ZHCSK74A August 2019 – April 2020 DRV425-Q1
PRODUCTION DATA.
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-Q1 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 BR and BL in Figure 72. The opposite fields cancel each other out in the middle of the hole. The high sensitivity and linearity of two DRV425-Q1 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.
Figure 71. Current Sensing in Busbars 
Figure 72. Magnetic Field Distribution Inside a Busbar Hole