Good day!

Which members of CH32(F/V) families are designed to support USB operations without crystal attached? Datasheets/RMs are not clear. Seems like CH32V203F8 has no XTAL pins, so probably it is an example.

Hello, if your USB operation here refers to USB download, the CH32 series MCU currently supports USB download mode except for the MCU that is not exported from the BOOT pin, and no external crystal oscillator is required. If the CH32V30 series MCU does not have an external crystal oscillator, the USB download can only be performed using the full-speed USB port. If you have any questions later, you can use email（ lzs@wch.cn ）Communicate with me

Some vendors clearly state that MCUs can be properly used as USB Device without crystal, due to presence of some special HW unit. Examples are:

Silabs: "Clock Recovery circuitry uses the incoming USB data stream to adjust the internal oscillator; this allows
the internal oscillator (and 4x Clock Multiplier) to meet the requirements for USB clock tolerance."

ST: "USB 2.0 full-speed interface, able to run from internal 48 MHz oscillator"

Nuvoton: "It supports a crystal-less USB 2.0 full speed device that can generate precise frequency required by USB protocol without the need of external crystal to reduce the BOM cost and PCB size"

So, the question is: does CH32V203F designed same way and can be reliable used as USB FS Device without crystal connected?

Hello, I have replied to you via email. Please check it carefully

在环境温度变化的情况下究竟是否能可靠工作在crystal-less模式下，是否有设计上的保证，手册上语焉不详，请详细说明一下

您好，在使用USB做设备的情况下，使用内部晶振可以满足大部分应用，但不排除存在一些兼容性问题；若使用USB做主机，建议使用外部晶振。