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ISO224: Input resistance (Rin) relationship with temperature

Jonathan Geronga
Expert 7930 points
Part Number: ISO224
Other Parts Discussed in Thread: AMC1301-Q1,

Hi Team,

We have a customer inquiry regarding the Input resistance (Rin) specification in the datasheet.
The input resistance is specified as 1.25 Mohm (typ) and 1 Mohm (min). Does the input resistance change with temperature?
If so, by how much? This is important to the design of the customer, as any drift over temperature may affect the overall system accuracy.

Please let me know if you need more information.

Thanks!

Jonathan
 

  • 0
    TI__Guru 55232 points

    Hi Jonathan,

    Thanks for the post. 

    I'll chat with my colleagues and let you know. 

  • 0 in reply to Alexander Smith
    TI__Guru 55232 points

    Like any resistance, there is going to be some amount of drift over temperature. However the resistors used on the input structure of this device are extremely low drift, especially when compared to the large  input impedance of 1.25Mohm typ. Furthermore, it is statistically uncommon to see devices near the minimum value of 1Mohm. In order to minimize the gain and offset error, keep the sensing resistor as small as possible, and consider performing a calibration for even better performance.

    This excel calculator can be loaded to calculate the expected gain and offset error for isolated amplifiers: https://e2e.ti.com/support/amplifiers/f/14/p/815789/3019110#3019110

    It is currently loaded with datasheet specifications for the AMC1301-Q1, but we will be releasing a new and improved version that features a pre-loaded configuration for the ISO224 soon.