L6758A datasheet(32/42 Pages) STMICROELECTRONICS

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Efficiency optimization

L6758A

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DocID023298 Rev 2

Efficiency optimization

As per VR12 specifications, the SVI master may define different power states for the VR

controller. This is performed by SetPS commands. The L6758A re-configures itself to

improve overall system efficiency according to

Table 14.

9.1

Dynamic phase management (DPM)

Dynamic phase management allows the number of working phases to be adjusted

according to the delivered current still maintaining the benefits of the multi-phase regulation.

Phase number is reduced by monitoring the voltage level across the IMON pin: the L6758A

reduces the number of working phases according to the strategy defined by the DPM

pinstrapping, see

Table 11.

The current at which the transition happens (I

DPM

) can be estimated as:

Equation 11

where V

DPM

thresholds are defined in

Table 15. A hysteresis (50 mV typ.) is provided for

each threshold in order to avoid multiple DPM actions triggering in steady load conditions.

When DPM is enabled, L6758A starts monitoring the IMON voltage for phase number

modifications after VR_RDY has transition high: the soft-start is then implemented in

interleaving mode with all the available phases enabled.

DPM is reset in case of a Set VID command that affects the CORE section and when LTB

Technology detects a load transient. After being reset, if the voltage across IMON is

compatible, DPM is re-enabled after proper delay.

Table 14. Efficiency optimization

Feature

PS00h

PS01h

DPM

According to pinstrapping

Active. 1phase/2phase according to Iout

VFDE

Active when in single-phase and

DPM enabled

Active when in single-phase

GDC

12 V driving

GDC set to 5 V

Table 15. VDPM Thresholds (IMON rising-50 mV Hyst)

Comp/Scomp

DPM threshold set

1/2 phase transition

2/N phase transition

33 k to GND

Set 3

Vimon=200 mV

Vimon=350 mV

17.5 k to GND

Set 2

Vimon=150 mV

Vimon=275 mV

12.5 k to GND

Set 1

n/a

Vimon=150 mV

5.6 k to GND

OFF

n/a

DP M

IMON

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

DC R

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

⋅

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