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The LM2941 output voltage is programmed to 5V, but it never exceeds 4V when the input voltage slowly rises. Why?

April 26, 2017exceeds input lm2941 output programmed rises voltage

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The LM2941 output voltage is programmed to 5V, but it never exceeds 4V when the input voltage slowly rises. Why?

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If the input voltage is not applied rapidly, the output voltage may not reach the programmed value. We believe the misoperation must be due to one of two things (the first one is more likely): 1) The input source is being loaded down because it can”t supply enough current to get the LM2941 through the saturation region. When the output is “stuck” at about 4V, what is the input voltage? If the input is 4 – 5V, that means you need a supply source with more current capability. It is not a latch-up, rather the infamous “carrot” spike in quiescent current associated with first generation LDOs (see the data sheet Typical Performance Characteristics, quiescent current vs input voltage). 2) Part is oscillating. Check the output when it is stuck at 4V. If you have an oscillation, you need to check the ESR on the output capacitor to be sure it is within the range specified in the product datasheet.