Ultra-low-power magnetic switches improve accuracy in battery-powered sensing

The Littelfuse TMR magnetic switch range integrates a TMR sensing element and CMOS signal processing into a single surface-mount package, reducing standby current to 160nA, and improving switching uncertainty caused by temperature drift and external magnetic interference. The range includes omnipolar and bipolar devices, triggering on a sufficient strength northern magnetic field, or triggering on any sufficient strength field respectively.

Ultra-low supply current is used to support battery-powered and energy-harvesting systems. The LF21112TMR is specified at 200nA, with a 50Hz response and operate and release thresholds of 7G and 5G, respectively. The LF21173TMR and LF21177TMR switches use the same 160nA class current specification, with different magnetic thresholds to suit low-field and higher-field trigger requirements.

Switching stability is supported by signal conditioning intended to reduce false triggers. The LF11215TMR datasheet describes offset cancellation and a Schmitt trigger stage that introduces switching hysteresis for noise rejection, alongside a temperature-compensated internal supply for consistent switching points across temperature. This approach is used to improve tolerance to stray field interference in proximity and position sensing installations where external magnetic fields and electrical noise can be present.