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LDO voltage regulator with under voltage shut down?

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nesse

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Hi all
Any one knows of a 5V regulator, preferably in SOT-23, that will disable its output if input voltage is below a set level?
 
Cant remember the part number but look at linear technology web site, they have some very good LDO regulators ect. Look at the energy harvesting page, some the stuff there has a voltage good pin and some have auto shutdown, they are designed for energy harvesting system's where that kind of feature is useful.
 
Thanks, but they're all Switch mode regulators. I need to keep component count down and would prefer an LDO that simply does not output any voltage below 5V or at least >=4.5V
 
Not easy to find.
I think you might search for a part with a "power good" pin. Probably not sot23
 
Thanks, but they're all Switch mode regulators. I need to keep component count down and would prefer an LDO that simply does not output any voltage below 5V or at least >=4.5V
Not true but there site can be awful to find things!! I will go hunting in my bits box, because I have such a beast from them, its a single chip solution with power good out put pin, it was used on a board to shut down the energy harvesting side when the power dropped below 5V and switch over to battery back up, so they do have the part, the tricky bit is finding the part number
 
Not SOT23, but:
https://www.linear.com/product/LT1521
Add a resistive divider circuit for your 5Vdc source (to achieve the slightly greater than 0.25Vdc needed) with its output to the SHDN pin.

Only a 300mA load capability.

Also, wouldn't turn back on until about 2.8Vdc on that pin. Sort of a one-shot "fuse like" safety.
 
https://www.linear.com/product/LT1521
Add a resistive divider circuit for your 5Vdc source (to achieve the slightly greater than 0.25Vdc needed) with its output to the SHDN pin.
The switching threshold voltage of the LT1521 shutdown pin has a massive range (from 0.25 to 0.75V), so you'd have to tune your resistors for every device you used.

It's much easier and more reliable to use a uC supervisor IC, e.g. MCP100 (https://www.farnell.com/datasheets/11601.pdf), to control the shutdown pin of a regulator. These ICs are made to signal a low supply voltage and have decent accuracy. They also come in SOT-23.
 
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