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ADE7758 - Questions about datasheet

Question asked by Faustin on Mar 31, 2015
Latest reply on Apr 3, 2015 by Faustin



I am currently working on the ADE7758, and more specifically on integrate Rogowski Coil (di/dt current sensor) on the current channel instead of classic Current Transformer.


I have some questions about the datasheet (I attached it) :


- First, in "Figure 41. Current Channel Signal Path" (page 19) it says that the data rage after integrator swings between 0xCB2E48 and 0x34D1B8 (for 50Hz) while in "Figure 63. Current RMS Signal Processing" (page 28) it says that this same data rage after integrator swings between 0xD7AE14 and 0x2851EC (same as the current signal output after the ADC)

So I would like to know which one is the good one, cause it seems that there is a contradiction, and why ?


- Then, in "Figure 39. Analog Gain Register" (page 18), bit 3 and 4 allow to select the current input full-scale (for the ADC right ?) between 0.5V, 0.25V and 0.125V, but, still in "Figure 41. Current Channel Signal Path" (page 19), we can see that the choice for the GAIN[4:3] register is between 2.42V, 1.21V and 0.6V (I think these values are the power supply for the ADC)
So again which one is the good one ? Or there is something and I don't understand very well.

Also, is the gain selection for the PGA (1, 2 or 4) has any influence on the current input full-scale select ?

And is the choice of this gain will depends on the output signal provides by the Rogowski coil ?



I hope I was clear, and thank you in advance for any help.