L6717 datasheet(38/56 Pages) STMICROELECTRONICS

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Output voltage positioning

L6717

38/56

Doc ID 17326 Rev 1

command (kDRPNB). RFB_NB gives the final gain to program the desired load-line slope

(Figure 9).

The output characteristic vs. load current is then given by:

Where RLL_NB is the resulting Load-Line resistance implemented by the NB Section.

kDRPNB value is determined by the Power Manager I

2C and its default value is 1/4.

RFB_NB resistor can be then designed according to the RLL_NB specifications and DRP_ADJ

setting as follow:

7.7

On-the-fly VID transitions

L6717 manages on-the-fly VID Transitions that allow the output voltage of both sections to

modify during normal device operation for CPU power management purposes. OV, UV and

PWRGOOD signals are masked during every OTF-VID Transition and they are re-activated

with a 16 clock cycle delay to prevent from false triggering.

When changing dynamically the regulated voltage (OTF-VID), the system needs to charge

or discharge the output capacitor accordingly. This means that an extra-current IOTF-VID

needs to be delivered (especially when increasing the output regulated voltage) and it must

be considered when setting the over current threshold of both the sections. This current

results:

where dVOUT / dTVID depends on the operative mode (3mV/μsec. in SVI or externally driven

in PVI).

Overcoming the OC threshold during the dynamic VID causes the device latch and disable.

Dynamic VID transition is managed in different ways according to the device operative

mode:

●

PVI mode.

L6717 checks for VID code modifications (See Figure 11) on the rising-edge of an

internal additional OTFVID-clock and waits for a confirmation on the following falling

edge. Once the new code is stable, on the next rising edge, the reference starts

stepping up or down in LSB increments every two OTFVID-clock cycle until the new

VID code is reached. During the transition, VID code changes are ignored; the device

re-starts monitoring VID after the transition has finished on the next rising-edge

available. OTFVID-clock frequency (FOTFVID) is 500 kHz.

If the new VID code is more than 1 LSB different from the previous, the device will

execute the transition stepping the reference with the OTFVID-clock frequency FOTFVID

OUT_NB=VID

FB_NB

DRPNB

DROOP_NB

⋅⋅

–

VID

FB_NB

DRPNB

DCR NB

()

G_NB

--------------------------- I

OUT

⋅⋅

⋅

–

VID

LL_NB

OUT_NB

⋅

–

FB_NB

LL_NB

DRPNB

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

G_NB

DCR NB

()

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

⋅

OTF-VID

OUT

VID

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

⋅

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