I used google translate to make an english version of the data sheet for the CH330 as I have some coming in for a project. It is hard to find information so I am sharing what I have.
I still need to clean up the text, this is just a straight copy and paste. The original can be found here.
USB to serial chip CH330
Manual Version: 1B http://wch.cn
The CH330 is a USB to serial port chip that is used to extend an asynchronous serial port for a computer or to upgrade a normal serial device to a USB bus.
Asynchronous serial port UART/RS232/RS485
● Simulate a standard serial port for upgrading the original serial peripheral device or adding an additional serial port via USB.
● The serial port application under the Windows operating system is fully compatible and does not need to be modified.
● Hardware full-duplex serial port with built-in independent transceiver buffer, supporting communication baud rate of 100bps~2Mbps.
● Support 7 or 8 data bits, support odd parity / even parity / flag check / blank check.
● Provides RS232, RS485 and other interfaces through the addition of level shifting devices.
● Support 5V power supply voltage and 3.3V power supply voltage.
3 The Package
4 The pins
5 function description
When the CH330 chip uses a 5V operating voltage, the VCC pin is input to an external 5V power supply, and the V3 pin is externally connected to a 0.1uF power supply decoupling capacitor. When the CH330 chip uses a 3.3V operating voltage, the V3 pin should be connected to the VCC pin and the external 3.3V input.
CH330 Manual 2
The power supply and other circuits connected to the CH330 must not exceed 3.3V.
The allowable baud rate error of the CH330 serial port receiving signal is not less than 2%, and the baud rate error of the serial port transmitting signal is less than 1.2%.
6.1. Absolute maximum value (critical or exceeding absolute maximum value may cause the chip to work abnormally or even damage)
6.2. Electrical parameters (test conditions: TA=25°C, VCC=5V, excluding the pins connected to the USB bus)
7 USB to RS232 serial port application
The figure below shows the USB to RS232 serial port implemented by CH330. The level shifting circuit U5 (MAX232/ICL232/SP232, etc.) is used to convert the TTL serial port to the RS232 serial port.
If you only need to implement USB to TTL serial port, you can remove U5 and capacitors C25/C26/C27/C28/C29 in the figure.
P1 is a USB port. If the CH330 chip and the low-power USB product directly use the 5V power supply provided by the USB bus, you can replace R1 in the figure with a protection resistor or short circuit. If the USB product provides a standing power supply through other power supply methods, the CH330 should also use the standing power supply. In the figure, R1 can be disconnected and the ground wires of the two are directly connected.
Capacitor C3 has a capacitance of 0.1μF for the internal 3.3V power supply node decoupling of the CH330. The C1 has a 0.1μF capacity for external power supply decoupling. Decoupling capacitors C2 and C1 should be placed as close as possible to the connected pins of the CH330.
CH330 Manual 3
8 connect the microcontroller serial port, each power supply
The following figure shows the reference circuit for USB communication between the MCU microcontroller and the CH330 chip through the TTL serial port in the dual power supply mode. The CH330 is powered by the USB bus. VBUS, the MCU uses another power supply VDD, and VDD supports 3V~5V. The diodes D6 and D7 in the figure are used to alleviate the problem of current backflow between the CH330 and the MCU through the RXD or RX internal diode in the dual power mode. In the figure, the RX pin of the MCU should enable the internal pull-up resistor. If not, it is recommended to add a resistor of 8KΩ~30KΩ to the RX pin.
Diode D6 is powerless for CH330 but the MCU is powered and TX is high to sink current to CH330 through RXD internal diode; Diode D7 is powerless to MCU but CH330 is energized and TXD is high to sink current to MCU through RX internal diode situation. If it is determined that a situation does not occur, the corresponding diode can be removed. For example, if the MCU has a permanent power supply, D7 can be short-circuited.
Diodes prefer a low-power Schottky Schottky diode, but common diodes such as the IN4148 are also commonly used.
In general, it is not recommended to separate the CH330 from the MCU and use it only when necessary.