MB3775 Datasheet, PDF (21/25 Pages) Fujitsu Component Limited. – SWITCHING REGULATOR CONTROLLER

MB3775
3. Measures for ensuring system stability when a low ESR smoothing capacitor is used
(Continued)
(2) As shown in Figure 37, a resistor (RP) is connected between the FB terminal and CP of the error amplifier to advance the phase.
The more RP is increased, the more the phase is advanced. However, the gain in the high-frequency range is also increased,
which causes instability. Therefore, select the optimum resistance (see Fig. 38).
Fig. 37 - External circuit example 2 to advance the phase
V0+
R2
+ IN
+
- IN
-
R1
FB
RP
CP
VREF
Fig. 38 - DC/DC Converter +5 V output
60
40
AV
20
0
-20
-40
10
VCC=10V
RL=25Ω
CP=0.1µF
Smoothing Capacitor
22µF OS-CON
RP=470Ω
R1=1.8kΩ
R2=5.6Ω
100
1K
Frequency f(Hz)
ϕ
45°
10K
180
90
0
-90
-180
100K
21