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DS90CR286 and DS90CR288 switching characteristics

Other Parts Discussed in Thread: DS90CR286, DS90CR288A, DS90CR286A, DS90CR287, DS90CR285

Hello,

My customer try to use the DS90CR286 or the DS90CR288.

He will use the device by 33MHz clock.

He wants to know the receiver switching characteristics at 33MHz clock.

Could you tell me a value of 'RSPos' and 'RSKM' at 33MHz clock?

Regards,

Naoki Aoyama

  • Hi Naoki-san,

    This is a difficult question to answer. We do not characterize either part's strobe position at 33 MHz during production, and therefore we can only estimate "typical" numbers when operating at 33 MHz.

    Please note that the DS90CR286 is NRND and the DS90CR288 is obsolete. For future designs, I recommend the DS90CR286A and DS90CR288A.

    Regarding "Rspos":

    For the DS90CR286A, the Rspos is only spec'd at 40 MHz and 66 MHz. The DS90CR288A is spec'd at 75 MHz only. To determine the typical value for the DS90CR286A or the DS90CR288A, we would need to extrapolate from the difference between typical position and ideal position from the nearest measured frequency data. For the DS90CR286A, this implies extrapolating from the data taken at 40 MHz, and for the DS90CR288A, this means extrapolating from 75 MHz. (less accurate due to bigger difference in operating frequency).  It is important to note that these are estimations only, and bench testing will need to be performed to verify the accuracy of these numbers, especially if the DS90CR288A is used.

    I have attached my estimates for the typical receiver switching characteristic at 33 MHz, rounded to 2 decimal places.

    DS90CR286A_DS90CR288A Typ Strobe Position Estimates.xlsx

    Regarding "RSKM":

    This is dependent on the Tx being used. Note that the DS90CR286A RSKM is spec'd with the assumption that DS90CR285A is the transmitter. If another transmitter is used, the RSKM may be different from what is shown in the datasheet. To calculate the RSKM, take the minimum value observed when subtracting RsPos_n+1 {min} - TxPos_n {max}. Since we do not have a min/max value performed at 33 MHz for these parts, we can only estimate what the RSKM can be. If we assume the DS90CR285 is the transmitter for the DS90CR286A, the typical RSKM should be approximately 490 ps, according to the datasheet. Likewise, if the DS90CR287 is the transmitter for the DS90CR288A, the RSKM is at least 290 ps (I estimate more, because the RSKM was determined at 85 MHz). I estimate the skew for RSKM is closer to the 490 ps posted for the DS90CR286A at 40 MHz.

    Thanks,

    Michael

  • Hi Michael,

    Thank you for your reply.
    I wrote a wrong device number, sorry. My customer uses the DS90CR286A
    and DS90CR288A.
    I understood a way to estimate for 'Rspos', the definition of 'RSKM'.

    I will feedback to my customer the information, check the characteristics of
    customer's transmitter.

    Thanks,

    Naoki Aoyama