1 Introduction

When using hall effect sensors in an electronic-shifter (E-shifter) application, there can be numerous approaches to achieving the system objective of detecting relative shifter stick position. Figure 1-1 shows two possible approaches that can be explored for an e-shifter. For those two approaches a dual die sensing design can be desired for redundancy which is not uncommon for automotive applications that frequently have functional safety requirements. Preferably for a redundant system, two separate sensors measure identical results. Yet this type of redundancy often is impossible because two different sensors must occupy two different places in space. This document explores the different Hall-element placements available for dual die sensors and illustrates how a device similar to the TMAG5170D-Q1 has both die arranged for reducing the discrepancy in measurements desired in a redundant system. To substantiate this assertion, let us go through the design process for the approaches below, then show the absolute error, standard deviation in calculated angle difference, and max difference in calculated angle for various mechanical errors that can occur in assembly.

Figure 1-1 Define Approach

Typical development for a design iteration of a particular application can follow a flow similar to what is illustrated in Figure 1-2. In this case, the system objective is to track position in a lever similar to what can be found in E-shifter. The approaches considered are those found in Figure 1-1. The constraints for a design can be sensing device location, the board size at the sensing location, magnet size, cost, resolution, and so on. The following analysis is only constrained by the above mentioned approaches and magnet sizes similar to what can be readily purchased. Post processing magnetic field values from sweeping a magnet through the expected path of motion can help determine a good magnet size and location for better placement. From a derived point, further processing of subsequent magnet parameter sweeps can be performed to quantify the possible error that can be observed for various mechanical assembly tolerances.

Figure 1-2 General Design Flow