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A1425
High Accuracy Analog Speed Sensor IC
with Integrated Filter Capacitor and Dual Zero-Crossing Output Signal
FEATURES AND BENEFITS
▪ Used in sensing motion of ring magnet or ferrous targets ▪ Integrated filter capacitor ▪ Wide operating temperature range ▪ Operation with magnetic input signal frequency from
20 Hz to 20 kHz ▪ Resistant to EMI ▪ 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 switch point
PACKAGE: 4 pin SIP (suffix K)
DESCRIPTION
The A1425 AC-coupled Hall-effect sensor IC is a monolithic integrated circuit that switches in response to changing differential magnetic fields created by rotating ring magnets and, when coupled with a magnet, by ferrous targets. The device is a true zero-crossing detector: the output switches precisely when the difference in magnetic field strength between the two Hall elements is zero. A unique dual-comparator scheme provides for accurate switching at the zero crossing on both the positive and negative-going regions of the differential signal, while utilizing hysteresis to prevent false switching. The zerocrossing nature of this device provides excellent repeatability and accuracy for crankshaft applications.
Changes in field strength at the device face, which are induced by a moving target, are sensed by the two integrated Hall transducers. The transducers generate signals that are differentially amplified by on-chip electronics. This differential design provides immunity to radial vibration within the operating air gap range of the A1425, by rejection of the common mode signal. Steady-state magnet and system offsets are eliminated using an on-chip differential band-pass filter. This filter also provides relative immunity to interference from electromagnetic sources.
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VS+
VCC (Pin 1)
Functional Block Diagram
Dual Hall Transducers
Regulator
0.1 uF
Hall Amp
Gain Stage
Bandpass Filter Integrated Tracking Capacitor
VREF
Diagnostic Circuitry
Comparator
TEST (Pin 3)
VOUT (Pin 2)
1425-DSa, Rev.5 MCO-0000608
GND (Pin 4)
(Required)
February 27, 2020
A1425
High Accuracy Analog Speed Sensor IC
with Integrated Filter Capacitor and Dual Zero-Crossing Output Signal
Description (continued) The device utilizes advanced temperature compensation for the high-pass filter, sensitivity, and Schmitt trigger switch points, to guarantee optimal operation to low frequencies over a wide range of air gaps and temperatures.
Each Hall effect digital integrated circuit includes a voltage regulator, two Hall effect elements, temperature compensating circuitry, a low-level amplifier, band-pass filter, Schmitt trigger,
and an output driver, which requires a pull-up resistor. The onboard regulator permits operation with supply voltages from 4.0 to 26.5 V. The output stage can easily switch 20 mA over the full fr.