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AURA SOM/AURA Hardware/Power and Reset/Power Supply Unit (PSU) and recommended power-up sequence

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<section end="History" />__FORCETOC__<section begin="Body" />This page provides an overview of the issues related to powering AURA SOM. For more details about the signals that are involved, please see also [[AURA SOM/AURA Hardware/Pinout Table|this page]].

== Power Supply Unit (PSU) and recommended power-up sequence ==

Implementing correct power-up sequence for i.MX93 ~~SOC~~ SoC processors is not a trivial task because several power rails are involved.

AURA SOM simplifies this task by embedding all the needed circuitry. The following picture shows a simplified block diagram of PSU/voltage monitoring circuitry:

The PSU is composed of two main blocks:

* power management integrated circuit(PMIC)* additional generic power management circuitry that completes PMIC functionalities.

The PSU:

* generates the proper power-up sequence required by the ~~SOC processor and~~ SoC, surrounding memories , and peripherals* synchronizes the powering up of carrier board 's circuitry to prevent back ~~power~~* provides some spare regulated voltages that can be used to power carrier board devicespowering.

=== Power-up sequence===

The typical power-up sequence is the following:

* # VIN_SOM (+3.~~3VIN~~ 3V) main power supply rail is powered.* SNVS domain signals are pulled up (unless carrier board circuitry keeps this signal low for any reason)* # CPU_PORn (active-low) is driven low by PMIC* RTC_RESET_B are internally released after 10ms* ; PMIC initiates power-up sequence needed by iMX93x processor.* # SOM_PGOOD goes up when all ~~CPU~~ SoC, memories, and I/O power ~~rail is~~ rails are ready.* # Finally PMIC releases CPU_PORn ~~is de-asserted after the last regulator to bring~~ ; this signal brings the processor out of reset.

==== Note on SOM_PGOOD usage ====

SOM_PGOOD is generally used on carrier board to drive loads such as DC/DC enable inputs or switch on/off control signalsin order to prevent back power.

Depending on the kind of such loads, SOM_PGOOD might not be able to drive them properly. ~~In these cases~~ On AURA SOM this signal is driven by a ~~simple 2~~push-~~input AND port can be used to address this issue. The following picture depicts a principle schematic showing this solution~~pull output at NVCC_3V3 rail, with max 20 mA output current.

~~VDD_SOM denotes the power rail used to power AURA SoM.~~ ~~[[File:AURA-power-good.png]]~~ ~~<section end~~=~~Body/>~~=== Note on CPU_PORn ====

Internally to the SOM, CPU_PORn is pulled-up with 100 kOhm.<section end="Body" />

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