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AD5933 frequency sweep command sequence

Question asked by ml1 on Jun 16, 2015
Latest reply on Jul 20, 2015 by musach

Hello,

 

I have some questions concerning the operation of AD5933. I want to control it with an fpga.

 

According to figure 28 of the datasheet, during the step 0, we program the frequency sweep parameters (start frequency, number of increment and frequency increment). My first question is: do we also program the number of settling time cycles in this step as well? If not, when do we do it?

 

In reference to section 'Frequency Sweep Command Sequence', at page 15 of the datasheet, in step 1, I have to program the control register to enter in stanby mode. This is also what the flow chart on figure 28 says.

 

In step 2, I have to program the control register to enter in initialize mode. "this mode allows the user full control of the settling time requirement before entering start frequency sweep mode where the impedance measurement takes place." Does it mean that I have to program a waiting time before going to the next step?

There is a  second paragraph of the step 2 on page 15. "An initialize with a start frequency command to the control register enters initialize mode. In this mode the impedance is excited with the programmed start frequency, but no measurement takes place. The user times out the required settling time before issuing a start frequency sweep command to the control register to enter the start frequency sweep mode." Does it mean that there are two different ways to do step 2?

 

In step 3, I have to program the control register to enter in start frequency sweep mode. The datasheet says "In this mode, the ADC starts measuring after the programmed number of settling time cycles has elapsed." I am confused, the waiting for the settling time is before the start frequency sweep mode, right? Does the chip wait itself? (I program it to enter in start frequency sweep mode, it waits a certain time and after that, the ADC starts measurements?)

 

 

Thank you in advance!

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