Figure 1: Open Loop Test Circuit.

A

2N2222

4.7K

Ω

1K

Ω

ERROR AMP.

ADJUST

4.7K

Ω

5K

Ω

ADJUST

100K

Ω

COMP

V

FB

1

2

3

4

C

T

7

6

5

8

V

i

OUTPUT

GROUND

0.1

µF

0.1

µF

V

i

OUTPUT

GROUND

1W

1K

Ω

D95IN343

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

Ω potentiometerareusedto samplethe oscillator

waveform and apply an adjustable ramp to pin 3.

10K

20K

30K

50K

100K

200K

300K

500K

fOSC(KHz)

1

2

5

10

20

50

D95IN333

C

C

C

C

RT

(K

Ω)

0.8

Figure 2: Timing Resistor vs. Oscillator Fre-

quency

10K

20K

30K

50K

100K

200K

300K

500K

fOSC(KHz)

1

2

3

5

10

20

30

50

%

D95IN334

Figure 3: Output Dead-Time vs. Oscillator Fre-

quency

UC2842B

UC2842B/3B/4B/5B - UC3842B/3B/4B/5B

5/15