Arduino Nano clone (CH340G)

This is one of these cheap Arduino Nano clones that are sold on Ebay for something around 2 USD. The main difference between the original and the clone is the USB to serial conversion chip. The original uses the popular FT232, but the clone uses CH340G - a cheap USB-UART converter. The cost of this Chinese chip can be under 0.5 USD / piece.

Schematic diagram

Schematic diagram
Schematic diagram (click for full resolution)


(color corrected)

Top side
Top side (click for full resolution)

Bottom side
Bottom side (click for full resolution)

Conclusion + diode replacement

This board works more or less as expected, it's basically the same thing as the original (the main IC - ATmega328 - is the same on both boards). The USB interface seems to work OK, at least on Linux (no extra drivers were required), but I got some problems with baud rates higher than.

A small problem with (as far as I know) all Arduino Nanos is the fact that there is no fuse on the USB port. +5V from the USB port is connected through a Schottky diode to the Arduino's +5V rail. This diode will prevent current from flowing back into the USB port. When overloaded, the diode will fail, either going short or open circuit (that's not a big problem to debug) or it will start behaving like a resistor, which can be very annoying and take some time to find. It also causes the voltage to drop a bit (0.2V under low currents up to 0.5V depending on the exact diode type). The original diode on my board was an MBR0540 (or 0520, which is a little bit better. It has lower maximum reverse voltage, which doesn't really matter, because there is only 5V anyway, and also has a lower voltage drop.) I replaced the old burnt diode with a new MBR0520 (several times already) and it works fine.


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