PM6670AS View Datasheet(PDF) - STMicroelectronics
Part Name
Description
MFG CO.
'PM6670AS' PDF : 54 Pages View PDF
PM6670AS
Device description
Equation 14
RTOT = ESR + RVESR
Moreover, the CINT capacitor must meet the following condition:
Equation 15
fSW
>
k ⋅ fZ
=
k
2π ⋅ Cout
⋅ RTOT
where RTOT is the sum of the ESR of the output capacitor and the equivalent ESR given by
the Virtual-ESR Network (RVESR). The k parameter must be greater than unity (k > 3) and
determines the minimum integrator capacitor value CINT:
Equation 16
CINT
>
2π ⋅ ⎜⎛
⎝
gm
fSW
k
− fZ
⎟⎞
⎠
⋅
Vr
Vout
The capacitor of the Virtual-ESR Network, C, is chosen as follows:
Equation 17
C > 5 ⋅ CINT
and R is calculated to provide the desired triangular ripple voltage:
Equation 18
R= L
RVESR ⋅ C
Finally the R1 resistor is calculated according to expression 19:
Equation 19
R1 =
R
⋅
⎜⎜⎝⎛
C
⋅
1
π⋅
fZ
⎟⎟⎠⎞
R− 1
C ⋅ π ⋅ fZ
Doc ID 14436 Rev 2
27/53
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