Prolific PL2303 knock-off USB-TTL adapter without timing crystal

Question

I recently got this bare-bones USB-TTL adapter which unsurprisingly contains a knock-off Prolific chip but on top of that it is entirely without the crystal oscillator. It seems to be missing some capacitors labeled C1 and C2 as well.

Has anyone come across a USB-TTL adapter based on clones of the PL-2303 (HX/HXA/XA) that needs no crystal? Is this adapter likely to work despite the unpopulated component footprints? Should I be suspicious of elevated risk to any devices I may connect to it?

(EDITED to add specific mention of the PL2303 chip)

Answer 1

There are a number of USB-TTL serial converters which do not require a crystal. For example this lineup from Prolific in Taiwan, with about 9 different part numbers.

Here is a datasheet of one that supports either internal clock or external crystal.

WCH (Jiangsu Qin Heng) also makes USB-serial chips and microcontrollers with USB interface (device and host) that do not require an external crystal.

NXP has Kinetis MCUs that support high speed (not just full speed) USB without a crystal.

As far as risk, anything electrically connected to your computer could involve non-zero risk of damage. The risk is exponentially greater if higher voltages than 5V or negative voltages with respect to ground are involved. Full speed/low speed isolators are available to minimize that risk at a relatively low cost. In most cases (eg. using a commercial eval board) they don't tend to get used.