L5986 View Datasheet(PDF) - STMicroelectronics
Part Name
Description
MFG CO.
'L5986' PDF : 39 Pages View PDF
Application information
Figure 10. Open loop gain: module bode diagram
L5986 - L5986A
The guidelines for positioning the poles and the zeroes and for calculating the component
values can be summarized as follow:
1. Choose a value for R1, usually between 1 k and 5 k.
2. Choose a gain (R4/R1) in order to have the required bandwidth (BW), that means:
Equation 18
R4
=
B-----W----
fLC
⋅
-1--
K
⋅
R1
where K is the feed forward constant and 1/K is equals to 9.
3. Calculate C4 by placing the zero at 50 % of the output filter double pole frequency (fLC):
Equation 19
C4
=
-------------1--------------
π ⋅ R4 ⋅ fLC
4. Calculate C5 by placing the second pole at four times the system bandwidth (BW):
Equation 20
C5 = 2----π-----⋅---R-----4----⋅---C----C4----⋅4---4-----⋅---B----W--------–----1--
5. Set also the first pole at four times the system bandwidth and also the second zero at
the output filter double pole:
20/39
Share Link: 
