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SN6505A: Oscillator Reliability and Guaranteed Device Performance

Part Number: SN6505A

Hello,

I would like to know if the internal oscillator has had any testing and certification done to confirm performance?

Specifically, have any safety organisations such as UL, TUV, VDE, etc. confirmed performance and reliability of this device?

I'm interested in the fail condition of the oscillator as well as part in general? Any test reports that have been done to confirm the circuitry would be great to see.

Thanks,

Arno

  • Hi Arno,

    Welcome to E2E! Internal oscillators are tested in production to meet datasheet performance for every SN6505 device TI ships.

    Our digital isolation devices are UL, TUV, VDE, and CSA certified, but since transformers provide isolation in an SN6505 system, the SN6505 itself is not certified by these organizations.

    In which conditions would you like to know the failure behavior for? Is this requirement for a safety application?


    Thank you for posting for E2E!


    Have a great weekend,
    Manuel Chavez

  • Hello Manuel,

    This is related to safety - I'm interested in using the device for a interlock circuit.

    Thus, the oscillator within the device should ideally be latch-up and short-circuit proof. Some MEMS oscillators have these features, but cannot drive over longer distances. The SN6505 would still be used with a transformer for the cable compensation.

    Alternatively, the SN6505 has a clock input - Is that internal circuity latch-up proof? How does internal oscillator and external clock interact with each other? This is not exactly clear to me what happens when external clock is not valid anymore, etc. and the associated impact on the internal oscillator.

    There is lot of hype around what is considered a fail-safe circuit - Safety organisation short device pins, etc. to ensure that circuit will not be damage or impact other circuitry negatively. Could the SN6505 handle a short circuit condition on the oscillator (transformer driver) output pins?

    Arno

  • Hi Arno,

    This device is not certified or marketed for functional safety applications, but it can be used in the interlock circuit if you decide so.

    ESD latch up is part of the qualification process for all of our parts as documented in their datasheets, and it covers every pin in each part. How long is the cable the SN6505 will supply power through?

    As mentioned above, the clock input pin is ESD rated, so exceeding this or other absolute maximum ratings likely will damage the device.

    When using an external clock, circuitry inside the SN6505 detects the clock signal and multiplexes it to the rest of the circuit instead of the internal spread-spectrum-clock, as shown in the datasheet clipping below:



    If the external clock reaches an invalid operation, the internal circuitry detects this, and the SN6505 resumes operation using the internal clock.

    The SN6505 is a robust device that has multiple self-preservation features. In the case where one of the transformer driver pins, D1 or D2, are shorted, the device would limit the current it consumes with internal current-limiting, and if the temperature rises due to the short condition, the device would power off with an internal thermal shutdown feature. Both of these operate on a cycle-by-cycle basis, so if the temperature or current return to normal, the SN6505 could return to normal operation.


    Thank you,
    Manuel Chavez