Housed in a subminiature SOT-23 (2.9 x 1.6 x 1.4 mm) surface mount package, the Nanopower anisotropic magnetoresistive (AMR) series sensor ICs provide the highest level of magnetic sensitivity — as low as 7 Gauss typical — while requiring just 360 nA at 1.8 V.
With respect to other widely used magnetic technologies, the AMR sensors offer design engineers a number of advantages. They are smaller, more durable, and more reliable than standard reed switches at essentially the same cost (typically less than $.50 in production quantities). Thus they suit those battery-powered applications where only reed switches could be used previously.
Further, the AMR sensors’ higher sensitivity allows sensing with air gaps two times the distance of Hall-effect sensors, thus improving design flexibility while potentially offering significant cost savings by allowing the use of smaller or lower-strength magnets. (For some potential applications, see the video below.)
The Nanopower Series is available in two versions — SM351LT and SM353LT — which have different magnetic sensitivities. The ultra-high-sensitivity SM351LT operates at 7 Gauss typical (11 Gauss max) at a typical current of 360 nA, while the very-high-sensitivity SM353LT typically operates at 14 Gauss ( 20 Gauss max) from a current of 310 nA typical.
The sensors’ omnipolarity allows them to be activated by either the magnet’s north or south pole, eliminating the need for polarity identification and thereby simplifying installation and potentially reducing system cost. Their push-pull (CMOS) output does not require external resistors and the non-chopper stabilized design eliminates electrical noise generated by the sensor. Supplied on tape and reel, the sensors can be handled by automated pick-and-place systems to reduce production costs.
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