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INA193: Negative and High power current sense

Max Pom
Intellectual 320 points
Part Number: INA193
Other Parts Discussed in Thread: INA290, INA281, INA280, INA293, INA195

Hello, 

I have to use a current sensor for -3.7V supply and +120V supply. The preferred solution is to use the same device covering both voltages, digital (I2C/SPI) is also preferred. The best solution I could find is to use 2 different analog power sensors (with conjunction with an ADC): INA193 for the negative voltage, and INA290 for the positive one. Can you suggest a better solution? (Digital/one common device for both voltages)? Thanks!

  • 0
    TI__Mastermind 26660 points

    Hello,

    I don't know if this will work because the INA193 has an Absolute Max VCM rating of 80V so it could break if exposed to a VCM>80V. Because of this I would recommend using the INA290+INA293 (or INA280+INA281, which are cheaper, but less accurate versions). Both of these devices will survive the -4V to +120V range. INA293 is specified to be accurate from -4V to +110V while the INA290 is specified to be accurate from 2.7V to 120V with a 122-V maximum survivable rating. So you will still need to make sure bus rail does not exceed 120V as to not break the INA293. If necessary you can place clamping diodes to clamp input voltage to 120V for the INA293 and/or place current-limiting input resistors to limit input ESD breakdown current if an electrical overstress condition (>120V) is possible. See section 8.1.2 in  INA290 datasheet for information on effects on gain and accuracy when using input filters. Note the INA280, INA290, INA281, and INA293 all have the same input bias stage front end so they all have the same "gain error factor" equation. The SPICE models we have also reflect this functionality. I also talk about the analysis process for our current sense amplifiers here: A quick tip is to take the gain error factor equation from datasheet and insert the input bias resistances with the + or - 20% tolerances to gain new expanded gain error range. 

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

    Another option is to use one our difference amplifiers; however, these devices will require larger and dual-polarity supply voltages in order to operate with the required VCM range. Consider the INA

    https://www.ti.com/amplifier-circuit/difference/products.html#p1169max=100;500

    Sincerely,

    Peter

  • 0 in reply to Peter Iliya
    Intellectual 320 points

    Hello Peter, 

    Thanks a lot!

    What about my original idea, INA290 +INA195? Is INA293 better than the INA195?

  • 0 in reply to Max Pom
    TI__Mastermind 26660 points

    Hey Max,

    This will not work because max survivable VCM for INA195 is 80V. Thus, once thus bus rail exceeds 80V the INA195 will blow up. This is why I recommended the INA293, which is a much more accurate device with a large survivable voltage range.

    Sincerely,

    Peter

  • 0 in reply to Peter Iliya
    Intellectual 320 points

    Hi Peter,

    I ment if I use 2 devices, the INA195 for -3.7V and INA290 for 120V. Is it ok, or INA293 is better for the -3.7V? Thanks!

  • 0 in reply to Max Pom
    TI__Mastermind 26660 points

    Hey Max,

    As long as the input VCM for the INA195 remains within its survivable range (-16V to +80V), then of course you can use this to measure current on a -3.7V rail. Whether the INA293 is better than the INA195 depends upon your system requirements. In general the newer INA293A3 is a better overall device compared to INA195 because it is faster, has more accurate and tightly controlled specifications, a larger survivable VCM range, and a larger dynamic range.'

    Better accuracy means you can use a smaller shunt resistor which will reduce shunt resistor power dissipation and this can be beneficial to save power in system. 

    Sincerely,

    Peter