The A1225, A1227 and A1229 from Allegro MicroSystems Europe are a family of Hall-effect latch ICs that operate over extended temperature ranges up to +150°C. The temperature-stable and stress-resistant sensor ICs are suitable for high-voltage transient protection close to the sensors where space or distance limits external protection devices. For example, they can be used in motor commutation in vehicle sunroofs and power windows. The company's advanced offset cancellation technique with high-speed four-phase chopping, gives lower noise on the output, less switch-point variation with temperature, and faster settling times. A Schmitt trigger circuit maintains operate and release point symmetry by compensating for temperature changes in the Hall element. In addition, the internal compensation circuitry provides magnetic switch points that become more sensitive with temperature, offsetting the usual degradation of the magnetic field with temperature. The symmetry capability makes these suitable for use in pulse-counting applications where duty cycle is an important parameter. High-voltage transient protection allows the devices to survive the tests specified in ISO 7637-2 and a 40 V load dump for less than 0.5s with minimal external protection. ESD protection is up to 8kV human body model without the need for external protection components. Each device includes a voltage regulator, Hall-voltage generator, temperature compensation circuit, signal amplifier, Schmitt trigger, and a buffered open-drain output to sink up to 25mA. The on-board regulator permits operation with supply voltages of 3.8 to 24 V. Two package styles provide a magnetically optimised package for most applications. There are two versions of each model, the LT is a SOT89/TO-243AA transistor package; UA is a three-lead ultra-miniature single-inline package.
