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LM27342: question about required min load.

Martin Chien
Expert 3590 points
Part Number: LM27342
Other Parts Discussed in Thread: TPS62147, TPS54202

Hello Team,

My customer is using LM27342 with 12Vin, 10Vout, at no load condition, the output loss regulation can't keep stable at 10V, I noticed a min load is required mentioned in datasheet when output is greater than 3.3V.

They are using the inductor is 2.2uH, at this condition, 20mA is required then output can be regulated. here are customer's questions:

1. Can you tell what's the reason of LM27342 min load is required?

2. How to determine the 20mA is good enough when considering MP? How to know the required min load in every design condition?

3. Min load 20mA for customer is too high, which similar part you can suggest to instead of LM27342?

Thanks,

Martin

  • 0
    TI__Mastermind 35115 points

    Hi Martin,

    Please see my answers below.

    1. Can you tell what's the reason of LM27342 min load is required?

      The minimum load is needed to ensure the BOOST cap stays charged high enough to turn on the high-side NFET. The BOOST cap is charged only when the SW node goes low and adding a minimum load ensures this happens frequently enough.

    2. How to determine the 20mA is good enough when considering MP? How to know the required min load in every design condition?

      This is a tough question to answer. The best route might be to use an alternate part since the 20 mA load is too high anyway.

    3. Min load 20mA for customer is too high, which similar part you can suggest to instead of LM27342?

      I suggest looking at the TPS54202 as an alternate part. If higher fsw is important for this application, the TPS62147 could also be a good alternate.

    Best Regards,
    Anthony