21/26

L6996

With our parameter:

Eq 25

Eq 26

3.8 Input divider

The input divider can be selected with the Eq1, Eq2, Eq3 . Choosing a switching frequency around 270kHz it

results:

αOSC = 0.048.

R1 = 560K

Ω

R2 = 27K

Ω

3.9 Current limit resistor

From the Eq12 it can be set the current limit resistor, for the positive current limit; it results:

R10 + R11 = 120K

Ω

The negative current limit is set by the time available for the negative dynamic transition; a value around 30K

Ω

for R10 is a match between negative peak current and time to end the dynamic transition (around 80mS).

R10=150KW

R11=30KW

3.10 Softstart capacitor

The soft start capacitor is selected once the soft start time is imposed. It can be consider a soft start time around

1ms. The soft start capacitor is given by:

Eq 27

Where

R

VP3

V

OUT I

,

0

=

V

PRO G

–

I

O F FSET

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

1

R

VP2

R

VP1

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

1

+

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

=

C

VP3

ESRC

OU T

C

OUT

⋅

R

VP 3

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

=

C

SS

I

lim

T

∆

⋅

V

ss

∆

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

=