The Si7210 I2C parts are programmable for many features. Some features such as the sleep timer are not user programmable.
The Si720x and Si721x series of parts are not user programmable.
There are many possible factory configuration options for the Si72xx series of Hall-effect sensors. Please contact your sales representative if you do not see the specific combination of output type, sensitivity, sample rate, etc. that you need.
The SOT-23 and TO92 versions of the Si72xx series of sensors are pin compatible with similar devices from many suppliers.
The Si72xx Hall effect sensors excel in:
low power
high sensitivity
linearity
low offset
accurate gain
The tamper detection feature (detection of a stronger than expected field) is unique. I2C parts which allow digital output of the magnetic field data and user programmed operate and release points are not common.
The simple 3 and 5 pin sensors in the Si720x and Si721x series generally do not need a driver or example code. Just apply power and ground and the output pin will go high or low with magnetic field. Decoding the PWM or SENT data from parts with these output type is included in the source code for the Si72xx-WD-Kit which is available in simplicity studio.
The Si7210 I2C sensors can be a little more difficult to work with and drivers are available through simplicity studio.
Example code and typical uses case descriptions are also available in AN1018.
The Si72xx-WD-Kit includes demonstrations for wheel position sensing, wheel rotation counting, and display of the magnetic field data from sensors and small postage stamp sized evaluation boards. This demonstration uses the MCU and display from a pre-programmed EFM32TM Happy Gecko STK.
The Si72xx-Eval-Kit will be available January 2018 and includes a USB adapter to power the postage stamp sized boards and a PC GUI to display the sensor data.
The Thunderboard Sense wireless multiprotocol sensor demonstration platform includes a hall-effect sensor and can display the sensor data through a mobile app.
We have noticed a small variation in offset related to package stress when the sensors are solders by hand. In most cases, this can be recovered by solder touch up. We have not seen issues related to other soldering techniques.
Hall-effect sensors are inherently more linear and do not have “hysteresis” effects from strong magnetic field. Some magneto-resistance sensors can be damaged by very strong field.
Magneto-resistive sensors are generally sensitive in the direction of magnetic field parallel to the PCB. In most cases, it is possible to order the magnet with a different polarization to produce magnetic field in the desired axis.
See AN1018 for a discussion of replacing reed switches with Hall effect magnetic sensors.
Hall effect sensors are generally more rugged in terms of shock and vibration
Hall effect sensors are surface mount compatible
It is much easier to detect tampering with the Si72xx series of hall effect sensors
While a reed switch is inherently zero power, less expensive SPST switches require a pull up resistor which consumes about as much power as the Si720x series of parts sampling at 5Hz
The Si72xx series of parts are sensitive to magnetic field in the axis normal to the package. For the SOT-23 and DFN packages this is also the axis normal to the PCB. For the T092 package the axis is parallel to the PCB plane.
Some magnetic position sensors (e.g. reed switches or GMR effect sensors) are sensitive to other axes of field. In most cases, it is possible to order the magnet with a different polarization to produce magetnic field in the desired axis.
The Si72xx series of parts are sensitive to magnetic field in the axis normal to the package. For the SOT-23 and DFN packages this is also the axis normal to the PCB. For the T092 package the axis is parallel to the PCB plane.
Some magnetic position sensors (e.g. reed switches or GMR effect sensors) are sensitive to other axes of field. In most cases, it is possible to order the magnet with a different polarization to produce magetnic field in the desired axis.
