MB3782PF FUJITSU [Fujitsu Component Limited.], MB3782PF Datasheet - Page 22

• Manufacturer Part Number: MB3782PF
• Description: ASSP Power Supplies BIPOLAR Switching Regulator Controller
• Manufacturer: FUJITSU [Fujitsu Component Limited.]

22
MB3782
APPLICATIONS
• Concerning Equivalent Series Resistance and Stability of Smoothing Capacitors
In DC/DC converters, the equivalent series resistance value (ESR) of smoothing capacitors has a major influence
on loop phase characteristics.
The ESR is a means by which phase characteristics approximate phase relationships to ideal capacitors in high-
frequency bands (see Graph 1), thus improving system stability. At the same time, the use of smoothing capacitors
with low ESR reduces system stability, so that care must be taken when using semiconductor electrolytic ca-
pacitors (OS capacitors) or tantalum capacitors with low ESR.
– 20
– 40
– 60
20
0
10
1 : Rc = 0
2
: Rc = 31 m
V
100
IN
Frequency vs.Gain
Frequency f (Hz)
Figure 7 Basic circuit for step-down voltage DC/DC converter
1 k
Tr
Graph 1
10 k
1
2
D
100 k
Frequency vs. gain and phase
L
– 180
– 90
0
10
1 : Rc = 0
2
: Rc = 31 m
C
Rc
100
Frequency vs.phase
Frequency f (Hz)
1 k
R
L
10 k
1
2
100 k