MB3785A_03 Datasheet, PDF (26/30 Pages) Fujitsu Component Limited. – Switching Regulator Controller (4 Channels plus High-Precision, High-Frequency Capabilities)

MB3785A
Reference data
If 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. 17 and 18).
DC/DC Converter AV vs. φ characteristic Test Circuit
VOUT
VO⁺
CNF
AV vs. φ characteristic
Between these points
−IN
FB
VIN
+IN
R2
R1
VREF/2
Error Amp.
60
40
20
0
−20
−40
10
60
40
20
0
−20
−40
10
26
Figure 17 DC/DC Converter +5 V output Gain vs. Phase
AV
100
VCC = 10 V
RL = 25 Ω
CP = 0.1 µF
180
φ
90
62 °
0
−90
−180
1k
10 k
100 k
VO⁺
AI Capacitor
+
220 µF (16 V)
− _{RC ≅ 1.0 Ω : fOSC = 1 kHz}
GND
Figure 18 DC/DC Converter +5 V output Gain vs. Phase
VCC = 10 V
AV
RL = 25 Ω
CP = 0.1 µF
180
90
φ
27 °
0
−90
100
1k
10 k
Frequency f (Hz)
−180
100 k
VO⁺
OS-CON^TM
+
22 µF (16 V)
− _{RC ≅ 0.2 Ω : fOSC = 1 kHz}
GND