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MB3782_1 Datasheet, PDF (23/27 Pages) Fujitsu Component Limited. – ASSP Power Supplies BIPOLAR Switching Regulator Controller | |||
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MB3782
⢠Reference data
Changing the smoothing capacitor from an aluminum electrolytic capacitor (RC â
1.0â¦) to a lower-ESR semi-
conductor electrolytic capacitor (OS capacitor: RC â
0.2 â¦) decreases the phase margin (see Graphs 2, 3).
V out
V0 +
CNF
AV and phase characteristics
measured between these points
â IN
FB
â
+ IN
+
VIN
R2
R1
VREF/2
Error amp
Figure 8 Measurement of DC/DC Capacitor AV and Phase (Ψ) Characteristics
Graph 2
DC/DC converter + 5 V output frequency vs.gain and phase
60
40
Av
20
Vcc = 10 v
RL = 25 â¦
Cp = 0.1 µF 180
Ï
90
62°
0
0
â 20
â 90
â 40
â 180
10
100
1k
10 k
100 k
Frequency f (Hz)
Graph 3
DC/DC converter + 5 V output frequency vs.gain and phase
60
Av
40
Vcc = 10 v
RL = 25 â¦
Cp = 0.1 µF
180
20
90
Ï
0
0
27°
â 20
â 90
â 40
10
100
1k
10 k
Frequency f (Hz)
â 180
100 k
V0 +
Aluminum electrolytic
+ capacitor
â 220 µF (16 V)
RC â
1.0 â¦
: fosc = 1 kHz
+ OS capacitor
â 22 µF (16 V)
RC â
0.2 â¦
: fosc = 1 kHz
23
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