DRV425 Datasheet, PDF (26/37 Pages) Texas Instruments – DRV425 Fluxgate Magnetic-Field Sensor

DRV425
SBOS729 – OCTOBER 2015
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8.2.2 Current Sensing in Busbars
In existing applications that use busbars for power distribution, closed-loop current modules are usually used to
accurately measure and control the current. These modules are usually bulky because of the required large
magnetic core. Additionally, because the compensation current generated inside the module is proportional to the
usually high busbar current, the power dissipation of this solution is usually as high as several watts.
Figure 71 shows an alternative approach with two DRV425 devices. If a hole is drilled in the middle of the
busbar, the current is split in two equal parts that generate magnetic field gradients with opposite directions
inside the hole. These magnetic fields are termed B_R and B_L in Figure 72. The opposite fields cancel each other
out in the middle of the hole. The high sensitivity and linearity of two DRV425 devices positioned at the same
distance from the middle of the hole allow the small opposite fields to be sensed and the current measured with
high-accuracy levels. The differential measurement rejects outside fields that generate a common-mode error
that is subtracted at the output.
Busbar
I/2
(Top View)
DRV425-1
Hole
I
I
DRV425-2
PCB
I/2
Figure 71. DRV425-Based Busbar Current Sensing
I
Axis of
cross-section
I/2
Cross-section
PCB
DRV425 - 1
BR
I/2
I/2
I/2
Y-Axis
BL
DRV425 - 2
Figure 72. Magnetic Field Distribution Inside a Busbar Hole
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