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INA303-Q1: Input voltage handling capabilities for the IC

Part Number: INA303-Q1
Other Parts Discussed in Thread: INA303

Hi,

I am trying to simulate INA303-Q1 for my application. The maximum input that can come across the positive and negative input of internal  OPAMP is 33V continuous input.

When I simulated the circuit for 33V input the output is coming as 1.9V. I have few questions and given it below.

Question 1:

Are there any clamping diodes used at input or output side of this IC?

Question 2:

I wanted to make sure that this Current Sense amplifier works fine if the voltage at input pin is 33V (Positive and negative input). Please let me know if it works fine for the given input condition.

Question 3:

Another condition is when there is input transient of 62V for 100uS comes at input pin of INA303 , Does TVS rated for 33 V  Break down voltage can handle the transient and protect the input pin?

Please help with your input.

Thanks,

Namita

  • Hi Namita,

    please post a schematic.

    Kai

  • Hey Namita,

    Thanks for the question. The model may have input clamps, but it should work at 33V input common-mode voltage (VCM) since the device is specified to perform accurately up to 36V max input VCM. Maybe your 33V TVS diodes are turning on and affecting the device measurements?

    Please post a schematic and/or the simulation file so I can debug the simulation directly.

    Input clamping TVS diodes at the input pins (IN+ and IN-) can certainly protect the device by clamping the input to a voltage at or below 40V (the Abs Max VCM, see section 6.1). However, some TVS diodes are only meant to protect against very specific types of voltage surges, which could be shorter than 100us, thus some TVS diodes may not be able to clamp the voltage for entire 100us. The power rating of the TVS diode will also need to be considered. The power rating must be greater than the power it will dissipate during the 62-V surge.

    Other types of diodes can be used to clamp input such as a Zener with reverse breakdown of ~36V-40V, but once again the power rating needs to be high enough to conduct the surge current, which will be dependent upon the how much current the source can drive during the voltage surge and if there is any current-limiting resistance in the path.

    You can place 10-Ohm resistors before the clamps at device input pins to limit current and reduce power rating. If you place resistors greater that 10-Ohm, then circuit gain will begin to become significantly attenuated. See section 8.1.2 and Table 4 to determine how much the gain will decrease and if this still works for you overall system requirements. Placing input resistors > 10-Ohm will also widen the gain error variation. This video explains why this happens for current sense amplifiers, the reason being that there is a low differential input resistance (5kOhm =Rbias for INA303) and that internal resistors can all vary by +/-20%.

    https://training.ti.com/ti-precision-labs-current-sense-amplifiers-input-filter-error

    https://www.youtube.com/watch?v=hLGN_wl-xgA

    https://www.ti.com/lit/an/sboa343/sboa343.pdf

    Hope this helps. Please post back if you need more information.

    Sincerely,

    Peter