UC384XA - UC284XA
Figure 4. 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
3
4
8
7
V
i
0.1µF
6
5
OUTPUT
GROUND
1W
1KΩ
OUTPUT
A
0.1µF
V
i
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
potentiometer are used to sample the oscillator waveform and apply an adjustable ramp to pin 3.
Figure 5. Oscillator Frequency vs Timing
Resistance
f
o
(Hz)
D96IN362
Figure 7. Oscillator Discharge Current vs.
Temperature.
I
dischg
(mA)
D95IN335
V
i
=15V
V
OSC
=2V
1M
CT
=4
70
pF
1nF
8.5
100K
2.2
nF
4.7
nF
8.0
10K
7.5
1K
300
1K
3K
10K
30K
R
T
(Ω)
7.0
-55
-25
0
25
50
75
100 T
A
(˚C)
Figure 6. Maximum Duty Cycle vs Timing
Resistor
f
o
(Hz)
D96IN363
Figure 8. Error Amp Open-Loop Gain and
Phase vs. Frequency.
(dB)
80
D95IN337
φ
30
60
90
120
150
80
Gain
60
V
i
=15V
V
O
=2V to 4V
R
L
=100K
T
A
=25˚C
60
40
40
Phase
20
20
0
-20
10
0
300
1K
3K
10K
30K
R
T
(Ω)
100
1K
10K
100K
1M
180
f(Hz)
5/16
STMICROELECTRONICS [ STMICROELECTRONICS ]
