UC2842B/3B/4B/5B - UC3842B/3B/4B/5B
Figure 1:
Open Loop Test Circuit.
V
REF
4.7KΩ
2N2222
100KΩ
ERROR AMP.
ADJUST
4.7KΩ
COMP
V
FB
1KΩ
I
SENSE
ADJUST
5KΩ
I
SENSE
R
T
/C
T
R
T
V
REF
1
2
8
7
V
i
0.1µF
OUTPUT
GROUND
1W
1KΩ
OUTPUT
A
0.1µF
V
i
UC2842B
3
4
6
5
C
T
D95IN343
GROUND
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
5 KΩ potentiometerareusedto samplethe oscillator
waveform and apply an adjustable ramp to pin 3.
Figure 2:
Timing Resistor vs. Oscillator Fre-
quency
RT
(KΩ)
50
C
T
=
D95IN333
Figure 3:
Output Dead-Time vs. Oscillator Fre-
quency
D95IN334
%
20
0p
F
C
50
10
0p
F
T
=
C
C
T
=2nF
30
C
T
=5nF
20
C
T
=1nF
C
T
=10nF
10
C
T
=500pF
T
=
20
C
T
=5nF
C
50
0p
F
T
=
1n
F
10
5
C
T
=2nF
C
T
=10nF
C
T
=200pF
5
C
T
=100pF
3
2
V
i
=15V
T
A
=25°C
1
20K
30K
50K
100K
200K
300K
500K
f
OSC
(KHz)
10K
2
V
i
=15V
T
A
=25°C
1
0.8
10K
20K
30K
50K
100K
200K
300K
500K fOSC(KHz)
5/15
STMICROELECTRONICS [ STMICROELECTRONICS ]
