LTC2497 Differential reference


I am using LTC2497. I wanted to clarify the following,

My Vs = 5v and I am planning to use a precision 2.5V as the Vref for differential ADC. I wanted to check if this is the correct value, the last sentence states, the Vref will set the full scale range for all input channel. My concern is that upon using the 2.5Vref, I can only read +/- 1.25V.

Please advise.

Thank you.

Top Replies

Parents Reply
  • 0
    •  Analog Employees 
    on Sep 24, 2020 7:52 PM 5 months ago in reply to SLee144

    Looking at Table 1 of the data sheet, you will see that the two LSBs are for overrange and sign. That is followed by 16 data bits and 6 zeros. With the data you provided that decodes to 5546Hex. Converting that to decimal is 21380. 21380/65535 * 2.5 = 0.8327V That is relative to the 2.5V that the -input is setting at, which makes the input voltage 3.3327V. That is still a sizeable error from 3.062V but if you are basing your reference voltage on the 5V from the USB, that much error is quite possible. Measure the voltages at REF+ and IN- and see if the number you are getting makes sense.