LDO for ESP32 DEVKIT V1

[paddynoob]

Hi everyone,

I plan to use an ESP32 DEVKIT V1 (30 GPIO version) at a battery powered setup. It gets feed by 3x AA NiMh battery

As power regulator, I use a MCP1702 LDO which converts battery voltage to 3.3. I added some electrolyte capacitors (220uF) at battery and at output of LDO. Also I use ceramic capacitors (1uF) as shown in MCP1702 datasheet at both sites, VIN and VOUT.

Most time, ESP is in deep sleep and ULP does the work. After a given period, ESP wakes up and sends data by wifi. Everything runs fine from USB power. But when I ran off battery, ESP wakes up and sends empty data captured by ULP. Because this happens at USB power only after initial boot, I assume I've got a power issue which results in re-initialization of whole ESP after WIFI is done.

It makes me bit curious that it sends data (sure initial data, but it sends over wifi) and crashes afterwards.

However, does any one know a good replacement for MCP1702? It should be an "solderable" package format like TO-92. Also it should have a low quiescent current and a low drop voltage like MCP1702 has. I've read of HT7833, but it's mostly impossible to purchase

I've read that I can put LDO in parallel to increase output current. This might also an option to me but I don't know how. Can I just hook them in parallel or do I need additional circuits?

Thanks

[lbdroidman]

The MCP1702 is possibly not big enough. Its spec shows 250 mA continuous, 500 mA peak.
The ESP32 has a recommended minimum supply current of 500 mA, and indeed, it will get up there when the wifi is transmitting.
A pretty common LDO for these is LM1117-3.3, which can supply 800 mA continuous.

You can also try to do some tricks to reduce power consumption while it is in operation;
- reduce the CPU frequence to minumum.
- shut down second CPU core.

[paddynoob]

Hi,

because it is a battery powered solution, I want to save as much current as possible. Too bad that MCP1702 could not handle that high current.

Now it runs with a MCP1826S-3302. It has a quiscent current of 120uA which is much higher than 2uA of 1702 but it can deliver up to 1A.

I need to save some more power because my batteries gets drawn quickly now. Most time, ESP is in deep sleep and wakes every 5 min. Meanwhile, ULP co-processor wakes every 10ms and does some checks. Because I'm more familiar with Arduino, I used Arduino IDE to program everything. Does someone know how to disable second core in Arduino and also how to reduce CPU clock speed?

Patrick