L6711 datasheet(37/50 Pages) STMICROELECTRONICS

37 / 50 page

L6711

Output voltage monitor and protections

37/50

Figure 18.

Constant current operation

14.6

Inductor sense over current (CS_SEL = SGND)

The device detects an over current when the IINFOx overcome the fixed threshold IOCTH.

Since the device always senses the current across the inductor, the IOCTH 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 LS mosfet of that phase until IINFOx 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 IOCPx 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, the FAULT pin is driven high 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.

where

·IO

x(I

)

ffe

a) Maximum current for each phase

b) Output Characteristic

OCPx max

() RSENSE max

()

⋅

OC TH min

()

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

OCPx

OUT OCP

()

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

∆

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

D-VID

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

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