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BQ25790: inductor selection

Part Number: BQ25790

Hi,

my customer is using BQ25790 operating in 1.5MHz.

In datasheet, it says 

Please note that the 1.5 MHz switching frequency only works with the 1µH inductor and the 750 kHz switching frequency only works with the 2.2µH inductor

Why so strict? 

My customer would like to use 0.68uH inductor at 1.5MHz, it would bring larger ripple than 1uH. If they can accept the ripple, what else is wrong with 0.68uH?

  • Hi Howard,

    We have only tested operation at 1uH+/-20% at 1.5 MHz, and therefore can only warranty operation with that inductance.  The inductance sets the large signal inductor current and slew rate.  To high of ripple current may prematurely trigger the cycle by cycle current limit at high output power.  Too fast of slew rate could prevent the current protection circuits from reacting fast enough to transients.  In addition, the inductance sets the pole for small signal stability which has internal compensated.. 

    Regards,

    Jeff