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SN65LVDS179-EP delay and jitter

Other Parts Discussed in Thread: SN65LVDS179-EP

Hi,

one of my Customers is using the SN65LVDS179-EP in the below configuration as transmitter only:

The transceivers are used to transmit the system clocks for boards NUM1 and NUM2 and therefore they need that the differential 40MHZ sent are as synchronized as possible.

 

The questions are:

1. Propagation delay: the datasheet specifies a maxim of 4.5ns over the full temperature range and 1.7ns typ. Is this propagation delay always constant for a certain temperature for a given part or could it vary and generate some jitter between the two LVDS clocks?

2. Jitter generation: Is the transceiver susceptible to add jitter to the input signal or will the LVDS clock signal have the same jitter/same output precession at the output as in the input?

3. Can you think about anything else that may cause some jitter or delay between both clocks?

 

Thanks, Beatriz.

  • Beatriz,
    1) The propagation times are a function of Voltage, Temperature, and Process parameters (VTP). In this case, a fixed device will not have process variation and will only be subject to variation from temperature and voltage. If these are fixed, the delay should also be fixed. There could be effects over time with aging. These effects should be minimal.
    2) All devices will have some impact to added jitter.
    3) Noise on power supplies could impact the voltage and influence the delays differently between devices.
    Routing length and any impedance mismatches could cause additional phase mismatch between clocks. Though these should be fixed for same VTP.
    Regards,
    Wade