L6985F datasheet(37/65 Pages) STMICROELECTRONICS

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L6985F

Closing the loop

Equation 19

Equation 20

where:

Equation 21

Sn represents the on time slope of the sensed inductor current, Se the on time slope of the

external ramp (VPP peak-to-peak amplitude) that implements the slope compensation to

avoid sub-harmonic oscillations at the duty cycle over 50%.

Se can be calculated from the parameter VPP × gCS given in Table 5 on page 8.

The sampling effect contribution FH(s) is:

Equation 22

where:

Equation 23



ESR COUT



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



RLOAD COUT



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

mc 1D

–





0.5

–

LCOUT fSW



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

------

VPP gCS fSW



VIN VOUT

–

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







FH s







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



---------

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



mc 1D

–

 0.5

–







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

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