Tech Briefs Magazine - June 2022 - Sensor-9

it suitable for both high-side and low-side
bi-directional current sensing. It produces
a voltage proportional to the magnetic
field created by the positive or negative
current in the current loop while rejecting
external magnetic interference.
The high bandwidth of 1.5MHz (3dB)
and low phase delay makes it ideal for
current sense feedback loops in motor
control, inverters, uninterruptible power
supplies, battery management, power factor
correction, high voltage distribution
bus converters, and power supply applications,
including those with fast switching
wide-bandgap SiC- and GaN-based power
stages.
EV Battery Charging
EV battery charging systems have critical
needs because they are always on,
use high switching speeds, and operate
at high power. Current monitoring is
required both for control and over- and
under-current protection. At the speeds
and power levels of EV charging systems,
traditional fuses do not provide adequate
Figure 3. AMR current sensing chip. (Image: ACEINNA)
tion, depending on the circuit topology, but because it is large
and heavy it isn't well-suited for automotive systems where
space and weight are issues, and it also tends to be expensive.
The Model MCA1101 contactless isolated current sensor
from ACEINNA is a single-chip solution using anisotropic magnetoresistive
(AMR) technology. It provides galvanic isolation
and essentially no power dissipation. Compared to the other
methods of current sensing, it is compact as well as high-performing.
The AMR technology offers a bandwidth of 1.5 megahertz
and has low offset and noise. In addition, it enables fast
readout while correcting offsets via active feedback loops, adjusting
the gain parameters, and actively compensating the
sensor offset. A further advantage is that since it is just a single
chip, it offers significant footprint savings over board-assembled
solutions. It offers the important combination of high accuracy
and high speed.
AMR Technology
AMR makes use of a common material, Permalloy, to act as a
magnetometer. The alloy's resistance depends on the angle between
the magnetization and the direction of current flow. The
film's properties cause it to change resistance in the presence
of a magnetic field. In the MCA1101, two of these resistors are
connected in a Wheatstone bridge configuration to permit the
measurement of the magnitude of the magnetic field produced
by the current. The sensor voltage is fed into a differential amplifier
followed by an instrumentation amplifier output stage
that provides a voltage as a measure of the current.
A fully isolated U-shaped current path is provided by a low resistance
copper conductor integrated into the package, making
Sensor Technology, June 2022
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Tech Briefs Magazine - June 2022

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