Post Go back to editing

LTC2495 not reading full Vref (5V) and marks +2.5V as Over range

Thread Summary

The user is experiencing issues with the LTC2495 ADC when measuring voltages above 2.5V, receiving an overvoltage error code (110000). The ADC's differential input range is ±2.5V with a 5V Vref and gain of 1, so voltages exceeding +2.5V trigger the overvoltage flag. The user also noted that grounding an ADC channel returns 2.499V instead of 0V.
AI Generated Content
Category: Hardware
Product Number: LTC2495

Hello, we are designing a circuit implementing the LTC2495 ADC. We have connected Vref+  to 5V and Vref- to GND. the COM pin is also grounded.
We are having issues measuring voltages above 2.5V. Whenever we doo, we get the 110000 error code and no voltage data from the ADC.
We already checked the data transmission, it sending the correct bus of data command to the ADC for Single Ended mode. We also checked and it can measure relatively correctly voltages under 2.5 V and above 0 V. We are also noticing that if we try to connect an ADC channel pin to GND, it loops back and returns 2.499V instead of 0V on the measurement.

(IMAGE CANNOT BE ATTACHED DUE TO PRIVACY)


We can assure that it isn't a coding issue, as the firmware and library code we are using in Python thru a CM4 from Raspberry send the correct data bus and is able to configure the ADC to return data. It is simple marking voltages above 2.5V as over range, yet we are not sure why, since we are using a Vref of 2.5V and a grounded COM

Edit Notes

Image privacy
[edited by: JCoboN3 at 6:02 PM (GMT -4) on 22 Sep 2025]
  • Hi,  .

    I will contact the product owner and get back to you.

    Regards,
    Jo

  • Hi  ,

    The LTC2495 accepts a differential input voltage (IN+ - IN-) within the range of -FS to +FS, where FS is 0.5Vref/gain.

    For example, with a gain of 1 and a reference voltage (Vref) of 5V, FS = 2.5V. This means that the allowable input voltage range is +/-2.5V. If the input voltage exceeds this range, the LTC2495 flags an overvoltage or undervoltage condition using distinct output code. Specifically:

    - When SIG = 1 and MSB = 1, it indicates an overvoltage condition

    - When SIG = 0 and MSB = 0, it indicates an undervoltage condition

    Your measured output code is 110000, where the first two bits, SIG and MSB, are both 1, indicating an overvoltage condition. So, if your input voltage goes above +2.5V (for gain = 1), it violates the allowable range and triggers an overvoltage flag.

    Hope this clarifies your inquiry.

    Regards,

    JC