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INA103 ESD protection

Frank Mayer
Prodigy 50 points

Other Parts Discussed in Thread: INA103, INA114, INA163

Dear Forum Members,

we are using the INA103 as a Input OPAMP in differential mode. We are using this device because of it's noise imunity and low offsets.

Now we need to make the EMC imunity test's as per EN61000-6-2 and we want to ensure that we not damage the devices. We would use either PRLL diodes or similar. many other where damaging their devices, but we can't find a solution.

The main question would be, how to place those diodes and between where.

Between the Input-Lines 16 and 1 would be o.k., but where to ground and what ground shall be used and what trigger voltage should be selected to protect the device.

 

Thanks,

 

Frank 

  • 0
    TI__Mastermind 25875 points

    Hello Frank,

    We are working on this and will get back with you soon.

  • 0
    TI__Mastermind 25875 points

    Hello Frank,

    Since the INA103 has an absolute maximum input voltage range rating equal to the supply voltage, you will need to use a bidirectional zener diode to ground on your inputs.  The voltage rating should be selected such that the diodes will fully break down before reaching the supply voltage.  Please see the attached TINA simulation.

    INA103_frank.TSC
  • 0 in reply to Pete%20Semig
    Prodigy 50 points

    Dear Peter,

    thanks for your answer!

    We suggesting this circuit:

    Do you agree on it, or could it be improved?

     

    Best regards,

     

    Frank

  • 0 in reply to Frank Mayer
    TI__Guru 64865 points

    Hi Frank,

    The 20V TVS diode will effectively limit the max differential voltage of the INA103 to +/-20V which is appropriate.  However the absolute maximum voltage on either the + or - terminals of this amplifier is +/-Vs.  This is not standard as most parts are listed as (+Vs + 0.3V) to (-Vs - 0.3V).  However since this part is specified the way it is, the diode clamps that you've implemented will not effectively protect the inputs of this device.  They will not turn on until the voltage on the inputs is greater than (+15V + 0.7V) or less than (-15V - 0.7V) so +/-15.7V.  Since the absolute maximum limitations in your configuration are +/-15V this protection method will not work.

    A solution similar to the one my colleague Peter implemented that limits the voltage to less than the +/-Vs voltage is required.

    Best Regards,
    Collin Wells
    Precision Linear Applications 

  • 0 in reply to Collin Wells
    Prodigy 50 points

    Dear Collin,

    it's a pitty that the INA103 can't withstand higher Voltages then Vs. Are there any Dif.-OpAmp similar to INA103 with better ESD characteristics? Maybe INA114? We where very happy with the performance of the INA103. As you maybe see in our sketch, we measure a shunt voltage (burden) in a value of 600Ohm to 1kOhm. The package will not be a matter for selection...

     

     

    Thanks for your advice!

    Frank

     

  • 0 in reply to Frank Mayer
    TI__Mastermind 25875 points

    Hello Frank,

    With +/-15V supply, the INA103's input common mode voltage range is +/-11V(min).  Therefore I do not fully understand why the original suggestion is not sufficient.

    With respect to a replacement device for the INA103, we do not have an instrumentation amplifier with similar bandwidth, which is why I assume you selected the device.  The INA114, for example, has a BW of 1MHz (at G=1) while the INA103 has a BW of 6MHz (at G=1).  

    However, I recommend considering the INA163 to replace the INA103.  Its BW is 3.4MHz (at G=1) and the abs max input voltage is listed as (V-)-0.5V and (V+)+0.5V.  The input common-mode voltage range is the same as the INA103.  The device is similarly noted for its low noise and low distortion.

    Please note that we have been discussing protecting the device from transient signals on the inputs that we thought are due to the aforementioned test.  If you're interested in system-level ESD/EMI protection, we have a portfolio of devices located at Products->Interface->ESD/EMI Protection (from http://www.ti.com).  There is also a dedicated E2E forum for those devices.

    I hope this helps!