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LMR16006 or LMR14006 at light load

Mihai Vintila
Intellectual 580 points
Other Parts Discussed in Thread: LMR14006, LMR16006

Hello, I am designing a board where I use LMR14006 (or LMR16006). The input voltage is 12 or 24V.

The board needs approx 100-200mA maximum load but the board will "sleep" for most of the time and I need a low current consumption (1-2mA).

Using webench I get an error if I use LMR140006 at low current (I used 5mA) which is a bit surprising as I understand that this device is supposed to work at light load.

With LMR16006 it works in webench at 5mA.

 Is there a difference between them at light load ? Should I use the 16006 ?

Thank you,

Mihai

  • 0
    TI__Genius 11085 points

    Hi Mihai,

    The light load behavior of the LMR14006 and LMR16006 should be very similar. The efficiency curves on both datasheets go down to 0.1mA load current. I don't think there's any issue using either of them for your application. Both of them will enter sleep mode or ECO mode at 1mA~2mA load.

    The Webench design meant to design for the max load for the application. I will ask them to check the calculation for the LMR14006 in sleep mode.

    Hope this helps.

    Yang

  • 0 in reply to YangZhang
    Intellectual 580 points

    Hello Yang,

    Thank you very much for the prompt and clear response.

    I have one more question:

    the datasheet mentions " If the input supply is located more than a few inches from the LMR16006, additional bulk capacitance may be required in addition to the ceramic input capacitors."

    The board will be used in an unit mounted in a car (so the cables will be quite long) and will sleep for most of the time (1-2mA), while at peak power it can take about 300mA. Using webench I get 4.7uF ceramic input capacitance (ESR 3 mOhm).

    Can you recommend the bulk capacitance to use at the input ?

    Thank you,

    Mihai

  • 0 in reply to Mihai Vintila
    TI__Genius 11085 points

    The additional bulk capacitor is needed when you have long wiring for power connection with any buck converter. The parasitic inductance of the wire will resonant with the ceramic capacitors if there's no enough damping. A bulk capacitor with much higher ESR than ceramic can prevent this resonant from happening.

    The LMR16006 EVM user guide has a footprint reserved for this bulk cap. A 10uF electroletic cap is used in the BOM. It should work for you as well.

    C1 EEE-FK1J100P CAP, AL, 10uF, 63V, +/-20%, 1.5ohm, SMD SM_RADIAL_D Panasonic

    -Yang