USB to Serial Port Chip CH9101


CH9101 is a USB bus converter chip, which converts USB to serial port. CH9101 provides standard MODEM signal, used to expand serial port for computer or upgrade directly from normal serial device or MCU to USB bus.


  • Full-speed USB device interface, USB 2.0 compatible.
  • Built-in firmware, emulate standard UART interface, used to upgrade the original serial peripheral or expand additional UART via USB.
  • Original serial applications are totally compatible without any modification in Windows operating systems.
  • Supports free installation OS which built-in CDC driver or multi-functional high-speed VCP vendor driver.
  • Hardware full duplex UART interface, integrated independent transmit-receive buffer, supports communication baud rate varies from 50bps to 3Mbps.
  • UART supports 5, 6, 7 or 8 data bits, and supports odd, even, space, mark and none 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, used for controlling RS485 to transmit-receive switch.
  • Supports RS232 interface, through external voltage conversion chip.
  • Supports 5V and 3.3V power supply voltages.
  • UART interface I/O powered independently, supports 5V, 3.3V, 2.5V, 1.8V power supply voltages.
  • Integrated power-on reset, integrated clock, no external crystal required.
  • CH9101U/H/Y/R Built-in EEPROM used to configure the chip of VID, PID, maximum current value, vendor and product information string, etc.
  • Integrated Unique ID (USB Serial Number).
  • RoHS compliant SSOP28, QFN32, QFN16, QSOP16 and SOP8 lead-free package.


Note: The backplane of CH9101H/CH9101Y is 0# pin GND, which is an optional but recommended connection; other GND are necessary connections.

The USB transceiver of CH9101 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.

CH9101N has no Built-in EEPROM.