DRV401AIDWPR datasheet(13/36 Pages) TI1

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DRV401

SBVS070B − JUNE 2006 − REVISED MAY 2009

www.ti.com

FUNCTIONAL DESCRIPTION

The DRV401 operates from a single +5V 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.

Dynamic error correction ensures high dc precision over

temperature and long-term accuracy. The DRV401 uses

analog signal conditioning; the internal loop filter and

integrator

are

switched

capacitor-based

circuits.

Therefore,

the

DRV401

allows

combination

with

high-precision sensors for exceptional accuracy and

resolution. The typical characteristic curve, DRV401 and

Sensor Linearity, shows an example of the linearity and

temperature stability achieved by the device.

A demagnetization cycle can be initiated on demand or on

power-up. This 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 is built on a highly reliable CMOS process.

Unique protection cells at critical connections enable the

design to handle inductive energy.

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 +5V (the supply voltage) through resistors

across the probe coil (see Figure 2a).

The probe core reaches saturation at a current of typically

28mA (see Figure 2a). The comparator is connected to

VREF by approximately 0.5V. A current comparator detects

the saturation and inverts the excitation voltage polarity,

causing the probe circuit to oscillate in a frequency range

of 250kHz to 550kHz. The oscillating frequency is a

function of the magnetic properties of the probe core and

its coil.

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 its 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.

Without external magnetic influence, the duty cycle is

exactly 50% because of the inherent symmetry of the

magnetic hysteresis; the probe inductor is driven from −B

saturation through the high inductance range to +B

saturation and back again in a time-symmetric manner

(see Figure 2b).

If the core material is magnetized in one direction, a long

and a short charge time result because the probe current

through the inductors generates a field that either

subtracts or adds to the flux in the probe core, either driving

the probe core out of saturation or further into saturation

(see Figure 2c). The current into the probe is limited by the

voltage drops across the probe driver resistors.

The DRV401 continuously monitors the logic magnetic flux

polarity state. In the case of distortion noise and excessive

overload that could fully saturate the probe, the overload

control circuit recovers the probe loop. During an overload

condition, the probe oscillation frequency increases to

approximately 1.6MHz until limited by the internal timing

control.

In an overload condition, the compensation current (ICOMP)

driver cannot deliver enough current into the sensor

secondary winding, and the magnetic flux in the sensor

main core becomes uncompensated.

DRV401AIDWPR Datasheet(PDF) 13 Page - Texas Instruments

DRV401AIDWPR Datasheet(HTML) 13 Page - Texas Instruments

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