A1421 Datasheet, PDF (1/15 Pages) Allegro MicroSystems – High Accuracy Analog Speed Sensor with Integrated Filter Capacitor

A1421, A1422, and A1423
High Precision Hall Effect AC-Coupled Differential Sensor IC
with Integrated Filter Capacitor
Features and Benefits
• Integrated tracking capacitor
• Used for sensing motion of ring magnet or ferrous targets
• Wide operating temperature range
• Operation with magnetic input signal frequency from
20 Hz to 30 kHz
• EMI/ESD-resistant
• Large effective air gaps
• 4.0 to 26.5 V supply operating range
• Output compatible with CMOS logic families
• Reverse battery protection
• Resistant to mechanical and thermal stress
• Accurate true zero crossing switchpoint (A1421 only)
• High vibration immunity, in running mode (A1423 only)
Package: 4 pin SIP (suffix K)
Description
The A1421, A1422, and A1423 are AC-coupled Hall-effect
sensor ICs which include monolithic integrated circuits that
switch in response to changing differential magnetic fields
created by rotating ring magnets or, when coupled with a
magnet, by ferrous targets. This family of devices also includes
an integrated capacitor that provides the high accuracy of analog
sensing without an external filter capacitor. This reduces cost
and components, while improving the reliability of the final
sensor solution.
Magnetic field changes affect the two integrated Hall
transducers and then are differentially amplified on the chip.
Differential design provides immunity to radial vibration,
within the device operating air gap range, by rejection of this
common-mode signal change. Steady-state system offsets
are eliminated using an on-chip differential bandpass filter
with integrated capacitor. This filter also provides relative
immunity to interference from electromagnetic sources. The
device utilizes advanced temperature compensation for the
high-pass filter, sensitivity, and Schmitt trigger switchpoints
to guarantee optimal operation to low frequencies over a wide
range of air gaps and temperatures.
Not to scale
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V_S+
VCC
(Pin 1)
Functional Block Diagram
Dual Hall
Transducers
Regulator
0.1 uF
Hall
Amp
Gain
Stage
Bandpass Filter Integrated
Tracking Capacitor
V_REF
Diagnostic
Circuitry
Comparator
TEST
(Pin 3)
VOUT
(Pin 2)
A1421a-DS, Rev. 4
GND
(Pin 4)
(Required)