FTM Board Club: ON Semiconductor’s Ultra-sensitive capacitive touch sensors detect a gloved finger / LC717A series

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LC717A capacitive sensors: automatic calibration at start-up

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ON Semiconductor has introduced a family of capacitive touch-sense controllers offering either 8 or 16 sensing channels.

The LC717A devices are high-performance, low-cost capacitance-to-digital converters which may be used to easily implement an electrostatic capacitive touch sensor. Extremely sensitive, they are capable of detecting tiny changes in capacitance, making them suitable for use in systems operated by users wearing gloves, or through a thick overlay.

The built-in logic circuit detects the on/off state of each input, and produces the result as a digital output. No external components are required for the measurement function.

Calibration is automatically performed by the logic circuit at start-up or whenever there are changes in the operating environment. In addition, once the operating parameters, such as gain, are configured, the LC717Ax0 converters can operate in stand-alone mode when the recommended switch pattern is applied.

Alternatively, the parameters can be modified by an external controller via the device’s I2C or SPI bus interfaces.

DeviceSensing InputsPackage
LC717A00AJ 8 (16 - 4x4 matrix)SSOP-30
LC717A00AR8 (16 - 4x4 matrix)VCT-28
LC717A10AJ16 (64 - 8x8 matrix)SSOP-30
LC717A10AR16 (64 – 8x8 matrix)VCT-28

FEATURES

  • Differential capacitance detection
  • 3ms minimum measurement interval
  • Automatic noise compensation
  • 320μA operating current at 2.8V input
  • Supply voltage range: 2.6V to 5.5V

APPLICATIONS

  • Security keypads
  • Video intercom systems
  • Remote controls
  • Bath and spa controls
  • PC keyboards
  • Thermostats
  • Proximity light switches
  • Door openers
  • Power saving circuit wake-up

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Prototyping Touch-sensing Designs
See board details below.

Orderable Part Numbers: LC717A00ARGEVK and TOUCHLRACOMBOGEVB

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Prototyping of touch-sensing designs: two new boards make it quicker

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ON Semiconductor has introduced two different development systems aimed at users of its LC717A series of capacitive touch controller ICs.

 

The LC717A00ARGEVK kit contains four capacitive touch-sensor evaluation boards, together with a multi-functional USB-to-I2C conversion module and a USB cable for connection to a PC. Three of the boards offer an array of 4×2 or 8×1 capacitive touch switches, which are mounted on a PCB underneath an opaque acrylic overlay. The touch switches are illuminated from below by a green LED which is mounted on the PCB. When the switch is touched, the light changes from green to red.

The fourth board allows users to design their own switch-array configurations.

ON Semiconductor also supplies the TOUCHLRACOMBOGEVB, which demonstrates the LC717A capacitive touch sensor alongside supporting devices to provide visual and audible feedback: the LC899301XA linear vibrator driver, and the LC87F1M16A 8-bit microcontroller.

FEATURES

  • Compatible with Windows® XP and Windows 7 operating systems
  • PC software for LC717A available online from ON Semiconductor
  • Power supplied by PC via USB, or via external 5V AC adapter

APPLICATIONS

  • Home appliances
  • Audio/visual equipment
  • Computer peripherals
  • Automotive instrument panels

 
 
 
 

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