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INA240: understand the good performance of current sense amplifier

Emma Wang
Expert 4810 points
Part Number: INA240
Other Parts Discussed in Thread: INA210,

Hi expert,

My customer meet low accuracy that using precision amplifier as differential amplifier, and I am promoting Current sense amplifier to them.

They hope to understand the difference and I send them this blog:

https://e2e.ti.com/blogs_/archives/b/thesignal/posts/difference-amplifiers-the-need-for-well-matched-resistors

In this article, it says: 

These ratios are accurately matched, temperature tracking and laser trimmed. The same issues apply to the internal difference amplifier that serves as the output stage of most instrumentation amplifiers.

so I really want to better understand the accuracy of INA210 and INA240 for the internal resistor, as well as the Resistor ratio.

And how to understand the temperature tracking and laser trimmed? does this means the ratios will maintain same regardless the temperature changes?

BR

Emma

  • 0
    TI__Mastermind 30810 points

    Hi Emma,

    • Q - “The accuracy of INA210 and INA240 for the internal resistor, as well as the Resistor ratio”

    A - The absolute values of the resistors are not as critical as their ratios. Laser trim is one way to achieve highly matching ratios that form the basis for achieving superior performance, such as gain, cmrr and offset. For INA210 and INA240, the absolute values can vary up to 20%, but ratio is bound by parameters mentioned, even though the ratio itself is not listed in the datasheet

    • Q - “how to understand the temperature tracking and laser trimmed? does this means the ratios will maintain same regardless the temperature changes?” -

    A - Resistor temperature tracking typically is not determined by laser trim. It is rather a property of resistor material of the individual fab technology, enhanced by certain design techniques. As a result, the ratio will remain largely constant in the entire temperature range. Again, resistor temperature tracking is not specified in the datasheet separately. It is bound by device drift specs.

    The document you quoted applies to current sense amplifier regarding the benefits of integrated resistors, in contrast to discrete solution. Here is another brief that points out a few differences between current sense amplifiers and difference amplifiers. You’re welcome to take a look.

    Regards, Guang