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CLC001: Using CLC001 to drive 100 ohm twisted shielded pair

Part Number: CLC001

Hello,

My question relates to the output 75 ohm resistors used  in the CLC001 application notes.  If the device is being used to drive a 100 ohm twisted pair cable, should the 75 ohm load resistors be replaced with 50 ohm load resistors?  Will changing the resistor load adversely affect the CLCL001 output performance?

Thanks for any help you can give,
Rob Curtis

  • Hi Robert,

    You are correct. I presume the figure you are referring to is Figure 6 (Twisted Pair Cable, DC-coupled) and Figure 7 (Twisted Pair Cable, AC- coupled). Assuming you drive a 100-ohm twisted pair cable, there should be 50-ohm load resistors for each output polarity.

    The only side effect I anticipate by driving a 50-ohm output is that, since the output is current mode, the driver amplitude for each output will be about 2/3 the amplitude when the resistor load is 75-ohm. Note though, that you may have different requirements for amplitude when driving differentially across the twisted pair.

    Voltage amplitude can be adjusted by modifying the R_REF resistor value. This value can be lowered to increase the drive voltage, and the value can be increased to decrease the drive voltage amplitude.

    Thanks,

    Michael