The SPI and nALERT signal timing to trigger a simultaneous conversion of the Z-axis and X-axis and read the data of all four 3D Hall-effect sensors at a 4kHz sample rate are shown in Figure 3-6.

Figure 3-6 TMAG5170 Simultaneous Sampling and SPI Timing

The host MCU such as the C2000 MCU generates an active low nALERT trigger pulse with 100ns width at a 4 kHz sample rate. Each of the four TMAG5170 initiates a Hall-effect sensor spin and integration. The TMAG5170 samples and converts the sequence XZX and the calculate the average X value. After the A/D conversion is complete, the C2000 MCU reads out each of the four TMAG5170 sequentially using an individual active low chip select signal. The effective sampling of the average X and Z axis data occurs approximately 47.5µs after the active low ALERT trigger pulse. The latency from the effective sample point until SPI transfer starts is around 57.5µs, the sequential SPI transfer of the 4 channels is completed after 15µs. Hence the total signal latency including SPI transfer is around 72.5µs.

A Heidenhain LC415 EnDat2.2 linear position encoder with 10um resolution was used as reference. The C2000 MCU reads the position of the LC415 EnDat2.2 encoder at the same time than sampling the Z and X axis of the four TMAG5170.