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DS30BA101 output termination

Richard Woodham1
Prodigy 210 points
Other Parts Discussed in Thread: DS30BA101

In the DS30BA101 datasheet an application circuit shows 75R load resistors & 1uF series capacitor, whereas in the DRIVECABLE04-TX Schematic the series capacitors are 4.7uF & , additionally, there is 75R//5.6nH in series with the output.  Which is recommended best practice?

  • 0
    TI__Mastermind 29655 points

    Hi Richard,

    For evaluation boards, we aim to accommodate the broadest possible number of applications, so determination of recommended best practice is dependent on the application. With that having been said, when in doubt, following the EVM design (in this case, DRIVECABLE04-TX) is a safe approach.

    The DRIVECABLE04-TX schematic shows a large AC coupling cap to accommodate for a variety of data coding schemes and frequency content. If there is not a concern for passing low frequency content, a smaller AC coupling cap will work.

    The 5.6nH parallel inductor is for input return loss compensation, and it is necessary to meet SMPTE return loss requirements. The actual value of the inductor depends on PCB design, but historically, the 5.6 nH value has worked well on many designs. If you do not need to meet a particular return loss spec with a compensation network, this inductor is not required.

    Thanks,

    Michael