DRV5056-Q1: DRV5056 sensor position

Ravi,

Thanks for your question.  If using this device to measure current, the magnetic field vector needs to be oriented from the bottom of the package towards the top.

The field produced by a current carrying wire follows the right hand rule. 

So for placement, the sensor needs to be offset horizontally somewhat from the current in order to result with a vertical magnetic field component.  Additionally, it would likely require that the current through the wire be quite large in order to produce a strong enough field to produce a measurable effect.

The field is calculated with this equation 

B = μ₀I/(2πr)

Where:

• B is the field 
• I is the current
• r is the distance from the wire
• and μ_{0 is the permeability of free space}

_{If your currents are not large enough to create a measurable field using the DRV5056, I would recommend you check out these devices which route the current you are trying to measure through the package and are specifically designed to measure current:}

_{https://www.ti.com/sensors/magnetic-sensors/products.html#-3=Hall-effect%20current%20sensors&}

_Thanks,

_Scott

Hello Ravi, 

Thanks for considering to use Texas Instruments. As the device detects field magnitudes normal to the top surface and b fields travel in loops around current carrying traces, you should put the device to the side of the current path in plane with it.  Close to the current path is best. However, unless you are sensing a lot of current the field might not be strong enough for good snr. 

Hello Patrick & Scott,

Appreciate the response, but my question is with respect to sensor orientation.

In both the options, the current direction is same. But the sensor orientation was different.

As the sensor is unipolar and responds to only south pole of magnetic flux density. 

In which option the sensor detects the signal (current path is same)?

Thanks,

Ravi

Hi Scott,

The direction of the current flow is on top of the sensor, i.e., the sensor was placed in parallel with other PCB where the trace will be in parallel with the sensor as mentioned earlier.

When measured the sensor output for both the options, the results are different.

Option 1: The sensor output voltage is 0.65V

Option 2: The sensor output voltage is -0.55V

Thanks,

Ravi

Hi Scott,

The direction of the current flow is on top of the sensor, i.e., the sensor was placed in parallel with other PCB where the trace will be in parallel with the sensor as shown below.

When measured the sensor output for both the options, the results are different.

Option 1: The sensor output voltage is 0.65V

Option 2: The sensor output voltage is -0.55V

Thanks,

Ravi

Ravi,

The Hall-element location of this sensor is located in the center of the package.

If your current trace is offset to the left or right of this, then there will be some vertical component.  Your result for option #1 seems to imply you are not receiving any input since the Quiescent output voltage for this device is 0.6-0.65V.  

I'm a bit unsure of your option #2 results.  The device should not be able to drive the output voltage below GND.  When you probe this output voltage it will be most accurate to measure as physically close to the device pins as possible.  If a negative field is applied, there may be some headroom to enable driving the output somewhere between 0-0.6V, but the voltage should remain above 0V.

Thanks,

Scott

Hi Scott,

Sorry for the typo. The sensor voltage for option#2 is 0.55V.

When there is no current, the measured sensor output is 0.6V.

When the current applied, the sensor output is 0.65V for option#1 and 0.55V for option#2.

Thanks,

Ravi

Hi Scott,

Thank you for the response. This makes sense and clarified my question.

Thanks,

Ravi