DocID8827 Rev 3

13/30

AN1517

Closing the loop

30

Equation 7

The zero of this transfer function is given by:

Equation 8

increase the phase margin of the loop.

The poles of the transfer function can be calculated through the following expression:

Equation 9

Equation 10

If the damping coefficient

 is very close to zero, the roots of the equation become a double

root whose value is

Equation 11

4.3

PWM comparator

The PWM gain is given by the following formula:

Equation 12

minimum value. A voltage feed-forward is implemented to ensure a constant GPWM. This is





s



+



s

2



s1

+



+



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

=

1

2





ESR





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

=

FPLC1 2



ESR COUT

ESR COUT





2

4L



COUT



–





–

2L



COUT



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

=

s

2

2





n



s



2

n

+



+

1

2









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

=



–



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

=