Design LTC2508-32 so as to perform precise voltage measurements

Hi,

I would like to design the LTC2508-32 into my hardware to perform accurate voltage measurements. The voltages I wish to measure range from just below zero to just above 4.1v.

I have been looking at this part and would like to use it. The plan would be to adjust the supplies. I would supply -0.5v to the gnd pins, and would adjust the Vdd, OVdd and Ref to accomodate this. 

Gnd = -0.5, Vdd = 2.0v, OVdd = 5v (looking at the max ratings 5v would also be ok) and Ref = 4.5v.  

I have the following questions:

(1) With regards to the exposed ground paddle, is this used as an electrical ground or is it for heat dissipation. If its an electrical ground then I will need to connect it to the -0.5v and would do so with mini power plane. If this not there for electrical purposes the I can connect it to the ground of my board which would be better for dissipating heat as the accurate ground plane of my board is very large.

(2) I plan on only using the filtered data, therefore I will be using the A output, I will be tying the RDLB input high. For best practice should I leave the SCLKB and SDOB float or should I tie these high or low.

(3) I have lately started using LTspice and find it very useful, I have downloaded the models for the LTC2508-32 from the website. I was wondering if you would be able to either help me or point me in the direction of some documentation regrading how I can import these to my LTspice app.

Regards,

Shane

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