Extend air gap in low-power sensing with omni-polar magnetic switch
For compact proximity, rotary, and utility-meter sensing, the LF21215TMR TMR switch from Littelfuse combines high magnetic sensitivity, low supply current, and omni-polar operation.
Reliable magnetic switching in battery-powered equipment depends on sensitivity, current consumption, and tolerance to the magnetic environment around the sensor. The LF21215TMR tunnelling magnetoresistance (TMR) switch integrates a magnetic sensing element and complementary metal-oxide semiconductor (CMOS) signal-processing circuitry in a compact SOT23-3 package. The switch provides a digital output when a magnetic field parallel to the sensing axis crosses the operating threshold, and draws only 1.5uA in low-power operations.
Unlike a unipolar switch, the LF21215TMR responds to either a north or south magnetic pole. This omni-polar behavior simplifies magnet placement in products where mechanical alignment varies during assembly or use. A push-pull output gives a digital signal to the host controller.
Switching hysteresis is provided by an internal Schmitt trigger, helping to reject noise around the threshold. This supports stable output behavior in applications exposed to vibration, changing magnet position, or external magnetic interference.
The LF21215TMR also includes an internal band-gap regulator, which provides a temperature-compensated supply for the internal circuits.