A1373LKB datasheet(12/23 Pages) ALLEGRO

12 / 23 page

A1373-DS, Rev. 3

Worcester, Massachusetts 01615-0036 (508) 853-5000

115 Northeast Cutoff, Box 15036

www.allegromicro.com

Allegro MicroSystems, Inc.

High Precision, Output Pin Programmable, Linear Hall Effect Sensors

A1373 and A1374

Chopper Stabilization Technique

Chopper stabilization is a unique approach used to minimize

Hall offset on the chip. The patented Allegro technique, namely

Dynamic Quadrature Offset Cancellation, removes key sources

of the output drift induced by thermal and mechanical stresses.

This offset reduction technique is based on a signal modulation-

demodulation process. The undesired offset signal is separated

from the magnetic field-induced signal in the frequency domain,

through modulation.

The subsequent demodulation acts as a modulation process for

the offset, causing the magnetic field-induced signal to recover

its original spectrum at baseband, while the dc offset becomes

a high-frequency signal. The magnetic-sourced signal then can

pass through a low-pass filter, while the modulated dc offset is

suppressed.

The chopper stabilization technique uses a 200 kHz high

frequency clock. For demodulation process, a sample and hold

technique is used, where the sampling is performed at twice the

chopper frequency (400 kHz). This high-frequency operation

allows a greater sampling rate, which results in higher accuracy

and faster signal-processing capability.

This approach desensitizes the chip to the effects of thermal and

mechanical stresses, and produces devices that have extremely

stable quiescent Hall output voltages and precise recoverabil-

ity after temperature cycling. This technique is made possible

through the use of a BiCMOS process, which allows the use of

low-offset, low-noise amplifiers in combination with high-den-

sity logic integration and sample-and-hold circuits.

Amp

Regulator

Clock/Logic

Hall Element

Low-Pass

Filter

Concept of Chopper Stabilization Technique

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