AnsweredAssumed Answered

3.08 MHz on VREF pin of AD9460???

Question asked by godtec on Oct 26, 2012
Latest reply on Oct 28, 2012 by godtec

Hi All:


I have designed I high speed ADC board with the AD9460.

After troubleshooting it now, I realized that I have forgotten to add the 0.1uF and the 10uF capacitor on the VREF pin.

I am using the VREF pin as an output to provide my amplifier circuit with 1.7V. So the sense pin is connected to AGND.


So recently I have noticed that when I probe, the VREF pin I have a "modified" Sin wave at 3.08Mhz approx.

More details, The FPGA digital interface section is working fine. The analog side is having problems.

I have made 2 prototype boards, and the problem is on both boards, with the similar 3 MHz.

REFT & REFB have the necessary caps on them as per page 20 of the datasheet.


2 questions:


1: If I add the resistors, should the 3 MHz go away. By, not adding the resistors could have I damaged the input section of the ADC.

2: IF I still add the 2 caps to ground and the 3 MHz is still there, Where else  in the analog section should I concentrate on to solve the problem?


Thanks in advance.

Mike K