ESP32 - LiPo 3.7V with diode forward voltage as power source?

tpayne03
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ESP32 - LiPo 3.7V with diode forward voltage as power source?

Postby tpayne03 » Thu Oct 12, 2017 9:40 pm

Has anyone tried powering the ESP32 using a standard silicone diode to drop the LiPo voltage to the operating range of the ESP32?

I have seen the SparkFun ESP32 implementation uses an LDO for their 3.7V battery; however, they are using USB. In our application, there is no USB so no 5V input to worry about.

I've used that in other embedded application to ensure that when the LiPo charges up to 4.2V it will drop by .65V to stay within the operating range.

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loboris
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Re: ESP32 - LiPo 3.7V with diode forward voltage as power source?

Postby loboris » Thu Oct 12, 2017 10:03 pm

It is a bad idea, and what would be the reason for that? You can use LDO to get 3.3V from LiPo battery.
If you want to run without LDO, use LiFePO4 battery, it can power ESP32 directly.

tpayne03
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Re: ESP32 - LiPo 3.7V with diode forward voltage as power source?

Postby tpayne03 » Fri Oct 13, 2017 12:16 am

Well... I have an LTE modem that runs off a 3.7v LiPo and a diode is a smaller footprint and less costly than an LDO....

Efficiency wise, diode current usage is pretty much equivalent to an LDO.

onehorse
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Re: ESP32 - LiPo 3.7V with diode forward voltage as power source?

Postby onehorse » Fri Oct 13, 2017 12:28 am

NCP161AMX330 is an ultra-low-noise 3V3 LDO. I use the one that comes in the DFN-4 package which is 1 mm x 1 mm and requires 2 0402 caps, Iq is 18 uA, current load minimum is 450 mA, perfect for the ESP32.

tpayne03
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Re: ESP32 - LiPo 3.7V with diode forward voltage as power source?

Postby tpayne03 » Fri Oct 13, 2017 2:21 am

I'll check that out. I was going to use a Taiwanese LDO if I go that route. Do you know if you could go as low as 300mA? I keep reading officially 500mA, but read anecdotes of 300mA...

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urbanze
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Re: ESP32 - LiPo 3.7V with diode forward voltage as power source?

Postby urbanze » Sat Oct 14, 2017 9:19 pm

Why diode is a bad idea? In my city, I cant find any "low drop out" with <1v voltage drop, my last solution is simple diode, but why is bad?

KanyeKanye
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Re: ESP32 - LiPo 3.7V with diode forward voltage as power source?

Postby KanyeKanye » Sat Oct 14, 2017 10:35 pm

Simple diode is okey solution keeping in mind its price.
Ldo is better because it do stabilization but caps are needed, more pins for soldering, current mustn't be too low and price is bigger

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urbanze
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Re: ESP32 - LiPo 3.7V with diode forward voltage as power source?

Postby urbanze » Sat Oct 14, 2017 10:40 pm

Diode can drop 1v with "high current" but it's suficient to supply esp32/66. Use this to "test and protoboard" is ok?

ESP_Angus
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Re: ESP32 - LiPo 3.7V with diode forward voltage as power source?

Postby ESP_Angus » Mon Oct 16, 2017 2:32 am

KanyeKanye wrote:Ldo is better because it do stabilization but caps are needed, more pins for soldering, current mustn't be too low and price is


If using a diode in place of an LDO then you should probably still place capacitors on both the battery and the ESP32 sides of the diode.

urbanze wrote:Diode can drop 1v with "high current" but it's suficient to supply esp32/66. Use this to "test and protoboard" is ok?


I think so. 1V drop means you can run the battery down to 3.3V before the output voltage falls below the ESP32 minimum 2.3V. So this is pretty good!

You will also need to check that the flash chip connected to the ESP32 can handle a voltage this low. You can find this information in the flash chip datasheet. For an ESP-WROOM32 module, the same voltage range (above 2.3V) applies.

In general, though, if you can find a suitable LDO with a dropout voltage lower than 1V then this will be a better choice.

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