Many products need only basic on/off touch controls rather than sliders, wheels, and proximity sensors. Engineers might want to replace a mechanical switch with a touch control. Even in these cases, designing the controls themselves and their associated circuits can seem complicated.  Cypress Semiconductor aims to change that perception and simplify sensor interfaces and designs. Now, engineers can easily add capacitive touch controls to many products where they hadn't thought to use them previously.

The new Cypress CapSense Express controller--CY8CMBR2044--relies on the company's auto-tuning technology that automatically adjusts for a sensor baseline and sensor threshold during power up and during use. So as environmental conditions change, the internal circuits detect them and adjust parameters so the switches continue to operate properly. The chip requires no code development and only a few external passive components, one of which controls whether an output acts like a toggle or only as a momentary pushbutton. Separate outputs reflect the state of each of four touch sensors.  You don't need an I2C or SPI port to interface this chip to a microcontroller, for example.  For a data sheet, visit: www.cypress.com/?docID=23419.  For information about other CapSense products and design support, visit: www.cypress.com/?id=1575.

The chip incorporates a flanking-sensor suppression (FSS) capability that lets it properly sense activity on one sensor, ever with some overlap on nearby sensors. You can enable or disable this operation.

Equipment designers unfamiliar with capacitive-sensing controls might worry about the types of sensors they must fabricate, the substrate materials they plan to use, distances between sensors and the CY8CMBR2044, and so on. Cypress anticipated these concerns and provides a Design Toolbox spreadsheet that lets designers specify materials, overlay thickness, dielectric constants, approximate scan rate, and other parameters. Then the toolbox software provides recommended sensor-design information.

Engineers who want to dig deeper into sensor design can download MultiChart software that helps analyze internal information from CapSense ICs, obtained via a standard serial port. Pulling one of the CapSense pins to ground through a 5600-ohm resistor places that pin in a serial-port mode. The data sheet noted above and the application note, "Design Aids -- CapSense Data Viewing Tool, AN2397," explain how to obtain internal test information. Find this application note at: www.cypress.com/?docID=2425. In all likelihood, you won't need to do any debugging or testing, but the capability exists if you need it.

The CY8CMBR2044 chip can operate with a supply voltage of 1.71 to 5.5 volts and in a deep-sleep mode, it draws only 100 nA. The chip comes in a 3 x 3 mm 16-pad QFN package. --Jon Titus