SERDES Evaluation Kit DS99R105/106 USB Version 0.1 Users Manual
National Semiconductor Corporation
Date: 5/14/2008
Page 20 of 37
Troubleshooting
NOTE: The DS99R105 and DS99R106 are NOT USB compliant and should not be
plugged into a USB device nor should a USB device be plugged into the demo
boards.
If the demo boards are not performing properly, use the following as a guide for quick
solutions to potential problems. If the problem persists, please contact the local Sales
Representative for assistance.
QUICK CHECKS:
1. Check that Power and Ground are connected to both Tx AND Rx boards.
2. Check the supply voltage (typical 3.3V) and also current draw with both Tx and Rx
boards. The Serializer board should draw about 40-50mA with clock and all data
bits switching at 40MHz. The De-serializer board should draw about 70-80mA with
clock and all data bits switching at 40MHz.
3. Verify input clock and input data signals meet requirements (VIL, VIH, tset, thold),
Also verify that data is strobed on the selected rising/falling (RFB pin) edge of the
clock.
4. Check that the Jumpers and Switches are set correctly.
5. Check that the cable is properly connected.
TROUBLESHOOTING CHART
Problem…
Solution…
There is only the output clock.
There is no output data.
Make sure the data is applied to the correct input pin.
Make sure data is valid at the input.
No output data and clock.
Make sure Power is on. Input data and clock are
active and connected correctly.
Make sure that the cable is secured to both demo
boards.
Power, ground, input data and
input clock are connected
correctly, but no outputs.
Check the Power Down pins of both Serializer and
De-serializer boards to make sure that the devices
are enabled (/PD=Vcc) for operation. Also check
DEN on the Serializer board and REN on the
Deserializer board is set HIGH.
The devices are pulling more
than 1A of current.
Check for shorts in the cables connecting the TX and
RX boards.
After powering up the demo
boards, the power supply
reads less than 3V when it is
set to 3.3V.
Use a larger power supply that will provide enough
current for the demo boards, a 500mA minimum
power supply is recommended.
