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PMP8740: DESIGN calculator

Madhura Gogate
Intellectual 1425 points
Part Number: PMP8740

Hello team,

Can you please share the design calculation file for Constant voltage and constant current section for the PMP8740?

Thanks and Regards,

Madhura

  • 0
    TI__Expert 5875 points

    Hello Madhura,

    For the PMP8740 I didn't use calculation tool, but I measured the basic poles and zeroes position by analyzing the bode plot (with the help of a network analyzer) and then I moved mainly the zeroes in order to get at least 60deg. phase margin and 12dB gain margin. The voltage loop is not critical because the battery voltage does not change rapidly, but I suggest to have a good bandwidth in the current loop (few hundred Hz up to few KHz) and avoid any overshoot in the output current, when quickly changing the set point of the constant current limit of the converter.

    Best regards,

    Roberto

  • 0 in reply to Roberto S.
    TI__Intellectual 1425 points

    Hello Roberto,

    Thanks for your feedback.

    Is there a calculator tool readily available for such a design?

    Regards,

    Madhura

  • 0 in reply to Madhura Gogate
    TI__Expert 5875 points

    Hello Madhura,

    I don't have specific calculator tool for closing the loop in CV and CC power supply, but I suggest to have a look to the 2018 Power Supply Design Seminar (PSDS) topic "Switch-mode power converter compensation made easy", accessible at the link:

    https://training.ti.com/psds?keyMatch=PSDS

    The CV loop can be closed as explained in the presentation, by considering the battery as an "infinite" output capacitor, while the CC loop should be analyzed by considering the battery as a short circuit in series with its own impedance. This way, any small change in the output voltage, divided by the battery impedance, will be translated into a current that the current sense amplifier will read and feed-back to the loop compensation circuit.

    Regards,

    Roberto