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LM2903: LM2903 applied CT current value overcurrent detection circuit configuration problem

Part Number: LM2903
Other Parts Discussed in Thread: LM393LV

Hi, TI expert.

The customer applied LM2903 and configured the CT current value overcurrent detection circuit, but there are the following problems.

Problem: Even though IN- does not exceed IN+, it falls to Low.  (See attached file content)

(LM2903) Circuit Review Problems.pptx

Q1) Can I know the cause of the problem phenomenon?

Q2) Is there any solution?

Please let me know if you need any additional information.

Please Check. Thank you.

  • Hi Grady,

    has your customer read section 8.2.2.1 of datasheet?

    Kai

  • Grady

    Thanks for your post.  As Kai mentioned, it appears that the output is going low because both inputs are going outside the recommended operating range.  When this occurs, the output goes low even though the inputs may not reflect an output low condition.  It appears that your operating voltage is 5V, so I suggest you switch to a comparator that has rail to rail input capability such as our new LM393LV.  This part is pin compatible with the LM2903 and this should solve your problem.

    Chuck