DRV401 Datasheet, PDF (12/28 Pages) Burr-Brown (TI) – Sensor Signal Conditioning IC for Closed-Loop Magnetic Current Sensor

DRV401
SBVS070A − JUNE 2006 − REVISED OCTOBER 2006
APPLICATIONS INFORMATION
FUNCTIONAL PRINCIPLE OF CLOSED-LOOP
CURRENT SENSORS WITH MAGNETIC
PROBE USING THE DRV401
Closed-loop current sensors measure current over wide
frequency ranges, including dc. These types of devices
offer a contact-free method as well as excellent galvanic
isolation performance combined with high resolution,
accuracy, and reliability.
At dc and in low-frequency ranges, the magnetic field
induced from the current in the primary winding is
compensated by a current flowing through a
compensation winding. A magnetic field probe, located in
the magnetic core loop, detects the magnetic flux. This
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probe delivers the signal to the amplifier that drives the
current through the compensation coil, bringing the
magnetic flux back to zero. This compensation current is
proportional to the primary current, relative to the winding
ratio.
In higher frequency ranges, the compensation winding
acts as the secondary winding in the current transformer,
while the H-bridge compensation driver is rolled off and
provides low output impedance.
A difference amplifier senses the voltage across a small
shunt resistor that is connected to the compensation loop.
This difference amplifier generates the output voltage that
is referenced to REF_IN and is proportional to the primary
current. Figure 1 shows the DRV401 used as a
compensation current sensor.
Compensation Winding
Primary Winding
Magnetic Core
Field Probe
I_P
Compensation
R_S
I_COMP1
I_COMP2
DRV401
Diff
Amp
IS2
IS1
Probe
Interface
Integrator
Filter
H−Bridge
Driver
Timing, Error Detection,
and Power Control
Degauss
V_REF
+5V GND
V_OUT
REF_IN
V_REF
Figure 1. Principle of Compensation Current Sensor with the DRV401
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