UCC2808-1, UCC2808-2, UCC3808-1, UCC3808-2

LOW POWER CURRENT MODE PUSH-PULL PWM

SLUS168D – APRIL 1999 – REVISED AUGUST 2002

1

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Configuration

Bandwidth Product

Peak Source Current, 1-A Peak Sink Current

description

The UCC3808 is a family of BiCMOS push-pull, high-speed, low-power, pulse-width modulators. The UCC3808

contains all of the control and drive circuitry required for off-line or dc-to-dc fixed frequency current-mode switching

power supplies with minimal external parts count.

The UCC3808 dual output drive stages are arranged in a push-pull configuration. Both outputs switch at half the

oscillator frequency using a toggle flip-flop. The dead time between the two outputs is typically 60 ns to 200 ns

depending on the values of the timing capacitor and resistors, thus limiting each output stage duty cycle to less than

50%. (continued)

block diagram

UDG-02116

3

1

2

8

7

6

5

4

OSCILLATOR

S

Q

R

RC

1.2R

R

0.5 V

PEAK CURRENT

COMPARATOR

Q

Q

T

S

Q

R

S

Q

R

VDD

VOLTAGE

REFERENCE

14 V

PWM

COMPARATOR

PWM

LATCH

SOFT START

0.5 V

VDD–1 V

0.75 V

2.2 V

2.0 V

FB

COMP

CS

VDD

OUTA

OUTB

GND

SLOPE = 1 V/ms

VDD OK

OVERCURRENT

COMPARATOR

22 k

Note: Pinout shown is for SOIC and PDIP packages. TSSOP pinout is different.

Ω

Copyright

 2002, 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.

1

2

3

4

8

7

6

5

COMP

FB

CS

RC

VDD

OUTA

OUTB

GND

D OR N PACKAGE

(TOP VIEW)

1

2

3

4

8

7

6

5

PW PACKAGE

(TOP VIEW)

OUTB

GND

RC

CS

OUTA

VDD

COMP

FB