DRV425: DRV425

David,

I quickly simulated this and this is too much field for the DRV425 to measure.  See attached.  If you don't have FEMM please see this tool that has steps to download it.  https://www.ti.com/lit/zip/sboc481

BusBar_E2E.fem

David Lam said:

Questions

1. Is this achievable approach for my current sensing application by using dual DRV425 devices for differential measurement?
2. What is the current sensing range up to for my application that magnetic field no exceeds designated +/- 2mT operating range?
3. What is the separation distance limit between two DRV425 devices so that the common mode fields cancel each other out? If the common mode fields or stray fields cannot completely cancelled out which caused by 20 mm separation distance between the two DRV425 devices (greater than 10 mm), what is the current sensing accuracy error will be?
4. Due to the physical construction of the busbar, placement of the sensors, as well as the sensor separation causes errors (assembly and manufacturing of the PCBA); do you have calibration software or tool for the system calibration? Can we calibrate error out of system by simply measuring the known current like 0 A, 100 A, 1000 A?

For the Dual DRV425 devices for differential measurement approach, can we still use the system parameter calculator SLOC331 to calculate the shunt resistor?

1. This is not be done with the DRV425 due to saturation.
2. These values are too high for the DRV425 as the sensor will measure over 20mT at 1500A.  The most you can measure is 150A with this method.  The reason for the cutout is to have a place to create zero field.  See https://www.ti.com/lit/an/sloa237/sloa237.pdf.  Also this is assuming 2mT max.  Using the same connection in the example would not work as the range is decreased in half.  See document for details.
3. The document above goes how the fields are calculated.  This depends on the external field expected.  Even the differential example in the document shows there are error with that approach.
4. So if this would work and the field were tolerable.  Each assembly would need to be calibrated at 0A and Max current.  This would give you the gain and offset of your system.  If the devices would not move or vibrate to much this should be enough to calibrate.

The calculator is for magnetic fields so if the field were in the range then you could use the calculator.  We have other busbar calculators but these assume a cuttout.  I would assume even with these dimensions and amplitude you would still have issues.  Those calculators and documents can be found in the DRV425 product page under "Technical Documents" and "Design and Develop".