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AD7764 Evaluation kit

Question asked by gourah on Jul 13, 2015
Latest reply on Aug 7, 2015 by gourah

Hi,

 

Recently, I bought AD7764  Evaluation kit. Initially I would like to test it in stand-alone mode. So, with the following configuration/settings I started to test the board.

a) MCLK : On-board 40 MHz

b) Decimate Rate pin: Floating (128x)

c) Input Differential voltage: DC voltage(Vin) is fed as per the figure 37 (Single ended to differential converison) in AD7764 Data sheet page.19

 

And I tapped SCO, FSO and SDO to oscilloscope. I observed SCO frequency as 20MHz, FSO is changing Low to High and High to Low, for 32 SCO cycles it is remaining in low state. So it seems SCO and FSO are working fine.  I could not found any data on SDO line, it is always low even when I changed the input voltage.

 

At Input voltage 0.5V at input of op-amp, the voltages at Modulator inputs are Vin+=1.7576V an Vin-=2.3866V

 

Please review and let me know what could be the reason for not getting data on SDO line.

 

Thanks in advance,

 

NS

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