L6996 View Datasheet(PDF) - STMicroelectronics
Part Name
Description
MFG CO.
'L6996' PDF : 26 Pages View PDF
L6996
With our parameter:
CVP1 = 7.8pF
No-load offset is obtained by RVP3 and of a current source internally connected to VFB+ pin. Thus:
Eq 25
RVP3 = V-----O----U----T---I,-O-I---=-F---F0---S--–--E--V--T--P----R----O----G-- --R--------V--------P----1--2------+-----1-
RVP1
where IOFFSET = 5µA.
The capacitor CVP3 in parallel to RVP3 is a filter which time constant can be the same as in Eq22, so
Eq 26
CVP3 = E-----S----R-----C----R-O---V-U---P-T---3-⋅---C-----O----U----T-
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 = 560KΩ
R2 = 27KΩ
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 = 120KΩ
The negative current limit is set by the time available for the negative dynamic transition; a value around 30KΩ
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
CSS = I--l--i∆-m---V---⋅-s--∆-s--T---
Where ∆VSS is the soft start active range and ∆T is the soft stat time. From Eq 28 results: CSS = 10nF.
21/26
Share Link: 
