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SM72445: SM72445 input voltage and current scaling

Andras Magyar
Intellectual 380 points
Part Number: SM72445

Dear Experts,

I would like to know how the SM72445 will know the exact input voltage if we put different resistor divider scaling on AVIN? Is it referenced to A0 scaling (Vout)?
Because for the output voltage and current I understand since the Vout and Iout are compared to A0 and A4 pin voltages so in these cases there is a reference.

I mean it has to know because it has to know the Pin=Vin*Vout for MPPT algorithm. Also, the question applies for the Iin (input current) as well.

Thanks and regards,

Andras

  • 0
    TI__Guru 50481 points

    Hi Andras,

    you are right the voltage level of the AVIN input is compared against the voltage set on the A0 input.
    So the resistor divider on AVIN in influencing the captured input voltage.

    Typically this resistors are fixed and not changed during operation.

    For the AIIN and external current sensing circuit has to provide a voltage signal proportional to the measured current.

    Best regards,

     Stefan

  • 0 in reply to Stefan Schauer
    Intellectual 380 points

    Hi Stefan,

    Thanks for the quick answer! Slight smile

    Ok, so the Input and output voltages are all references to A0 (From 0 to AVDD which is typically 5V).

    In case of input current I understand that I have to translate current to voltage and provide it to AIIN. So I guess the algorithm works in a way that it multiplies the AVIN*AIIN voltages (in reality it is P=Vin*Iin) and while this product grows it raises the duty cycle of buck or boost switches and the user has to know that what AIIN voltage means what current level and the SM72445 does not have to know that. We only have to make sure that they are between 0 and AVDD.

    Regards,

    Andras

  • 0 in reply to Andras Magyar
    TI__Guru 50481 points

    HI Andras,

    yes, this is right.

    Best regards,

     Stefan

  • +1 in reply to Stefan Schauer
    TI__Guru 50481 points

    Hi Andras,

    I have not seen an update for the last 10 days, so I assume the questions are/or answered and the issue is solved.
    I close this thread now. If there is still something open reply and the thread will get open again.
    If you have any other question or of the thread gets locked, please open a new one.

    Clicking the Resolved Button also helps us to maintain this forum.

    Best regards,
    Stefan