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Capacitive sensor signal-conditioning IC delivers 14bit resolution at low power

Dresden, Germany – ZMD AG has added the ZMD31210 cLite IC to its family of capacitive sensor signal conditioning devices. Capacitive sensors offer several benefits, including very low power operation, and the ZMD31210 supports this with a low 60uA current draw over a supply voltage range as low as 1.8V or as high as 5.5V.

The ZMD31210 can be configured to interface with capacitive sensors from 2 to 260 pF with sensitivity as low as 125 atto-Farads (aF) per digital bit. The part accommodates both single and differential input sensor configurations. All calibration is digital, and completed in one pass; eliminating the cost of laser trimming and speeding production of fully-calibrated sensor modules.

Capacitive sensors are widely found in many MEMS sensing elements. Examples include pressure sensors for hydraulic control systems, humidity sensors and liquid level gauges. Capacitive sensors are often favoured for their small size and lower power consumption over resistive bridge sensors.

Capacitive sensors do not touch or make direct contact with the system being sensed, which makes them a preferred option for industrial linear and angular position sensors and contactless potentiometers, where harsh or explosive environments make other sensor technologies impractical.

“In close cooperation with key customers, we developed a digital technique to correct not only first-order, but second-order nonlinearity errors difficult or impossible to correct with a pure analog signal path”, says Thilo von Selchow, CEO at ZMD. “Second-order correction is especially useful in humidity and pressure applications, but it can of course correct for sensor imperfections in almost any situation.”

The ZMD31210 connects to micro-controllers but can also be used in stand-alone designs for transducer and switch applications. The mixed signal design of cLite offers 14bit capacitive-to-digital conversion and full 14bit compensation of sensor offset, sensitivity and temperature via an internal digital signal processor running a correction algorithm. Calibration coefficients are stored in an on-board non-volatile EEPROM. The system interface offers I2C, SPI, PDM or alarm outputs.

The standard supply voltage is 2.7 to 5.5V. At this voltage, accuracy is 0.25% over the -20 to +85°C range, and 0.5% from -40 to +125°C. The ZMD31210 offers a 'Vcore' pin option for operation from 1.8V to 3.6V, with an accuracy of 1% from -20 to +85°C. Depending upon configuration, current consumption can be as low as 60¼A.

The Sleep Mode feature reduces consumption to less than 1¼A, making the device ideal for battery-based and other power-sensitive applications.

Programming and single-pass calibration of the capacitive sensor and the ZMD31210 is available through a standard PC environment using the ZMD31210KIT development tools. The package includes TSSOP14 samples, a development board, USB cable and calibration software.

The ZMD31210 is targeted for production in Q4/2009. Samples and kits are available. The devices are available in TSSOP14 packages. Unit prices start at 2.09 EUR, or USD 2.93, in volumes of 1k devices or more.

Please note: The above text is the public part of the press release obtained from the manufacturer (with minor modifications). EETimes Europe/ADLE cannot be held responsible for the claims and statements made by the manufacturer.

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