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TLV9051: Inquiry for input level and high-side application

MJ Jeon
Genius 5240 points
Part Number: TLV9051
Other Parts Discussed in Thread: OPA325, INA180, OPA2992

Hi, TI support team

We are reviewing a product using TLV9051IDCKR.

Please confirm the inquiries below.

Q1. The difference in voltage input to both ends of Rshunt, that is, In+ and In-, is 20 to 35 mV.

Is it possible to print normally due to the level difference mentioned above?

Q2. The datasheet only mentions low-side current sensing.

Can't it be used as high-side current sensing?

Among products with the same performance, please recommend a product capable of high-side current sensing.

Or, if there is a cheaper current sensor product, please recommend it.

Thanks.

Regards,

MJ

  • 0
    Guru 258280 points

    1. The TLV9051 has a worst-case offset voltage of 2 mV. You have to decide yourself if this is accurate enough for you.

    2. The TLV9051 has rail-to-rail inputs, but the offset voltage becomes worse at about 1 V below the positive supply:

    There are general-purpose opamps with better performance near the positive supply, such as the OPA325, with a higher price.

    But consider the INA180/181, a current-sense amplifier with fixed voltage gains.

  • 0 in reply to Clemens Ladisch
    TI__Mastermind 22280 points

    Hi MJ, 

    Clemens did a really great explanation for both questions so I apologize for any repeat I have in mine. 

    1.  Clemens is correct. Your worse case offset voltage is 2mV across temperature. Most devices won't have a 2mV offset, but you will need to take that into account when designing your system. Here's the distribution of offset voltage that we show in the datasheet. 

    2. Again Clemens is right. When using an op-amp in high side current sensing, you have to take into account that you will see a shift in the offset voltage. We have a document that goes over Using An Op Amp for High-Side Current Sensing  that I highly recommend taking a look at since it goes into a more in depth explanation than here. Please note that will the document talks about the OPA2992 and other higher voltage devices, the principles still apply to low voltage devices like the TLV9051. 

    Let me know if you have any additional questions. 

    Best Regards,

    Robert Clifton