UNISONIC TECHNOLOGIES CO., LTD

UC3856

Preliminary

LINEAR INTEGRATED CIRCUIT

www.unisonic.com.tw

1 of 9

Copyright © 2014 Unisonic Technologies Co., Ltd

Qw-R103-077.a

LOW COST POWER-SAVING

MODE PWM CONTROLLER

FOR FLYBACK CONVERTERS



DESCRIPTION

The UTC UC3856 is a high performance current mode PWM

controller ideally suited for low standby power. An externally

JFET’s gate pin is connected the ST pin, It can achieve HV start,

and when start was overed, it is no long consume current to

reliable on startup 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 power-saving mode for lower standby

power, decreasing frequency for Higher conversion efficiency at

light load condition.

The UTC UC3856 contains protection with automatic recovery

including OLP (over load protection), OTP (over temperature

the power MOSFET, Gate-drive output is fixed up to 15V max. The UTC UC3856 contains protection OCP

(cycle-by-cycle current limiting).

The internal slope compensation improves system stability at high PWM duty cycle output. Leading-edge

blanking on current sense input removes the signal glitch, which offering minimal external component count in the

design. Excellent EMI performance is achieved with UTC proprietary frequency hopping technique

(ZL201020615247.1) together with soft driver control. Audio noise is eliminated due to switch frequency more than

20kHz during operation.

The UTC UC3856 has such applications as: battery charger, power adaptor, set-top box power supplies, ink jet

printers, open-frame SMPS.



FEATURES

* UTC proprietary frequency hopping technology for

Improved EMI performance.

* Power-saving mode for high light-load and standby

efficiency

* Dynamic peak current limiting for constant output power

* Built-in synchronized slope compensation

* High efficiency HV start

* Gate output voltage clamped at 15V

* Low start-up current

* Cycle-by-cycle current limiting

* Under voltage lockout (UVLO)

* Few external components required

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ORDERING INFORMATION

Ordering Number

Package

Packing

Lead Free

Halogen Free

UC3856L-AG6-R

UC3856G-AG6-R

SOT-26

Tape Reel