A1421, A1422, A1423
High Precision Hall Effect AC-Coupled Differential Sensor
with Integrated Filter Capacitor
Package K, 4-pin SIP
The A1421, A1422 and A1423 are ac-coupled Hall-effect sensors 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 are sensed by two integrated Hall transducers and then
are differentially amplified on the chip. Differential sensing 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.
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Each device includes: a voltage regulator, two Hall transducers, temperature compensating circuitry, a low-level amplifier, bandpass filter, Schmitt trigger, and an
output driver. The on-board regulator permits operation with supply voltages from
4.0 to 26.5 V. The output stage can switch 20 mA over the full frequency response
range of the sensor, and is compatible with TTL and CMOS logic circuits.
Continued on next page…
1. VCC
2. VOUT
3. TEST
4. GND
ABSOLUTE MAXIMUM RATINGS
Supply Voltage, VCC ........................................ 28 V*
Reverse-Supply Voltage, VRCC ........................ –18 V
Output Current, IOUT .......................................25 mA
Reverse-Output Current, IROUT.....................–50 mA
Operating Temperature
Ambient, TA, Range L ................ –40ºC to 150ºC
Maximum Junction, TJ(max)........................165ºC
Storage Temperature, TS .................. –65ºC to 170ºC
*Refer to Power Derating section.
A1421-DS, Rev.1
Features and Benefits
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Integrated tracking capacitor
Senses 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 both TTL and 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)
Allegro MicroSystems, Inc.
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com
