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F29H850TU: F29P329-F29H850TU Motor Driver Current Reading

Batuhan Kaya
Prodigy 160 points

Part Number: F29H850TU

Hi all,

I'm implementing FOC motor control with F29P329S using TLE4973 current sensors (5V VDD). My system runs on 3.3V VREF.

Configuration Options:

  1. Single-ended: Read only sensor output directly. (Sensor needs external VREF and typical sensor VREF is 2.5V)
  2. Semi-differential: Read both sensor output AND internal VREF, then subtract in software

My Concern:

With semi-differential approach, I need 2 ADC readings per phase per PWM cycle (6 total ADC readings for 3-phase or 4 total ADC reading for 2-phase). Does F29P329S support true differential ADC reading, or do I need separate conversions?

Questions:

  1. Will reading 2 ADC channels per phase (output + VREF) every PWM cycle cause timing issues for FOC algorithm?
  2. Is there delay between consecutive ADC readings that could affect current measurement accuracy?
  3. What's TI's recommended approach for this configuration?

My switching frequency is 8-15kHz.

Regards

  • +1
    TI__Mastermind 40330 points

    Hi Batuhan,

    Can you provide the expected voltage output of the TLE4973 current sensor for the min and max motor driver current.  It would probably be more efficient to implement this using the ratio of current sensor VREF to ADC VREF of the F29P329 rather than doing a conversion on the sensor VREF each time sensor output is converted.  VREF should always be constant so there really is no reason to convert VREF every time.  You would also free up a channel by not converting VREF.

    The F29P329 ADC can sense and convert an analog signal in 260ns so ADC throughput should not be an issue compared to the switching rate.

    Regards,

    Joseph

  • 0 in reply to Joseph Casuga
    Prodigy 160 points

    Hey Joseph,

    TLE4973 expected voltage output range: 0-5V VDD,

    Typical AREF is 2.5V.

    Max motor driver current is 600A.

    Regards

  • 0 in reply to Batuhan Kaya
    TI__Mastermind 40330 points

    Hi Batuhan,

    Can you also please share the voltage reference used for the F29P329S and for TLE4793, it the AREF at 2.5V and the 0-5V output is bipolar (meaning 0 to 2.5V is for negative currents to 0amps and 2.5V to 5.0V is for 0amps to positive currents?

    Thanks,

    Joseph  

  • 0 in reply to Joseph Casuga
    Prodigy 160 points

    Hi Joseph,

    Yes, you're correct - the 0-5V output is bipolar (bidirectional current measurement).

    Here's the detailed explanation of our semi-differential configuration:

    VREF Setup: We're using TPS653860 PMIC LDO4 output as both ADC VREF and TLE4973 AREF.

    Regards

  • +1 in reply to Batuhan Kaya
    TI__Mastermind 40330 points

    Hi Batuhan,

    Ok, if that is the case, then can you have a voltage divider (div by 2) in the output of the TLE4973 current sensor.  You can directly convert the div 2 tap on the voltage divider to the F29P329S ADC, configure the VREFHI of the F29P329S as 2.5V then you do not have to have an extra channel to convert VREF.  The ADC result conversion from the F29P329S will be the sensed current.  If you want the results to be bipolar on the ADC, there is a feature on the ADC PPB where you can introduce an offset so that the converted results can be translated as bipolar as well.  Let me know if this will work for you.

    Regards,

    Joseph