• Resolved

LM2904: Please recommand High side current sensing using the LM2904

Part Number: LM2904

To whom it may concern

I'm going to design High side current sensing using the LM2904

so could you support the reference schematic

I don't like to INAxx series because cost is expensive

if design is impossible pls recommand other device

like, LM2903 or LM358 etc

thanks  

  • SPEC is 50mA to 600mA, i'll used 10mOhm shunt thanks
  • In reply to Seong Nam Park:

    Seong Nam,

    The first step is to consider input signal level. In this case 0.5mV to 6mV (Iout * Rsense)
    Then determine how much error is acceptable, I'll assume +/-20mA offset error. This is 0.2mV
    Therefore the Vio (Vos) input offset error of the op amp chosen must be less than 200uV

    Second step is to consider common mode rejection needed.
    This is high side voltage divided Rsense voltage
    I'll guess high side is 12V and Rsense voltage is 200uV, CMRR = 12V / 200uV = 96dB = 60,000
    1/60,000 = 0.0017%, that means 0.001% resistors should be used.

    At this point the INA instruments amplifiers would be less expensive in the end.

    Regards,
    Ronald Michallick
    Linear Applications

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