Comments on: ESP8266 Voltage Regulator (LiPo and Li-ion Batteries)

By: Martin

Martin — Tue, 08 Nov 2022 10:50:04 +0000

Shouldn’t you also use a supervisor to turn off the power if the voltage is too low?

By: Pit Hermann

Pit Hermann — Tue, 26 Apr 2022 14:38:07 +0000

Hi,
It’s really not recommend to add a capacitor of this value to the OUTPUT of a voltage regulator.

For MCP1700 series the datasheet shows up 1µF and NOT 1000µF
such a huge capacitor can, depending on the regulator , have negative effects on regulation behavior or simply destroy it while attaching or removing the battery

By: schuh

schuh — Mon, 11 Oct 2021 15:44:25 +0000

In reply to Bud Schuh.

OK, found several errors I made. The actual useful battery capacity on the MPC1700 is about 70% of lipo capacity (read the graph wrong … my bad 🙁 ). So that makes it about 70% for the MPC 1700, 95% for the diode and about 88% for an HT7333. BUT all that’s assuming that the LDO’s cut off completely when input voltage = regulated voltage + dropout voltage. I have since learned that some LDO’s cut all output at that point and some continue to supply current, but at a reduced voltage, That would increase the usuable amount from the lipo but drag the voltage dangerously low for lipo health. Best of all worlds would be a LDO that cuts off all output when the input voltage reaches 3.2 volts and with a dropout voltage less than 100 mV. All this in a TO92 package. Anyone …anyone …………

By: Bud Schuh

Bud Schuh — Tue, 05 Oct 2021 16:37:04 +0000

I am comparing the MCP1700 with a simple diode for voltage drop. Assuming a 8266 will operate between 2.5 and 3.6 volts (per spec sheet):
The MCP1700 has a dropout voltage of approximately 0.2 volts. which means it will power an 8266 from full charge (4.2 volts) down to dropout which would be 3.3+0.2 or 3.5 volts. Using the black line in the lipo graph above that’s about 45% of the lipo’s charge that will be available. quiescent current is 1,6 uA.
Comparing with a simple diode with a forward drop of 0.7 volts: The lipo should now power the 8266 from full charge down to 3.2 volts (3.2V – .7V = 2.5 V which is the 8266 low voltage cutoff) This uses about 95% of the lipo’s charge and no quiescent current.
Obviously I’m missing something here as the simplicity of the diode, the non existent quiescent current and about 50% greater use of the lipo seem to make it a better choice. Where did I go wrong? Or did I?
Thanks for any comments.
Schuh

By: StanJ

StanJ — Tue, 25 May 2021 10:44:34 +0000

To answer Vit Zaoral’s question from 2 years ago, you need to use a 3.0V regulator instead of a 3.3V regulator with 18650 Li-Ion batteries or you lose 15-20% of the total battery charge with that 3.5V cutoff. Your discharge curve above is for LiPo; the Li-Ion has a steeper discharge curve (more like alkalines) so you want to have somewhere around a 3.2V minimum input voltage to get the most out of the battery. Additionally, the ESP32 and ESP8266 both draw in excess of 400mA during WiFi transmission, so you’re better served with a 500mA regulator instead of a 250mA model. You need a $$ 270uF tantalum electrolytic to supply those large current spikes during WiFi otherwise.
A TI TLV75530P would be a better LDO choice with 18650 batteries, https://www.ti.com/lit/ds/symlink/tlv755p.pdf although several other 3.0V 450-500mA LDO regulators would also work with the ESPs.

By: Mathias

Mathias — Wed, 24 Mar 2021 21:45:57 +0000

In reply to Ola Dunk. Yes thanks, that is correct, but ESP datasheet suggests of using one 10uF ceramic and one 100nF ceramic capacitor so why use 1000uF electrolytic capacitor instead?

By: Ola Dunk

Ola Dunk — Sun, 21 Mar 2021 13:56:51 +0000

In reply to Mathias. The 1000 uF capacitor will supply more current when the ESP is transmitting. It will work as a reservoir. You can start with a smaller capacitor like 100, 220,330,470 if you don't have a 1000 uF capacitor.

By: Mathias

Mathias — Tue, 16 Feb 2021 21:08:17 +0000

Hello.
The manufacturer suggests in the MCP1700 datasheet to use one 1uF capacitor in the V_in and one 1uF capacitor in the V_out so I am curious why are you using one 1000uF electrolytic capacitor and one 100nF ceramic capacitor?
Thanks.

MCP1700 datasheet:

ww1.microchip.com/downloads/en/DeviceDoc/MCP1700-Low-Quiescent-Current-LDO-20001826E.pdf

By: Sara Santos

Sara Santos — Sun, 20 Sep 2020 23:29:31 +0000

In reply to Kai.

Hi.
Unfortunately, we don’t have that fritzing part.
Regards,
Sara

By: Kai

Kai — Sun, 20 Sep 2020 20:24:42 +0000

Hi,
I am trying to build a fritzing diagram including the MCP1700-3302E but cannot find this part online. The included voltage regulator has the wrong pin-out in the PCB. Is there any chance to get the version you created?

Kind regards
Kai