L6758A datasheet(21/42 Pages) STMICROELECTRONICS

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L6758A

Output voltage positioning

Output voltage positioning is performed by selecting the controller operative-mode (

CPU,

VSA and GFX) for the two sections and by programming the droop function effect (see

Figure 5). The controller reads the current delivered by each section by monitoring the

voltage drop across the DCR inductors. The current (I

DROOP

/ I

SDROOP

) sourced from the

FB / SFB pins, directly proportional to the read current, causes the related section output

voltage to vary according to the external R

/ R

SFB

resistor, therefore implementing the

desired load-line effect.

The L6758A embeds a dual remote-sense buffer to sense remotely the regulated voltage of

each section without any additional external components. In this way, the output voltage

programmed is regulated compensating for board and socket losses. Keeping the sense

traces parallel and guarded by a power plane results in common mode coupling for any

picked-up noise.

Figure 5. Voltage positioning

6.1

Multi-phase section: phase # programming

The multi-phase section implements a flexible two-to-four interleaved-phase converter. To

program the desired number of phases, pull up to VCC5 the PWMx signal that is not

required to be used, according to

Table 6.

Caution:

For the disabled phase(s), the current reading pins must be properly connected to avoid

errors in current sharing and voltage positioning: CSxP must be connected to the regulated

output voltage while CSxN must be connected to CSxP through the same R

resistor used

for the active phases.

AM11138v1

REFERENCE

COMP

VSEN

RGND

RFB

To VddCORE

(Remote Sense)

Protection

Monitor

from DAC...

ROS

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