I am designing and using a USB 2.0 (High-Speed) specification circuit.
The circuit is shown as below.
Sometimes CPU cannot recognize the USB stick (USB 2.0 High speed).
At first, I changed the resistors from 0 ohms to 27 ohms. However, CPU still could not recognize the USB stick.
So, when I removed both the 22 pF capacitors (open status), CPU can recognize the USB stick very well.
What is the problem?
I know the role of 22pF capacitors with the series resistors is to remove ringing of the signal causing the EMI.
But when I removed the capacitors, the problem was solved (with still 0 ohms series remaining). Indeed, I can not understand the difference between the existence of capacitors of open circuit (removing capacitor) on the USB data differential signal by using an oscilloscope.
What is the problem here?