A3245EUA-T Allegro Microsystems Inc, A3245EUA-T Datasheet - Page 10

• Manufacturer Part Number: A3245EUA-T
• Description: IC SW HALL EFFECT OMNI 3-SIP
• Manufacturer: Allegro Microsystems Inc
• Type: Omnipolar Switchr

Specifications of A3245EUA-T

• Sensing Range: ±55G Trip, ±6G Release
• Voltage - Supply: 3.6 V ~ 24 V
• Current - Supply: 3.5mA
• Output Type: Digital, Open Drain
• Features: Regulated Voltage
• Operating Temperature: -40°C ~ 85°C
• Package / Case: 3-SIP
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Current - Output (max): -

A3245
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 element. This makes it diffi cult to process the signal while
maintaining an accurate, reliable output over the specifi ed 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-fi eld-induced signal in the frequency domain,
through modulation. The subsequent demodulation acts as a
modulation process for the offset, causing the magnetic-fi eld-
induced signal to recover its original spectrum at baseband,
while the dc offset becomes a high-frequency signal. The
magnetic-fi eld-induced signal then can pass through a low-pass
fi lter, while the modulated dc offset is suppressed. This confi gu-
ration is illustrated in fi gure 2.
Figure 2. Chopper Stabilization Circuit (Dynamic Quadrature Offset Cancellation)
Hall Element
Chopper-Stabilized Omnipolar Hall Effect Switches
Regulator
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
amplifi ers in combination with high-density logic integration and
sample-and-hold circuits.
The repeatability of magnetic-fi eld-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 fi elds; for
example, speed sensing of ring-magnet targets. For such applica-
tions, Allegro recommends its digital device families with lower
sensitivity to jitter. For more information on those devices,
contact your Allegro sales representative.
Clock/Logic
Amp
115 Northeast Cutoff, Box 15036
Allegro MicroSystems, Inc.
Worcester, Massachusetts 01615-0036 [phone]
www.allegromicro.com
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