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Inductor Current Sampling at middle of rising edge at frequency more than 20kHz using TMS320F28335

NITESH JHA
Prodigy 50 points
Other Parts Discussed in Thread: TMS320F28335, CONTROLSUITE, AMC1200

What should i use to create isolation between Input and DSP as well as give output signal without any phase shift from input?

I also want to know how to sample at middle of rising edge using DSP TMS320F28335

  • 0
    TI__Genius 15760 points
    Hi Nitesh,

    I am not clear about your request. I am moving your question to the Micro group. I have seen they have answered questions related to TMS devices in the past. If you are interested in any current shunt monitor solution please provide more information and schematic of what you are trying to achieve.

    Regards,
  • 0 in reply to Mayrim Verdejo
    TI__Guru 57255 points

    Hi Nitesh,

    If isolation is not necessary between input and output of the 'inverter' box and there are few communication interfaces, often the controller IC will be put on the hot-side ground with the inverter FETs.  In higher power systems or when lots of communication occurs with the outside world, it may make sense to put the controller IC on the cold side and isolate the interface between the controller and the FETs & between the controller and its sensing circuit. 

    In the former system, isolation of the communication lines is done via digital isolators and shunt current sensing is often used.

    In the latter system, gate-drive transformers and LEM or sigma-delta/delta-sigma sensing may be used.

    Sigma-delta systems are often more precise than shunts but often will have a bit more lag, often a tolerable amount. 

    ===

    The F28335 family of devices have a precise ADC and has features that allow it to measure the shunt or LEM sensor at the midpoint.  This is most often done by outputting symmetric (up-down count) PWM signals and sensing when the PWM counter is at 0.  You can take a look at some of the TMDSHVMTRPFCKIT examples within controlSUITE for more information:
    \controlSUITE\development_kits\HVMotorCtrl+PfcKit_v2.1\

    ===

    The F2837*D/F2837*S/F2807* have a sigma-delta demodulator peripheral built-in to the device.  This allows it to interface directly up to something like a AMC1200 modulator chip.  These chips also have a very capable ADC.

    The TMDSIDDK379D is a very good example showing how to use the F28379D in industrial drive systems.  This kit allows for the evaluation of various isolation and current sensing methods (including shunt, sigma-delta and LEM).
    \controlSUITE\development_kits\TMDSIDDK_v2.0\

    ===

    Hopefully this helps!


    Thank you,
    Brett