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High-Performance Power ICs and Hall-Effect Sensors
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A1425: High Accuracy Analog Speed Sensor with Integrated Filter Capacitor and Dual Zero-Crossing Output Signal (PDF)
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Hall-Effect Sensors,
Highly Accurate, Analog Speed Sensors with Digital Outputs
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A1425: Allegro Announces a New High-Accuracy Speed Sensor with Integrated Tracking Capacitor
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A1425
High Accuracy Analog Speed Sensor with Integrated Filter Capacitor
and Dual Zero-Crossing Output Signal
Features and Benefits
- Senses 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 switchpoint
Description
The A1425 ac-coupled Hall-effect sensor 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 zero-crossing 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 sensing 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.
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.
Each Hall effect digital integrated circuit includes a voltage regulator, two Hall effect sensing elements, temperature compensating circuitry, a low-level amplifier, band-pass filter, Schmitt trigger, and an output driver, which requires a pull-up resistor. The on-board regulator permits operation with supply voltages from 4.0 to 26.5 V. The output stage can easily switch 20 mA over the full frequency response range of the sensor, and is compatible with both TTL and CMOS logic circuits.
The device is packaged in a 4-pin plastic SIP. The lead (Pb) free version (suffix –T) has a 100% matte tin plated leadframe.
Functional Block Diagram
| Part Number | Package Type | RoHS Compliant |
Part Composition/ RoHS Data |
Temperature | Comments | Samples | Distributor Stock |
|---|---|---|---|---|---|---|---|
| A1425LK-T | 4-pin SIP | Yes | view data | -40 °C to 150 °C | samples not available |
Allegro's products are not to be used in life support devices or systems, if a failure of an Allegro product can reasonably be expected to cause the failure of that life support device or system, or to affect the safety or effectiveness of that device or system.