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DRV401: Application questions

Jiawei Hu1
Expert 5555 points
Part Number: DRV401

Hi team,

For DRV401, could you kindly help on below questions? Thanks!

  1. What is the degaussing mechanism of DRV401?
  2. What is the degaussing capability of the DRV401? What is the range of residual magnetism that the chip can eliminate?
  3. And within what temperature range can the chip's degaussing function work properly? Under what conditions will the chip lose its degaussing ability?
  4. Do we have reference schematic?

BR

Jiawei

  • 0
    TI__Mastermind 32210 points

    Hello Jiawei,

    1.  The degauss mechanism is described in the datasheet.  Basically there is a decaying AC alternating field that reduce the magnetic field left on the magnetic core.

    2.  The max current for the degauss is limited by the Rshunt and the compensation coil and inductance.  The timing is described in the datasheet as the h-bride tries to go to max voltage and will be limited by the factors I mentioned.  The core material properties will also play a part as some materials are softer magnetically.  

    3. The device will drive the h-bridge through the operating temperature range.  All the above properties could change like the drive capability of the H-bridge, rshunt, compensation coil resistance, inductance and is a system issue.  Understanding the saturation point of the core will determine if it will be capable of getting degaussed.

    4. There is a reference schematic in the datasheet.

    Regards,

    Javier

  • 0 in reply to Javier Contreras4
    TI__Expert 5555 points

    Hi Javier,

    Could you kindly help another three questions? Thanks!

    1. What is the difference between degaussing when VCC is powered down and then on again, and degaussing when VREF is connected to GND? Please provide the waveform diagrams of VREF to ground reset ICOMP2 and VOUT. There are only waveform diagrams corresponding to VCC power-off reset in the specification sheet.
    2. Will the chip start degaussing 100% when the above two conditions are reset respectively?
    3. How to determine whether the chip has activated the degaussing function?

    BR

    Jiawei

  • 0 in reply to Jiawei Hu1
    TI__Mastermind 32210 points

    Hello Jaiwei,

    1.  There is no difference expect your Vout will get railed as the current on the compensation coil will go positive and negative causing the +/- difference voltage.  I am assuming that the DEMAG is connected to VCC.  VREF(in) is an input voltage and is high impedance.  VRef(Out) is a DC voltage that after power up is a DC voltage.  ICOMP2 is ICOMP1 are inverse of each other.  If you need me to explain how the degauss works please let me know. 

    2.  Demag happens when powered on(Cycle VCC) and Demag is high.  In the datasheet it states if you want to avoid a degauss then you must hold Demag low to avoid a DEMAG cycle during a power up or a brownout condition.  I think the datasheet covers this pretty well.  Please let me know if something specifically is unclear.

    3.  While a degauss is running the Rshunt is large enough and the compensation coil resistance is not limiting the current you should see the Vout rail on both high and low during the degauss cycle.  The is because the max current initial should run through the the Rshunt initially as it decays with time you will get a lower Vout voltage as the inductance will reduce the current through each cycle as less time for the current to be active.  Also the Error flag will be low for 106ms as shown in the datasheet.

    Regards,

    Javier  

  • 0 in reply to Javier Contreras4
    TI__Expert 5555 points

    Hi Javier,

    Javier Contreras4 said:
    If you need me to explain how the degauss works please let me know. 

    Could you kindly help explain how the degauss work? Thanks!

    BR

    Jiawei

  • 0 in reply to Jiawei Hu1
    TI__Mastermind 32210 points

    Hello Jaiwai,

    Basically to degauss what we are doing is randomizing the magnetic filed by saturating the core in both directions.  Not just saturating it but we are decaying the saturation with time.  I think the image below form https://cestriom.com/en/technology/demagnetization-basics/ has the best image to describe it.  We do not have a decaying sine wave of voltage but I less time square wave which after going through an inductor would look similar to a decaying sine wave.

    If you would like more then setup an internal call.

    Regards,

    Javier