L6751 datasheet(43/59 Pages) STMICROELECTRONICS

43 / 59 page

L6751

Efficiency optimization

Doc ID 023992 Rev 1

43/59

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 L6751 re-configures itself to improve

overall system efficiency, according to Table 15.

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 L6751

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

pinstrapping and/or PMBus (TM) commands received (see Table 11). DPM12 refers to the

current at which the controller changes from 1 to 2 phases. In the same way, DPM23 defines

the current at which the controller changes from 2 to 3 phases and so on.

When DPM is enabled, the L6751 starts monitoring the IMON voltage for phase number

modification 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 the case of an SetVID 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.

Delay in the intervention of DPM can be adjusted by properly sizing the filter across the

IMON pin. Increasing the capacitance results in increased delay in the DPM intervention.

See Section 7.2.1 for guidelines in designing the IMON load indicator.

Note:

During load transients with light slope, the filtering of IMON may result too slow for the IC to

set the correct number of phases required for the current effectively loading the system (LTB

does not trigger in the case of light slopes). The L6751 features a safety mechanism which

re-enables phases that were switched off by comparing ILIM and IMON pin voltage. In fact,

the ILIM pin is lightly filtered in order to perform fast reaction of OC protection while IMON is

heavily filtered to perform correct averaging of the information. While working continuously

in DPM, the device compares the information of IMON and ILIM: ILIM voltage is divided in N

steps whose width is VOCP/(2*N) (where VOCP = 2.5 V and N the number of stuffed phases).

If the DPM phase number resulting from IMON is not coherent with the step in which ILIM

stays, the phase number is increased accordingly. The mechanism is active only to increase

the phase number which is reduced again by DPM.

Table 15.

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

L6751 датащи(PDF) 43 Page - STMicroelectronics

L6751 датащи(HTML) 43 Page - STMicroelectronics

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59

датащи скачать

ссылки URL