UCC25705, UCC25706, UCC35705, UCC35706

HIGHSPEED VOLTAGE MODE PULSE WIDTH MODULATOR

SLUS473A – NOVEMBER 1999 – REVISED MARCH 2001

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Compensation

Package Minimizes Board Area and Height

description

The UCC35705 and UCC35706 devices are 8-pin voltage mode primary side controllers with fast over-current

protection. These devices are used as core high-speed building blocks in high performance isolated and non-isolated

power converters.

UCC35705/UCC35706 devices feature a high speed oscillator with integrated feed-forward compensation for

improved converter performance. A typical current sense to output delay time of 25 ns provides fast response to

overload conditions. The IC also provides an accurate programmable maximum duty cycle clamp for increased

protection which can also be disabled for the oscillator to run at maximum possible duty cycle.

Two UVLO options are offered. The UCC35705 with lower turn-on voltage is intended for dc-to-dc converters while

the higher turn-on voltage and the wider UVLO range of the UCC35706 is better suited for offline applications.

The UCC35705/UCC35706 family is offered in 8-pin MSOP (DGK), SOIC (D) and PDIP (P) packages.

typical application schematic

UDG-99181

VDD

OUT

GND

RC

ILIM

VFF

DISCH

UCC35705/6

+

–

+

V

IN

SOFT

START

CIRCUIT

4

5

3

6

8

7

1

TPS2829

–

FB

2

MODE = 1

FET DRIVER

Copyright

 2001, Texas Instruments Incorporated

PRODUCTION DATA information is current as of publication date.

Products conform to specifications per the terms of Texas Instruments

standard warranty. Production processing does not necessarily include

testing of all parameters.

Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of

Texas Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet.

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2

3

4

8

7

6

5

ILIM

FB

VFF

DISCH

VDD

OUT

GND

RC

D, OR P PACKAGE

(TOP VIEW)

ILIM

2

1

4

3

7

8

5

6

FB

VFF

DISCH

VDD

OUT

GND

RC

DGK PACKAGE

(TOP VIEW)