Why I use MCP1640 can not get 3.3v

Thread Starter


Joined Mar 16, 2023
When I build the circuit on the circuit breadboard. the input voltage is 1.3,but output only 2.0v without load resistance. when I input 3v with two cells batteries,the ouput only 2.8v without load. If I add load for circuit, the output voltage is lowee. So why? Is that any problem with official datasheet? Please somebody can help me?


Joined Feb 24, 2006
I find it curious that your schematic has no pin numbers on it. I hope you did not depend on your memory to remember the pin numbers that go with the names.
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Joined Aug 7, 2020
How big is your alkaline cell? What is its terminal voltage on load? Remember that it has to supply 250mA.


Joined Aug 21, 2008
Are you sure that the inductor is not saturating ? What is the full specification ofthe inductor ?

Good point! It is fairly common for people to use a small signal inductor in this kind of circuit. Small signal inductors sometimes have high resistance or saturate too easily.

I will also add that those plastic breadboards often make high resistance or intermittent contact with components and jumpers.

Also, go back and re-read post #2.


Joined Jan 30, 2016
Could be breadboard, they are notorious for bad connections - for something this simple I'd 'rats-nest' in free air! But my guess is wrong type of inductor - common mistake!


Joined Jan 8, 2017
The spec for the inductor looks OK. I can't read the marking on the capacitors but they look too small to be 10 uF. They look more like 10 nF ceramic capacitors. Can you post a close up of the markings on the capacitors.
I also think the capacitor and inducter should be connected to the MCP1640 with much shorter wires.

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