DRV421_16 Datasheet, PDF (22/44 Pages) Texas Instruments – Integrated Magnetic Fluxgate Sensor for Closed-Loop Current Sensing

DRV421
SBOS704B – MAY 2015 – REVISED MARCH 2016
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7.3.7 Overload Detection and Control
Magnetic fluxgate sensors have a very high sensitivity and allow detection of small magnetic fields. These
sensors are ideally suited for use in closed-loop current modules appllications because the high sensitivity makes
sure that the field inside the core gap is accurately driven to zero. However, for large fields, the fluxgate
saturates and causes the output to return to zero, as shown in Figure 59.
V
Fluxgate
sensor
saturated
Fluxgate
sensor
saturated
-1 mT
1 mT
B
Normal
operation
area
Figure 59. Typical Fluxgate Sensor Response to Magnetic Fields
In normal operation, the feedback loop keeps the magnetic field close to zero. However, large overload currents
that exceed the measurement range (for example, short-circuit currents) saturates the fluxgate. The behavior is
shown in Figure 60, where the compensation current, magnetic field in the core, and fluxgate output are shown
for the case of a 1000-A primary current step.
Primary Current
Compensation Current
1000 A
1A
0A
t
Fluxgate Sensor Output
Saturation Detection Level
0A
t
Magnetic Field in the Core
1.7 mT
0 mT
t
t
Figure 60. Closed-Loop Current Sensor Response to an Overloaded Step Current
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