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LM62460: external parts selection

liping pan
Intellectual 460 points
Part Number: LM62460
Other Parts Discussed in Thread: LMR51450

My application:

1) input voltage: 20V~24V

2) output voltage: 7V~18V, will be changed by using potentiometer to set feedback resistor divider.  The output voltage will be changed based on MCU controll the potentiometer.

3) output current: 100uA ~ 5A.

Inductor selection:

Based on datasheet section 9.2.2.3 equation 5), it can be calculated = 1.9 uH.

Question: This is calculated based on max current. Should it work fine under light load 100uA?

Cff capacitor selection:

Based on WEBENCH, it gives different value based on different output voltage.

Then how should I choose a common one for flexible output voltage for my application?

  • 0
    TI__Guru 50120 points

    Hello,

    Since this application is for a dynamic output voltage system, it would be best to design it for the worse case output capacitance which occurs at the lowest output voltage regulation in your system.

    In this case, please design your output capacitance for 7Vout and it would work for 18Vout as well. 

    I would also suggest to not sure a feedforward network since the output capacitance is a very large range. Usually the Cff/Rff are meant to target a specific output voltage to get improvements in PM but in this case it could impact the loop response given the 7V-18V wide output voltage range. 

    Regards,

    Jimmy 

  • 0 in reply to Jimmy Hua
    Intellectual 460 points

    Thanks, how about question for inductor selection?

  • 0 in reply to Jimmy Hua
    Intellectual 460 points

    One more question, for my application, compared LM62460 and LMR51450, what's your best recommendation?

  • 0 in reply to liping pan
    TI__Guru 50120 points

    Hello,

    The inductor selection is calculated based on the DC current rating of the device. In the case for the LM62460, IOUT_MAX is 6A. 

    The inductor will for your application's output current range yes.

    For performance I would pick the LM62460. For cost I would pick the LMR51450. 

    Regards,

    Jimmy