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AD9914 Negative Ramps

Question asked by amchardy on Mar 11, 2014
Latest reply on Mar 17, 2014 by Quang

Hi all,

 

I'm looking to use an AD9914 to generate some negative frequency ramps, however, it looks a little more complicated than I had imagined.

 

My understanding from the datasheet is that when using the DRG, the accumulator will always start at the lower limit. This means that in order to do a negative ramp I must first do a positive ramp until the accumulator hits the upper limit and then pull the DRCTRL pin low in order to start the negative ramp.

 

Is there anyway to start a negative ramp without first having done a positive ramp?

 

What if I use the no-dwell low mode and start with the DRCTRL pin high. When I pull the DRCTRL pin low (i.e. a negative transition) will the DRG immediately jump to the upper limit (because the accumulator is already sitting at the lower limit) or will it sit doing nothing at the lower limit?

 

Thanks in advance.

Alex

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