This example is a clone with a CH340G USB UART.

The clones are very cheap and are nano 3.0 compatible with a ATMEGA328P micro-controller and 16 MHz XTAL.

               +--------------+
               |   5 3 1 ISP  |
               |   6 4 2      |
               |  RX TX PW L  |
D1 TX         1|   PD0        |30 VIN
D0 RX         2|   PD1        |29 GND
RESET         3|     RESET    |28 RESET
GND           4|              |27 5V
D2 INT0       5|   PD2 ADC7   |26 A7
D3 INT1       6|   PD3 ADC6   |25 A6
D4            7|   PD4 PC5    |24 A5 SCL
D5            8|   PD5 PC4    |23 A4 SDA
D6            9|   PD6 PC3    |22 A3
D7           10|   PD7 PC2    |21 A2
D8           11|   PB0 PC1    |20 A1
D9           12|   PB1 PC0    |19 A0
D10 SS       13|   PB2        |18 AREF
D11 MOSI     14|   PB3        |17 3V3
D12 MISO     15|   PB4 PB5    |16 D13 LED SCK
               +--------------+
ISP
===
D12 MISO PB4 |1 2| VDD
D13 SCK  PB5 |3 4| D11 MOSI PB3
RESET        |5 6| GND

This device is either powered from the USB bus of from VIN which feeds a 5V LDO regulator.

The CH340G chip on pin4 (V3) supplies the 3V3 output of the nano on I/O pin 17.