Skip to main content
Log in
STMicroelectronics UC3844BNST — Power Management (PMIC / Gate Driver)

UC3844BNST PWM Controller, 48% Duty Cycle

MPNUC3844BNST
Obsolete

STMicroelectronics UC3844BNST, current-mode PWM controller, 48% max duty cycle, up to 500 kHz switching, 10V-30V supply, 8-DIP through-hole package, 0°C to 70°C operating temperature.

$0.6800Ref. price · indicative, final on quote
STMicroelectronics UC3844BNST datasheet (PDF)
Independent supplier — new & surplus stockAuthenticity-screened · ESD-safe packingListing updated Jul 2026

Specifications

UC3844BNST specifications
ParameterValue
Output typeTransistor Driver
MountingThrough Hole
Voltage - supply (Vcc (Vdd))10V ~ 30V
Frequency - switchingUp to 500kHz
I/O channels1
Output phases1
Duty cycle48%
Operating temperature0°C ~ 70°C (TJ)
PackageTube
FunctionStep-Up, Step-Up/Step-Down
TopologyBoost, Flyback
Clock syncNo
Case8-DIP (0.300\", 7.62mm)
Control featuresFrequency Control
Output configurationPositive, Isolation Capable
Synchronous rectifierNo

Product details

Current-mode PWM controller for flyback and boost converters

The UC3844BNST: It delivers a single transistor-driver output with a maximum duty cycle of 48% — the key parametric that distinguishes it from the UC3842 (96%) and UC3843 (100%) siblings. Switching frequency runs up to 500 kHz, letting the designer shrink the transformer core while trading off switching losses.

48% duty cycle — the flyback transformer constraint

The 48% duty cycle ceiling is hard: the controller blanks the output for the remaining 52% of each cycle. In a flyback converter this sets the volt-second balance across the primary inductance and determines the turns ratio for a given input and output voltage. A design that needs more than 48% on-time must move to the UC3842 (96% max) or UC3843 (100% max) — same pinout, different duty-cycle limit.

Sourcing an obsolete controller — what to expect

Sourcing runs through independent distribution — sealed reels with consistent date-codes are the preferred lot, not mixed-date auction stock.

Frequently asked questions

How can I order the UC3844BNST or check current availability?

The UC3844BNST is obsolete, so standard distributor stock is depleted. Submit a request with your target quantity and we will confirm availability and pricing at quote time.

What is the maximum duty cycle of the UC3844BNST?

The maximum duty cycle is 48%, which limits the on-time in flyback and boost converters. This is the defining difference from the UC3842 (96%) and UC3843 (100%) controllers.

Can the UC3842 replace the UC3844BNST?

The UC3842 is pin-compatible and has a 96% maximum duty cycle, so it can replace the UC3844BNST in most flyback designs. However, the higher duty cycle may require re-evaluating the transformer turns ratio and the soft-start timing to avoid core saturation on startup.