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DRV421EVM: Suitability for LMG3411

Part Number: DRV421EVM
Other Parts Discussed in Thread: DRV421, INA253EVM, , DRV425, INA253, AMC1300, AMC1200, DRV5053, AMC1301EVM, DRV425EVM

Hello,

We have LMG3411EVM-18 daughter boards and we want to use them in closed current loop mode. We found 2 EVMs that we think can help us. These are;

·       DRV421 EVM. If this EVM can do the job we would then need 3 of these modules for 3-phase system measurement....correct?

·       INA253EVM. We wonder about the -4V limitation. Normal AC voltage will vary from 80V to -80V

 

Please let us know if you think if these are appropriate choices, and whether we need to complement them with other LMG EVMs.

Regards

Sam

  • Hello Sam,

    The DRV421EVM will need a external magnetic core as the EVM only has the device with supporting components and supporting components to evaluate the DRV421.  This would need a core design and there is technical documentation and tool to help with this design.

    We also have the DRV425 that measures magnetic field and can be used.  There is an reference design here and I have some advice on how to help improve accuracy.

    We also have a this reference design to measure current using a hall sensor DRV5053 .

    The INA253 is limited to -4V and cannot support the -80V.  

    We have isolation amplifiers AMC1200 and AMC1300 that may be an option.  These would need to have a floating supply.

  • Hello Javier,
    Thanks for your response

    Our application is closed-loop. DRV425 is for open-loop applications...correct?.....what is the reason? bandwidth (34 KHz is quick enough for closed-loop) or accuracy (2%)?

    DRV5053. LEM (current sensor company) states that their flux-gate technology give more accurate current sensing as compared to their hall-effect Technology. Does the same apply to TI technologies?

    You are mentioned the amplifiers in case we want to use shunt resistors.....correct?

    INA253 can be perfectly used with inverters where the DC supply is 80VDC and current is +/-15Amp..... correct?

    It seems to me that INA253 EVM is the quickest way to start create the closed loop without designing anything......just EVM off the shelf....do you agree?


    Regards
    Sam
  • Javier,
    Two more issues;
    Do you have any EVM (not reference design) that includes Hall-effect sensors to measure 3-phase current?

    In an inverter application to control AC motors where the DC bus volt is 80VDC and current is +/-15Amp ..... NA253 will be exposed to negative volt that is higher than -4 Volt....correct?


    Regards
    Sam
  • Sam,

    For open loop it means there is no closed loop for the current sensing like the DRV421. The DRV425 would measure the magnetic field created by the current. Accuracy I would say could be calibrated but it would be required. More due to mechanical toleraces as the field sensed will change depending on the physical dimensions

    In general this is correct due to the noise, drift and range of the sensor technologies. Typically flux gate sensors measure magnetic field with more accuracy, less noise but there are other considerations such as magnetic field range. Fluxgates typically measure low fields and this is why the DRV421 requires a feed back system to calculate current.

    Yes. I mentioned the AMC1200/AMC1300 in case you wanted to use a shunt resistor.

    INA253 will work for the keep in mind that the temperature range of -40°C to 85°C and if you layout your own board keep in mind the heat dissipation required.

    I agree if you are not going below -4V common mode. Also be careful with any voltage spikes you may have and that it will work. The operating VCM Voltage is 80V and the Absolute Maximum rating for the INA253 is 90V VCM.

    So that means in no condition should you never go above 90V VCM. The device should be operated below 80V. If you operate above VCM = 80V the specifications may not be met.
  • Sam,

    Normally we do not have EVM with a large scale design and we normally only highlight a specific device that would be evaluated.

    This is also dependent on where you are measuring the current.  if you are measuring on the low side you will always be around ground.  See this paper from EDN from a colleague.

    EDN paper link.

  • Javier

    You have EVM to measure +/- 15 Amp current using INA253. Do you have an EVM that measures the same current using Hall-effect. That EVM might have more than hall-effect current sensing.....we would accept that.


    Regards

    Sam



  • Sam,

    The INA253EVM does measure +/- 15Amp current.  I just pointed out layout was done to makes sure the dissipation of heat was good and able to meet the hotter ambient temperature.  See users Guide.  Here is the link for INA253EVM.

    We currently do not have an EVM with a hall sensor to measure current.  You would need to design one using the reference designs I mentioned above to meet your needs.

    We have a DRV425 bus bar evaluation module but this is much larger and would also need to be redesigned for your needs.

  • Javier,

    Thanks for your advice so far.

    We will put an order now so we want final confirmations.  Please just confirm the following or otherwise.


    Our aim is to close current loops of several inverters we design. The following are possible options for measuring the current for that sake;

    • INA253-EVM will measure +/- 15Amp if the DC bus of the inverter is 0 to 80VDC (pending temp limit). No need to add anything to that EVM to get voltage that is proportional to the measured current. That measured current can be used to close current loops. Correct?
    • AMC1301EVM can also be used...in that case we need one of those to measure each phase current and we would also need to add our own shunt resistor. That measured current can be used to close current loops. Correct?


    Further I understood that

    • DRV425 can be used as per the reference design you provided.
    • DRV425EVM can NOT be used as it is to measure current. It needs more than software scaling factor to scale from Magnetic field to electric current. Correct?


    Regards

    Sam




  • Sam,

    INA253EVM can measure the current up to 15A from -40°C to 85°C so this should be fine.

    AMC1301EVM can be used but you please review the User's Guide as I am not as familiar with this device and EVM.

    The DRV425 measure magnetic field and the DRV425 Bus Bar reference design is done to measure 100A and would need to be modified for your application. I would recommend reading the Bus Bar Theory of Operation to see if it will work for your application.

    The DRV425EVM would only measure magnetic field and you need to verify distance and orientation to get a good voltage out vs current. Also external magnetic fields will be a larger influence. Reference designs documentation describe this and why two DRV425s are used in the current measurements.