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LT3081 Parallel Different Sources

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jmoschetti45:
I have a few LT3081's laying around. I know you can parallel them for more current handling. I was wondering if I could use them in parallel for redundancy instead. Basically, 3 power supplies into 1 combined output. It doesn't matter if one or two are doing more work than the other(s), this would be purely for redundancy. I know I can just design a redundant supply, but this seems like a quick and dirty easy solution. Thoughts?

jbb:
I’d worry about a device failing as a short circuit to ground...

digsys:
Definitely. One of my past favourite regulators, may still have several around myself. If you check their app notes, they show you ONE method of paralleling them, pretty easy to figure out something that suits you, as it has nice control pins. Maybe use Shottky ORing diodes / "ideal diode" switches (for near zero loss if needed) etc on the outputs.
Then, depending on how fancy you want to go, maybe simple individual Isense / Vsense / switch etc etc
I've made many dozens of of production linear P/Supplies .. it's fun to play with. If you have any specific questions, feel free to ask. We especially need to know your min / max requirements / specs you're trying to achieve.

jmoschetti45:
3.3V @ 400mA. Pretty low power application.


--- Quote from: digsys on February 11, 2020, 07:50:11 am ---Maybe use Shottky ORing diodes / "ideal diode" switches (for near zero loss if needed) etc on the outputs.
Then, depending on how fancy you want to go, maybe simple individual Isense / Vsense / switch etc etc

--- End quote ---

I thought of that after I had posted. Wouldn't be hard to compensate for voltage drop with even a plain schottky diode.

digsys:

--- Quote from: jmoschetti45 --- ....  Wouldn't be hard to compensate for voltage drop with even a plain schottky diode
--- End quote ---
One "cheap" trick I've used for many years (dozens products, 100s units) is - I OR the outputs with appropriate Polyfuses, then shrink-tube them together.
With outputs separate, adjust to match as close as possible, with say 75% load, then link the outputs. As ONE regulator starts to deliver a bit more current, the Poly heats up and reduces its contribution. This "trick" is used in many systems out there.
IF you have a very rapid high current switching load, you'd need to whip up a test load though. What I did was set up a series of switches with different loads and rapidly switch them In/Out and monitor on a DSO. This is really only necessary for very dynamic loads. I've tied up to 4x regs together this way.

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