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AD7690 Readings / Output code


Hopefully someone may be able to help me out...

I am testing out an AD7690 18-bit ADC for an application. Currently I can get a reading from the ADC, though it is not what I expect.

Vref is set to 2.048 V and there is 1.45 V onto IN+, IN- is connected to ground.

I assume that I should still get a code between 0x00000 and 0x1FFFFF for IN+, so I would expect to see roughly 0x16A80 (192800 decimal) for the 1.45 V, what I am getting however is around 0x1284B (75851 decimal). Working with the calculation of 15.625 uV per bit, (2.048*2 / 2^18).

My question really is given that I have IN- connected to ground, can I still expect to be able to read a code as above? Or does it not work that way? If I am expecting the correct code then it may well be the communications that is the issue.

Best Regards