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Single chip for capacitance and impedance measurements

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Analog Devices has introduced families of capacitance-to-digital converters (CDCs) and impedance-to-digital converters (IDCs) said to simplify instrumentation and sensor design in industrial, automotive and medical applications.

The company says that the fully integrated converters address the “complex and difficult signal processing challenges of direct capacitance-to-digital and impedance-to-digital conversion”. According to the US-based firm, by combining signal processing techniques with high levels of integration, the devices attain a level of precision previously only possible with conventional analogue voltage-to-digital converters aided by a significant number of discrete components.

The new approach is said to provide designers with advantages over existing discrete solutions for capacitance- and impedance-sensing applications that have historically lacked precision and proven difficult and expensive to design. The devices are suitable for a wide range of instrumentation and sensing applications, from blood pressure monitors and glucose analysers to position sensors for vehicles and industrial corrosion analysis systems.

The CDC, dubbed the AD7745, integrates all stages of capacitance-to-digital conversion on one chip reducing costs associated with traditional multi-chip solutions by a claimed 65 percent. The device has 24-bit resolution.

The IDC, called the AD5933, combines direct digital synthesis (DDS), analogue-to-digital conversion and digital signal processing techniques to provide a compact, integrated solution for precision impedance measurement.

“Designers of instrumentation equipment have long recognised the benefits of using capacitive and impedance techniques for applications requiring highly accurate measurements, but up until now they were constrained by complexities in implementation and by the significant design cost involved,” claims Mike Britchfield, product line director, Precision Converters, Analog Devices. “[These devices] solve these design challenges.”

Analog has also introduced a lens driver chip designed for next-generation camera-enabled mobiles. The lens driver chip, dubbed the AD5398, addresses handset and camera phone manufacturers’ need for integrated drivers that enable significant space and cost reduction.

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