Datasheet

Closing the loop ST1S14
18/46 DocID17977 Rev 2
Equation 7
6.2 Error amplifier compensation network
The ST1S14 embeds the error amplifier (see Figure 10) and a pre-defined compensation
network which is effective in stabilizing the system in most of the application conditions.
Figure 10. 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 is 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
Q
P
1
π m
C
1D–()0.5–⋅[]⋅
--------------------------------------------------------------- -=


#
0
2
#
#
#
&"
#/-0
6
2

'
M
6
6

%!
2
#
#
#
#
0
#

$09
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
⋅⋅ ⋅
------------------------------------------=