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DS64MB201 Floating I/O and I/O Polarity

daniel_o
Genius 10580 points
Other Parts Discussed in Thread: DS64MB201

Team,

I have 2 questions regarding DS64MB201

  1. What does a channel do if the inputs and outputs are floating?  Will a channel automatically power down if the channel is not connected?
  2. Can the polarity of the inputs and outputs be reversed to improve the routing of signal pairs on the PCB?

Thanks for the help!

-Daniel Ogilvie

  • 0
    TI__Mastermind 29635 points

    Hi Daniel,

    Please see answers below:

    1. If the inputs and outputs are floating, the channel goes into electrical IDLE where the outputs are muted. This is effectively the same thing as the channels being powered down. When an input is applied that is greater than the input idle threshold, than the channel automatically goes active again. See p. 12 of the datasheet for more details.

    2. Yes, the input/output polarity can be reversed to improve routing. It is important to keep track of the polarity throughout the routing to ensure consistency when the differential lines reach the Rx after the mux buffer.

    Thanks,

    Michael

  • 0 in reply to Michael Lu (Santa Clara)
    TI__Genius 10580 points

    Thanks Michael,

    One follow-up question: The minimum recommended operating temperature according to the data sheet is -40C, but it also says that "OOB signal pass-through limited to a minimum ambient temperature of -10C."  What happens to OBB signals at temperatures less than -10C?  Is there complete failure or do they function but just not completely within specifications?

    Regards,

    Daniel

  • 0 in reply to daniel_o
    TI__Mastermind 29635 points

    Hi Daniel,

    The device still functions, but it may not meet the specifications of SAS/SATA. The OOB (Out-of-Band) signaling is a quick burst signal that is used to transition a channel from idle-to-active.

    This requires a fast turn-on/turn-off. When the device is operated at cold temperatures, below -10C, the driver takes longer to turn-on/turn-off than is required by the 106.6 ns nominal COMWAKE signal.

    If the turn-on/turn-off signal detection feature of the DS64MB201 is not fast enough to catch these quick OOB burst signals, particularly that of COMWAKE, then the endpoint will not receive the OOB signal. This also would cause the DS64MB201 to potentially go out of compliance. In order to have enough margin to pass OOB in SAS/SATA applications, please operate the device at ambient temperatures of at least -10C.

    Thanks,

    Michael