Hall-effect sensor design: What is the best way to suppress switching jitter?

February 25, 2015 // By David Muthers, Thomas Kauther, Micronas
As an integral part in the automotive industry, Hall-effect sensors are used to detect end-position or to measure linear or angular movements in an extremely wide range of chassis, safety, body, security, and powertrain applications. An important topic currently dominating R&D discussions in the automotive industry is Functional Safety. Functional safety affects the design and feature set of components in all application systems including Hall sensors.

Hall sensors are increasingly preferred sensing solutions in many applications thanks to their contactless measurement principle and resulting high reliability.
For instance, one trend shows the increasing use of Hall-effect sensors over mechanical switches due to their insensitivity against environmental conditions (e.g. dust, humidity, and vibrations), their constant measurement results under the harshest environmental temperature conditions from -40°C up to 150°C, and their highly repeatable operation without degradation over time. All while maintaining a high level of quality for unlimited use.

In order to fulfil this ever evolving safety and reliability feature, highest accuracy of the switching threshold is the essential parameter in the Hall switch specification.
The actual switching operation, triggered by a magnetic signal crossing the switching threshold, is affected by different effects like switching delay, sampling jitter and threshold noise. All of these are undesirable as an ideal switch should react instantaneously, however they cannot be completely avoided due to the Hall IC’s internal signal processing.

In order to achieve an optimal switching performance, the signal processing inside the latest Hall-effect switch family from Micronas – the HAL 15xy family, was designed to feature the highest suppression of such negative side effects.
This paper provides insight to how the signal path design influences the jitter performance of the output signal and the diverse design approaches taken to solve this problem.

A brief introduction of the signal path and the static switching behavior of a Hall switch are presented in the following section.

Signal path of Hall switches

The simplified signal path of a Hall switch consists of several basic components, as depicted in figure 1:

Figure 1: Simplified Hall switch signal path

Design category: