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LMR36506-Q1: PFM mode

Yuto Kitamura
Expert 4000 points
Part Number: LMR36506-Q1

Hi team,

One of my customer is using LMR36506MSCQRPERQ1.

It will work with PFM mode when the output goes low.

1. Are there lower limit of switching frequency in PFM mode?

2. How much is the on-time in PFM mode? Also, is it fixed value? 

3. How will the relationship between on-time and off-time be in PFM mode?

Best regards,

Yuto

  • +1
    TI__Genius 15895 points

    Hi Yuto

    1. the lowest frequency should happens when ton=tonmin=57ns,toff=toffmax=9us, fsw is 110kHz;

    2.In PFM mode, HS turns off when iL reaches IPEAK-MIN, which you can see in the datasheet is 0.19A,  ton will be (0.19*L/(Vin-Vo)) ,but keep in mind ton will never be less than tonmin;

    3.As said in '2', HS turns off when iL reaches IPEAK-MIN, Then Vo decreases, when VFB reaches Vref, HS turns on again.

    Best regards.