SABRE-LL-I datasheet(32/141 Pages) STMICROELECTRONICS

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Power saving modes

SABRE-LL-I

32/141

Power saving modes

10.1

Overview

Saving power is very important for today platforms: S.A.B.Re implements different functions

to achieve different levels of power saving.

Sections here below describe these different power saving modes.

10.2

Standby mode

Almost all low voltage circuitry inside S.A.B.Re are powered by V3v3 internal regulator; this

regulator is a linear regulator powered by VSupplyInt. This means that all the current provided

by V3v3 regulator is directly coming from VSupplyInt and therefore the total power

consumption is:

Low voltage power = VSupply* IV3v3.

because VSupplyInt is feeded by VSupply, directly or with a resistor in series.

This power could be reduced by using a switching buck regulator to supply V3v3: in this

case, assuming the buck regulator efficiency near to 100%, the dissipated power would

become:

Low voltage power

≈ 3.3V * I

V3v3.

To achieve this result there is the need to switch off the internal V3v3 linear regulator and to

use an additional pin to provide a 3.3V supply to internal circuits. S.A.B.Re can do this by

using the low voltage switch implemented on GPIO6 pin. This switch internally connects

VGPIOSpi voltage to GPIO6 output so, by externally connecting GPIO6 to V3v3 pin, the

VGPIOSpi voltage can be provided to low voltage circuitry inside S.A.B.Re.

Figure 5.

Standby mode function description

3.3V

GPIO6

VGPIOSpi

VSupplyInt

V3v3

Regulator

StdByMode

3.3 V

1.9 V

External

connection

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