UCC28083, UCC28084, UCC28085, UCC28086

UCC38083, UCC38084, UCC38085, UCC38086

SLUS488E − SEPTEMBER 2002 − REVISED JULY 2009

5

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functional block diagram

UDG−01081

Q

Q

T

+

8

2

3

4

7

6

5

1

CTRL

VDD

CS

ISET

GND

RT

OUTA

OUTB

0.75V

0.5V

1.5V

0.2V

SQ

R

SQ

R

0.5V

Vdd−1

VREF

SQ

R

ISLOPE

Css

Iss

SQ

R

Soft Start and Fault Latch

PWM Comparator/Latch

Output Driver

Oscillator

CS Circuitry

Slope Circuit

Bias/UVLO

ISLOPE =

5 x I SET

ICT

CT

1.5V

CT

80 k

Ω

60 k

Ω

0.3 V

Terminal Functions

TERMINAL

NAME

PACKAGE

I/O

DESCRIPTION

NAME

D OR P

I/O

DESCRIPTION

CS

3

I

The current-sense input to the PWM comparator, the cycle-by-cycle peak current comparator, and the

overcurrent comparator. The overcurrent comparator is only intended for fault sensing. Exceeding the

overcurrent threshold causes a soft-start cycle. An internal MOSFET discharges the current-sense filter

capacitor to improve dynamic performance of the power converter.

CTRL

1

I

Error voltage input to PWM comparator.

GND

5

−

Reference ground and power ground for all functions. Due to high currents, and high-frequency operation

of the IC, a low-impedance circuit board ground plane is highly recommended.

ISET

2

I

Current selection for slope compensation.

OUTA

7

O

Alternating high-current output stages.

OUTB

6

O

Alternating high-current output stages.

RT

4

I

Programs the oscillator.

VDD

8

I

Power input connection.