A1384ELHLT-T Просмотр технического описания (PDF) - Allegro MicroSystems

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A1384ELHLT-T

Programmable Linear Hall Effect Sensors with Analog Output Available in a Miniature Thin Profile Surface Mount Package

Allegro MicroSystems 

A1381, A1382,

A1383, and A1384

Programmable Linear Hall Effect Sensors with Analog Output

Available in a Miniature Thin Profile Surface Mount Package

Typical Application Drawing

V+

VCC

VOUT

CBYPASS

CL

GND

Chopper Stabilization Technique

When using Hall-effect technology, a limiting factor for

switchpoint accuracy is the small signal voltage developed across

the Hall element. This voltage is disproportionally small relative

to the offset that can be produced at the output of the Hall sensor.

This makes it difficult to process the signal while maintaining an

accurate, reliable output over the specified operating temperature

and voltage ranges. 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 demodu-

lation acts as a modulation process for the offset, causing the

magnetic field-induced signal to recover its original spectrum at

base band, 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 170 kHz high frequency clock. For

the demodulation process, a sample and hold technique is used,

where the sampling is performed at twice the chopper frequency

(340 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 recoverability 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-density logic integration and sample-and-hold circuits.

Regulator

Hall Element

Clock/Logic

Amp

Low-Pass

Filter

Concept of Chopper Stabilization Technique

Allegro MicroSystems, Inc.

10

115 Northeast Cutoff, Box 15036

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

www.allegromicro.com

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