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AD9650 offset adjust lsb weight

Question asked by crabbyjacket on Jul 23, 2013
Latest reply on Nov 14, 2013 by David.Buchanan

According to the AD9650 register description, address 0x10 is Offset adjust in LSBs from +127 to −128

In that context, I assumed lsb means conversion lsb.  But on the first article of my new AD9650 design, a change of 1 lsb of this register has a measurement change of 128 quanta.  Is this correct, or could my device be damaged?  I have only measured terminated-input so far, and won't have a suitable signal generator to test signal gain for a few more days.

Example: write 0 to R10 - noise input mean is -105q

write 1 to R10 - measurement mean is 23q

write 2 to R10 - measurement mean is 151q


I have double checked RBIAS resistor = 10K (in-circuit measure 9.88K).  VREF is external at 1.95V