The AH1802 is a high sensitivity， micropower omnipolar Hall Effect switch IC designed for portable and battery powered equipment such as cellular phones， PDA’s and portable PC’s. Based on two sensitive Hall Effect plates and a chopper stabilized architecture the AH1802 provides a reliable solution over the whole operating range. To support portable and battery powered equipment the design has been optimized to operate over the supply range of 2.5V to 5.5V and consumes only 24μW with a supply of 3V. The single open drain output can switched on with either a north or south pole of sufficient strength. When the magnetic flux density （B） perpendicular the part marking surface is larger than operate point （Bop） the output is switched on （pulled low）。 The output is turned off when B becomes lower than the release point （Brp）。 The output will remain off when there is no magnetic field.