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

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.