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current sensing on the output of LMZ1200

Greg Kopins
Prodigy 30 points
Other Parts Discussed in Thread: LMZ12001EXT, LMZ12001, INA128

Can you tell me about the caveats to using the LMZ12001EXT in a circuit that takes +12V input and produces +3.3V on the output?  What is the best way to handle current sensing on the output, in order to avoid degrading the loop response/stability? 

 

  • 0
    Prodigy 5 points

    Hello Greg,
    The LMZ12001 is rated for 20VIn max and 1Amp output max.
    It will work fine to create 3.3V from a 12V input.

    With loading less than 50% you may see the output voltage tend to rise 2-3%.
    This is in the area where the modules output inductor is discontinuous operation.
    The output is fully in regulation, it just may rise a little.

    LMZ14001H does not exhibit this behavior.  (H version)
    EXT extended temperature range is not shown to be available at this time.
    However the LMZ14001H is fully pin compatible with the LMZ12001, allowing a 42V input maximum vs the 12001's 20V maximum.

    Do you need the EXT version for this application?

    As for current sensing on the output, place any sense resitor and circuitry AFTER the required external output capacitor.
    The output capacitor, selected per datasheet guidelines, will dominate the loop properly.

    We have many current shunt monitors that may be an option for output sensing.
    TI Home   > Amplifiers and Linear     > Current Shunt Monitors

  • 0 in reply to Ed Walker
    TI__Expert 7589 points

    I have used INA128 as a current monitor while using DC/DC converters. The output of DC/DC will have ripple. If you are looking at accurate current measurements across sense resistor then its a good idea to have a RC filter prior to the inputs of the INA differential inputs so the INA inputs are somewhat ripple free.