CURRENT MODE PWM CONTROLLER

DESCRIPTION

The UTC UC3849 is a highly integrated low cost current mode

PWM controller.

The PWM switching frequency can be programmed at normal

operation externally and trimmed to tight range. The circuit works in

extended ‘burst mode’ under no load or light load condition, which

aims at minimizing switching loss. This can achieve lower standby

power and higher conversion efficiency.

With a low startup current, the UTC UC3849 could use a large

value start-up resistor. Built-in slope compensation enhances the

stability of the system. Leading-edge blanking on sense input

removes the signal glitch due to snubber circuit diode reverse

recovery.

The UTC UC3849 includes protection function like: OCP

(Cycle-by-Cycle current limiting), OLP (over load protection), UVLO

(under voltage lockout). The OCP threshold compensation is

internally-designed to reach constant output power. With UTC

advanced frequency shuffing technique, EMI performance is greatly

improved.

It has such application as laptop/power adaptor, PC/TV/set-top

box power supplies, open-frame SMPS, battery charge and so on.

SOP-8

FEATURES

* Low VIN/VDD Startup Current: 3.5μA

* Low Operating Current: 0.8mA

* Under Voltage Lockout (UVLO)

* Burst Mode Control for Improved Efficiency

* Minimum Standby Power Design

* Audio Noise Free Operation

* Programmable PWM Frequency

* Built-in Synchronized Slope Compensation

* Leading Edge Blanking on Sense Input

* Complete Protection Coverage with Auto Self-Recovery

- External Programmable over Temperature Protection (OTP)

- With or Without On-chip VDD OVP for System OVP

- Under Voltage Lockout with Hysteresis (UVLO)

- Gate Output Maximum Voltage Clamp (16V)

- Line Compensated Cycle-by-Cycle Over-Current Threshold Setting For Constant Output Current Limiting Over

Universal Input Voltage Range (OCP)

- Over Load Protection. (OLP)