MB3817_03 Datasheet, PDF (25/28 Pages) Fujitsu Component Limited. – Switching Regulator Controller

MB3817
Reference data
In an aluminum electrolytic smoothing capacitor (RC =: 1.0 Ω) is replaced with a low ESR electrolytic capacitor
(OS-CON^TM : RC =: 0.2 Ω) , the phase margin is reduced by half (see Fig. 37 and 38) .
Figure 36 DC/DC Converter AV vs. φ characteristic Test Circuit
VOUT
VO+
CNF
AV vs. φ characteristic
Between this point
−IN
−
VIN
FB
+IN
R2
+
R1
60
40
20
0
−20
−40
10
60
40
20
0
−20
−40
10
Error Amp.
VREF/2
Figure 37 DC/DC Converter +5 V output Gain vs. Phase
VCC = 10 V
RL = 25 Ω
CP = 0.1 µF
180
AV
φ
90
62°
0
−90
VO+
+
AI Condenser
220 µF (16 V)
− _{RC ≅ 1.0 Ω : fOSC = 1 kHz}
GND
100
1k
10 k
Frequency f (Hz)
−180
100 k
Figure 38 DC/DC Converter +5 V output Gain vs. Phase
AV
VCC = 10 V
RL = 25 Ω
CP = 0.1 µF
180
VO+
90
φ
27°
0
+
OS-CON^TM
−
22 µF (16 V)
RC ≅ 0.2 Ω : fOSC = 1 kHz
−90
GND
100
1k
10 k
Frequency f (Hz)
−180
100 k
25