SLUS390 - MARCH 1998

FEATURES

•

Compatible with Voltage or Current

Mode Control Methods

•

Practical Operation at Switching

Frequencies to 4MHz

•

50ns Propagation Delay to Output

•

High Current Complementary

Outputs

•

Programmable Dead Time and

Frequency Oscillator

•

Pulse by Pulse Current Limiting

•

Latched Overcurrent Comparator

with Full Cycle Restart

•

Programmable Undervoltage

Lockout (UVLO)

•

Adjustable Blanking for Leading

Edge Noise Tolerance

High Speed PWM Controller

UDG-98043

UCC1829-1/-2/-3

UCC2829-1/-2/-3

UCC3829-1/-2/-3

PRELIMINARY

DESCRIPTION

The UCC3829 is a BiCMOS High Speed PWM Controller IC. It is opti-

mized for high frequency switched mode power supply applications. The

IC can be used in both voltage mode and current mode control applica-

tions. Care was given to minimizing the propagation delays through the

comparators and logic circuitry while maximizing the bandwidth and slew

rate of the error amplifier. The oscillator frequency and deadtime can be

programmed via two external resistors and a capacitor. The undervolt-

age lockout threshold can be programmed using an external resistor di-

vider. The current limit and overcurrent threshold can be set externally.

The IC is available in push-pull (-1), single ended (-2), or complementary

(-3) output configuration.

Fault protection circuitry includes undervoltage detection for the internal

bias supply, and overcurrent detection. The fault detection logic sets a

latch that ensures full discharge of the soft start capacitor before allowing

a restart. While the fault latch is set, the outputs are in a low state. In the

event of continuous faults, the soft start capacitor is fully charged before

discharging to insure that the fault frequency does not exceed the de-

signed soft start period.

15

13

18

14

18

VDD

PGND

OUTA

OUTB

GND

10

SS

S

R

D

Q

Q

1V

2

INV

1

NINV

V

BIAS

3

EAOUT

5

RAMP

4

19

LEB

1.5V

1.2V

4V

6

RT2

7

CT

CLOCK

V

BIAS

8

RT1

9

BISYNC

S

R

Q

Q

T

>

Q

Q

V

BIAS

1.25V

0.9V

3V

REFERENCE

11

23

17

VREF

CL–

UVLO

2.1V

3V/2.5V

14.2V/9V

12

CL+

PWCONT

BLOCK DIAGRAM