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I have a circuit that I designed myself. In summary, I feed the circuit with 2 CR2032 type batteries and try to get 3.3 V output from the LD1117 type regulator. However, I get 4.7 V output from the regulator. I also observe a drop in battery voltage, interestingly when I feed it on battery. By voltage drop, I mean it happens instantaneously, maybe it would be more correct to specify it as voltage loss.

Let me share with you the situations I have examined.

There was no change of state when I first connected parallel capacitors to the circuit. edit: I mean 10uf and 100nF(capacitors on the datasheet)

I tested the battery packs and batteries also out of circuit. There is no problem with them either.

When I set the same regulator up to the bluepill supply in the breadbord and tried to supply it without capacitor, I got a constant 3.3V output. However, when I supply the circuit with DC supply 6V from the outside, I constantly get 4.7V from the regulator output. And when I feed it with the battery, it initially comes to 4.7 in the same way, then the voltage of the batteries starts to decrease in a short time. When I deactivate, their voltage comes back to 3V.

I haven't had the opportunity to test it yet, but I'm thinking about the question of whether reverse current is coming from somewhere. Do you think putting a diode on the regulator output can solve it? I am open to your suggestions, thanks in advance.

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    \$\begingroup\$ The datasheet Figure 4 shows 100 nF on the input and 10 uF on the output. Your schematic doesn't. Did you feel that they were optional? ;^) \$\endgroup\$ – Transistor Sep 18 '20 at 20:01
  • \$\begingroup\$ As I said "There was no change of state when I first connected parallel capacitors to the circuit." I also tried adding capacitors to the circuit, but it did not change :/ \$\endgroup\$ – magnesian Sep 18 '20 at 20:16
  • \$\begingroup\$ OK. Just checking all the silly stuff. The pinout is 1, 2, 3: GND, Vout, Vin. Nothing mixed up there? \$\endgroup\$ – Transistor Sep 18 '20 at 20:22
  • \$\begingroup\$ Give it some dummy load with a resistor. \$\endgroup\$ – winny Sep 18 '20 at 20:29
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    \$\begingroup\$ By "connect ~100 ohm into Vin" I presume you mean you connect it in series between the 6 V source and the regulator input. With a 6 V supply and a 100 ohm load the max current you could get would be 60 mA. It sounds as though you have connected a 100 ohm resistor across the 6 V battery. How about a good sharp, well cropped photo of your setup? \$\endgroup\$ – Transistor Sep 18 '20 at 21:35

I think the problem has been solved as of yesterday. I noticed a voltage of about 30mV in the ground of my circuit board. For the same reason the regulator seems to be raising the voltage above 3.3 by taking the ref voltage. I think this is caused by the ground touch of one of the solders I made on the circuit. Because I did not have a problem with my other pcbs with the same feature. Thank you 👍


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