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LM317A: LM317A

Stefano Casilli
Prodigy 40 points
Part Number: LM317A
Other Parts Discussed in Thread: LM317

Dear sirs,

I am using the LM317A to have 37V at the output side with 48V at the input side. This should be possible according the specific regarding the input output maximum difference voltage in maximum ratings of data sheet. But in product details in Texas Instruments web site and in device comparison of data sheet the input voltage range is 4.25-40V so it seems i can't enter a voltage >48V.

Which of the two is correct?

Kindest regards

Stefano Casilli

  • TI__Genius 13085 points

    Hi Stefano, 

    Yes you can regulate 48V to 37V with LM317. This LDO uses a floating topology and as you stated the Abs max allows for a Vin to Vout differential of up to 40V, so the current flowing through the resistor from Adj to GND (R2 in the datasheet schematics) causes the ground/reference voltage of the IC to be higher than 0V, this is what allows the input voltage to be higher.