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High side current measurement

Ramakrishna Challa
Prodigy 160 points
Other Parts Discussed in Thread: OPA350, INA282, INA170, INA148

Dear all,

 I have 0.005Ohm current sense resistor.

What's the best differential amplifier to measure the current (max 1A).

Specifications

1) High side current measurement

2) The bus voltage is 48V while the Op-amp would be supplied by 5V.

3) need to measurement the current in both the directions

OPA350 is suitable for this application?

 V=IR Drop across current resistor = 0.005*1 = 5mV, this is very small voltage

Any referense schematics would be of great help.

Thanks and regards

Ramakrishna

  • 0
    TI__Mastermind 25805 points

    Hello Ramakrishna,

     

    It appears as though you have submitted 3 separate high-side current sensing applications questions.  They all appear to be very similar with the exception of the common-mode voltage and maximum current.  Next time it may be more effective to put these requirements in 1 post.

     

    For all of these applications, what is the minimum load current? 

     

    The first request was for a common-mode voltage of 60V.  That was answered last week.

     

    The other 2 posts were for 48V and 125V.

     

    For the 48V case I recommend the INA282 again, but it may be worthwhile to look at the INA170.  Please note the INA170 is current-output.  Also please note the INA170’s Vos is larger than that of the INA282.

     

    For 125V common-mode, we do not have any dedicated current-shunt monitors that can withstand that voltage.  Given your supply voltage requirement of 5V, none of our difference amplifier will work either.  Please note the INA148 can accept a Vcm of +/-200V, but that is with dual supplies.  The Vcm of the device with a single 5V supply is 75V.  

     

    Concerning the OPA350, is there a particular reason for the interest in this device?  It has a lot of GBW (38MHz).  Is this a concern for your application?

     

    Also, can you please provide me with some background information concerning the application?

  • 0 in reply to Pete%20Semig
    Prodigy 160 points

    Hello Pete,

    Please Can you provide the PSPICE file (that is usefull in ORCAD simulation) of INA282?

    Application:

    I have the fuse of 500mA. I need to replace this bi-direction fuse with small sensing circuit.

    I have attached the my proposed circuit. Please go through it and provide your comments. I don`t have TINA software for doing simulation. Can you provide the schematic in pdf or image format that will be usefull forme

     

    Thanks & Regards

    Ramakrishna

     

    6330.fuse.pdf