USB to Serial Port Chip CH340


CH340 is a USB bus converter chip which converts USB to serial port or printer port. In UART mode, CH340 provides standard MODEM signals, used to extend serial port for computers, or upgrade directly from normal serial device to USB bus. For more information about converting USB to printer interface, please refer to the CH340DS2 datasheet.


  • Full-speed USB device interface, USB 2.0 compatible.
  • Emulate standard UART interface, used to upgrade the original serial peripheral or expand additional UART via USB.
  • Original UART applications are totally compatible without any modification in Windows operating systems.
  • Hardware full duplex UART interface, integrated transmit-receive buffer, supports communication baud rate varies from 50bps to 2Mbps.
  • Supports common MODEM interface signals RTS, DTR, DCD, RI, DSR and CTS.
  • Provides further RS232, RS485, RS422 interface, etc. through external voltage conversion chip.
  • CH340R supports IrDA criterion SIR infrared communication, supports baud rate varies from 2400bps to 115200bps.
  • Built-in firmware, software compatible with CH341, use VCP driver of CH341 directly.
  • Supports 5V and 3.3V power supply voltages.
  • CH340C/N/K/E/X/B have integrated clock, no external crystal required, CH340B also integrates EEPROM used to configure the serial number, etc.
  • RoHS compliant SOP-16, SOP-8, SSOP-20 and ESSOP-10, MSOP-10 lead-free package.


CH340C, CH340N, CH340K, CH340E, CH340X and CH340B have integrated clock, no external crystal required. CH340B has integrated EEPROM used to configure serial number, some functions can be customized, etc. CH340K has 3 built-in diodes to reduce current flow backwards between the I/O pins of the MCU. The EPAD of CH340K is 0# pin (GND), which is an optional connection; the 3# pin (GND) is the necessary connection. CH340X is improved based on CH340E, with 5V tolerant characteristic added when the power supply is 3.3V. 6# pin of CH340X can be changed from TNOW to DTR# when an external resistor is connected, see Section 5.3 for the two configurations. CH340C whose batch number begins with 4 and last 3-digit greater than B40, 8# pin can be changed to DTR# when a 4.7KΩ pull-down resistor is connected. CH340R provides reverse polarity TXD and MODEM interface signals, discontinued. The USB transceiver of CH340 is designed according to the built-in design of USB2.0, and it is recommended that no external resistor is in series with UD+ and UD- pins.

relation files

file name file content
CH341SER.EXE CH340/CH341 USB to serial port Windows driver, supports Windows XP/Vista/7/8/8.1/10/11/ SERVER 2003/2008/2012/2016/2019/2022 -32/64bit, Microsoft WHQL Certified, supports USB to 3-line and 9-line serial port. Used to distribute to user with the product.
CH341DS1.PDF CH341 datasheet, USB bus converter chip with multiple communication interfaces, such as USB to serial port/parallel port/printer port/I2C interface etc. Drivers support for Windows/Linux/Android/Mac, etc. The datasheet is the description of USB to serial port and printer port.
CH432DS1.PDF CH432 datasheet. Dual-UART expander. Compatible with 16C550. 8-bit parallel port or SPI to UART. Each UART receive/transmit data independently. Up to 4Mbps baud rate. Can be used for MCU dual-UART expansion. CH432 supports full-duplex/half-duplex/infrared modes.
CH438DS1.PDF CH438 datasheet. CH438 is an 8-UART extension chip. Each UART receive/transmit has independent 128-byte FIFO. The maximum baud rate is 4Mbps. It supports hardware flow control, compatible with 16C550/16C750. It provides 8-bit parallel interface, used for MCU 8-UART extension.
CH341SER_ANDROID.ZIP CH340/CH341 USB to serial port Android free drive application library, for Android OS 3.1 and above version which supports USB Host mode already, no need to load Android kernel driver, no root privileges. Contains apk, lib library file (Java Driver), App Demo Example (USB to UART Demo SDK).
CH9340DS.PDF CH9340 datasheet, USB CDC to single serial port, built-in crystal oscillator, supports built-in CDC driver in operating system.