Datasheet

Data Sheet ADP2381
Rev. 0 | Page 19 of 28
• C
CP
is optional, and it can be used to cancel the zero caused
by the ESR of the output capacitors.
C
OUT
ESR
CP
R
CR
C
×
=
Compensation Network Between COMP and FB
The compensation RC network can also be placed between
COMP and FB, as shown in Figure 34.
Figure 34. Small Signal Circuit with Compensation Network Between COMP
and FB
When connecting the compensation network as shown in
Figure 34, it should have the same pole and zero as in Figure 33
to maintain the same compensation performance.
Assuming that the compensation networks of Figure 33 and
Figure 34 have the same pole and zero,
)1)(//)((
)(
)(
)1)(//(
__
____
___
___
__
__
0
m
BOTTOP
EACEACP
EACEACEACEACP
0
CCCCP
0
0
m
BOTTOP
EACPEACEAC
EACPEACEAC
0
CPCC
0
m
EACEACP
EACEACCC
rgRRCC
CRCCr
CRCCr
rgRRCCR
CCRrCCRr
g
CC
CRCR
×++
+++
=++
×+
+=
+
−=
where:
r
0
is the equivalent output impedance of the trans-conductance
amplifier, 40 MΩ.
BOTTOP
BOTTOP
BOTTOP
RR
RR
RR
+
=//
Solve the preceding equations to obtain:
))((
))((
_
_
_
_
ArCRB
CCRr
C
C
CRB
R
ArCRB
CCRr
gBC
0
CC
CPCC
0
EACP
EAC
CC
EAC
0
CC
CPCC
0
m
EAC
++
=
+
=
+
+
−×=
where:
)(1
)(
)1)(//(
0
m
CCP
0
0
m
BOTTOP
rAg
CCr
B
rgRRA
++
+
=
×+=
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R
ESR
R
+
–
g
m
C
OUT
R
TOP
R
BOT
–
+
A
VI
V
OUT
V
COMP
V
OUT
10209-034
ADP2381
GND
COMP
FB
C
CP_EA
R
C_EA
C
C_EA