Schematic Review Checklist for EZ-USB® FX2LP™ – KBA90551
Question: Is there a schematic review checklist for FX2LP™?
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.
The crystal should be according to the following spec:
24 MHz ± 100 ppm
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.