L6706 datasheet(28/47 Pages) STMICROELECTRONICS

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Dynamic VID transitions

L6706

28/47

Doc ID 15698 Rev 2

Dynamic VID transitions

The device is able to manage dynamic VID code changes that allow output voltage

modification during normal device operation.

OVP and UVP signals are masked during every VID transition and they are re-activated

after the transition finishes with a 15 µs (typ) delay to prevent from false triggering due to the

transition.

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

discharge the output capacitor accordingly. This means that an extra-current ID-VID needs to

be delivered, especially when increasing the output regulated voltage and it must be

considered when setting the over current threshold.

This current can be estimated using the following relationships:

where dVOUT is the selected DAC LSB (6.25 mV for VR11.1) and TVID is the time interval

between each LSB transition (externally driven).

Overcoming the OC threshold during the dynamic VID causes the device to enter the

constant current limitation slowing down the output voltage dV/dt also causing the failure in

the D-VID test. In order to avoid this situation the device automatically increases the OCP

threshold to 150% of the selected OCP threshold during every VID transition (adding an

extra 15 µs of delay).

L6706 checks for VID code modifications (see Figure 12) on the rising edge of an internal

additional DVID-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 VID-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. VID-clock frequency (FDVID) is in the range of 1.8

MHz to assure compatibility with the specifications.

Note:

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 DVID-clock frequency FDVID until the new code

has reached: for this reason it is recommended to carefully control the VID change rate in

order to carefully control the slope of the output voltage.

DVID

–

OUT

VID

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