Robust inductive force sensor simplifies touchscreen assembly

The new IQS7366 inductive sensor IC from Azoteq provides for a simpler and cheaper mechanical assembly in touchpads and other force-sensing applications than solutions based on a traditional strain gauge. 

Force sensing is an attractive user interface which allows for an adjustable trigger level based on the amount of force applied. A tactile sensation, which is normally provided by a haptic actuator, is also customizable. Previously, force sensing has required the use of electro-mechanical strain gauges in assemblies which are bulky and complicated to produce. 

A member of the Azoteq ProxFusion^® family, the surface-mount IQS7366 enables the OEM to create a much simpler assembly. The IQS7366 interfaces with an inductive coil formed by traces on the PCB. This means that the entire force-sensing interface can be assembled with standard electronics manufacturing techniques, and requires no manual labor.

The input force is sensed through a minute movement of a spring-mounted target above the inductive coil. On-chip calculation allows for an evenly spread force trigger across the touchpad or touchscreen. Because of the IQS7366 high force-measurement accuracy, the interface works well with a reduced resolution touchscreen, and eliminates the need for an ITO layer, for capacitive touch-sensing, or a resistive touch screen. 

A force-sensing screen based on the IQS7366 is immune to interference from water or moisture, making it ideal for marine and outdoor applications. The inductive technology also enables operation by a user wearing gloves.