AN628 APPLICATION NOTE

8/35

where:

and rewritten as:

Figure 9.

Figure 10.

defines the high frequency C/A gain (1 +

):

To define the Cf value, it's useful to consider the current openloop gain, defined by the ratio between the voltage

across Rs and the current amplifier output signal:

G

ca

V

srp

f

sw

L

⋅⋅

V

O

R

s

⋅

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

≤

Ri'

Ri

Cf

Rf

Rs

OSC

C/A

+

-

PWM

5

9

8

CA OUT

D94IN063

R

f

R

i

-----

R

f

R

i

-----

V

srp

f

sw

L

⋅⋅

V

O

R

S

⋅

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

1

–

≤

G

avg

v

rs

v

ca

--------

=