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AM2431: AM243X MCSPI, UART, GPIO Min/Max Slew rates..

Newman
Expert 5925 points
Part Number: AM2431

Tool/software:

Hi Team AM243x,

My customer is having difficulty meeting the Min/Max Slew rates specified for MCSPI (and UART, GPIO, etc).  Can these specs be relaxed or must the datasheet numbers be met to ensure proper operation of MCSPI, etc? 

Looks like the Schmitt trigger inputs can be enabled for each IO.  If enabled, must the slew rate input specs still be met?  Do the slew rate specs change w/ Schmitt trigger enabled/disabled?

Any way to provide for a slower (than 2V/nSec) min slew rate spec?

Ref:

Thanks, Merril

  • 0
    TI__Genius 13880 points

    Hi Merril,

    This thread was moved as requested. I'll assign to a team member to comment. Please allow some time for a response.

    Thanks,

    Anshu

  • 0 in reply to Anshu Madwesh
    TI__Guru**** 166599 points

    Hello  Merril

    I am checking with the expert.

    The timing is closed at the max rated frequency.

    For the above query, are you looking to run the interfaces at max frequency ?

    Regards,

    Sreenivasa

  • 0 in reply to Kallikuppa Sreenivasa
    TI__Expert 5925 points

    Hi Sreenivasa,

    Thanks!  Their signals are actually slower than the minimum spec.  Looking to understand if this could/would be OK.

    Thx, Merril

  • 0 in reply to Newman
    TI__Guru**** 166599 points

    Hello  Merril

    Thank you. 

    Newman said:
    Their signals are actually slower than the minimum spec

    Please eloborate.

    Regards,

    Sreenivasa

  • 0 in reply to Kallikuppa Sreenivasa
    TI__Expert 5925 points

    Hi Sreenivasa,

    Thx!  For example..

    TI Spec: Min Input Slew Rate: 2V/nSec

    Actual: Min Input Slew Rate: 1V/nSec

    Thx, Merril

  • 0 in reply to Newman
    TI__Guru**** 166599 points

    Hello  Merril

    Thank you. 

    Let me check with the device expert.

    I suspect customer is not looking to or would want to run at full speed - any thoughts please.

    Regards,

    Sreenivasa

  • 0 in reply to Kallikuppa Sreenivasa
    TI__Expert 5925 points

    Hi Sreenivasa,

    No, they do not need to run at full speed.

    Thx, Merril

  • 0 in reply to Newman
    TI__Expert 5925 points

    Hi Sreenivasa,

    Any update?  How can customers be expected to meet these requirements?  Seems kinda impossible to me.  I think these specs must be relaxed.

    Thanks, Merril

  • 0 in reply to Newman
    TI__Guru**** 166599 points

    Hello  Merril

    Thank you. 

    I checked with the device expert.

    The STA team closed the timing for these peripherals at maximum speed and the parameters in the data sheet represent the max speed.

    Refer below inputs i received form the device expert:

    We do not know how much the slew rate can be relaxed for a specific operating frequency because there are many operating frequency options, and it is not possible to check the slew rate limit for each possible option.

     The only slew rate limits we know are those that apply to the maximum operating frequency.  The customer can operate at any frequency up to the maximum when their system is constrained to operate within our datasheet slew rate limits.  That is the only data points that we have.  We do not know what slew rate limits would apply at any other operating frequency.

    Regards,

    Sreenivasa

  • 0 in reply to Kallikuppa Sreenivasa
    TI__Expert 5925 points

    Hi Sreenivasa,

    Thanks for the detailed response.  When running at max frequency, could our device be expected to fail w/ "slower than spec'd" inputs.. or has it just not been characterized at these slower rise-times?  ?  What do you recommend the customer do?  They have an external device that is slower than our spec'd minimum.  I think that many customers may have ~similar issue(s) and just have not checked/noticed.  Are you OK to have a call with them to discuss?

    Thanks, Merril

  • 0 in reply to Newman
    TI__Guru**** 166599 points

    Hello  Merril

    Thank you. 

    Newman said:
    When running at max frequency, could our device be expected to fail w/ "slower than spec'd" inputs.. or has it just not been characterized at these slower rise-times?  ?

    As i understand to meet the timing requirements at max speed, the slew rate is required to be in the specified range.

    Newman said:
    What do you recommend the customer do? 

    Is customer doing analysis or seeing some functional or performance issues.

    With a slower operating frequence, i suspect the slew rate requirements would change but as mentioned above this has not been characterized.

    I would refer to below section for the LVCMOS slew rate

    7.7.6 LVCMOS Electrical Characteristics

    Regards,

    Sreenivasa