AD8420: +/-1V differential input voltage a rule or suggestion?

I am using an AD8420 in a current-sensing application.The differential input range during operation won't exceed +/-1V, but when the device is in standby mode, a relay opens, and the inputs are exposed to greater differential input voltages.

Is the +/-1V limit on the datasheet a design guideline, or a limit to prevent device damage?  Will I need to put voltage steering diodes on these inputs?

  • 0
    •  Analog Employees 
    on Sep 16, 2015 11:47 PM

    Hi Matthew,

    There is actually a discussion on its datasheets about the Large differential input voltage. It says that the device can handle large differential input voltages,regardless of the amount of gain applied, without damage. It also shown on figure 9, 10, 11 and 12 on its datasheet.

    AD8420 has a internal diodes that limits the input voltage seeing by the internal opamp to +/- 1V. Once we have a differential input voltage greater than +/- 1 V, these diodes will draw current but it is limited internally to value that is safe for the device. You may want to read page 20 of its datasheet for more detailed discussion.

    Let me know if you need anything else.

    Best regards,

    Emman

  • To clarify, the input pins are currently protected by 4.7kOhm resistors, but no external steering diodes.