CH340 USB to Serial Converter Chip – Features, Specifications & Variants
CH340 is a popular low-cost USB-to-serial (UART) converter chip from Nanjing Qinheng Microelectronics (WCH). It converts a USB interface to a standard asynchronous serial port (or printer port in some variants), making it widely used for adding USB connectivity to microcontrollers, Arduino-compatible boards, ESP modules, and other serial devices.
CH340 USB to Serial Converter Chip – Features, Specifications & Variants
Key Features
- USB Interface: Full-speed USB 2.0 device interface (compatible with USB V2.0). Includes built-in USB pull-up resistor.
- UART Emulation: Emulates a standard UART interface. Existing serial applications (especially on Windows) work without modification. Hardware full-duplex operation with integrated transmit/receive buffers.
- Baud Rate Support: 50 bps to 2 Mbps. Supports common rates including 50, 75, 100, 110, 134.5, 150, 300, 600, 900, 1200, 1800, 2400, 3600, 4800, 9600, 14400, 19200, 28800, 33600, 38400, 56000, 57600, 76800, 115200, 128000, 153600, 230400, 460800, 921600, 1.5 Mbps, and 2 Mbps. Typical baud rate error is low (<0.3% transmit).
- Serial Data Format: 1 start bit (low), 5–8 data bits, optional parity (odd/even/mark/space), 1 or 2 stop bits (high). Supports simplex, half-duplex, or full-duplex.
- Modem Control Signals: Supports common signals including RTS, DTR, DCD, RI, DSR, and CTS (availability varies slightly by package/variant).
- External Interface Expansion: Can interface with RS-232, RS-485, or RS-422 using external level-shifting chips.
- IrDA Support (specific variants, e.g., CH340R): Supports IrDA SIR infrared communication at 2400–115200 bps when paired with an infrared transceiver.
- Power Supply: Supports 5V and 3.3V operation (some notes mention down to ~3V). Typical operating current is low (around 7–20 mA depending on conditions and voltage).
- Clock: Many modern variants (CH340C, CH340N, CH340K, CH340E, CH340X, CH340B) have an integrated clock oscillator — no external crystal required. Older variants (e.g., CH340G) typically need an external crystal.
- EEPROM (CH340B): Integrated EEPROM for configuring serial number and some customizable functions.
- Software Compatibility: Built-in firmware; software-compatible with CH341. Uses the CH341 VCP (Virtual COM Port) driver.
- Packages: RoHS-compliant options including SOP-16, SOP-8, SSOP-20, ESSOP-10, and MSOP-10.
- Other Notes:
- CH340K includes built-in diodes to help prevent reverse current from MCU I/O pins during independent powering.
- Some variants (e.g., CH340X) add improvements like 5V-tolerant I/O when powered at 3.3V.
- Also supports USB-to-printer port mode in certain configurations (see separate datasheet CH340DS2).
Common Variants
Popular versions include CH340G (classic, often needs external crystal), CH340C (integrated clock, common in adapters), CH340N (small package), CH340K, CH340E/X, and CH340B (with EEPROM). Exact pinouts and features can vary slightly by package.
Drivers and Compatibility
Official drivers from WCH (CH341SER series) support Windows, macOS, and Linux. Many modern OS versions handle basic detection, but installing the official driver is recommended for best reliability. It appears as a standard COM port.
The CH340 is a cost-effective alternative to chips like FTDI FT232 or Silicon Labs CP210x, widely used in DIY electronics, development boards, and USB-TTL adapters. For full electrical characteristics, pinouts, and application circuits, refer to the official WCH datasheet (CH340DS1).
