LTC3774

In LTC3774 datasheet page 16 regarding Inductor DCR sensing if we disable the SNSD+ pin will we:

  • Need a separate sense resistor?
  • Or A simple R1 & C1 RC filter on SNSA+ pin suffice?

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  • +1
    •  Analog Employees 
    on Nov 21, 2019 11:34 PM

    Hello,

    If the SNSD+ pin is shorted to ground, a separate sense resistor is not required. An RC filter tied to the SNSA+ pin (R2&C2 in Figure 4) is all that is required. For applications using DCR sensing with SNSD+ disabled, keep in mind the following:

    • Vsense(max) will be 5x larger than the specified value. The inductor chosen should have a DCR high enough to provide an accurate current limit.
    • The RC time constant of the filter should now be set equal to L/DCR instead of L/DCR/5.

    Best regards,

    Mike

Reply
  • +1
    •  Analog Employees 
    on Nov 21, 2019 11:34 PM

    Hello,

    If the SNSD+ pin is shorted to ground, a separate sense resistor is not required. An RC filter tied to the SNSA+ pin (R2&C2 in Figure 4) is all that is required. For applications using DCR sensing with SNSD+ disabled, keep in mind the following:

    • Vsense(max) will be 5x larger than the specified value. The inductor chosen should have a DCR high enough to provide an accurate current limit.
    • The RC time constant of the filter should now be set equal to L/DCR instead of L/DCR/5.

    Best regards,

    Mike

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