Hi Aaron
The regulator will have SOME drop out voltage even if it is small. So the input voltage to the regulator MUST be above the output my a minimum of the drop out voltage.
The chart in the data sheet says that for a load of 120mA the drop out voltage should be 0.22V to 0.35V so the input to the regulator should be a minimum of 3.65V. to allow for worst case. This will increase with an increase in load current.
Cheers Bob
Bob, that is what I was thinking of, but the sensor chip can run on sub 3V
The data sheet says 3.0 is typical, so a 3.3V supply should be enough.
Hi Michael
So the schematic is misleading. If that bit of schematic is part of the overall for a board I would say that it is quality assurance at its finest.
You are correct, that -30 does signify 3V. But to my thinking the quoted 3.3V input is still stretching it a bit. You might just get a regulator that has a drop out of 0.35V. Still within manufacturers spec but might not work too well. Too tight for my liking and in my world would never get out of the drawing office.
But these days things seem to be expected to be reliable even when operated just within absolute limits or even outside limits. Like operating 5V relays at 3.3V. Well outside manufacturers spec. But still sell these things as 3.3V operable (probably a lot slower which would not be good for high loads). But I have already expressed my thoughts re using these relays @ 3.3V in the past so will comment no further.
Cheers Bob
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Hi Bob,
Thanks for helping out. Gotta love a cost cutting measure like this. Hopefully that datasheet gets updated at some point to more accurately reflect how the sensor actually works.
Thanks, Sam.
Hi Sam
Don’t hold your breath.
Cheers Bob
Add on:-
Seems to be just a linear voltage regulator (which have some comments above) and a couple of data level shifters. The rest is contained it that chip. So I think you are meant to read the chip data sheet to get any more info
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