DRV401-Q1 Datasheet, PDF (15/39 Pages) Texas Instruments – DRV401-Q1 Sensor Signal Conditioning Device for Closed-Loop Magnetic Current Sensor

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DRV401-Q1
SBOS814 – DECEMBER 2016
7.3 Feature Description
The DRV401-Q1 operates from a single 5-V supply. The DRV401-Q1 is a complete sensor signal conditioning
circuit that directly connects to the current sensor, providing all necessary functions for the sensor operation. The
DRV401-Q1 device provides magnetic field probe excitation, signal conditioning, and compensation coil driver
amplification. In addition, the device 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 is used for comparator, analog-to-digital converter (ADC), or bipolar zero
reference voltages.
Dynamic error correction ensures high dc precision over temperature and long-term accuracy. The DRV401-Q1
uses analog signal conditioning, and the internal loop filter and integrator are switched capacitor-based circuits.
Therefore, the DRV401-Q1 device allows combination with high-precision sensors for exceptional accuracy and
resolution.
A demagnetization cycle initiates on demand or on power-up. The cycle reduces offset and restores high
performance after a strong overload condition. An internal clock and counter logic generate the degauss function.
The same clock controls power-up, overload detection and recovery, error, and time-out conditions.
The DRV401-Q1 device is built on a highly reliable CMOS process. Unique protection cells at critical connections
enable the design to handle inductive energy.
7.3.1 Magnetic Probe (Sensor) Interface
The magnetic field probe consists of an inductor wound on a soft magnetic core. The probe is connected
between pins IS1 and IS2 of the probe driver that applies approximately 5 V (the supply voltage) through
resistors across the probe coil, as shown in Figure 36.
Typically, the probe core reaches saturation at a current of 28 mA, as shown in Figure 36. The comparator is
connected to V_REF by approximately 0.5 V. A current comparator detects the saturation and inverts the excitation
voltage polarity, causing the probe circuit to oscillate in a frequency range of 250 kHz to 550 kHz. The oscillating
frequency is a function of the magnetic properties of the probe core and the coil.
55 W
Probe
55 W
V_DD1
IS2
IS1
18 W
CMP
PWM
V_REF = 0.5 V
NOTE: MOS components function as switches only.
Copyright © 2016, Texas Instruments Incorporated
The probe is connected between S1 and S2.
Figure 36. Magnetic Probe, Hysteresis, and Duty Cycle: Simplified Probe Circuit
The current rise rate is a function of the coil inductance: dI = L × V × dT. However, the inductance of the field
probe is low while the core material is in saturation (the horizontal part of the hysteresis curve) and is high at the
vertical part of the hysteresis curve. The resulting inductance and the series resistance determine the output
voltage and current versus time performance characteristic.
Copyright © 2016, Texas Instruments Incorporated
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