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TMS320F28069MPZT pin impedances

Angela Brock
Intellectual 480 points
Other Parts Discussed in Thread: TMS320F28069

I am trying to determine termination resistor values between the TMS320F28069MPZT and XDS100v2 cTI 20 for pins TDO, TCK and RTCK.  In order to do this I need to know the device (I am assuming of the TMS320F28069MPZT) pin impedances and that of the XDS cable (quoted as normally 50 ohms).  As far as I can see there is no ibis model for the TMS320F28069MPZT and I read in Appendix H of Emulation and Trace Headers Technical Reference Manual to contact a TI field service representative to get the output impedance.  Can anyone help with those values?

Thanks.

  • 0
    Intellectual 480 points

    I think I may have found the ibis model if PZP package refers to the TMS320F28069MPZT.  For TDO the model name is BQ0393F which translates from Emulation and Trace Headers Technical Reference Manual Appendix H as having supply voltage of .3 and impedance of 93 ohms.   TCK model name is given as BC3350AFHYPU which would mean 3.3 supply voltage and impedance of 50 ohm.  Do I have these correct?  If these are correct and the XDS cable is 50 ohms does that mean termination resistors are unecessary?

  • 0 in reply to Angela Brock
    TI__Expert 8105 points

    Angela,

    There is one IBIS file that applies to all packages of TMS320F28069 so the model that you found on TI website is good for this device. Your PZT designation is actually PZ package with T temperature grade.


    REgards,
    PEter

  • 0 in reply to Peter Galicki
    Intellectual 480 points

    Did I read the model for TDO (BQ0393F which translates from Emulation and Trace Headers Technical Reference Manual Appendix H as having supply voltage of .3 and impedance of 93 ohms) correctly?  It's not in the same form as the TCK pin.

  • 0 in reply to Angela Brock
    TI__Expert 8105 points

    Angela,

    We are still waiting for clarification on this from another team that sourced this document, in the mean time I have noticed that when comparing TCK to TDO they have different buffers because the first one is an input while the second one is an output. I should have the complete answer for you on Mon.

    Regards<
    Peter

  • 0 in reply to Peter Galicki
    TI__Expert 8105 points
    Angela,

    We received some additional information - BQ0393F supply is 3.3V and the impedence spread is 25 Ohms in Strong , 36 in Nom and 70 Ohms in weak corner.

    Regards,
    PEter