L6714 Datasheet, PDF (53/70 Pages) STMicroelectronics – 4 phase controller with embedded drivers for Intel VR10, VR11 and AMD 6Bit CPUs

L6714
18.2
Over current protection
Inductor sense over current
The device detects an over current when the II_NFOx overcome the fixed threshold I_OCTH.
Since the device always senses the current across the inductor, the I_OCTH crossing will
happen during the HS conduction time: as a consequence of OCP detection, the device will
turn OFF the HS MOSFET and turns ON the LSMOSFET of that phase until I_INFOx re-cross
the threshold or until the next clock cycle. This implies that the device limits the peak of the
inductor current.
In any case, the inductor current won't overcome the I_OCPx value and this will represent the
maximum peak value to consider in the OC design.
The device works in Constant-Current, and the output voltage decreases as the load
increase, until the output voltage reaches the UVP threshold. When this threshold is
crossed, all MOSFETs are turned off and the device stops working. Cycle the power supply
or the OUTEN pin to restart operation.
The transconductance resistor Rg can be designed considering that the device limits the
inductor current ripple peak. Moreover, when designing D-VID systems, the additional
current due to the output filter charge during dynamic VID transitions must be considered.
Rg = ^I--^O----^C----^P----^x--⁽--^m----^a---^x---⁾---^â‹------^R----^S----^E---^N----^S----^E---⁽--^m----^a---^x---⁾
I_OCTH(min)
where
I_OCPx
=
I_{--O----U----T---(--O----C----P---) + -}∆_----I_{-P----P- +} I_{--D-----–---V----I--D-}
N
2
N
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