termination resistor values for daisy chained LVDS app

I am using ADN4665 & ADN4666 to extend an SPI bus. My cables are twisted pair. I have 100 ohm termination resistors on each board of which there can be a total of 4 daisy chained. Three run fine. When I add the 4th I have weird things happening to my signals. I suspect that my total termination R is too low at this point. Does someone have experience along these lines and perhaps can suggest what termination R might work?

Thanks for your help.

Edd

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    •  Analog Employees 
    on Dec 8, 2014 10:19 AM

    Hi Ed,

    Can you please provide me with a sketch of your system setup?

    Usually if you are using a network with just ADN4665 Drivers and ADN4666 Receivers, then the last receiver on the link has a termination resistor. The resistor value matches the characteristic impedance of the cable.

    Adding multiple terminations can lead to a situation where the impedance presented to the Driver is too low, in effect overloading the bus.

    Regards,

    Richard

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  • 0
    •  Analog Employees 
    on Dec 8, 2014 10:19 AM

    Hi Ed,

    Can you please provide me with a sketch of your system setup?

    Usually if you are using a network with just ADN4665 Drivers and ADN4666 Receivers, then the last receiver on the link has a termination resistor. The resistor value matches the characteristic impedance of the cable.

    Adding multiple terminations can lead to a situation where the impedance presented to the Driver is too low, in effect overloading the bus.

    Regards,

    Richard

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