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DM6433 CLKIN

Kazuaki Ohshita
Intellectual 2280 points

The DM6433 datasheet shows that the Transition time, MXI/CLKIN is 0.05C(max). In the case of 27MHz clock, C = 37.037nS and the transition time is 1.85nS(max).  This transition time seems to be very severe.  Is there a crystal controlled oscillator which satisfies the transition specification and reasonable cost ?  Also, DM6437EVM uses the oscillator ASFL3-27.000MHz-EK-T which transition specification (tr/tf) is 10nS. We do not understand how the ASFL3-27.000MHz-EK-T was selected and can be used on the DM6437EVM.  So, please advice what specification of  crystal oscillator can we select and use?

Best regards, Kazuaki Ohshita

  • 0
    TI__Expert 5955 points

    Ohshita-san,

    I had consulted this issue with other DM643x apps team member and they are aware of that this issue had been brought up before. They had suggested that it seems that this particular specification might have come from the generic specification of the PLL module used on the DM643x and also agree that the specification should have been relaxed (and we will revise this specification soon). Note that this parameter is not as important as the other five, as long as you meet all other five parameters of the "Timing Requirements for MXI/CLKIN" you should be okay.

    Thanks and best regards,

    Tai Nguyen

  • 0 in reply to Tai Nguyen
    TI__Intellectual 2280 points

    Nguyen-san,

    Thanks a lot for your clear explanation. 

    The information is very helpful for us.

    Best regards,
    Kazuaki Ohshita