USB Bus Converter Chip (USB to Serial)
Add a UART, RS-232, RS-485 or RS-422 port to any host with a USB port.
What is it?
A USB bus converter chip is a USB-to-serial bridge. It connects to the host as a full-speed USB device and gives your board a UART (TXD / RXD plus modem control lines). On Windows the driver makes it appear as a standard serial (COM) port, so existing serial software works without changes. Add an external transceiver to turn the UART into RS-232, RS-485 or RS-422.
When do you need it?
- Adding serial ports to a PC, laptop or tablet that only has USB.
- Upgrading an existing serial peripheral (instrument, modem, controller) to a USB connection.
- USB to RS-485 / RS-422 adapters for industrial buses, with an external transceiver.
- Debug and service ports on embedded boards.
- Android devices in USB host mode that talk to serial equipment.
How to pick the right one
- Clock source
- A built-in clock saves the crystal and its capacitors. An external 12 MHz crystal gives tighter baud-rate accuracy (MI4220: transmit error below 1% with the internal clock, below 0.3% with a crystal).
- Supply and I/O voltage
- 5 V or 3.3 V. Match the I/O level of the UART or transceiver you connect; in 3.3 V mode the connected circuits must not exceed 3.3 V.
- Baud rate
- Check the highest rate your equipment uses. MI4220 covers 200 bps to 2 Mbps.
- Modem control lines
- Full RS-232 needs RTS / CTS / DTR / DSR / DCD / RI. A simple UART link needs only TXD / RXD.
- Driver support
- Make sure drivers exist for every host OS you ship to (MI4220: Windows, Linux, macOS, Android).
- Package
- SOP-16 for easy assembly, QFN4x4-16L for small boards.
What Magnias offers
MI4220 Series USB bus converter chips: full-speed USB to UART with modem control lines, 200 bps to 2 Mbps, 5 V or 3.3 V supply, -40 to +85 °C. MI4220C-P16 (SOP-16) and MI4220QC-N44 (QFN4x4-16L) have a built-in clock; MI4220G-P16 and MI4220QG-N44 use an external 12 MHz crystal. Drivers cover Windows, Linux, macOS and Android (USB host mode). Add an external level converter for RS-232, RS-485 or RS-422.