Is it possible to clock USB module with IRC?

[allankliu]

Recently I am considering to design a macro USB dongle for Android (as HID/CDC device). Due to its limited space, I am trying to find a USB micro which can operate without external crystal. I know Microchip/Cypress can do, but STM claims that USB has to work with external crystal.

Can I use IRC(4MHz) of KL24/25Z as clock source for USB OTG?

Allan

[egoodii]

For just CDC, the CP2105 is a tiny self-contained UBS-to-serial device.  Smaller & cheaper than an osc.

[pavel_krenek · Accepted solution]

It is impossible to use IRC for USB module because the internal reference clock does not have required accuracy which is strictly needed for peripheral USB.

Regard

Pavel

[DerekLau]

It's not recommended to use internal clock for USB applications.