Техническая Спецификация для STMicroelectronics Evaluation board for A5970AD EVALA5970AD EVALA5970AD

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The output L-C filter of a step-down converter contributes with 180 degrees 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 

C

 and C

C

 introduce a pole and a zero in the 

open 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:

Where A

 = G

m

 · R

o

The poles of this transfer function are (if C

c

 

>> C

0

+C

P

):

A

0

s

 

A

V0

1 s

+

R

c

C

c











s

2

R

0



C

0

C

p

+



 R

c

C

c

s

R

0

C

c



R

0

C

0

C

p

+



 R

c

C

c



+



+



 1

+



+







---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

=

F

P1

1

2





R

0



C

c



-------------------------------------

=

F

P2

1

2





R

c



C

0

C

p

+







--------------------------------------------------------

=