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Highly integrated capacitive-digital converter

25th January 2017

Posted By Paul Boughton


ON Semiconductor has introduced a new touch/proximity sensing solution that combines industry-leading performance, cost effectiveness and convenience in a single chip.

The LC717A30UJ high dynamic range capacitance-to-digital converter uses mutual capacitance to detect changes in capacitance down to femtofarad (fF) levels. Parasitic capacitance cancellation raises the detector sensitivity, while its built-in noise rejection mechanism combats the effects of electromagnetic interference (EMI).

The eight capacitance-sensing input channels make the LC717A30UJ highly optimised for use in systems where an array of switches is required.

The device includes an integrated multiplexer for input channel selection, analogue-to-digital converter, dual-stage amplifier that determines capacitance changes plus outputs analogue amplitude values, system clock, power-on reset circuit, and all the necessary control logic to create a total solution. Both I2C and SPI interfaces are selectable based on the system application needs.

As the device’s sensitivity has a range of 150 millimetres (mm) - beyond the scope of any competing device on the market – its higher sensitivity enables gesture motions as well as offering conventional touch functionality, thereby enhancing users’ control options to address a wide range of application scenarios.

In addition, it is capable of operating with an airgap between the sensor/PCB and the protective cover - so engineers can eliminate the inclusion of a light guide from the assembly and reduce overall complexity. This device also includes an integrated automatic calibration function which optimises and self-calibrates total capacitance according to electrode, line capacitance, and surrounding environment, thus significantly accelerating  system development cycle time as well as robustness in the field.

The LC717A30UJ delivers rapid responsiveness, with a measurement time of 16 milliseconds (ms) for its 8 sensing channels and runs off a +2.6 volt (V) to +5.5 V supply with a low-power standby mode of one microampere (µA).

The high degree of integration means that minimal external components are required, thereby further reducing the bill of materials.

To support the needs of automotive applications such as vehicle entry systems and dashboard controls, the device is AEC-Q100 compliant. With its high integration level and wide dynamic range, it can also be employed in a range of touch or gesture human interfaces in industrial and consumer end products such as induction cookers, refrigerators, home entertainment systems, building automation equipment, industrial equipment, and lighting controls. 







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