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LMH0074: MUTEref pin wiring when pin is not left unconnected

franziskus
Expert 8249 points
Part Number: LMH0074

Hi,

my customer would like to use the device, but needs more information how to implement when the MUTEref pin is not left unconnected.
Can you clarify what circuit should look like?

Additional questions:

  • How is the formula to calculate the cable length?
  • Can the Vcc voltage be used with a resistor divider or is a bandgap ref voltage necessary? Or is it better to let it left unconnected?

Thanks

  • 0
    TI__Guru* 93670 points

    Greetings,

    MUTEREF is an input that sets the threshold for carrier detect. In effect, it sets the amount of cable to equalize before triggering carrier detect. The reference voltage can be applied using a simple voltage divider. 


    The table below shows the minimum MUTEREF input voltage required - based on lab measurement -  to mute the outputs with a 270 Mbps and HD input signal for Belden 1694A cable. For example, if a 270 Mbps input signal is passed through 300m Belden 1694A to the LMH0074, then a voltage of 2.51V or higher must be applied to MUTEREF to force carrier detect to inactive. If either the MUTEREF voltage is decreased or the cable length is decreased, carrier detect will be active.

    Regards,, Nasser