Paralleling LDOs to Create More Output Current

Document created by analog-archivist Employee on Feb 23, 2016
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I am using an ADP1741 to step down 2.0V to 1.8V. I need output current of 2A +
1A in overhead.

My proposal is to have 2 x ADP1741s in parallel. Will this work?

 

You could use ballast resistors to ensure that the LDOs will share.  Size the
ballast resistors to give you a voltage drop of 2% of the output voltage at
half the shared load current (1.5A in your case for a 3A total).

It sounds like you are using the adjustable (ADP1741) LDO.  If that’s the case,
you can also improve your chances of sharing by using a single output voltage
divider and connect the sense/adjust pin of the two ADP1741’s together.  This
will eliminate the error caused by using two separate voltage dividers.

If the LDOs don’t share, one will carry most of the load and eventually enter
thermal shutdown, then the other one takes over.  The parts won’t be damaged
but the output may have a fair amount of low frequency ripple as the LDOs turn
on and off

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