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

9

VSCLAMP

VREF

10

CT

7RT

6

VFF

13

GND

V

V

RGND

R10

RCS

R8

R7

R6

C2

R8

R

F

R5

R4

R3

R2

R1

V

OUT

UCC35701

C1

C4

C6

R12

C6

C5

R11

R13

C7

R14

V

OUT

R15

TYPICAL APPLICATION DIAGRAM

SLUS293A - JANUARY 2000

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

• 130µA Start-up Current

• 750µA Operating Current

UDG-98005-1

application

INFO

available