Switch Your Switch

　　技術(shù)的進(jìn)步使得磁性傳感器比以往任何時候都更小、更低功率和更敏感。由于這些進(jìn)步，磁阻（MR）傳感器，它總是提供顯著的好處霍爾效應(yīng)和里德交換機(jī)，應(yīng)著眼于設(shè)計(jì)新的系統(tǒng)時，需要一個位置開關(guān)。

　　MR傳感器是固態(tài)開關(guān)，沒有機(jī)械部件來操作開關(guān)。他們是全極性的性質(zhì)，將動時是南北極的磁鐵的磁場在感應(yīng)范圍。MR設(shè)備的感應(yīng)方向是在IC的平行平面，它不同于霍爾傳感器，它感應(yīng)垂直于IC的磁場（圖1）。該開關(guān)關(guān)閉時，磁場被刪除從傳感器。此外，MR傳感器比霍爾效應(yīng)更敏感的磁場，并可以提供更多的靈活性，并要求在應(yīng)用中使用的成本較低的磁鐵。

　　Figure 1： A Hall sensor responds to magnetic fields placed perpendicular to its body while an MR device responds to magnetic fields applied in a direction parallel to the sensor.

　　Advances in circuit design now allow for magnetic sensors to utilize much lower power than ever before. Most magnetic sensor manufacturers offer sensors that only use microamp supply current to power the sensor. As this technology continues to develop， more design engineers are turning to low-power sensors to replace mechanical switches in battery-powered applications.

　　Honeywell recently introduced their new Magnetoresistive Sensor ICs， Nanopower Series that includes two sensors， SM351LT and SM353LT， which draw only 360 nA and 310 nA， respectively， at 1.8 VDC. These sensors are housed in a tiny SOT-23 package （Figure 2）， have an operating temperature of -40?C to 85?C， and are a great switch for most battery-powered applications.