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TPSI3050: Auxiliary circuit from VDDH

Egoitz Toledo
Prodigy 30 points
Part Number: TPSI3050


Hello,

I have not found any application or example circuit where the VDDH is used to supply the auxiliary circuit of the isolated side, so I wonder if this could be possible.

Thank you and regards.

  • +1
    TI__Expert 3575 points

    Hello Egoitz Toledo, 

    Thank you very much for reaching out. 

    This is possible, however, keep in mind that the power transfer for the device remains the same and now you will be drawing twice the power as when comparing with using the VDDM rail. For example, when using power from the VDDM rail, it is possible to draw up to 10mA. This would directly affect the maximum achievable switching frequency. When it comes to the VDDH rail, since you will be supplying double the voltage, the current available would be less. As long as you leave maxim for your design switching frequency this should work. 

    These are a few questions that would help to provide for detailed feedback.   

    How much current do you need for your auxiliary circuits?

    What is you maximum switching frequency? 

    What is your load is VDRV ? How much capacitance or charge you have. 

    Sincerely, 

    Francisco Lauzurique

  • 0 in reply to Francisco Lauzurique
    TI__Expert 3575 points

    Hello Egoitz Toledo, 

    Let us know if you have any further questions. 

    Sincerely, 

    Francisco Lauzurique

  • 0 in reply to Francisco Lauzurique
    Prodigy 30 points

    Hello Francisco,

    First of all, thank you for your answer.

    I made the question because as explained in the datasheet, VDDH has UVLO protection, but about VDDM, is nothing said, so I thought that using VDDH would have an advantage in front of VDDM. More or less I will need 5mA for the auxiliary circuit so considering that the current from VDDH will be around the half of the current from VDDM, I may have a problem there. Taking this into account, I have a new question, VDDH and VDDM are totally dependent and an undervoltage of VDDM will provoke an UVLO or they are independent an it could exist the situation where VDDM is in undervoltage and VDDH not?
    If they are dependent, the threshold voltages are exactly the half of VDDH for VDDM?

    Thank ypu and regards.

  • +1 in reply to Egoitz Toledo
    TI__Expert 3575 points

    Hello Egoitz, 

    These two voltage are floating supplies. Basically we have 10V from VDDH-VSSS because we have 5V from VDDM-VSSS and 5V from VDDH-VSSS. VDDM does have an UVLO because VDDH is dependent on VDDM. If VDDM where to drop to 0V, then VDDH will be 5V and this would trigger an UVLO in VDDH.  

    Let me know if this answers your question. 

    Sincerely 

    Francisco Lauzurique

  • 0 in reply to Francisco Lauzurique
    Prodigy 30 points

    Thank you very much for your help!