DRV421_16 Datasheet, PDF (29/44 Pages) Texas Instruments – Integrated Magnetic Fluxgate Sensor for Closed-Loop Current Sensing

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DRV421
SBOS704B – MAY 2015 – REVISED MARCH 2016
8.2 Typical Application
8.2.1 Closed-Loop Current Sensing Module
Closed-loop current sensor modules (Figure 65) measure currents over a wide frequency range, including dc
currents. These sensor modules offer a contact-free sensing method and excellent galvanic isolation
performance, combined with high resolution, accuracy, and reliability. The DRV421 is designed for use in this
kind of application.
At dc and in low-frequency range, the magnetic field induced by the primary current is sensed by the DRV421
fluxgate sensor. The sensed signal is filtered by the DRV421 and the internal H-bridge driver generates a
proportional compensation current. The compensation current flows through the compensation coil, and
generates a magnetic field. This magnetic field drives the original magnetic flux in the core back to zero. The
value of this magnetic field is increased by the number of compensation coil windings. Therefore, use Equation 1
to calculate the required compensation current for a given primary current.
At higher frequencies, the magnetic field induced by the primary current directly couples into the compensation
coil and generates a current. The low impedance of the H-bridge driver does not influence the value of this
current. Also in this case, the value of the compensation current is the value of the primary current divided by the
number of compensation coil windings.
VDD
optional
Closed-Loop Current Module
magnetic
core
compensation
coil
primary
current
conductor
RSHUNT
GSEL0
GSEL1
RSEL0
RSEL1
DRV421
VOUT
REFIN
REFOUT
DEMAG
OR
ER
MCU
GPIO0
GPIO1
GPIO2
ADC
C1
C2
R1
R2
VDD
Figure 65. Closed-Loop Current Sensing Module
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