A1383ELHLT-T Allegro, A1383ELHLT-T Datasheet - Page 10

• Manufacturer Part Number: A1383ELHLT-T
• Manufacturer: Allegro

A1381, A1382,
A1383, and A1384
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
Hall Element
Concept of Chopper Stabilization Technique
Programmable Linear Hall Effect Sensors with Analog Output
Available in a Miniature Thin Profile Surface Mount Package
C
Chopper Stabilization Technique
BYPASS
Typical Application Drawing
V+
Regulator
VCC
GND
VOUT
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.
Clock/Logic
Amp
C
L
Low-Pass
Filter
115 Northeast Cutoff, Box 15036
Allegro MicroSystems, Inc.
Worcester, Massachusetts 01615-0036 [phone]
www.allegromicro.com
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