L6759D datasheet(45/51 Pages) STMICROELECTRONICS

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L6759D

PMBus support

Doc ID 023240 Rev 1

45/51

12.1

Enabling the device through PMBus

The default condition for the L6759D is to power up through the EN pin ignoring PMBus

commands. By properly setting the ON_OFF_CONFIG command, it is also possible to let

the device ignore the EN pin acting only as a consequence of the OPERATION command

issued.

12.2

Controlling Vout through PMBus

Vout can be set independently from the SetVID commands issued through the SVI interface

by using PMBus. Two main modes can be identified:

●

Offset above SVI commanded voltage. By enabling the MARGIN mode through the

OPERATION command and by commanding the MARGIN_HIGH and MARGIN_LOW

registers, it is possible to dynamically control an offset above the output voltage

commanded through the SVI bus.

●

Fixed Vout regardless of SVI.It is necessary to enter DEBUG_MODE. In this condition,

commands from SVI are acknowledged but not executed and VOUT_COMMAND

controls the voltage regulated on the output.The L6759D can enter and exit

DEBUG_MODE anytime. Upon any transition, Vout remains unchanged and only the

next-coming command affects the output voltage positioning (i.e. when exiting

DEBUG_MODE, returning to SVI domain, the output voltage remains unchanged until

the next SetVID command).

Figure 18.

Device initialization: PMBus controlling Vout

VCC5

VDRV

VIN

UVLO

2mSec POR

UVLO

50uSec

SVI BUS

PMBus

VDDQ / VTT

ENVTT (Ignored by ON_OFF_Config setting)

VRRDY / SVRRDY

64uSec

ON-OFF_Config

Operation

Command Rejected

Command ACK but not executed

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