A1126LLHLT-T2 查看數據表（PDF） - Allegro MicroSystems

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A1126LLHLT-T2

Chopper-Stabilized Omnipolar Hall-Effect Switch

Allegro MicroSystems 

A1126

Chopper-Stabilized Omnipolar Hall-Effect Switch

Application Information

V+

CBYPASS

0.1 µF

VCC

A1126

VOUT

GND

RLOAD

Figure 2. Typical Application Circuit

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

chip. This makes it difficult to process the signal while main-

taining 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 Cancella-

tion, 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 spec-

trum 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 400 kHz high frequency

clock. For demodulation process, a sample-and-hold technique is

used, where the sampling is performed at twice the chopper fre-

quency. 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

Figure 3. Concept of Chopper Stabilization Technique

Allegro MicroSystems, LLC

10

115 Northeast Cutoff

Worcester, Massachusetts 01615-0036 U.S.A.

1.508.853.5000; www.allegromicro.com

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