3507

Calibrated linear Hall devices, which can be used to determine the actual flux density presented to the sensor in a particular application, are available.

For safe, reliable operation, the output should not be pulled above the supply voltage or pulled below the device ground.

For optimum performance, a 100 pF capacitor between the output and ground should be added.

The nominal sensitivity is factory set to compensate for the temperature coefficient of samarium-cobalt magnets (-0.02%/°C).

The ratiometric feature is especially valuable when these devices are used with an analog-to-digital converter.  A/D converters typically derive their LSB step size by ratioing off a reference voltage line.  If the reference voltage varies, the LSB will vary proportionally.  This is a major error source in many sensing systems.  The A3507/08 can eliminate this source of error by their ratiometric operation.  Because their gain and offsets are proportional to the supply voltage, if they are powered from the A/D reference voltage, the sensor output voltage will track changes in the LSB value.

Hall-effect applications information is available in the application note "Linear Hall-Effect Sensors" (AN 27702), which can be found in the latest issue of Allegro Electronic Data Book, AMS-702, or at www.allegromicro.com