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TPS7H4001-SP: Questions about the Slope Compensation

Kazuhiko Hirano
Genius 15008 points
Part Number: TPS7H4001-SP

Tool/software:

Hello,

My customer has a couple of questions about the Slope Compensation as follows.

Q1:
In 8.2 Functional Block Diagram, the output voltage of the Slope Compensation block is RSC x SC?

Q2:
My customer complains In 8.2 Functional Block Diagram, the HS MOSFET Comparator monitors high side FET current. If so, my customer is mentioning the equation (10) on page 37 should be SCideal = (Vin-Vout)/L, not Vout/L. Is their thought correct?

Best regards,

K.Hirano

  • +1
    TI__Expert 5071 points

    Hello Hirano-san,

    Q1:

    The functional block diagram is meant to be a high-level representation of the internal workings of the device.

    The slope compensation block works by adding an additional ramp signal to the current sensed by the HS Current Comparator. The slope of this ramp is configured using the RSC resistor connected to the RSC pin.

    Q2:

    (Vin-Vout)/L is the correct equation for the rising (up) slope of the inductor current. The relevant value for slope compensation however is the falling (down) slope of the inductor current. This can be calculated using Vout/L.

    If I may recommend an excellent resource for deeper understanding of current-mode converter operation, the application note "MODELLING, ANALYSIS AND COMPENSATION OF THE CURRENT-MODE CONVERTER" provides a great look at slope compensation.

    Thanks,

    Andy