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UC3842AD8TRG4

UC3842AD8TRG4 Current-Mode PWM Controller, 500 kHz, 8-SOIC

MPNUC3842AD8TRG4
End of Life

Texas Instruments UC3842AD8TRG4, current-mode PWM controller, up to 500 kHz switching, 96% max duty cycle, 10V to 30V supply, 8-SOIC package.

$0.4480Ref. price · indicative, final on quote
Texas Instruments UC3842AD8TRG4 datasheet (PDF)
Independent supplier — new & surplus stockAuthenticity-screened · ESD-safe packingListing updated Jul 2026

Specifications

UC3842AD8TRG4 specifications
ParameterValue
Output typeTransistor Driver
MountingSurface Mount
Voltage - supply (Vcc (Vdd))10V ~ 30V
Frequency - switchingUp to 500kHz
I/O channels1
Output phases1
Duty cycle96%
Operating temperature0°C~70°C(TA)
PackageTape & Reel (TR)
FunctionStep-Up, Step-Down, Step-Up/Step-Down
TopologyBoost, Buck, Flyback, Forward
Clock syncNo
Case8-SOIC (0.154\", 3.90mm Width)
Control featuresFrequency Control
Output configurationPositive, Isolation Capable
Synchronous rectifierNo

Product details

Current-mode PWM controller for offline flyback and forward converters

The Texas Instruments UC3842AD8TRG4 is a current-mode PWM controller designed for step-up, step-down, and step-up/step-down topologies including boost, buck, flyback, and forward converters. It drives a single transistor output stage at switching frequencies up to 500 kHz, with a maximum duty cycle of 96% — wide enough for offline flyback designs where the input voltage dips below 100 VAC.

Switching frequency and duty cycle — sizing the transformer and snubber

The 500 kHz ceiling lets you shrink the magnetic core in a flyback transformer compared to a 100 kHz design, but the trade-off is higher switching losses in the MOSFET and snubber. The 96% max duty cycle keeps the controller running through low-line conditions — at 85 VAC input a flyback converter still regulates the output without dropping out of cycle-by-cycle current limit. Supply voltage range of 10 V to 30 V on Vcc/Vdd sets the startup resistor value and the UVLO thresholds. At 10 V the controller is fully operational; below that the undervoltage lockout holds the output off, preventing the MOSFET from operating in the linear region during brownout.

The tape-and-reel delivery (TR suffix) matches pick-and-place feeders for volume assembly.

Frequently asked questions

Is UC3842AD8TRG4 obsolete?

No. There is no end-of-life or last-time-buy notice on file.

Can UC3842AD8TRG4 be used in a flyback converter?

Yes. The UC3842AD8TRG4 is explicitly rated for flyback topology as part of its step-up/step-down capability. The 96% max duty cycle and up to 500 kHz switching frequency are well suited for offline flyback designs.

What is the difference between UC3842 and UC3842AD8TRG4?

The base part UC3842 is the generic current-mode PWM controller; the UC3842AD8TRG4 suffix indicates the specific variant in an 8-SOIC package (AD8) supplied in tape and reel (TR). The functional specifications — up to 500 kHz switching, 96% duty cycle, 10 V to 30 V supply — are identical across the family.

What is the equivalent of UC3842AD8TRG4?

The UC3842AD8TRG4 is a standard current-mode PWM controller. Pin-compatible equivalents from other manufacturers include the KA3842A (Fairchild/ON Semiconductor) and the SG3842 (Microsemi). All share the same 8-pin SOIC pinout and similar UVLO thresholds. Confirm the exact switching frequency and duty cycle limits against your design margins.