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LM117 - output capacitor question

LM117 Protection Diodes The LM117 datasheet states the following "When an output capacitor is connected to a regulator and the input is shorted, the output capacitor will discharge into the output of the regulator. The discharge current depends on the value of the capacitor, the output voltage of the regulator, and the rate of decrease of VIN. In the LM117, this discharge path is through a large junction that is able to sustain 15A surge with no problem. This is not true of other types of positive regulators. For output capacitors of 25 μF or less, there is no need to use diodes." Does this apply to all types of capacitors including those with virtually no ESR, such as ceramics, or does it only apply to types of capacitors with an appreciable amount of ESR such as tantalums?

3 Replies

  • LM317-n; Literature Number: SNVS774L

    This applies to all capacitor types.

  • In reply to Donald Jones:

    The lit # points to the datasheet. Did you intend to point to an applicaion note?

  • In reply to Matthew Day:

    "... Did you intend to point to an application note? ..."

    Michael,

    No. My intent was only to specify which of the several LM317 datasheets this is for, so that there is no confusion.

    Datasheet SNVS774L contains the quote, that's the literature #  that I referenced.

    Datasheet SLVS044U does not contain the questioned quote, so anyone looking at SLVS044U, and believing that SLVS044U is the only LM317 datasheet available, will not have any idea what this thread is about.

     

     

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