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LM4040-N: output voltage of the reference not correct

Part Number: LM4040-N


       I am trying to use the LM4040BIM3-2.5 to generate dual polar power supply similar to the circuit described in TIDA-00445, and the circuit I am doing is shown below.

The output from U10 is 24V, I am testing D10 and D11 under no load condition. Now the positive output is 2.62V and the negative output is -2.24V.  Could anyone tell me if there is anything wrong with the circuit?

Plus, 2.62V and -2.24V are the two measurements if the connection of my probe is reversed, i.e., if  I have +probe to 2V5P and -probe to GND, it is 2.62V, while having -probe to 2V5P and +probe to GND, it is -2.24V. Could anyone give me some ideas on what should I do for a correct output voltages?

Thank you!

  • I found that this is a measurement issue. If I use 1v/div, the result is correct, using 2v/div , result is still fine, but using 5v/div gave me the wired results. Is this normal ?
  • In reply to Lee Young:

    Hi Li,

    Yes that is normal. It is likely that you are using an 8-bit oscilloscope. In that case, when you have 5V/div, you resolution is about 0.2V (5V*10div/2^8) without accounting for noise.

    Regards, Diego Lewis