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LMR33620: SCH review

Part Number: LMR33620

Hi team,

Could you please help to double check the SCH of LMr33620?

  • Hello Amelie,

    The inductor L2 should be reselected. The rated inductance value is acceptable, however the datasheet shows that severe de-rating will occur at the 2A output condition, see below screenshot of inductor datasheet specifically the inductance vs. DC current curve: http://sunlordinc.com/UploadFiles/2014/03/191507413A204AE9.pdf

    The minimum inductance value to ensure stable operation is 0.97uH which is violated in the given condition according to the datasheet. A new inductor should be selected to ensure that this minimum inductance value is not violated across the load current range.

    Otherwise the schematic looks good.

     Regards,

    Harrison Overturf

  • Hi Harrison,

    Thanks for your reply.

    I have a question. After the circuit is stepped down, the actual power consumption of the 3.8V output will not exceed 500mA. In the case of 500mA power consumption demand, do customer still need to choose the 2.2uH inductance value of the 2A rated current?

    What is the impact if customer still use the currently selected model?

  • Hi Amelie,

    We recommend never allowing the inductor to saturate because although this device utilizes valley current limit to prevent current runaway, a saturated inductor core allows the inductor current to ramp up to high values very rapidly which leads to component damage. Select an inductor with a saturation current rating that is at least the typical HS current limit or 3.5A for this device. More information can be found in Inductor Selection section 9.2.2.4 in the datasheet.

    If the customer chooses to use the currently selected inductor, the device is not guaranteed to operate as expected under the conditions outlined in the datasheet and they run the risk of component damage during short circuit conditions as well as design instability at higher load currents.

    Regards,

    Harrison Overturf