DRV401-Q1: the problem about the probe core reachs saturation

Hello Jie Quan,

Thanks for using the forum again.  How interested are you in using a DRV421 if we get an automotive version out?

The probe with 70mA will not reach saturation which is what is required for the probe to operate as expected.  In normal operation the probe is saturated in both directions and the PWM signal should be at 50%.  The compensation coil is driven to make the flux at the probe equal to zero.  If it never reaches saturation in both directions it will not function correctly as the DRV401 expects to see the satruation of the probe.

You need to use the 10mA probe and verify the impedance of the probe can be driven and is fast enough.  Two large of an inductance or resistance can also limit the probe saturation.

Hello Javior!

I have a huge interest to use the DRV421 automotive version. and when will you release an automotive version?

though the 70mA probe which i made a test with 401Q1, not reach saturation,  but the test result was good ,  the linearity error was about 0.02%, it seems normal, and made me confused.

why  this happened?

another question, if the probe 20mA saturation, and the current to be measured made a magnetic field in the probe core , it will take 10mA in probe coils  to compensate this additonal magnetic field, so the probe 20mA saturation will saturation at 10mA(20-10=10) in one directon and 30mA(20+10=30) in another directon, but when the probe coil got 28mA, system will confirm it was saturated but actually ,the probe core was not saturated yet, in this conditon, it will work normally? why?

Hello Jie Quan,

The DRV421 automotive version question was to gauge the interest. No date for a release is set.

The reason the is the core could be partially saturated enough to trip the comparator. You can duplicate the scope shot on figure 2 of the datasheet to confirm. This is not a good practice as this will work under these conditions but not through the whole operating range or variation of probes and DRV401 devices. Consider the variation of the comparator threshold current variation from 22mA to 34mA and resistance from IS1, IS2 pins to the supply pins.

In normal operation the field at the probe will be equal to zero and will create a 50% duty cycle on the PWM mode. This is done by driving the compensation coil that then forces the field at the probe to zero. So in normal operation you will not see the large difference in saturation levels unless you have an overload condition which is described in detail in the "Magnetic Probe (Sensor) Interface" section of the datasheet.

Hello Javier!
Thank you for your professional sugestions, and which saturation range is suitable for the probe core? probe core saturated 22±6mA is ok?
Best Regards!