DRV401-EP Datasheet, PDF (13/33 Pages) Texas Instruments – SENSOR SIGNAL CONDITIONING IC FOR CLOSED-LOOP MAGNETIC CURRENT SENSOR

DRV401-EP
www.ti.com............................................................................................................................................................................................... SBVS104 – JANUARY 2008
APPLICATION 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 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 REFIN 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
FUNCTIONAL DESCRIPTION
The DRV401 operates from a single +5 V supply. It is a complete sensor signal conditioning circuit that directly
connects to the current sensor, providing all necessary functions for the sensor operation. The DRV401 provides
magnetic field probe excitation, signal conditioning, and compensation coil driver amplification. In addition, it
detects error conditions and handles overload situations. A precise differential amplifier allows translation of the
compensation current into an output voltage using a small shunt resistor. A buffered voltage reference can be
used for comparator, analog-to-digital converter (ADC), or bipolar zero reference voltages.
Copyright © 2008, Texas Instruments Incorporated
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