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AD7764 Overrange functionality

Question asked by snikinma on May 8, 2015
Latest reply on May 11, 2015 by snikinma



Before going deeper into my project I would like to ask following question.


I am working with my first project with Analog Devices AD-converter. I got a 32MZ pic connected to AD7764 through framed SPI interface on sefl-designed PCB. The data transport from AD7764 to PIC seemed to function well and there were no problems with framesync and clock pulses that I know of. Only issue I had so far was that overrange bit kept toggling and the FIR filter could not set itself. I tried to solve this by supplying the differential input amplifier with low amplitude signal (10mV) and even connecting the input pins together with no success.


As I was looking a reason from the PCB for this I noticed that my AD7764 overrange pin (pin number 9) is pulled high (2,52V) on power up when the AD7764 is in reset state and doesn't have master clock supplied to it. Is is normal behavior or should the overrange pin reset on device reset?


I tried to check if I have accidently routed 2.5V power supply to this pin but that is not the case so I have little ideas why the pin is pulled high.


Please ask any additional information needed in helping me.


Thank you for the help!