ADC : Simultaneous Sampling Mode

Maxime Torrelli

Hello,

Now I work with F28069M. I see in the Reference Manual and there is a guide how to sample simultaneously 2 signals. But when I read the description it's said that the ADCINA will convert first, and the ADCINB will convert second. So basically, it's not really simultaneous. It samples 2 signals in the same time but not convert them. In fact, I have to read 2 signals Output of a Hall effect sensor. They are analogue (One is Sin, one is cos) and have to be read in the same time to calculate the angle.

If anyone have an explanation or solution for my work ? I consider if you have a code example.

Thanks for all your help,

Max

over 9 years ago

0 Devin Cottier over 9 years ago

TI__Guru 60865 points

Hi Maxime,

The analog voltages are captured at the instant the S+H window closes, so the conversion results should indeed be simultaneous from the standpoint of calculating the angle.

0 Maxime Torrelli over 9 years ago in reply to Devin Cottier

Intellectual 610 points

So it will work well with my application ? My only concern that the conversion time is quick enough. I intend to use sample time of 50 us and with the time ADC (following TI reference ) of 445 ns, I hope it dont make too much diffrence in my result

0 Devin Cottier over 9 years ago in reply to Maxime Torrelli

TI__Guru 60865 points

The sample-to-output latency won't affect the conversion results. What it will affect is whatever control loop you are running. What is the intended application?

0 Maxime Torrelli over 9 years ago in reply to Devin Cottier

Intellectual 610 points

I use it for my FOC control. That's why if the angle is not right, the transformation Park will make the difference in the signal of reference.

0 Ramesh Ramamoorthy over 9 years ago in reply to Maxime Torrelli

TI__Mastermind 27240 points

Devin is right. Ffrom a digital control stand point, a snap shot of the system variables of interest should be taken at the same time for control. It means that the samples are to be taken at the same instant. So long as the ADC represents the true eqvt of analog signal, it is sufficient. How soon you read the samples, process them and generate control action is another issue.

rgds,

ramesh

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ADC : Simultaneous Sampling Mode