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TPS43061: ISNS noise filter

Dice-K
Mastermind 7818 points

Part Number: TPS43061

Tool/software:

Hi support team,

Is it okay to change C12 from 100pF to 0.01μF?

When I lowered the input voltage, the output voltage dropped.
When I increased the capacitance of C12, the output voltage was maintained.
Noise may be present on the ISNS, causing the current limit to malfunction.

Dice-K

  • 0
    TI__Mastermind 19715 points

    Hello Dice-K,

    Increasing the capacitance of this filter is not really recommended.
    This would not only filter some noise, it will also slow down the reaction time of the control loop.
    It would basically turn the peak current control loop into an average current regulation, which cannot quickly react on changes of the load or the input voltage.

    There are multiple possible reasons why the output voltage vannot be reached for a lower input voltage (inductor size, current sense resistor, compensation network, etc.).
    Please verify and re-calculate these components first.
    If some noise on the current sense lines is to blame (as you suggest), then there is a fundamental issue with the design. For example, big ringing on the switch node, poor layout, etc.

    Best regards
    Harry