Datasheet

AN4164 Feedback loop calculation guidelines
Doc ID 023660 Rev 1 25/38
At this point the bode diagram of G1(f)*C(f) can be plotted, in order to check the phase
margin for the stability. If the margin is not high enough, another choice for fZc, fPc and
fcross_sel should be made, and the procedure repeated. When the stability is ensured, the
next step is to find the values of the schematic components, which can be calculated, using
the above formulas, as follows:
Equation 10
Equation 11
Equation 12
Equation 13
1
3.3
−
=
V
Vout
RfbH
RfbL
Rf bHRf bL
Rf bL
C
Gm
fPc
fZc
Cp
+
⋅⋅=
0
⎟
⎟
⎠
⎞
⎜
⎜
⎝
⎛
−⋅= 1
fZ c
fPc
CpCc
CpCcfP c
CpCc
Rc
⋅⋅⋅⋅
+
=
π 2