DRV425-BUSBAR-EVM: DRV425

MASH123

Part Number: DRV425-BUSBAR-EVM
Other Parts Discussed in Thread: DRV425

Hello

I am trying to measure the rms noise level of DRV425 using its evaluation kit. I am using 24 bits ADC and ADC's measured rms noise level is under 10uv, but when I am connecting the DRV425 output and its reference voltage to the ADC in the differential mode, the rms noise that I am measuring is over 50uv. According to the datasheet it suppose to be under 20uv (17nTrms) with the resistor that I am using.

Please let me know how I can reach to this noise level.

Thanks

over 3 years ago

0 Javier Contreras4 over 3 years ago

TI__Mastermind 28870 points

Hello,

There could be two issues with the noise. What is you sampling rate. The noise mentioned in the datasheet is typical and is between 0.1H and 10Hz. Please look at these post regarding noise and frequency.

https://e2e.ti.com/support/sensors-group/sensors/f/sensors-forum/976335/drv425-noise-analysis

https://e2e.ti.com/support/amplifiers-group/amplifiers/f/amplifiers-forum/606174/drv425-what-is-the-minimum-resolution-of-drv425-is-it-possible-to-mesure-a-current-of-1-ma-magnetic-field-of-0-1-ut

The other issue could be is external magnetic interference. The noise of this device is measured with no external interference.

Please let me know if this does not resolve you issue.

Regards,

Javier Contreras

0 MASH123 over 3 years ago in reply to Javier Contreras4

Prodigy 30 points

Hello Javier

Thanks for you comments, I already read all those posts. According to the data sheet the rms noise from 0.1HZ to 10HZ should be 17nT which is the noise dominant range. Even I used two sensor to have it in differential mode to remove all possible interference but I am not getting under 43uv rms noise.

Please let me know the test condition that I can get under 25nV noise level if you know.

Thanks

Mike

0 Javier Contreras4 over 3 years ago in reply to MASH123

TI__Mastermind 28870 points

Hello Mike,

I would assume the the noise for two would add as sum of squares in this situation but this does not account for all the noise you are observing. I would assume you have an external magnetic field that is causing this. The dual configuration does reduce the error from an external field but does not remove them. An example calculation is done Bus Bar Theory of Operations. In section 4.1.4.

Also the value is typical and guaranteed for every device.

This measurement was also done in a Zero Gauss chamber so that the test was noise only from the DRV425.

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DRV425-BUSBAR-EVM: DRV425