Azoteq — IQS269A Capacitive Touch & Proximity Controller

Azoteq has implemented a novel, patent-pending technique for force sensing in the latest version of its IQS269A multi-sensor product, to provide a solution for waterproof buttons, sliders and rotary sensors in wearable and consumer electronics devices.

A force-sensing button enables the user to squeeze the housing of a device to signal a command, such as Play or Pause in earbuds’ audio playback function. Force sensing is a popular form of user interface in True Wireless Stereo (TWS) earbuds, as it avoids the risk of false activation when the earbud is handled or placed on a surface. It is also a more robust and reliable user-interface technology than capacitive sensing in applications that tend to get wet or damp, such as fitness trackers or sports earbuds.

In contrast to existing implementations of force detection based on capacitive sensing, the Azoteq solution uses inductive technology. When the housing is compressed the sensor detects the decrease in distance between a metal plate and an inductive coil, producing an output voltage. This method allows designers to completely seal the circuitry inside the housing, making it waterproof.

The Azoteq solution is easy to implement and calibrate in any TWS earbud design. The metal target, inductive coil and sensor are assembled on a small, folded Flexible Printed Circuit (FPC) which slides into the stem of the earbud housing. The IQS269A sensor can be calibrated to trigger an action only when a specified amount of pressure is exerted, allowing manufacturers to achieve a repeatable user experience across a population of production units.

Azoteq’s inductive technology can also be used to design a contactless and waterproof slider or knob. In kitchen appliances, the inductive knob can be made removable to ease cleaning and to make the appliance safe from tampering by children.

The IQS269A multi-sensor IC in which the inductive force-sensing capability is implemented also supports capacitive touch sensing, and performs magnetic docking detection and capacitive wear detection in the same chip. This enables device manufacturers to save board space and power, and reduce bill-of-materials and assembly costs.