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TUSB2036 Crystal not swing

Other Parts Discussed in Thread: TUSB2036

The crystal is within spec and is connected to two 22pF load capacitors to ground and one series 1.5 kohm resistor to XTAL2, just like the datasheet recommends. (well actually they are supposed to be 27pF but I used 22pF).

According to my trace debug, and o'scope, the TUSB chip never really starts the clock, I am viewing XTAL1 and there is no swing

My question is, what circuit parameter did I violate? Should I swap out the capacitors for a lower or higher value?

Crystal :7382.6MHz_fox_Crys.pdf

  • Hello Lucas 

       The TUSB2036 requires a power on reset pulse of between 100 us to 10ms. If the recommended external RC circuit is installed (15K pull-up resistor and 1 uF cap) then the RESET# will be held low for somewhere within the 100 us to 1 ms range. Anything less than 100 us is too short, therefore, can interfere with USB enumeration.

    Regards.