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EMB1499Q: single-ended current sensing

Dimitrios Papadopoulos
Intellectual 640 points
Part Number: EMB1499Q

Hello all

I noticed that EMB1499Q uses single-ended inputs for sensing in both current control loops (primary & secondary). Usually, this is a call for switching noise coupling, esp. for high balancing currents. It is possible to convert these ports to differential ones, eg via instrumentation amplifiers or current transformers. However, an amount of delay will be introduced. What is the upper limit for this delay? Other ideas?

Thank you in advance

  • 0
    TI__Mastermind 19795 points

    Hi Dimitrios,

    Thank you for your question! Unfortunately we do not support differential inputs for the control loops. If you are looking to use the device outside of its intended design specifications, you will need to handle characterization of the delay introduced.

    Kind regards,

    Vince

  • 0 in reply to Vince
    Intellectual 640 points

    Hello Vince,

    Thank you very much for replying. Before closing this thread as resolved, is it possible for you to disclose just the maximum tolerable delay for an external sensing circuit? At least, that would be useful for inserting a simple resistor-capacitor EMI filter.

    Thank you in advance

  • 0 in reply to Dimitrios Papadopoulos
    TI__Mastermind 19795 points

    Hi Dimitrios,

    Unfortunately tolerable delay is something that is highly dependent on the system design you choose. For instance, choosing the sense resistor affects the voltage differential that occurs for a given load step, which itself needs to be characterized. Moreover, it also depends highly on the amount of tolerance your input/outputs are to a given load step. Each of these is highly interconnected, and requires thorough characterization. For this reason, it is very difficult for us to provide a specific tolerable delay for the external sensing circuit.

    Despite this, I do have some recommendations for you to keep in mind while designing this:

    • Ensure output of the external sensing circuit provides sufficient margin to remain within the ranges specified in the "Electrical Characteristics: Feedback Voltage" section of the datasheet.
    • Ensure operation within the maximum duty cycle of the converter ("Power Stage Designer" is a great tool for quick calculations using various converter topologies)
    • Follow the "Application Hints" section of the datasheet for details on sense resistors, that may be applicable to your external circuit.

    Again, I apologize that we cannot provide more details, but this is indeed very application-specific.

    Regards,

    Vince

  • 0 in reply to Vince
    Intellectual 640 points

    Hello Vince,

    You provided a considerable amount of information that we will take into account.

    Thank you very much,