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LM3940 IPM 3.3V

Lebing Jin
Intellectual 390 points
Other Parts Discussed in Thread: LM3940

Hi,

I want to get 3.3V from LM3940 regulator which can convert 5V to 3.3V. Around LM3940 I only soldered capacitors as datasheet suggested, but I get 4.8V or 4.2V as output. Do I also need to add some resistors to the output? Because the datasheet mentions 3.3V @1A.

Thank you in advance.

 

Lebing

  • 0
    TI__Intellectual 1990 points

    Hi Lebing,

    You do not need to add resistors to the output. As long as your capacitance on the output was at least 33uF (larger values are ok as well). Also make sure that your capacitor's equivalent series resistance fits within the stable region showed in the graph below.

    If everything still checks out, I would ask that you check whether you are getting power from another part of your board on the output. You should not be seeing 4.8 or 4.2V on the output with this device.

    Thanks,

    Nate

  • 0 in reply to Nathaniel Wilson
    Intellectual 390 points

    Hi Nate,

    The problem was solved. Now I have the 3.3V as the output. The capacitance I used before was smaller than 33uF.

    Thank you very much!

    Lebing