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MB3778 Datasheet, PDF (23/29 Pages) Fujitsu Component Limited. – Switching Regulator Controller | |||
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MB3778
s APPLICATION
1. Equivalent series resistor and stability of smoothing capacitor
The equivalent series resistor (ESR) of the smoothing capacitor in the DC/DC converter greatly affects the loop
phase characteristic.
The stability of the system is improved so that the phase characteristic may advance the phase to the ideal
capacitor by ESR in the high frequency region (see âGain vs. Frequencyâ and âPhase vs. Frequencyâ).
A smoothing capacitor with a low ESR reduces system stability. Use care when using low ESR electrolytic
capacitors (OS CONTM) and tantalum capacitors.
Note: OS CON is the trademark of Sanyo Electnic Co., Ltd.
DC/DC Converter Basic Circuit
Tr
L
RC
VIN
D
RL
C
Gain vs. Frequency
20
0
â20
(2)
â40
(1) : RC = 0 â¦
(2) : RC = 31 mâ¦
(1)
â60
10
100
1k
10 k
Frequency f (Hz)
100 k
Phase vs. Frequency
0
(2)
â90
(1) : RC = 0 â¦
(1)
(2) : RC = 31 mâ¦
â180
10
100
1k
10 k
100 k
Frequency f (Hz)
23
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