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Capacitive sensor conditioning IC delivers 14-bit resolution

Wed, 10/05/2011 - 7:29am
ZSSC3123Dresden, Germany -- October 5, 2011 – ZMD AG has expanded its family of capacitive sensor signal conditioning devices with the wide-dynamic-range ZSSC3123 integrated circuit (IC). The chip delivers 14-bit resolution and 0.25 % accuracy over a wide range of sensor capacitances and temperatures. Target applications include low power battery driven sensor applications, sensors for humidity, weight scales, load and compression sensing, as well as tension control.

Capacitive sensors are often favored for their small size and lower power consumption. The ZSSC3123, designed for low-power operation, complements these features and provides to designers an optimal solution for their system designs. The device is particularly suited for MEMS-based sensor elements, such as pressure sensors for hydraulic control systems, humidity sensors, and liquid level gauges.

"Responding to sensor system designer needs, we have developed a digital technique to correct both first-order and third-order nonlinearity errors that were difficult or impossible to correct with a pure analog signal path,” stated Steve Ramdin, Product Manager at ZMDI. "Third-order correction is especially useful in humidity and pressure applications, but it can correct for sensor imperfections in almost any situation.”

The ZSSC3123 connects to microcontrollers but can also be utilized in stand-alone designs for transducer and switch applications. The ZSSC3123 features an operating current as low as 60uA over the entire voltage range of 2.3V to 5.5V. A built-in sleep mode lowers the current consumption to <1uA for temperatures up to 85°C.

The ZSSC3123 can be configured to interface with capacitive sensors from 0.5 to 260 pF, with sensitivity as low as 125 atto-Farads (aF) per digital bit. The part can be used in both single- and differential-input sensor configurations. The device offers a full 14-bit resolution for compensation of sensor offset, sensitivity and temperature.

All calibration is digital and completed in one pass, eliminating the cost of laser trimming, and speeds up calibration of sensor modules in production. Programming and single-pass calibration of the capacitive sensor and the ZSSC3123 is accomplished through a standard PC environment using the ZSSC3123 kit and development tools. The kit includes a TSSOP14, development board, USB cable and calibration software.

At the standard supply voltage of 2.3 to 5.5 V, the device is accurate to 0.25 % over the -20 to +85°C range, and 0.5 % from -40 to +125°C. The ZSSC3123 part provides I2C and SPI interfaces as well as PDM or alarm outputs.

The ZSSC3123 is available in production. Unit prices start at 2.85 EUR, or USD 3.82, in volumes of 1k devices. More information is available at www.ZMDI.com.

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