DreamCity Innovations

WCH CH340G Datasheet

4. Pinout

5. Application Notes

CH340 chip have built in USB bus pull-up resistors and on-chip signal termination, UD+ and

UD- pins should be connected to the USB bus lines directly.

CH340 have built in power on reset circuitry.

During operation CH340 requires a 12MHz clock signal present at XI pin. Generally this clock

signal is provided by connecting a 12MHz crystal resonator and load capacitors between XI

and XO pins, and the built-in crystal resonator will provide the required clock signal. When

using an external oscillator feed the clock signal into XI pin, and leave XO pin unconnected.

CH340 supports 5V and 3.3V operation. When using 5V operation, supply 5V to VCC pin, and

decouple the internal 3.3V reference with a capacitor of 4.7-20nF from V3 pin to ground.

When using 3.3V operation, tie V3 pin to VCC pin and supply 3.3V power.

CH340 supports USB device suspension to reduce energy consumption. When NOS# signal

is active this feature is disabled. (Note: CH340G does not have this pin.)

Supported hardware flow control signals: CTS#, DSR#, RI#, DCD#, DTR# and RTS#. All flow

control pins are software controlled.

Auxiliary pins: IR#, R232, CKO and ACT#. (Note: only R232 is present on CH340G) When

R232 signal is asserted the RXD signal is inverted. R232 is latched during Power-On Reset.

Pin # Name Direction Comment

1

GND

Power

Ground reference of the chip. Connect to the ground pin of USB bus.

2

TXD

Output

UART Data Transmit output.

3

RXD

Input

UART Data Receive input.

4

V3

Power

Internal 3.3V reference for USB physical layer. Decouple with a 4.7-20nF

capacitor when in 5V operation, or tie to VCC when in 3.3V operation.

5

UD+

Analog

USB D+ signal.

6

UD-

Analog

USB D- signal.

7

XI

Input

Input of the crystal oscillator. Connect to the crystal resonator and load

capacitors.

8

XO

Output

Output of the crystal oscillator. Connect to the crystal resonator and load

capacitors.

9

CTS#

Input

UART flow control signal Clear to Send.

10

DSR#

Input

UART flow control signal Data Set Ready.

11

RI#

Input

UART flow control signal Ring In.

12

DCD#

Input

UART flow control signal Data Carrier Detect.

13

DTR#

Output

UART flow control signal Data Terminal Ready.

14

RTS#

Output

UART flow control signal Request to Send.

15

R232

Input

Auxiliary RS232 enable. Active high, internal pull down.

16

VCC

Power

Supply rail for the chip.

DreamCity Innovations

Page of

4

6

WCH CH340G Datasheet