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INA148-Q1: INA148-Q1 for 24V BDC inputs under reverse polarity conditions?

D J
Prodigy 110 points
Part Number: INA148-Q1
Other Parts Discussed in Thread: INA148, INA592, INA149

Hello,

I plan to use this as part of a current sense amplifier circuit due to its wide Abs max for inputs and high common mode range.

For 48V reverse polarity, the part is unpowered (and its input is RPP protected through an ideal diode ckt)

However the inputs can backfeed thru input resistors across current sense resistro (shown on right 200uOhmx2).

However abs max shows +/-200V on input regardless of input voltage.

So if there is no power supply under RPP condition, the inputs will survive this condition, correct?


  • 0
    TI__Guru 54576 points

    HI DJ,

    Yes, as you have mentioned, during a fault condition, per the Absolute Maximum Ratings table, the INA148 can withstand ±200V continuous during a fault at the input terminals without damage.

    During normal operation, the INA148 while powered with bipolar ±5V supplies can operate in linear range with an input common-mode range of -100V to +80V and while powered with bipolar ±15V supplies can operate in linear range with an input common-mode range of -200V to +200V

    The gain of the INA148 device is 1 V/V, and the input offset error of the INA148 is ±1mV typical  (±4mV max); therefore there will be an error in the measurement.

    When the current is 200A across the 200uOhm||200uOhm shunt, the input voltage across the shunt is 20mV, so there can be up to 4mV of error in the measurement.

     

    Thank you and Regards,

    Luis

  • 0 in reply to Luis Chioye
    Prodigy 110 points

    Luis,

    Thank you for confirming that. Considering the input offset,

    Would you recommend INA592 as a better option for this application with ~40uV max input offset?

  • 0 in reply to D J
    TI__Guru 54576 points

    HI DJ,

    The INA592, when configured in gain of 1/2 has an internal input resistor of 12kΩ, and during the 48V fault, an input current of ~4mA can flow through the device.  The INA592 can withstand up to ±10mA through the inputs during a fault condition.

    If during normal operation, the input common-mode is +24V, and you powered the device with  ±15V supplies, the INA592 can be configured on Gain of 1/2 V/V, and the input offset error is ±14uV typical  (±40uV max).  The simulation below shows a total error of 778µV due to the common-mode voltage error, but it is more accurate than the INA148.

    See below:

     Thank you and Regards,

    Luis

  • +1 in reply to Luis Chioye
    TI__Guru 54576 points

    HI DJ,

    It is also worth considering the INA149.

    The device can withstand common-mode voltage range up to 300V during a fault.

    The INA149  device will offer you gain of 1V/V. and higher common-mode rejection at 100dB.  It offers you relatively low offset at 350uV typical, hence will provide you very good accuracy.

    Thank you and Regards,

    Luis