Quick question about the V3 pin

[HankLloydRight]

First, thanks for this design, very helpful! Thank you.

I'm trying to integrate this on my own custom PCB with the ESP32-WROOM, but I find conflicting information about the V3 pin #4.

In your design, you have V3 going to a 100nF cap to ground, which many CH340C designs have when powering with a 3.3v source on VCC.

But in the datasheet for CH304C, it says: "When using 3.3V power voltage, connects V3 with VCC, both input 3.3V power voltage, and the other circuit voltage which connected with CH340 cannot exceed 3.3V" which is what I'm doing, because that's how the LOLIND32 dev board has, which is what I based my design off of (see: https://www.wemos.cc/en/latest/_static/files/sch_d32_v1.0.0.pdf )

So why the discrepancy with V3, and what difference does it create? My circuit is drawing nearly 800ma which is more than twice it should be pulling, I'm wondering if it's because I have VCC and V3 tied together like the datasheet says.

thank you.

[DoganM95]

As far as i remember on the 3V pin:

• Leaving it floating: Windows device manager fails to recognize the hardware
• Connecting to GND with 100nF in between: worked fine (see readme section 'Takeaways")
• Connecting it to VCC (3.3Volt): forgot the outcome, but the bigger the voltage difference bewteen your 3.3V power source (AMS1117 in my case) and the 3V pin, the more current will be drawn, since the higher voltage tries to "chagre" the lower one until equilibrium is reached i guess

However, according to chatGPT:

The "3V" pin on the CH340C can be used in different ways depending on the power configuration:

• As an Output: The "3V" pin can provide a regulated 3.3V output if the CH340C is powered by a higher voltage (e.g., 5V).
• As an Input: The "3V" pin can be used to supply a regulated 3.3V if the CH340C is operated at 3.3V directly.

I chose to not use the 3V pin as a power source anyway, and the 100nF cap to GND fixed any connectivity issues. Powering the system via USB ch340c running only a loop printing "hello world" every second, it draws less than 10mA, since the USB meter shows 0.00A.

Hope this info is somewhat helpful to you

[HankLloydRight]

That's really helpful, thank you. Since I currently have VCC connected to the 3V pin, the voltages at both are obviously the same, but your explanation causing higher current sounds possible and what might be happening to me now.

And I don't need to use the 3V pin as a power source, as I have a 3V3 rail on my board already (also from a AMS1117-33).

But I'm not sure I can get in there with my iron to pluck off just pin #4 in order to add a cap and ground it to see if my over-current problem goes away.