Discussion created by aswain571 on Feb 5, 2013
Latest reply on Feb 11, 2013 by David.Buchanan

I am trying to send a LVCMOS, 40MHz signal to the clock input pin (pin 49) of this ADC, but the signal stops short of the device.  It is a single ended clock that is being used and the suggested layout (figure 60) from the data sheet is being used. The signal coming from the driver is good and the ADC is receiving the suggested power to the correct pins and there are no shorts from the CMOS driver to the clock input of the ADC. As I mentioned the signal looks fine from the CMOS driver, but when it reaches the other side of the suggested 100 ohm resistor, the signal dies. I have tried connecting the driver directly to the ADC clock input and even just taking out the optional 100 ohm resistor. I have even had the ADC replaced with a new chip in case the original was defective. My question is, "Are there any suggestions for what may be causing this, such as the internal circuitry of the ADC, some impedance matching issue, or is there another layout that can be used?"