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AD9280 behaviour when out of range


I have looked at the AD9280 and for our application it looks like it is exactly what we need.

There is one thing which is not 100% clear: the chips have an OTR output indicating an input signal being out of range.

The datasheet also says that in case OTR is ON the highest data bit indicates on which side (high or low voltage) the signal is out of range.

What I would like to now is: what is the state of the other data bits in case OTR is on ? Are they all 0 or 1 as one would expect ?

I am going to capture the digital data in 4k x 9 bit FIFO RAMs so I could capture both the digital data and the OTR status.

Unfortunately I need to capture another signal as well so in case all bits go to 0 or 1 in case of OTR I could use that instead of the OTR signal and use the spare bit in FIFO RAM to capture the other signal.

Any help/suggestion much appreciated.

  • The output of the AD9280 is straight binary as described in fig 32 on pg 15 of the datasheet. Output bits are all "0" at -FS and all "1" at +FS. The OTR bit toggles high whenever the Analog Input +/-FS range is exceeded.

    Best Regards,