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LTC3260 LDO+ Inrush current

Osamu
on Jul 20, 2021

Hello.

When the LTC3260 is started up, an inrush current of nearly 100mA is generated in LDO +. Is this okay?
This can also be confirmed with the standard circuit of LTSPICE.
Although it was not stated in the absolute maximum rating, it is stated in FEATURES as 50mA MAX.

Thank you.

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  • +1
    •  Analog Employees 
    on Sep 29, 2021 11:53 AM

    Hi Osamu,

    Sorry for late reply. i hope you found an answer earlier. The soft-start for the LDOs is only about 75us (page 9 of datasheet). Current limit is about 100mA (page 3 of datasheet). When the part starts-up, it needs to charge the 10uF LDO output capacitor up to 12V (page 1). Based on the Ic = Cdv/dt where C is 10uF, dv is 12V, and dt is 75us, the current needed is much greater, 1.6A. Therefore current limit is going to limit the current into the capacitor. Since current limit is 100mA it is expected that the LDO will operate in current limit, ~100mA during startup. This is designed to be able to handle operating in current limit and will not damage the LTC3260.

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  • +1
    •  Analog Employees 
    on Sep 29, 2021 11:53 AM

    Hi Osamu,

    Sorry for late reply. i hope you found an answer earlier. The soft-start for the LDOs is only about 75us (page 9 of datasheet). Current limit is about 100mA (page 3 of datasheet). When the part starts-up, it needs to charge the 10uF LDO output capacitor up to 12V (page 1). Based on the Ic = Cdv/dt where C is 10uF, dv is 12V, and dt is 75us, the current needed is much greater, 1.6A. Therefore current limit is going to limit the current into the capacitor. Since current limit is 100mA it is expected that the LDO will operate in current limit, ~100mA during startup. This is designed to be able to handle operating in current limit and will not damage the LTC3260.

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