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AD9744 Output Transient

Question asked by harrycheung on Nov 19, 2013
Latest reply on Nov 28, 2013 by harrycheung

Hi all,

 

I am using the DAC AD9744 in a frequency counter circuit. I send in a clock signal to initiate the data conversion. However I see a spike of the frequency of the clock signal at the DAC output.  The yellow trace is the AC-coupled output signal after a buffer and there is a clear spike signal that occurs regularly.

scope_133.png

 

The clock signal into the DAC is routed directly under the output traces of the DAC, so I suspect that may be pick up noise, but I am not certain whether its magnitude would be this large. The thick blue trace on the right side of the DAC is the input clock signal.

 

CMOS_counter_PCB.png

 

My question is: what happens to the DAC current output during conversion? Can I expect it is always in the range between output current corresponding to previous digital input and output current of the digital input that it is converting?

 

Thanks

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