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Current sensor amplifier and Common-Mode Voltage with a 3.3V supply

Lucas PERBET
Prodigy 30 points
Other Parts Discussed in Thread: INA282-Q1, LMP8602, INA282

Hello everyone,

I am facing a problem for which I can't seem to find a solution.

I need to measure a current through a shunt resistor and current sensor amplifier, for which "standard" components and designs already exist at TI, but here's the catch :

-The amplifier is supposed to be supplied with a 3.3V supply

-The signal of which current will be measured has a common mode of maximum 40V (if the acceptable common-mode of the component is higher, it would be even better).

-Preferably the component should be Automotive-Grade, and with a 50:1 gain

I have identified devices such as the INA 282 Q1, the INA 148-Q1, the TSC1031 and the LMP8602Q1, but either information is lacking regarding the acceptable common-mode under a 3.3V supply, either it is given but too low for my application.

I may add that precision and speed of the measurement are not critical.

Would anyone have any advice regarding my issue ?

Thanks in advance,

L Perbet

  • 0
    TI__Mastermind 21805 points

    Hello Lucas,

    Thanks for considering to use Texas Instruments.  I am not sure exactly what you mean by information is lacking.  The electrical characteristics table of the datasheet does show that these devices can operate for your conditions.  If you are wanting to know what the output range is, that is determined by the swing to supply and swing to ground specifications, which can be used to determine the shunt resistor needed to measure your full expected load.  If you are wanting to determine the percent error for your operating conditions, you can extrapolate from the values we have in our tables.  The training videos here show how to calculate the contribution of all error sources.  Alternatively, we have a tool on the product page that shows the error curve.  If none of the items above are able to provide you with the information you need, you will need to clarify what you are looking for.

    Electrical characteristics Table for INA282-Q1

  • 0 in reply to Patrick Simmons
    Prodigy 30 points

    Hello Patrick,

    First of all thank you for your quick reply.

    I am sorry for not being clear enough in my question, let me develop : I am actually talking about the acceptable INPUT common-mode. Let me take for instance the case of the LMP8602 : it is specified that the common-mode of the measured signal is dependent on the supply voltage :

    With this in mind, I was wondering if the acceptable CM voltage of the measured signal was supply-dependent for the other devices, such as the INA282.

    Indeed, the INA282 datasheet specifies the CMVR for a supply of 12V :

    So, my question is : is it acceptable to supply for instance an INA282 with 3.3V and still measure the current of a signal which CM voltage is around 40V ?

    Best Regards,

    L. Perbet

  • 0 in reply to Lucas PERBET
    Guru 140200 points

    Hi L,

    you wrote:

    "So, my question is : is it acceptable to supply for instance an INA282 with 3.3V and still measure the current of a signal which CM voltage is around 40V ?"

    Yes, of course. Read again section 9 of datasheet.

    Kai

  • 0 in reply to kai klaas69
    Prodigy 30 points
    Thanks you very much for your answers, it's crystal clear now ;)