APPLICATION INFORMATION

Oscillator Frequency vs Timing Resistance

Maximum Duty Cycle vs Timing Resistor

V

REF

V

CC

OUTPUT

GND

C

T

1 kW 1 W

0.1 µF

0.1 µF

R

T

2N2222

5 k

I

Adjust

W

SENSE

4.7 kW

4.7 kW

1 k

Error Amp

Adjust

W

COMP

UC2843A

V

FB

I

SENSE

R /C

T

T

GND

OUTPUT

V

CC

V

REF

100 kW

1

2

3

4

5

6

7

8

UC2843A-Q1

Figure 6. Oscillator

A.

High peak currents associated with capacitive loads necessitate careful grounding techniques. Timing and bypass

capacitors should be connected close to pin 5 in a single point ground. The transistor and 5k potentiometer are used

to sample the oscillator waveform and apply an adjustable ramp to pin 3.

Figure 7. Open-Loop Laboratory Text Fixture

Copyright © 2008, Texas Instruments Incorporated

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Product Folder Link(s): UC2843A-Q1