UCC15701/2

UCC25701/2

UCC35701/2

Advanced Voltage Mode Pulse Width Modulator

DESCRIPTION

The UCC35701/UCC35702 family of pulse width modulators is intended for

isolated switching power supplies using primary side control. They can be

used for both off-line applications and DC/DC converter designs such as in

a distributed power system architecture or as a telecom power source.

The devices feature low startup current, allowing for efficient off-line start-

ing, yet have sufficient output drive to switch power MOSFETs in excess of

500kHz.

Voltage feed forward compensation is operational over a 5:1 input range

and provides fast and accurate response to input voltage changes over a

4:1 range. An accurate volt-second clamp and maximum duty cycle limit

are also featured.

Fault protection is provided by pulse by pulse current limiting as well as the

ability to latch off after a programmable number of repetitive faults has oc-

curred.

Two UVLO options are offered. UCC35701 family has turn-on and turn-off

thresholds of 13V/9V and UCC35702 family has thresholds of 9.6V/8.8V.

The UCC35701/2 and the UCC25701/2 are offered in the 14 pin SOIC (D),

14 pin PDIP (N) or in 14 pin TSSOP (PW) packages. The UCC15701/2 is

offered in the 14 pin CDIP (J) package.

3

VDD

12

VREF

8FB

4

OUT

2

ILIM

5

PGND

C3

1

COUNT

14

SS

11

SYNC

9VSCLAMP

VREF

10

CT

7RT

6

VFF

13

GND

RGND

R10

RCS

R8

R7

R6

C2

R8

R5

R4

R3

R2

R1

UCC35701

C1

C4

C6

R12

C6

C5

R11

R13

C7

R14

R15

TYPICAL APPLICATION DIAGRAM

SLUS293C - JANUARY 2000 - REVISED JUNE 2005

FEATURES

700kHz Operation

Integrated Oscillator/ Voltage Feed

Forward Compensation

Accurate Duty Cycle Limit

Accurate Volt-second Clamp

Optocoupler Interface

Fault Counting Shutdown

Fault Latch off or Automatic Shutdown

Soft Stop Optimized for Synchronous

Rectification

1A Peak Gate Drive Output

130

mA Start-up Current

750

mA Operating Current

UDG-98005-1

application

INFO

available