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I'm more of a hobbyist than a pro so forgive me if I'm asking the wrong questions however I have put some time into finding a solution to this problem.

In essence I want to run an ESP8266(esp-12f to be specific) on a single 3.7v liion cell. However reading into the esp's voltage tolerances it appears as though it's important to use 3.3v to prevent damage or browning out. As such do I need to use a voltage regulator like the lm1117 or would be acceptable to run the esp directly from the cell.

If the latter is acceptable, would I need some form of low voltage cut off circuit to prevent draining the cell too much?

Thanks in advance

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Do not connect the battery directly if you want this ESP8266 to last. 3.7V is the nominal voltage but it can be a little higher when they are charged. You can place an ld1117 but even though they are marked as LDO (low drop out regulator) they do have some significant dropout, over 1V. And since Li-ion batteries have a voltage curve (their voltage drops when discharged) you will end up with a voltage close to the minimum for the ESP8266.

I wouldn't recommend using a standard ld1117. Find another regulator with a much lower dropout but make sure it can handle 300mA since the ESP8266 has 300mA peaks (I've measured) when transmitting at full power.

Or better yet, use a switching regulador (step-down), they are cheap and ultra easy to use. You can search in mouser.com, there are many easy to use regulators, you can even use the classic MC34063A.

Or another thing you can do, which I've done some times, is placing a schottky diode in series with the battery, the diode will drop around 0.4V so you will end up with 3.3-3.4 when the battery is charged, and drop down to 2.8 when it's almost empty.

On your last question, most Li-ion batteries come with a protection built in that avoid over discharge damage and short circuit damage. Just make sure your battery has that little pcb (most do). So you don't have to do anything special, when the battery is very low, this protection circuit will disconnect it from your circuit to avoid damage.

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  • \$\begingroup\$ NMOS LDOs are the current kings of ultra-low-dropout performance btw -- the REG102 is but one of many examples. \$\endgroup\$ – ThreePhaseEel Feb 7 '16 at 22:40
  • \$\begingroup\$ Yes, ThreePhaseEel is right. Those can work pretty good, just look for one with a little higher current capacity. \$\endgroup\$ – scrafy Feb 8 '16 at 23:38
  • \$\begingroup\$ While there are some thoughtful points here, the nbers are simply wrong. A charged lithium cell will be 4.2 volts, making the diode idea dubious. And only a minority have protection circuits. \$\endgroup\$ – Chris Stratton Dec 29 '18 at 15:19
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ZLDO330 ultra low dropout regulator might fill the bill.

Or TDA3663, ST1L08,

ST has a nice chart at: http://www.st.com/en/power-management/ultra-low-dropout-ldo-regulators.html?querycriteria=productId=SS1733

Also the TJ1118 might work too.

Update: Just found this on digikey dot com... 3.3V fixed, .15V dropout voltage (so if Vbatt is less than 3.45V regulation stops), low quiescent current of 105uA

https://www.digikey.com/product-detail/en/analog-devices-inc/ADP122AUJZ-3.3-R7/ADP122AUJZ-3.3-R7TR-ND/2237672

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