Hello! I design the board in EAGLE and is now busy with the issue of reliable power for my microcontroller (Atmega328P) and several sensors. The total load is about 250mA, the board is connected to 12V, and for powering the sensors and microcontroller it is necessary to supply 5V. For these purposes, I looked at the stabilizer AMS1117 5.0, capable of converting from 12V to 5V. I read his datasheet, where tantalum capacitors were indicated in the circuits, which I can not get at the moment. So I decided to put ceramic at 10uF and 100nF. Scheme attached from below. Questions: Did I choose the capacitance of ceramic capacitors for these purposes correctly, is this circuit reliable or is it worth replacing it? It is necessary that the microcontroller and sensors work stably. Thank you very much for your help!
Maybe, maybe not - you're outside of spec. Sometimes the regulator depends on the ESR of the capacitor for stability...
Why use the AMS1117, with it's particular cap requirements? Why not use ZLDO1117, or one of the other 1117's that is spec'ed for use with ceramic capacitors?
Suyano:
The total load is about 250mA, the board is connected to 12V...
Then you also have to consider thermal problems.
7volt difference with 250mA draw dissipates 1.75watt inside the regulator.
Quite a lot for an SOT-223 on a circuit board.
You will need some board copper area on the tab to prevent the regulator from shutting down.
Leo..
I've not had problems with the 1117 regulator family and ceramic+aluminium electrolytic. You don't normally
need much capacitance on the input, its the output that is fussy.
Before ordering a PCB you should always breadboard your circuit to check its going to work, much
easier to fix problems beforehand. Then you get confidence that its likely to work first time on the board.
You eventually will have problems using aluminium electrolytic caps next to a regulator that dissipates 1.75watt onto the circuit board. Designers of consumer electronics do this frequently (planned obsolescence).
Leo..
I'll put electrolytic capacitors. Thanks for the help!