Charge-transfer sensor is smaller touch interface

A single-channel sensing chip comes in an RoHS-compliant 6-SOT-23 package.

Quantum Research Group has announced the QT100 a single-channel sensing chip in an RoHS-compliant, 6-SOT-23 package.

Designed primarily for use in handheld products - mobile phones and MP3 players - this is the smallest charge-transfer device in the company's product range but there is no compromise with respect to the features needed for stable and reliable operation.

The QT100 can sense touch, or near proximity, through any kind of dielectric including glass, plastic, stone, ceramic or wood.

Designers therefore have a high degree of flexibility in the physical and aesthetic design of their products.

Furthermore, touch sensors eliminate the reliability and manufacturing complexity issues associated with electromechanical switches and membrane keypads.

The QT100 only needs three external passive components, two capacitors and a resistor, to complete the sensor.

The sense electrode can be any conductive surface, from a simple printed circuit board pad or an area of conductive indium tin oxide (ITO) printed onto a transparent touch screen.

Sensitivity is easily adjusted through the design of sense electrodes or by changing capacitor values.

The device features self-calibration on power-up with automatic drift compensation.

A consensus filter, and the use of spread-spectrum signal acquisition, ensures high noise immunity and low RF emissions.

The QT100 operates from a single 2 to 5V supply and consumes only 10uA at 2V in low power mode, maximising battery life in portable equipment.

Where speed and response time are critical, the chip offers a fast mode with just 1ms between bursts.

A sync mode, where the device sleeps after each measurement burst, enables multiple QT100s to be synchronised, while preventing cross-interference.

The operating mode is selected though the status of the sync pin.

The sensor chip is available now.

It costs $0.50 in 100,000-unit quantities.

Evaluation boards are also available.

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