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A1142EUATI-T4 参数 Datasheet PDF下载

A1142EUATI-T4图片预览
型号: A1142EUATI-T4
PDF下载: 下载PDF文件 查看货源
内容描述: 灵敏双线式稳定斩波型单极霍尔效应开关 [Sensitive Two-Wire Chopper-Stabilized Unipolar Hall Effect Switches]
分类和应用: 开关
文件页数/大小: 13 页 / 344 K
品牌: ALLEGRO [ ALLEGRO MICROSYSTEMS ]
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Sensitive Two-Wire Chopper-Stabilized  
Unipolar Hall Effect Switches  
A1140, A1141,  
A1142, and A1143  
Chopper Stabilization Technique  
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 desensi-  
tizes 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.  
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 oper-  
ating 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 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. This configuration is illus-  
trated in figure 2.  
The repeatability of magnetic field-induced switching is affected  
slightly by a chopper technique. However, the Allegro high-  
frequency chopping approach minimizes the affect of jitter and  
makes it imperceptible in most applications. Applications that  
are more likely to be sensitive to such degradation are those  
requiring precise sensing of alternating magnetic fields; for  
example, speed sensing of ring-magnet targets. For such applica-  
tions, Allegro recommends its digital sensor families with lower  
sensitivity to jitter. For more information on those devices,  
contact your Allegro sales representative.  
Regulator  
Clock/Logic  
Low-Pass  
Filter  
Hall Element  
Amp  
Figure 2. Chopper stabilization circuit (Dynamic Quadrature Offset Cancellation)  
Allegro MicroSystems, Inc.  
8
115 Northeast Cutoff, Box 15036  
Worcester, Massachusetts 01615-0036 (508) 853-5000  
www.allegromicro.com