Data Sheet

The Data Sheet of CH340 (the first) 4
CH340B chip also provides EEPROM for configuring data ar
ea, prod
uct serial number and other
information could be customized for each chip by specific software tools, configurable data area is shown in the
table below.
Byte
Address
Abbreviati
on
Description of chip configuration data area Default
00H SIG
For CH340B: Internal configuration information valid reg,
must be 58H.
For CH340H/S: External configuration information valid
reg, must be 53H.
Invalid for other value
00H
01H MODE Serial mode, must be 23H 23H
02H CFG
Specific configuration of chip,
bit5 is used to configure product Serial Number:
0= valid; 1= invalid.
FEH
03H WP
Internal configuration information write protect flag，57H
imply read only, otherwise can be rewrite
00H
05~04H VID
Vendor ID, high byte is behind, any value. Set to 0000H or
0FFFFH implies VID and PID using vendor default value
1A86H
07~06H PID Product ID, high byte is behind, any value 7523H
0AH PWR Max Power, The maximum supply current in 2mA units 31H
17~10H SN
Serial Number, the length of ASCII string is 8, disable the
Serial number when the first byte is not ASCII character
(21H~7FH)
12345678
3FH~1AH PROD
For CH340B: Product String, Unicode string for Product
description. The first byte is by total bytes (less than 26H),
the next byte is 03H, Unicode string after that, using vendor
default description when do not meet characteristics above.
Using product
default
description when
the first byte is
00H
Others (Reserved unit) 00H or FFH
CH340 chip supports 5V and 3.3V power voltage. When using 5V source power, the VCC pin input 5V
power and the V3 pin should connect with decoupling 0.1uF capacitor. When using 3.3V power voltage,
connects V3 with VCC,
both input 3.3V power voltage, and the other circuit voltage which connected with
CH340 cannot exceed 3.3V.
CH340 supports USB device suspending automatically to save power. USB device suspend is forbidden
when NOS# is driven low.
The DTR# pin of CH340 is used as a configuration input pin before the USB configuration is complete. An
external 4.7KΩ pull-down resistor can be connected with this pin to generate default low level during USB
enumeration, apply larger supply current to the USB bus via the configuration descriptor.
In UART mode, CH340 chip contains these pins: data transfer pins, MODEM liaison signal pins and
assistant pins.