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CH343 - High-Speed USB to Serial Chip

The CH343 is a USB bus converter chip, which converts USB to a high-speed serial UART interface. Compared with its predecessor CH340, it supports a higher data rate (up to 6Mbps) and more serial port IO levels (5V / 3.3V / 2.5V / 1.8V). We can use CH343 seamlessly when a USB connection needs to be converted to a serial interface. It supports automatic identification and dynamic adaptation of communication baud rate of 115200bps and below. The IC supports commonly used MODEM contact signals RTS, DTR, DCD, RI, DSR, and CTS. This IC is compatible with USB V2.0 and supports 5V and 3.3V. It has an inbuilt 3.3v regulator and we can utilize that 3.3v supply through Pin V3. The CH343 is available in the SOP16 package.

CH343 Pinout Configuration

Here are the pinout details for CH343.     

Pin No
Pin No
Pin No
Pin Name Pin Type Pin Description
16 4 3 VDD5 POWER The power supply voltage input of the power regulator requires an external decoupling capacitor
15 7 1 VIO POWER I/O port power input requires an external decoupling capacitor
1 3,0 2,0 GND POWER Ground
4 10 6 V3 POWER Internal power regulator output, core and USB power input connect to VDD5 when VDD5 is less than 3.6V, connect to decoupling capacitor when VDD5 is more than 3.6V
5 1 7 UD+ USB signal   Connect to USB D+ Signal directly, no external resistor
6 2 8 UD- USB signal  Connect to USB D- Signal directly, no external resistor
7 NONE 9 VBUS IN VBUS status detection input of USB bus, integrated pull-down resistor
2 8 4 TXD OUT Transmit asynchronous data output, idle state is high level
3 9 5 RXD IN Receive asynchronous data input, integrated pull-up resistor
13   15 CTS IN The MODEM input signal is clear to send, active low
  6   CTS
or DTR 
Default input, switch to output automatically The default is MODEM input signal, clear to send, active low, when the computer software setting DTR is valid, automatically switch to the MODEM output signal, data terminal ready, active low
12 NONE 14 DSR IN The MODEM input signal, data set ready, active low
14 NONE 16 RI IN The MODEM input signal, ring indicator, active low
9 NONE 11 DCD IN MODEM input signal, data carrier detect, active low
10 NONE 12



OUT MODEM output signal, data terminal ready, active low, if an external pull-down resistor is detected during power-on, switch to a status indication about the serial port sending is in progress, active high
11 5 13 RTS OUT MODEM output signal, request to send, active low
8 NONE 10 ACT# OUT USB configuration completed state output, active low, if an external pull-down resistor is detected during power-on, switch to communication baud rate adaptive mode, software can also use this mode

CH343 Specifications

CH343 USB to Serial converter has the following key features:

  • I/O independent power supply, supports 5V, 3.3V, 2. 5 V and 1.8V power supply.
  • Integrated power-on reset, integrated 12MHz clock, no external crystal required.
  • CH343P integrates EEPROM used to configure the chip of VID, PID, maximum current value, vendor and product information string, etc.
  • Chip has integrated Unique ID (USB Serial Number).
  • Full-speed USB device interface, USB 2.0 compatibility.
  • Built-in firmware, emulates standard UART interface, used to upgrade the original serial peripherals or expand additional serial UART via USB.
  • Original serial applications are totally compatible without any modification.
  • Supports free installation OS with built-in CDC driver or multifunctional high-speed VCP vendor driver.
  • Hardware full-duplex serial UART interface, integrated independent transmit-receive buffer, supports communication baud rate varies from 50bps to 6Mbps.
  • Supports automatic identification and dynamic adaptation of common communication baud rate of 115200bps and below.
  • Supports 5, 6, 7 or 8 data bits, supports odd, even, space, mark and no parity.
  • Supports common MODEM interface signals RTS, DTR, DCD, RI, DSR and CTS.
  • Supports CTS and RTS hardware automatic flow control.
  • Supports half-duplex, provides sending status TNOW which supports RS485 to switch.
  • Supports RS232 interface, through external voltage conversion chip.
  • Supports USB port 5V and 3.3V power supply.
  • RoHS-compliant SOP-16, ESSOP-10 and QFN16 lead-free package.

Manufacturers of CH343:

The CH343 is manufactured by There are no alternative manufacturers for the same part number as of the date of writing this article.

CH343 Variants

The CH343 comes in 3 different packages SOP16, ESSP10 and QFN16. 

CH343 Variants

Package Pin Pitch Pin Pitch Parts Marking
SOP16 1.27mm 50mil CH343G
ESSOP10 1.00mm 39mil CH343K
QFN16-3X3 0.5mm 19.7mil CH343P

CH343 Equivalents

If you are looking for an equivalent or replacement for CH343, we weren’t able to find any other chip that is pin-to-pin compatible.

CH343 Alternatives

If you are looking for an alternative for CH343 you can look at the other IC from these.

CH340, MA112AS16, FT230x, CP2102, PL2303341, CH9102, MCP2200, CP2110, FT232

Note: Complete technical details can be found in the CH343 datasheet at this page’s end.

CH343 Schematics

The following image shows the typical circuit diagram for CH343.

CH343 Circuit Diagram

 This circuit shows the basic configuration of the CH343 IC as you can see, the data lines of the USB are directly connected to the D+ and D- pins of the IC the capacitors connected across the power supply is to stabilize the voltage and reduce the noise. We can connect the Tx and Rx lines of CH343 to any microcontroller or similar circuits. Remember to connect the Tx to the Rx of the receiver and the Rx to the Tx of the receiver.

Problems with using CH343?

I made a USB-to-serial converter using CH343, but I am unable to communicate?

It's due to several reasons but you can check these:

  • Double-check all connections between the CH343 chip and the other components of your circuit. Make sure that the TX and RX lines are connected correctly to the devices you are trying to communicate with.
  • Check that the voltage levels of the signals (TX, RX, etc.) are compatible with the devices you are connecting to. 
  • Sometimes, the issue could be with the USB cable itself. Try using a different USB cable to see if that resolves the problem.
  • make sure you have selected the correct baud rate and other settings.

How can I test if my CH343 is working properly?

Make sure that the serial settings (baud rate) on your computer match those of the device you are trying to communicate with. Try connecting the TX and RX pins of the CH343 together (a loopback test). Send some data from your computer, and if it's received correctly, it indicates that the CH343 is working.

My computer is not recognizing the CH343 circuit.

  • Make sure that you have the correct drivers installed for the CH343 chip on your computer. The drivers are necessary for the computer to recognize and communicate with the chip. You can download CH343 Driver and install on your computer. 
  • In Windows, check the Device Manager to see if the CH343 is recognized correctly without any error messages. If there are errors, it could indicate a driver issue or a problem with the hardware connection.

Design Choices to be Considered with CH343

What are the design considerations when designing a PCB using CH343?

  • Place the USB port near the CH343 IC, and the data lines track should route straight forward.
  • Minimize the via count in data lines.
  • Should use filter capacitors and also keep all components tightly.

Applications of CH343

  • Microcontroller Programming
  • Debugging and Testing
  • Industrial Control Systems
  • DIY Electronics Projects
  • Legacy Device Support
  • Automation and Robotics

Footprint Information and Dimensions of CH343

Here you can find the mechanical drawings of CH343 along with its dimensions. The dimensions can be used to create custom footprints of the IC and be used for PCB or CAD modelling.

CH343G SOP16

CH343K eSSOP10

CH343P QFN16

Component Datasheet

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