MB3817 Fujitsu Microelectronics, Inc., MB3817 Datasheet - Page 24

• Manufacturer Part Number: MB3817
• Description: Switching Regulator Controller
• Manufacturer: Fujitsu Microelectronics, Inc.

24
MB3817
1. Equivalent series resistance and stability of smoothing capacitor
Note : OS-CON is the trademark of Sanyo Electric Co.,Ltd.
APPLICATION
The equivalent series resistance (ESR) of the smoothing capacitor in the DC/DC converter greatly affects the
loop phase characteristic.
A smoothing capacitor with a high ESR improves system stability because the phase is advanced into the high-
frequency range of an ideal capacitor (see Fig. 34 and 35) . A smoothing capacitor with a low ESR reduces
system stability. Use care when using low ESR electrolytic capacitors (OS-CON
20
20
40
60
0
10
Figure 34 Gain vs. Frequency
(1) : R
(2) : R
C
C
V
100
IN
0
31 m
Frequency f (Hz)
1 k
Figure 33 DC/DC Converter Basic Circuit
Tr
10 k
(1)
D
(2)
100 k
L
180
90
0
10
Figure 35 Phase vs. Frequency
(1) : R
(2) : R
C
C
C
R
100
C
0
31 m
Frequency f (Hz)
TM
) and tantalum capacitors.
1 k
R
L
10 k
(1)
(2)
100 k