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DRV421: about output error

user4308845
Intellectual 475 points
Part Number: DRV421


In fact, if the ratio is the same (N/Rshunt) , the output error should be the same as the following calculation method, but I tried many groups of chips and found that the smaller  Rshunt, the smaller the output error ,It

has little to do with proportions，why？

N=1000,Rshunt=1k：

8µT/(500µT/A) = 16mA (Primary current error)
This they calculates as 16mA/1000 = 16µA on compensation coil
With Rshunt = 1kΩ there is a 16mV at the input of the differential amplifier
Therefore after the differential amplifier you can get 64mV.

N=200,Rshunt=200：

The output should be consistent with the above theory，but actually the output error is smaller about 20mV ，I tested at least 10 pcs about drv421

  • 0
    TI__Mastermind 32410 points

    Hello user4308845,

    Are you powering up with the degauss function?  If so this could change the offset due to the magnetization of the core.  If the core has a magnetization this could lead to a different offset.  The magnetic offset may not only come from the DRV421 but from the core being magnetized.  Also the degauss function with larger Rshunt will not work as effective due to the current forcing limitation.