L6714 datasheet(50/70 Pages) STMICROELECTRONICS

50 / 70 page

Over current protection

L6714

50/70

Over current protection

Depending on the current reading method selected, the device limits the peak or the bottom

of the inductor current entering in constant current until setting UVP as below explained.

The Over Current threshold has to be programmed, by designing the Rg resistors, to a safe

value, in order to be sure that the device doesn't enter OCP during normal operation of the

device. This value must take into consideration also the extra current needed during the

Dynamic VID Transition ID-VID and, since the device reads across MOSFET RdsON or

inductor DCR, the process spread and temperature variations of these sensing elements.

Moreover, since also the internal threshold spreads, the Rg design has to consider the

minimum value IOCTH(min) of the threshold as follow:

where IOCPx is the current measured by the current reading circuitry when the device enters

Quasi-Constant-Current. IOCPx must be calculated starting from the corresponding output

current value IOUT(OCP) as follow (ID-VID must also be considered when D-VID are

implemented) considering that the device performs Track & Hold only for the LS sense

mode:

where IOUT(OCP) is still the output current value at which the device enters Quasi-Constant-

Current, IPP is the inductor current ripple in each phase ID-VID is the additional current

required by D-VID (when applicable) and N the number of phases. In particular, since the

device limits the peak or the valley of the inductor current (according to DAC/CS_SEL

status), the ripple entity, when not negligible, impacts on the real OC threshold value and

must be considered.

OCPx max

()

SENSE max

()

⋅

OCTH min

()

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

OCPx

OUT OCP

()

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

∆I

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

DVID

–

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

–

LowSideMosfetSense

OUT OCP

()

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

∆I

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

DVID

–

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

InductorDCRSense

⎩

⎪

⎨

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