Switching and latching applications that involve detecting the presence of a moving object can be complicated to design and plagued by reliability problems. Examples include implementing tamper detection for opening and closing doors, or measuring the rotational speed of a gear regularly exposed to dust or oil that could block the sensor and cause failures.
Additional challenges exist depending on the specific technology used for the switching application, including:
The introduction of TI’s LDC0851 differential inductive switch enables a new approach that offers a temperature-stable switching threshold accurate to 1% of the coil diameter, eliminating the need for production calibration.
LDC0851 differential inductive switching theory
The LDC0851, as shown in Figure 1, uses inductive sensing to perform a simple inductance comparison between two matched printed circuit board (PCB) coils. The output switches high or low depending on which coil has less inductance.
Figure 1: LDC0851 differential inductive switch functional diagram
This new approach to switching applications offers benefits for two main categories of applications:
Figure 2: Proximity detection for an example button application
Figure 3: Adjustable threshold to fine tune button response
Figure 4: LDC0851-based encoder-knob reference design
Prototyping tools and resources
A simple coin-cell battery-powered evaluation module (EVM), shown in Figure 5, demonstrates close-range proximity sensing as well as simple on/off metal-button detection. This EVM includes a perforation that enables you to replace the default sensor with a custom sensor.
If you’re interested in learning more about the new inductive switch, the WEBENCH® coil design tool can help simplify the design of stacked coils for the LDC0851. In the next post, we will go through a design example and show you how to use the new tool.
All content and materials on this site are provided "as is". TI and its respective suppliers and providers of content make no representations about the suitability of these materials for any purpose and disclaim all warranties and conditions with regard to these materials, including but not limited to all implied warranties and conditions of merchantability, fitness for a particular purpose, title and non-infringement of any third party intellectual property right. No license, either express or implied, by estoppel or otherwise, is granted by TI. Use of the information on this site may require a license from a third party, or a license from TI.
TI is a global semiconductor design and manufacturing company. Innovate with 100,000+ analog ICs andembedded processors, along with software, tools and the industry’s largest sales/support staff.