DRV411_15 Datasheet, PDF (21/34 Pages) Texas Instruments – Sensor Signal Conditioning IC for Closed-Loop Magnetic Current Sensors

DRV411
www.ti.com
SBOS693B – AUGUST 2013 – REVISED DECEMBER 2013
APPLICATION INFORMATION
FUNCTIONAL PRINCIPLE OF CLOSED-LOOP CURRENT SENSORS WITH A HALL SENSOR
Closed-loop current sensors measure currents over wide frequency ranges, including dc currents. 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 driven through a compensation coil. A magnetic field
probe (Hall sensor) located in the magnetic core loop detects the magnetic flux. This probe delivers the signal to
the signal conditioning circuitry 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 proportional to the primary current. Figure
Figure 54 shows the principle of a closed-loop current sensor.
Primary Winding
Magnetic Core
IComp
RSense
Compensation
Coil Windings
Signal
Conditioning
Coil
Driver
IPRIM
Field Probe
Sense
Amplifier
VOUT
Figure 54. Principle of a Closed-Loop Current Sensor
USING DRV411 IN ±15-V SENSOR APPLICATIONS
To take advantage of the current spinning architecture for ±15-V sensor modules, the application circuit shown in
Figure 55 can be used. The DRV411 max supply voltage is 5.5 V; therefore, the ±15V supplies must be
externally regulated to less than 5.5 V across the power supply pins of the DRV411. In addition, an external
power driver stage must be implemented that then drives the compensation coil. These techniques allow the
design of exceptionally precise and stable ±15-V current-sense modules.
+15 V
5V
LDO
VDD
HALL1
HALL1
HALL3
HALL4
-15 V
Signal
Conditioning
H-Bridge
Driver
ICOMP1
ICOMP2
External
Driver
GND
DRV411
Compensation
Coil
RSHUNT
Figure 55. DRV411 Application Example: ±15-V Sensor Modules
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