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I am currently designing a battery powered IoT device, which maximum voltage is 3.3V. When it comes to battery choice, the CR2032 (3V) is totally fine, but its capacity is only 250mAh. How can I power my circuit from single 18650 Li-ion cell? The problem is that this battery can achieve 4.2V when fully charged. What would be the basic circuit and which voltage regulator to choose? I currently ordered SPX3819. I am afraid it will discharge my battery faster then NRF24l01 and ATtiny84 attached to it.

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  • \$\begingroup\$ Use a voltage regulator. \$\endgroup\$ – Andy aka Apr 27 '20 at 10:18
  • \$\begingroup\$ which voltage regulator to use? I am talking about ultra low power aplication. AMS1117 will not work. SPX3819 I think has high quiscent current. \$\endgroup\$ – Markiyan Pyekh Apr 27 '20 at 11:50
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    \$\begingroup\$ Shopping questions are off topic because answers will quickly become outdated as new devices come along. The questions and answers on this site are intended to pass the test of time where possible. \$\endgroup\$ – Andy aka Apr 27 '20 at 11:54
  • \$\begingroup\$ Do you need a rechargeable cell? CR123As are the same non-rechargeable 3V chemistry of a CR2032, but 1/2 the size of an 18650 and ~1500mAh. They also have lower self discharge rates. \$\endgroup\$ – SomeoneSomewhereSupportsMonica Apr 27 '20 at 13:51
  • \$\begingroup\$ CR123A is a good ideia, I have not though agout this battery. And its 3V, which excludes the LDO \$\endgroup\$ – Markiyan Pyekh Apr 27 '20 at 18:25
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Some companies sell 1uA standby_current LDOs. Is 1Ua low enough?

Even those LDOs will have lots of random output noise, because the internal voltage dividers will have 10,000,000 ohm values although in a slow feedback loop (not much charge available to operate the big onchip power FET quickly).

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  • \$\begingroup\$ yes, 1uA would be enough. \$\endgroup\$ – Markiyan Pyekh Apr 27 '20 at 18:24

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