Data Sheet

The Data Sheet of CH340 (the first)
3
pull-up resistor
XO OUT
CH340T/R/G: Output of crystal oscillator, connect to
crystal and capacitor
10 8 NONE
NC. NONE CH340C/B: No Connection, must be suspended
6 5 1 UD+ USB signal Directly connect to D+ data wire of USB bus
7 6 2 UD- USB signal Directly connect to D- data wire of USB bus
20 NONE NONE NOS# IN
Forbid USB device suspending, active low, built-in pull-up
resistor
3 2 8 TXD OUT
Transmit asynchronous data output(reverse output for
CH340R)
4 3 9 RXD IN
Receive asynchronous data input, built-in configurable
pull-up and pull-down resistor
11 9 5 CTS# IN
MODEM liaison input signal, clear to send, active
low(high)
12 10 NONE DSR# IN
MODEM liaison input signal, data set ready, active
low(high)
13 11 NONE RI# IN
MODEM liaison input signal, ring indicator , active
low(high)
14 12 NONE DCD# IN
MODEM liaison input signal, data carrier detect, active
low(high)
15 13 NONE DTR# OUT
MODEM liaison output signal, data terminal ready, active
low(high)
16 14 4 RTS# OUT
MODEM liaison output signal, request to send, active
low(high)
2 NONE NONE ACT# OUT USB configuration completed state output, active low
18 15 NONE R232 IN
CH340T/R/G/C: Assistant RS232 enable, active high,
built-in pull-down resistor
TNOW OUT
CH340T/E/B: Ongoing data transmission status indicator,
active high
17 15 6
IR# IN
CH340R:Serial mode input setting, built-in pull-up resistor,
SIR infrared serial interface when low, common serial
interface when high
CK0 OUT CH340T: clock output
1 NONE NONE
NC. NONE CH340R:No Connection, must be suspend
5. Function Description
CH340 chip has built-in USB pull-up resistor, UD+ and UD-
pins must be connected to USB bus directly.
CH340 chip has built-in power-on reset circuit. CH340B also provides low active external reset pin.
CH340G/CH340T/CH340R chips need to work with 12MHz clock signal supplied to XI pin. Generally,
clock signal is generated crystal oscillation with inverter in CH340. The peripheral circuit needs to place a crystal
of 12MHz between XI and XO, and connect to a capacitor to ground separately.
CH340C, CH340E and CH340B chip have built-in clock generator, no external crystal and oscillating
capacitor required.