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Constant Current Source with highside sensing

Graham Brooker
Prodigy 30 points
Other Parts Discussed in Thread: LM3409

Please can anybody suggest if there is a suitable driver to implement a simple hjghside current source from a 24V supply providing between 50 and 100mA with an integrated highside current sense? I’ve tried to search using the Parametric tables with no joy.

  • 0
    TI__Mastermind 25500 points
    We have devices with high side current sense, but I am not sure what you mean by integrated. The error amplifier is integrated, but you do need an external current sense resistor. What to recommend depends on what your output voltage will be to determine if you need a buck, a boost, or a buck-boost.
  • 0 in reply to Clinton Jensen
    Prodigy 30 points
    Thanks Clinton
    I apologise for not being entirely specific, but in more detail the requirement for this applications boils down to :
    Vin 16 to 32 volts
    Io 50 to 100mA (adjustable)
    Ilim set to 100mA
    Vo 10 to 14V – (indicative. Io will be the controlling parameter)
    Load Essentially resistive, reference one end to 0V (thus need high side sensing)
    Temp -20 to +70 typical
    EMC conducted (and radiated) from input to be limited.
    Low power shutdown
    Small board area probably more critical than BOM cost, thus the interest in an ‘integrated’ product.
    Any pointers or suggestions would be welcomed.
  • 0 in reply to Graham Brooker
    TI__Mastermind 25500 points
    In this case you need a buck converter with high side sense. Check out the LM3409. It is designed to be able to do much more power, but it is a controller so for these current levels you could have a very small external FET, sense resistor, etc... and the end solution could be very small. That is your best option if you need one end of the load grounded. It does have analog adjust so you can control the current level as well as low power shutdown. It would likely require some input filtering like any buck converter if you have EMC concerns, but at this power level that should not be difficult.
  • 0 in reply to Clinton Jensen
    Prodigy 30 points
    Thanks Clinton – Much appreciated. I think this stands a good chance of solving the problem.