CH340G USB-to-UART bridge pinout

The CH340G bridges USB Full Speed to an asynchronous logic-level UART. Its XI and XO leads need a 12 MHz crystal circuit.

SOP-16

16 contacts Current package

WCH · 3.9 mm body width · 1.27 mm lead pitch

SOP-16 pinout

Top view. Match pin 1 to the package mark. The numbers advance counterclockwise.

Selected pin details

15 · R232

Input · Control

Optional receive-polarity control. Leave open for the normal UART circuit.

WCH CH340DS1, version 3B, §§3–5

Electrical limits · Link to this pin

All 16 pins

Pin	Signal	Direction	Function
1	GND Return	Return	Connect to the circuit ground plane.
2	TXD Output	Output	Asynchronous transmit. Connect to the receiver of the external logic-level UART.
3	RXD Input	Input	Asynchronous receive. Connect to the transmitter of the external logic-level UART.
4	V3 Regulator terminal	Regulator terminal	At 5 V VCC, bypass this node to ground with 100 nF. With a regulated 3.3 V supply, connect V3 and VCC together.
5	UD+ Bidirectional	Bidirectional	USB D+ line. Route with the other data line as a differential pair and use the manufacturer’s reference circuit.
6	UD− Bidirectional	Bidirectional	USB D− line. Route with the other data line as a differential pair and use the manufacturer’s reference circuit.
7	XI Input	Input	Input of the 12 MHz crystal oscillator. Keep the crystal network close to the part.
8	XO Output	Output	Output of the 12 MHz crystal oscillator.
9	CTS# Input	Input	Clear to Send, active low.
10	DSR# Input	Input	Data Set Ready, active low.
11	RI# Input	Input	Ring Indicator, active low.
12	DCD# Input	Input	Data Carrier Detect, active low.
13	DTR# Output	Output	Data Terminal Ready, active low.
14	RTS# Output	Output	Request to Send, active low.
15	R232 Input	Input	Optional receive-polarity control. Leave open for the normal UART circuit.
16	VCC Supply input	Supply input	Main supply input. Connect to the specified operating rail and decouple locally.

Signal assignments

USB data pair

Keep the D+ and D− polarity consistent at the connector and the bridge. Use the package-specific application circuit for matching and bypass components.

Asynchronous UART

Use the receive and transmit pair with a common ground. The signals use logic-level voltages. A separate transceiver is needed for bipolar RS-232.

Electrical limits

Parameter	Limit	Conditions and source
5 V supply mode5 V nominal	5 V nominal	VCC takes the supply. Bypass V3 to ground with 100 nF. WCH CH340DS1, version 3B, §5.1
3.3 V supply mode3.3 V nominal	3.3 V nominal	Tie V3 to VCC and keep the connected circuits at or below 3.3 V. WCH CH340DS1, version 3B, §5.1
External oscillator12 MHz	12 MHz	The example uses 33 pF load capacitors. Select the actual values to suit the crystal and PCB parasitics. WCH CH340DS1, version 3B, §7.2
UART data rate50 bit/s to 2 Mbit/s	50 bit/s to 2 Mbit/s	Use a rate supported by the driver and both ends of the UART. WCH CH340DS1, version 3B, §2

Models and documents

The interactive map covers the CH340G SOP-16. See CH340DS1 §3 for CH340C, CH340B and the smaller CH340 packages. Some variants use an internal clock and assign pins 7 and 8 differently.

CH340G: 3.9 mm body width · 1.27 mm lead pitch

WCH CH340DS1 download· Original manufacturer document page.
WCH CH340DS1 version 3B· Manufacturer’s document hosted by SparkFun. Pinout, power modes and application circuits.