TMAG5170: Rotary positon sensors

Jonathan,

The TMAG5170 and TMAG5273 are both 3D linear Hall-effect sensors. These devices will measure the absolute magnetic field.  In rotation application they will provide the absolute 0-360 degree measurement only.

TMAG5110 and TMAG5111 are 2D latch Hall-effect sensors.  TMAG5110 outputs the binary output from the latch directly on the two output pins.  There are 4 output combinations that are stepped through for each magnetic pole pair observed during the rotation.  For a standard dipole magnet there will be 4 states, but for a 20 pole magnet (10 pair), there will be 40 output states.  TMAG5111 decodes the quadrature of TMAG5110 and translates these states to a single clock-like output and then calculates direction as a second output.  In both cases these devices can only determine relative changes in angle from the start of measurement point.

We do have an AMR sensor with a low power turns counter, however.  This device is TMAG6181.  This device creates differential sine and cosine outputs which can be sampled and used in an arctangent measurement.  AMR sensors will produce two output cycles per revolution of a standard dipole magnet.  The turns counter in this device is implemented by integrating a secondary Hall-effect latch that tracks the quadrant of rotation.  In the low power state, the outputs are all Hi-z, but the turns counter will track clockwise and counterclockwise quadrant changes.  When brought out of sleep mode the device will restore the PWM turns count signal based on the change in the number of rotations.  In this device the turns count increments at each quadrant change, so one full revolution will change the PWM by 4 codes. Without tracking the turns counter, it is not possible to differentiate 45 degrees from 225 degrees, but as long as the device remains powered, it should be possible to determine absolute angle and the number of turns that have occurred. 

Thanks,

Scott