Ch340 Datasheet (I) 1 usb to Serial Port Chip ch340

CH340 Datasheet (I)
4 
low(high) 
13 
11 
NONE 
NONE 
RI# 
IN 
MODEM input signal, ring indicator , active 
low(high) 
14 
12 
NONE 
NONE DCD# 
IN 
MODEM input signal, data carrier detect, 
active low(high) 
15 
13 
4 
NONE DTR# 
OUT 
MODEM output signal, data terminal ready, 
active low(high) 
16 
14 
6 
4 
RTS# 
OUT 
MODEM output signal, request to send, 
active low(high) 
2 
NONE 
NONE 
NONE ACT# 
OUT 
USB configuration completed state output, 
active low 
18 
15 
NONE 
NONE 
R232 
IN 
CH340T/R/G/C: Assistant RS232 enable, 
active high, integrated pull-down resistor 
TNOW 
OUT 
CH340T/E/X/B: Ongoing data transmission 
status indicator, active high. CH340X can 
switch to DTR# optionally by connecting an 
external resistor 
17 
15 
NONE 
NONE 
IR# 
IN 
CH340R:Serial 
mode 
input 
setting, 
integrated pull-up resistor, works on SIR 
infrared UART mode when the pin is low 
and normal UART mode when the pin is 
high 
CK0 
OUT CH340T: clock output 
1 
NONE 
NONE 
NONE 
NC. 
NONE CH340R:No Connection, do not connect 
Note: Unused I/O pins of CH340 should be NC. The application diagram takes CH340T as an example and 
also applies to CH340G/C/N/K/E/X/B, etc. 
5. Function descriptions 
5.1. Clock, reset, power, connect 
CH340G/CH340T/CH340R need to work with 12MHz clock signal supplied to XI pin. Generally, clock 
signal is generated by the inverter in CH340 through crystal oscillation. The peripheral circuit needs to place 
a crystal of 12MHz between XI and XO, and connect to a capacitor to ground separately. 
CH340C/N/K/E/X/B have integrated clock generator, no external crystal and oscillating capacitor required.
CH340 has integrated power-on reset circuit. CH340B also provides an external reset pin (active low). 
CH340 supports 5V and 3.3V power supply. When using 5V power supply, the VCC pin connects 5V power 
and the V3 pin should connect with a 0.1uF decoupling capacitor. When using 3.3V power supply, V3 
should connect with VCC, both powered with 3.3V power supply, and the other circuit voltage which 
connected with CH340 cannot exceed 3.3V. 

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