These Hall-effect latches are extremely temperature-stable and stress resistant sensors especially suited for operation over extended temperature ranges to +150°C. Superior high-temperature performance is made possible through a novel Schmitt trigger circuit that maintains operate and release point symmetry by compensating for temperature changes in the Hall element. Additionally, internal compensation provides magnetic switch points that become more sensitive with temperature, hence offsetting the usual degradation of the magnetic field with temperature. The symmetry capability makes these devices ideal for use in pulse-counting applications where duty cycle is an important parameter. The four basic devices (3185, 3187, 3188, and 3189) are identical except for magnetic switch points.
Each device includes on a single silicon chip a voltage regulator, quadratic Hall-voltage generator, temperature compensation circuit, signal amplifier, Schmitt trigger, and a buffered open-collector output to sink up to 25 mA. The on-board regulator permits operation with supply voltages of 3.8 to 24 volts.
The first character of the part number suffix determines the device operating temperature range. Suffix ‘E–’ is for -40°C to +85°C, and suffix ‘L–’ is for -40°C to +150°C. Three package styles provide a magnetically optimized package for most applications. Suffix ‘–LT’ is a miniature SOT89/TO-243AA transistor package for surface-mount applications; suffix ‘–UA’ is a three-lead ultra-mini-SIP.

FEATURES
■ Symmetrical Switch Points
■ Superior Temperature Stability
■ Operation From Unregulated Supply
■ Open-Collector 25 mA Output
■ Reverse Battery Protection
■ Activate With Small, Commercially Available Permanent Magnets
■ Solid-State Reliability
■ Small Size
■ Resistant to Physical Stress