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DRV401: Evaluation method of probe interface without coil

Masanori Tachibana
Genius 5350 points
Part Number: DRV401
Other Parts Discussed in Thread: DRV421

Hello support team,

Our customer is studying DRV401 now.
He wants to evaluate the linearity of the magnetic probe interface circuit without using coils.
Could you teach me how to evaluate it ?
What is the appropriate external circuit should he evaluate?
Should he apply a DC current of less than ± 75 mA between IS1 and IS2 from an external constant current source?

Best regards,
M. Tachibana

  • 0
    TI__Genius 15760 points

    Hi Masanori-san,

    Thanks for using TI E2E forums. I will ask our DRV applications engineer to review your question and get back to you. 

    Regards,

  • 0
    TI__Mastermind 32260 points

    Hello Masanori,

    The DRV401 uses the magnetic probe interface to drive the probe pins IS1 and IS2 and drives in one direction until it determines a saturation point then flips the other direction until it see the saturation in the other direction.  If there is no external magnetic filed the duty cycle is 50 percent and can be seen on the PWM outputs.  If the field is no balanced then the duty cycle is not 50% and shifted in one direction there is a field.  This is described in more detail in the Datasheet in the magnetic probe section.  When there is an imbalance the pins Icomp1 and Icomp2 drive a current to attempt to bring that field back to zero.  This is a feedback system and all the components play a part in the linearity so testing only one part of the system will not benefit the system results.

    The IS1 and IS2 pins drive the current and determine when the probe saturates?

    The DRV421 has the magnetic probe integrated into the device and you can look at that to see if that is of interest.  The DRV421 will not require the field probe as it is integrated into the device.  Please let me know if this is a path they could consider.  The DRV421 device requires a magnetic core with an air gap and windings.

  • 0 in reply to Javier Contreras4
    Genius 5350 points
    Hello Javier-san,

    Sorry for the late reply.
    I understood as follows.
    - The current is driven to pins IS1 and IS2 from the H bridge circuit as shown in Figure 2 of the data sheet.
    - And the polarity of drive current is reversed when scaling out is detected by the comparator.
    - The feedback circuit that is consisted of ICOMP1 and ICOMP2 is needed.
    - It is not possible to evaluate the linearity of the system without looking at the feedback current.
    Is my understanding correct?

    Best regards,
    M. Tachibana