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Using a LT1999 for unidirectional current sense

Category: Hardware
Product Number: LT1999-50

I have a need for a multipurpose current sense amplifier. Our current circuit uses a LT1999-50 and works fine using the reference voltage generated from the chip,
but we are trying to combine designs where another current sense is not bidirectional. Is it OK to ground the REF pin to use the full range of the output of the device in a unidirectional fashion?
Due to supply chain issues our choices are small, but if there is a recommendation to use another device that would be fine as well, but at this point I would really like to know if the REF pin can be grounded.

  • Hi,

    Moving this to the amplifiers community.

    Thanks,

    Kristine

  • Hello Glenn,

    I would not recommend connecting the REF pin to ground.
    From the datasheet, there is a specification for REF pin voltage input range. This range ensures that the part does not heat up outside the full operating temperature range.
    Now if you check the internal circuit connected to the REF pin, you will see that the REF pin is internally connected to the supply voltage and ground through 160kohm resistances.
    If you connect the REF pin to ground, then the supply voltage will then be connected to ground through just a 160kohm resistance (instead of 2 160kohm in series) which will then generate a larger current through it.
    A larger current could heat up the part, so operation is not guaranteed.

    Is the range of one direction of the bi-directional LT1999 not enough for your application?

    Best Regards,
    Sham