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INA381: Rhys selection limitation

Expert 3745 points
Part Number: INA381

Dear E2E Support,

Is there any limitation in the choice of Rhys value?

Can we increase the hysteresis voltage up to 1.5V for example?

Regards,

  • Hi Tisl,

    keep in mind that the internal 4µA current source might show some manufacturing tolerance. Also, increasing Rhys to much higher values than shown in table 3, eventually increases the risk of mistriggering due to capacitive stray coupling. So, there might be a good reason for making the table stop at 300mV. Having said this, there shouldn't actually be a hard limit for Rhys. So, I think you will be able to increase it a bit.

    Kai

  • Hello TISL,

    The fundamental limitation to Rhys is the headroom voltage needed for the 4 uA current source and this headroom voltage is not specified. So while hysteresis might increase to 1.5V for a 325 kOhm Rhys, dynamic range will be diminished. The 4uA source's headroom voltage should be equal to VS - 4uA*(12.5k + Rhys) - Vout, so by increasing Rhys so dramatically, you are decreasing how high Vout can go in the system and the hysteresis 4uA source still work.

    Hope this makes sense.

    Best,

    Peter