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[FAQ] AM2432: AM2x - Boot pins pull down/up requirements

Prasad Jondhale
Mastermind 27743 points
Part Number: AM2432

Hi TI Experts,

This is regarding the boot pins configuration requirements.

We want to know if we need explicit pull down or pull up resistor for all boot pins? We want to use QSPI(4S) boot mode and set all boot pin to 0. Do we need explicit pull down resistor on all 4 boot pins? What happen if we just leave pin float or connects to peripheral chips like QSPI flash directly?

Regards,

Prasad

  • 0
    TI__Mastermind 27743 points

    Hi,

    There were a few points of feedback which usually comes during a schematic reviews regarding boot mode pins:

    1) We recommend explicit pull resistors for all boot pins to ensure stability. They should not be left floating -

    You shouldn't allow any input buffers which are enabled to have a mid-supply voltage applied. All enabled input buffers must be pulled below its VILSS potential or pulled above its VIHSS potential as defined in the respective Electrical Characteristics section of the datasheet. Any input buffers allowed to float between VILSS and VIHSS are very likely to be compromised. Therefore it is very important that your design does not allow any enabled inputs to float.

    2) An additional unpopulated resistor option could (should) be added to enable a secondary boot mode configuration in case of failures in the primary boot mode.

    3) We recommend implementing a method of disconnecting the SOP bootmode state-latch on PORz reset from the functional operation of peripheral pin. See attached file for AM263x CC example. /cfs-file/__key/communityserver-discussions-components-files/908/AM263xCC_5F00_BootmodeIsolationExample.pdf

    Your design must account for the following critical factors for these signals and associated PCB trace:

    -QSPI device: pin voltage/timing requirements

    -AM2x device: SOP bootmode state-latch and related PORz timing requirements

    -AM2x device: QSPI IP Module pin voltage/timing requirements

    -System: General channel strength/integrity/stability

     

    Regards,

    Prasad, Zack