L6714 View Datasheet(PDF) - STMicroelectronics
Part Name
Description
MFG CO.
L6714
STMicroelectronics
'L6714' PDF : 70 Pages View PDF
Over current protection
18 Over current protection
L6714
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:
Rg = I--O----C----P----x--(--m----a---x---)---⋅------R----S----E---N----S----E---(--m----a---x---)
IOCTH(min)
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:
⎧
⎪
I--O----U----T---(--O----C----P---)
–
∆----I--P----P-
+
I--D-----–---V----I--D-
⎪N
2
N
IOCPx
=
⎨
⎪
⎪
⎩
-I-O----U----T---(--O----C----P---)
N
+
-∆----I-P----P-
2
+
I--D-----–---V----I--D-
N
LowSideMosfetSense
InductorDCRSense
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.
50/70
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