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INA296A: Can I use this in 0 to 12V out variable output applications?

Li Wang
Prodigy 50 points
Part Number: INA296A
Other Parts Discussed in Thread: INA250

Hi,

I have output voltage range from 0 to 12V and output current from 0 to 100A

can I use the A1 part paired with a 0.0005 ohm current shunt ?

Regards,

Li

  • 0
    TI__Mastermind 33050 points

    Hello Li,

    Is the 12V the input to the INA296 or the VS or the INA296?  For VCM input this is fine.  For the supply this is also fine.  If this is a voltage that is PWM signal and switching from 0 to 12V then I would suggest the INA241.

    Either way if you have a input current of 100A * 0.0005Ω then the gain of the A1 0f 10V/V.  The output would be 0.5V.  

    This may be fine for the high currents but you may not get enough signal for your lower current measurements. 

    Keep in mind you need to account for the offset for the lower currents.  This will be a tradeoff on power and resistor you use.

    We have some training on resistor selection and offset error and other topics here: training.ti.com/ti-precision-labs-current-sense-amplifiers

  • 0 in reply to Javier Contreras4
    Prodigy 50 points

    Hi Javier,

    thanks for the response. We will use a Gain of 50 version so I will get about 2.5V max to the ADC. 

    It is used in 2 applications 

    1. Output from a quarter brick from 6 -18V (switching supply) 100A

    2. Output from a LDO from 0 to 6.5V (linear supply) 3A

    We will use different CSR values to maintain the Vout from the CSA is ~ 2.5V (we are using a 5V reference and allow some headrooms for peak current ) 

    One more question, for the input offset current, is that means the error term when I Load = 0 A? In that case, I can trim it out in software?

  • 0 in reply to Li Wang
    TI__Mastermind 33050 points

    Hello Li,

    What do you mean input offset current?  Are you talking about the IB(Input bias Current of the In+ and In-.  If so, then this will contribute to the error of the output at 0A but this should be in the µA range and normally is not an issue.  If you use resistors to filter the input this because a larger issue as it changes your input voltages at the INA296.

    Please calculate your output and be aware your range changes depending on how you connect the reference and if you use it in unidirectional mode or bidirectional mode.  Examples are in the datasheet.

    For your switching supply as long as you are not sensing on the side that switches the voltage then you can use the INA296.  If you are sensing on the other side then I would suggest the INA241.

  • 0 in reply to Javier Contreras4
    Prodigy 50 points

    Hi Javier,

    Sorry I was referring to the INA250 which have an offset current of 50mA max that I wasn't sure if the same thing carried to the INA296.  My understanding is this is the output offset when I_LOAD is 0 A. 

    We are using single direction only and this is mostly used as a telemetry function read of the output current. so everything is GND referenced. 

    Regards,

    Li

  • 0 in reply to Li Wang
    TI__Mastermind 33050 points

    Li,

    For the INA250A2 the 50mA offset is the error expected when the input is zero is correct.  So for example with the gain of 500mV/A you would get an output voltage between +/- 25mV from the Vref.  If Vref is connected to GND then you have to account for the output not being able to reach below 50mV as it will be limited by swing low.