i started a little project using LTC2368-24 ( LTC2368CMS24 ) and the reference voltage source is using a 3.3volt from LTC6655BHMS8-3.3.
Using 3.3v for vref, i expect to have aprox 0.196 uV/ LSB.
All voltages for the adc chip are buffered with 100n & 47 uf capacitors.
The design is on a 2 layer pcb.
I am stil in the debug phase with this project, so i wanted to see how low can it measure.
So i have shorted to ground both IN+ and IN- and see how low it measures., and i cannot read bellow 97-200 uV.
Tried also with shorting only IN+ & IN-, and the read voltage is a little lower... near 100uV
Tryied even with multiple filtering samples ( 1,32,64... even with 8192 samples), the results are mostly the same.
Most of the read values are in the 0x002XXX .. 0x001FXX hex range.
I also measured the voltage ac ripple on the vref line & the 2v5 line, 1-2mV ripple, didn't saw something noticable.
So at this point i am considering to move everything to a 4 layer pcb, but before i said to ask.
I know in the datasheet there is specified a noise for specific sampling rates, for example at 1 sample is specified 68LSBs, but at 3.3V ref, this would yeld arround 13 uV noise.
But 100-200uV is quite far away, so i am wondering what i measure is it normal?