Datasheet

LED5000 Application notes - buck conversion
Doc ID 023951 Rev 1 15/51
Figure 7. Transconductance embedded error amplifier
R
C
and C
C
introduce a pole and a zero in the open loop gain. C
P
does not significantly affect
system stability but it can be useful to reduce the noise at the output of the error amplifier.
The transfer function of the error amplifier and its compensation network is:
Equation 8
Where A
vo
= G
m
· R
o
The poles of this transfer function are (if C
c
>> C
0
+C
P
):
Equation 9
Equation 10
whereas the zero is defined as:
Equation 11
AM13491v1
+
-
C
P
R
C
C
C
FB
COMP
dV
R
0
G
m
dV
V
+
E/A
R
C
C
C
C
P
C
0
A
0
s()
A
V0
1s+ R
c
C
c
⋅⋅()⋅
s
2
R
0
C
0
C
p
+()R
c
C
c
sR
0
C
c
⋅ R
0
C
0
C
p
+()R
c
C
c
⋅+⋅+()1+⋅+⋅⋅ ⋅⋅
---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------=
f
P LF
1
2 π R
0
C
c
⋅⋅ ⋅
------------------------------------------=
f
P HF
1
2 π R
c
C
0
C
p
+()⋅⋅ ⋅
------------------------------------------------------------=
F
Z
1
2 π R
c
C
c
⋅⋅ ⋅
------------------------------------------=