SABRE-LL-I datasheet(31/141 Pages) STMICROELECTRONICS

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SABRE-LL-I

Power sequencing

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Power sequencing

9.1

Overview

As soon as VSupply and VSupplyInt are above their power on reset level, S.A.B.Re will start

the charge pump circuit; once VPump voltage reaches its under voltage rising threshold,

S.A.B.Re begins a sequence that starts the regulators considered system regulators.

A regulator is considered a System regulator if:

–

It has to start in on state without any user action.

–

It is included in the power-up sequence.

–

Its under-voltage event is considered by S.A.B.Re as an error condition to be

signaled through nRESET pin.

Once VSupply and VSupplyInt, VPump and all the system regulators are over their under

voltage rising threshold, S.A.B.Re enters in the normal operating state, that will release

nRESET pin and will wait for SPI commands.

S.A.B.Re will reduce the noise introduced in the system by switching out of phase all its

power circuits (switching regulators, bridges and charge pump).

The S.A.B.Re's startup sequence of operation is the following:

–

start V3v3 internal linear regulator

–

sample startup configuration

–

wait enable if slave device

–

start charge pump

–

start system regulators (see order in Section 8.7)

–

send enable to slave device, if master

–

wait until VGPIO_SPI becomes ok

SABRE-LL-I Datasheet(PDF) 31 Page - STMicroelectronics