. No clock sync input, so multiple controllers on the same board will beat unless you add external sync circuitry.

Fine for benchtop power supplies, office equipment, appliance control boards, and indoor industrial gear. Not for an engine bay, a rooftop telecom enclosure, or a freezer.

Frequently asked questions

Does the UC3845D8G4 support 48% duty cycle in both boost and flyback topologies?

Yes. The 48% maximum duty cycle applies across all supported topologies — boost, buck, buck-boost, flyback, and forward. In a flyback, that 48% cap limits the stored energy per cycle and forces a specific turns ratio; in a boost, it sets the maximum step-up ratio. If you need more than 48%, look at the UC3843 (100%) or UC3844 (50%) variants.

What is the recommended equivalent or replacement for the UC3845D8G4?

No official TI replacement is listed, but the UC3845 family is a standard industry pinout. A generic UC3845D8 in the same SOIC-8 package from another qualified manufacturer is a functional equivalent — same 48% duty cycle, same 500 kHz ceiling, same pin-for-pin footprint. Confirm the operating temperature grade and supply range match your BOM before swapping.