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INA500: INA500 input clamping voltage?

Oliver Betz
Prodigy 20 points

Part Number: INA500

Tool/software:

the INA500 data sheet specifies 10mA max input current but no voltage causing current flow.

Figure 7-7 in Chapter 7.3.5 "Electrical Overstress" shows bidirectional clamping diodes on the inputs but the data sheet doesn't state the clamping voltage of these protection diodes.

What DC voltages can the INA500 inputs tolerate?

  • 0
    TI__Mastermind 29720 points

    Hi Oliver,

    Let me ask the team and I'll get back to you as quickly as possible.

    Best Regards,

    Robert Clifton 

  • +1 in reply to Robert Clifton56
    TI__Mastermind 29720 points

    Hi Oliver,

    Sorry for the delay. I talked with the team and the DC voltages that the INA500 inputs can tolerate are (V-) + 30V to (V-) – 25V. 

    We are planning to update the datasheet to include this information.

    Best Regards,

    Robert Clifton 

  • 0 in reply to Robert Clifton56
    Prodigy 20 points

    Hi Robert,

    thanks for the information. The limits are a bit lower than I expected.

    Two more questions:

    * Is this the clamping voltage of the protection diodes?

    * Is the 10mA abs max rating still valid?

    If so, adding 8kOhm series resistors to both inputs would increase the allowed (transient) input voltage to ~100V, reduce the gain by 0.5% and have little effect on CMRR, correct?

    Best regards,

    Oliver

  • 0 in reply to Oliver Betz
    TI__Mastermind 29720 points

    Hi Oliver,

    Oliver Betz said:
    * Is this the clamping voltage of the protection diodes?

    That is correct. 

    Oliver Betz said:
    * Is the 10mA abs max rating still valid?

    Very much so. 10mA abs max rating is still critical. 

    Oliver Betz said:
    If so, adding 8kOhm series resistors to both inputs would increase the allowed (transient) input voltage to ~100V, reduce the gain by 0.5% and have little effect on CMRR, correct?

    CMRR is going to be affected by how closely matched the resistors are to each other. Unless they are identical in values to one another, CMRR will be degraded. 

    Best Regards,

    Robert Clifton

  • 0 in reply to Robert Clifton56
    Prodigy 20 points

    There is also a uncertainty how the resistors in the INA500 P and N path are matched (for INA500 precision, only the ratios of the P and N divider must be matched, but not the absolute values).

    But since the protection resistors are only 0.5% of the internal resistors, even a 10% mismatch would still result in good CMRR.