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Original question:

LM317: Recommended part#

LM317: parallel LM317

user5327551
Intellectual 830 points
Part Number: LM317

Hi

  I have a PSU with 55V /5.5A and I want to use LM317 to drop to 52V/5.5A

In order to do that , I need to put them in parallel . On your datasheet you have a circuit at page 16 but voltage and A are not suitale for us. Can you please explain how to modify to get 52V/5.5A ?

  • 0
    TI__Guru 55940 points
    Hi ,

    The same concept that is shown in Figure 22 can be applied to your application as well. Please note that while the theory should work for your application, we have not actually attempted it. We highly recommend that you prototype your application before committing to it.

    You will want to make sure that you use additional LM317 regulators in parallel in order to achieve the higher current as well as reduce the power dissipation in each regulator for thermal reasons.

    In order to adjust the voltage, you will need to modify the resistor(s) on the non-inverting input for the amp. This is your R2 for the resistor divider. R1 is the 100 Ohm resistor. You will also have any voltage inaccuracies in your transistor and op-amp.

    Other than than you need to make sure that your transistor and op-amp are sized properly for your application voltages.

    When you layout your board, it is important to minimize any resistance between the ADJUST pins of your LM317 regulators. Any resistance in these pins will reduce the current sharing accuracy.

    Very Respectfully,
    Ryan