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DS90CR285: about Transmitter Switching Characteristics and Receiver Switching Characteristics

R.Fukunaga
Expert 2445 points
Part Number: DS90CR285

Tool/software:

Hi all,

I have some questions about the following data sheet.

DS90CR285/DS90CR286 3.3V Rising Edge Data Strobe LVDS 28Bit Channel Link- 66MHz datasheet (Rev. C)

(1)At f=66.6666 MHz

TPPos0,TPPos1,TPPos2,TPPos3,TPPos4,TPPos5,TPPos6

For RSPos0, RSPos1, RSPos2, RSPos3, RSPos4, RSPos5, and RSPos,

are there Tmin/Ttyp/Tmax values for each?

The data sheet only shows values for 40 MHz and 66 MHz.

(2) For RSPos (n) at f=66 MHz

When we look at the value of the typ value, it is always RSPos (n) - RSPos (n-1) =2.2 [ns].

Based on this, assuming RSPos7, it is 16.5 ns (typ), and RSPos7-RSPos0=16.5 - 1.1=15.4 [ns].

However, it does not match the period of 15.1515...ns at f=66 MHz.

Could you tell us why the behavior and behavior in this area do not match?

Best Regards,

Ryusuke

  • 0
    TI__Mastermind 22830 points

    Hi Ryusuke,

    1. The datasheet has this information for RSPosx info in the "Receiver Switching Characteristics" table for 40 MHz and 66 MHz only, and has min and max values. Is this what you were looking for?

    2. For how the LVDS is serialized, you can find on "Figure 21. Receiver LVDS Input Strobe Position" table that there are only 7 positions (RSPos0 - RSPos6). So RSPos7 is not applicable.

    This specification basically defines where each strobe position must be for valid data to be strobed by the receiver.

    The rate on the RxIN lanes will be 7xRxCLKIN.
    For 66 MHz, RxIN rate = 7 x 66 MHz = 462 MHz, which corresponds to 1/(462 MHz) = 2.16 ns





    Best regards,
    Ikram

  • 0 in reply to Ikram Haque
    Expert 2445 points

    Hi Ikram,

    Thank you for checking.

    (1)I would like to ask about the value at 66.6666Mhz.

    TPPos0,TPPos1,TPPos2,TPPos3,TPPos4,TPPos5,TPPos6

    RSPos0, RSPos1, RSPos2, RSPos3, RSPos4, RSPos5, and RSPos6

    Are there any Tmin/Ttyp/Tmax values for each?

    I would appreciate any data that I can refer to.

    Best Regards,

    Ryusuke

  • +1 in reply to R.Fukunaga
    TI__Mastermind 22830 points

    Hi Ryusuke,

    The datasheet only has values for the 40 MHz and 66 MHz examples. You could use the 66 MHz values as a close estimate.

    Best regards,
    Ikram