L6751B datasheet(28/58 Pages) STMICROELECTRONICS

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Device description and operation

L6751B

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Doc ID 024028 Rev 1

Device description and operation

The L6751B is a programmable 4/5/6-phase PWM controller that provides complete control

logic and protection to realize a high performance step-down DC-DC voltage regulator

optimized for advanced microprocessor and memory power supply. The device features 2nd

generation LTB Technology: through a load transient detector, it is able to turn on all the

phases simultaneously. This allows the output voltage deviation to be to minimized and, in

turn, also the system costs by providing the fastest response to a load transition.

The L6751B implements current reading across the inductor in fully differential mode. A

sense resistor in series to the inductor can also be considered to improve reading precision.

The current information read corrects the PWM output in order to equalize the average

current carried by each phase.

The controller supports Intel and AMD SVI bus and all the required registers. The platform

may configure and program the defaults for the device through dedicated pinstrapping.

A complete set of protections is available: overvoltage, undervoltage, overcurrent (per-

phase and total) and feedback disconnection guarantee the load to be safe in all

circumstances.

Special power management features like DPM, VFDE(a) and GDC modify phase number,

gate driving voltage and switching frequency to optimize efficiency over the load range.

The L6751B is available in VFQFPN68 8x8 mm package.

VFDE feature can be enabled using dedicated PMBus command. See Section 12 for details.

Figure 5.

Device initialization

SVI Packet

VCC5

VDRV

VIN

UVLO

μSec POR

UVLO

SVI BUS

PMBus

V_SinglePhase

ENVTT

SVRRDY

V_MultiPhase

VRRDY

SVI Packet

Command rejected

Command ACK but not executed

μsec

50μsec

AM14837v1

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