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SN65LVDS33-EP: Max Frequency and Fail Safe Circuit

Frank Albanese
Prodigy 10 points
Part Number: SN65LVDS33-EP

Original details: 2 questions on the SN65LVDS33-EP (i.e. SN65LVDS33MDREP), Quad LVDS Diff Line Rx
1. I am using this part to convert a differential LVDS 100 MHz clock to TTL for a frequency measurement on a scope. Can you tell me what is the maximum Frequency that can be supported by this 400 Mbps device? If this device cannot support a 100 MHz clock input, is there any other equivalent device LVDS/LVTTL that supports a higher bit rate?

2. With regards to the Fail Safe circuit, the datasheet implies that it will detect if both inputs are missing, but it is not clear if it will detect only 1 input missing? Can you please tell me if this device will detect only 1 of the 2 inputs missing with no external circuitry? If not, can you suggest any external circuitry that will help detect 1 of the 2 inputs missing. I do not want any false PASSES because of a missing input due to noise.

  • 0
    TI__Guru 62930 points

    Frank,

    I will try to answer your questions.

    1) The device is indicated to operate up to 400Mbps (200Mhz equivalent clock).   Operating at 100Mhz should not be an issue.  However, quality of the signal at the RX could impact performance.

    2) It is unable to detect a single missing input vs both.  It can only monitor the differential voltage to make decisions regarding the failsafe. 

    However, with the external 100ohm termination, a floating input should track with the driven input, and thus trigger the failsafe due to the low differential.  This assumes that the termination is not part of the open circuit.

    This device uses a unique active failsafe technique that looks at a time window in order to determine if failsafe should be triggered.   You can reference this app note on its use and implementation.

    If this answers your question, please click "This Resolved My Issue"
    Regards,
    Wade