a5975d STMicroelectronics, a5975d Datasheet - Page 19

• Manufacturer Part Number: a5975d
• Description: Up To 3 A Step-down Switching Regulator For Automotive Applications
• Manufacturer: STMicroelectronics

A5975D
7
7.1
Closing the loop
Figure 9.
Error amplifier and compensation network
The output LC filter of a step-down converter contributes with 180-degree phase shift in the
control loop. For this reason a compensation network between the COMP pin and GROUND
is added. The simplest compensation network, together with the equivalent circuit of the
error amplifier, are shown in
loop gain. CP does not significantly affect system stability but it is useful to reduce the noise
of the COMP pin.
The transfer function of the error amplifier and its compensation network is:
Equation 2
where A
vo
A
0
= G
s ( )
Block diagram of the loop
m
=
· R
---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- -
s
2
⋅
o
.
R
0
⋅
(
C
0
+
Figure
Doc ID 018760 Rev 1
C
p
) R
⋅
10. R
c
⋅
C
A
c
V0
C
+
and C
s
⋅
(
⋅
1
(
R
+
0
s
C
⋅
⋅
C
R
introduce a pole and a zero in the open
c
c
+
⋅
C
R
c
0
)
⋅
(
C
0
+
C
p
)
+
R
c
⋅
C
Closing the loop
c
)
+
1
19/50