Low power USB device

[hello188]

Hi

I would like to design the system in which the PIC operates at less than 2 mA when USB is not connected with low frequency (about 1MHz or 4MHz internal Oscillator).

When USB is connected, the PIC switches to 48MHz(which is required I think) clock and draws power from the USB connection.

Is 12MHz Crystal Absolutely required for USB operation?

If so, when I want to operate at low power mode, would 12MHz crystal connection raise my current consumption?

Thank you.

[Ttelmah]

Even running a 'traditional' USB PIC, 12MHz, is not needed (what is required is a multiple of 4MHz).
However what you need to do, is look at one of the newer PIC's which support operating the USB off a PLL from the USB itself. Devices like the 18F46J50, support running the chip from the internal RC oscillator, and the USB PLL, from the USB bus itself.

Best Wishes

[hello188]

Thanks.

For those who are looking for the similar parts, I've found the devices that support active clock tuning for USB.
They are PIC16F145x, PIC18F2X/4xK50 and PIC18FxxJ94

Thank you.