CH9350 - USB keyboard and mouse to UART conversion controller LQFP-48

Description

The CH9350 is an integrated circuit designed to convert USB communication from HID devices (keyboard, mouse, and selected peripherals) to a UART interface. This solution allows for the extension of USB keyboard and mouse connections to serial communication, including via an RS485 bus, which is useful in KVM systems, KM switches, multi-station synchronization, and industrial remote control systems.

The circuit supports USB 2.0 Full Speed ​​(12 Mbps) and Low Speed ​​(1.5 Mbps) and operates compliant with the HID standard without the need for additional driver installation in Windows, Linux, and macOS. It can operate in two modes:

• Upper Computer Mode - connection to a USB host (e.g., a computer)
• Lower Computer Mode - support for up to two USB devices (DP/DM and HP/HM)

In lower mode, the circuit supports two independent pairs of USB lines, allowing simultaneous connection of a keyboard and mouse. Operating mode configuration is achieved via the SEL pin during reset or power-up.

The CH9350 offers five operating states (State 0–4), allowing for customization of functionality to a specific application. Depending on the configuration, it can operate the mouse in relative or absolute mode (up to 10-bit coordinate resolution), support switching between extended screens, IO synchronization, VID/PID switching, and unidirectional communication in selected modes.

The UART interface operates at a 3.3V logic level (5V compatible) and supports configurable baud rates: 38400, 57600, 115200 (default), and 300000 bps. Transmission format: 8 data bits, 1 stop bit, no parity. The device also provides a TNOW pin for controlling the transmission direction in half-duplex RS485 systems.

Power can be supplied from 5V (with a built-in 3.3V regulator) or directly from 3.3V. The device includes an internal oscillator and power-on reset circuitry, simplifying the PCB design and minimizing the number of external components.

Applications include: industrial control systems, KVM solutions (including VGA/DVI/HDMI extensions), video surveillance, digital signage systems, computer control in distributed environments, and keyboard and mouse synchronization across multiple hosts.

Features

• USB 2.0 Full Speed ​​12 Mbps and Low Speed ​​1.5 Mbps support
• HID Class Compliance without driver installation
• Two operating modes: Upper Computer Mode / Lower Computer Mode
• Up to two USB ports in lower mode (DP/DM and HP/HM)
• Five operating states (State 0–4)
• Relative and absolute mouse support (up to 10-bit resolution)
• VID/PID customization
• Configurable UART speed: 38400 / 57600 / 115200 / 300000 bps
• 3.3 V UART logic levels with 5 V tolerance
• TNOW pin for RS485 direction control
• Built-in oscillator and Power-On Reset
• 5 V or 3.3 V power supply
• LQFP-48 package, 0.5 mm pitch, dimensions 7 × 7 mm
• Operating temperature range: -40°C to +85°C