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Question asked by AndrewMiller on Apr 10, 2018
Latest reply on Apr 11, 2018 by AndrewMiller

I have a customer using the LTC2358-16. The device is able to accept different input voltage ranges, but in this case I am referring to the true bi-polar input. The device should operate between +10.24 and -10-24 on the inputs. They are only seeing +/- 6 Vdc and I was wondering if it had to do with the SoftSpan configuarations?. 

The datasheet indicates the following;


For channels configured in SoftSpan ranges 7, 6, 3, or 2, the LTC2358-16 digitizes the differential analog input voltage (VIN+ – VIN–) over a bipolar span of ±2.5 • VREFBUF, ±2.5 • VREFBUF/1.024, ±1.25 • VREFBUF, or ±1.25 • VREFBUF/1.024, respectively, as shown in Table 1a. These SoftSpan ranges are useful for digitizing input signals where IN+ and IN– swing above and below each other.




Does this mean I am losing some of the Vin capabilities due to the digitization ?? 

To deal with this "offset" the customer is raising the input voltage to +/- 15 Vdc, so that they can see +/- 10.24 at the inputs. 

Are they going about this the wrong way ??