Schematic Review Checklist for EZ-USB® FX2LP™ – KBA90551

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    Version: **

     

    Question: Is there a schematic review checklist for FX2LP™?

     

    Answer:

    Please check that your hardware meets the following requirements:

    •   USB data lines: D+/D-
        There should be nothing wired on these sensitive high-speed data lines.
    •   There must be pull ups on the SCL and SDA lines.
        Recommended values: 2 kΩ -10 kΩ
    •   WAKEUP# pin:
        The WAKEUP pin should be in a de-asserted state on power up. The default polarity of the WAKEUP pin is active low. You should have the pin tied high. Do not leave it floating.
    •   RESERVED pin:
        Make sure it is grounded directly, as specified in the datasheet.
    •   RESET#:
        Make sure the Reset time is adequate and meets the minimum of 5 ms (measured from the time when power ramps up). The max reset time is 100 ms to meet the USB spec.
    •   Crystal:  
          
      •     The crystal should be according to the following spec:    
              
        •       24 MHz ± 100 ppm
        •     
        •       Parallel resonant
        •     
        •       Fundamental mode
        •     
        •       500 μW drive level
        •     
        •       12 pF (5 percent tolerance) load cap
        •    
          
      •   
      •     One of the recommended parts is Ecliptek: EC-12-24.000M.
      •  
    •   Make sure that the VCC ramp-up rate meets what is specified in the datasheet. The input must turn on to a valid voltage (3.0 V to 3.6 V) over a 200 μs period. This equates to an 18 V-per-millisecond ramp-up rate. Powering up the input too quickly will latch the internal regulator and cause problems powering up the core. Many 3.3 V regulators have turn-on times that are long enough to properly power up the internal regulator. One such regulator is the LT1763CS8-3.3.

    For FX2LP hardware design, please refer to the application note AN15456 - Guide to a Successful EZ-USB® FX2LP™ Hardware Design.