UNISONIC TECHNOLOGIES CO., LTD

UB3846

LINEAR INTEGRATED CIRCUIT

www.unisonic.com.tw

1 of 10

Copyright © 2012 Unisonic Technologies Co., Ltd

QW-R103-053.C

LOW COST POWER-SAVING

MODE PWM CONTROLLER

FOR FLYBACK CONVERTERS

DESCRIPTION

The UTC UB3846 is a high performance current mode PWM

controller ideally suited for low standby power and cost effective

off-line flyback converter.

design and a large value resistor could be used in the startup

circuit to minimize the standby power. At no load condition, the

IC operates in burst mode for lower standby power and in

decreasing frequency for higher conversion efficiency at light

load condition. The PWM switching frequency is programmable

externally at normal operation.

The UTC UB3846 contains protection coverage with

automatic self-recovery including OCP (cycle-by-cycle current

voltage clamp and under voltage lockout).To protect the power

MOSFET, Gate-drive output is fixed up to 15V max.

The internal slope compensation improves system stability at

high PWM duty cycle output. Leading-edge blanking on current

sense (CS) input removes the signal glitch that offers minimal

reqnirement of external component and lower system cost.

Excellent EMI performance is achieved by UTC proprietary

frequency hopping technique together with soft driver control.

Audio noise is eliminated because switch frequency is more

than 20kHz during operation.

The UTC UC3846 can be used in the applications, such as

battery charger, power adaptor, set-top box power supplies, ink

jet printers open-frame SMPS

DIP-8

SOT-26

4

5

3

2

1

6

FEATURES

* UTC proprietary frequency hopping technology

for Improved EMI

* Performance.

* Power-saving mode for high light-load efficiency

* Burst mode for minimum standby power

* Dynamic peak current limiting for constant output

power

* Built-in synchronized slope compensation

* Programmable PWM Frequency

* Gate output voltage clamped at 15V

* Low start-up current

* Cycle-by-cycle Current Limiting

* Under voltage lockout (UVLO)

* Few external components required

ORDERING INFORMATION

Ordering Number

Package

Packing

Lead Free

Halogen Free

UB3846L-AG6-R

UB3846G-AG6-R

SOT-26

Tape Reel

UB3846L-D08-T

UB3846G-D08-T

DIP-8

Tube

(1) T: Tube, R: Tape Reel

(2) AG6: SOT-26, D08: DIP-8

(3) G: Halogen Free, L: Lead Free

UB3846L-AG6-R

(1)Packing Type

(2)Package Type

(3)Lead Free