What are the recommended/required specs for the system and USB XTALs (freq, tolerance, stability, etc.)? Can the USB share the SYS XTAL?
1. For USB XTAL specification you can refer to latest BF70x datasheet - Page No. 97, Table 62. USB On-The-Go – Receive and Transmit Timing. For quick reference Table 62 is shown below:
a. (USB_XI Frequency) = 24MHz Min and 24MHz Max
(USB_XI Clock Frequency Stability) = -50ppm Min and +50ppm Max
b. For reference you can look at the specification for the part number ABM8-24.000MHZ-B2-T for USB XTAL.
2. Please refer to BF70x datasheet under “TIMING SPECIFICATION” section, “Clock and Reset Timing” subsection for range of values of SYS_CLKIN. For reference you can look at the specification for the part number ABM8-25.000MHZ-B2-T for SYS_XTAL.
3. No USB cannot share SYS XTAL
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