Features: • Senses motion of ring magnet targets
• Integrated fi lter capacitor
• Wide operating temperature range
• Operation with frequency of sensed transitions from 20 Hz to 30 kHz
• EMI-resistant
• Large working air gaps
• 4.0 to 26.5 V operating range
• Output compatible with both TTL and CMOS logic families
• Reverse battery protectionSpecificationsSupply Voltage, VCC ....................................... ..28 V
Reverse-Supply Voltage, VRCC .......................18 V
Output Current, IOUT.................................... .25 mA
Reverse-Output Current, IROUT...................50 mA
Reverse-Output Voltage, VROUT .................50 mA
Operating Temperature
Ambient, TA....................................40ºC to 150ºC
Maximum Junction, TJ(max).............................165ºC
Storage Temperature, TS ...............65ºC to 170ºCDescriptionThe 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 A1425 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 A1425 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. A1425 filter also provides relative immunity to interference from electromagnetic sources.
The A1425 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 of A1425 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, A1425 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 A1425 is packaged in a 4-pin plastic SIP. The lead (Pb) free version (suffix T) has a 100% matte tin plated leadframe.
A1425 Data Sheet
