Configurable sensor AFE solution aims to simplify sensor systems designs, speeds time-to-market

National Semiconductor Corp. is unveiling an innovative design engineering solution which aims to slash the time taken to create a modern sensor design system from weeks, or even months, to a matter of minutes. The company plans to revolutionize how sensor systems are designed by simplifying the design process and speed time-to-market with the launch of two configurable sensor analog front-end (AFE) integrated circuits supported by a new bench-top evaluation tool.

National believes the new sensor AFE devices coupled with the evaluation tool will work together to fast-track signal path designs for a variety of sensors from major global manufacturers.  The configurable sensor AFE ICs and WEBENCH Sensor AFE Designer tool will enable design engineers to select a sensor, design and configure the solution and download configuration data to the sensor AFE. 

The goal is to replace a typical sensor system application, which today may require several boards and numerous components to implement, with just one of National’s sensor AFE ICs.  

National says the LMP91000 is the industry’s first fully configurable, low-power potentiostat that provides a complete, integrated signal path solution between a sensor and analog-to-digital converter (ADC).  The company’s other new device, the LMP90100, lays claim to be the industry’s first multi-channel, low power, 24-bit sensor AFE with true continuous background calibration and diagnostics for high performance transmitter and transducer applications.  

Modern sensor systems, which are ever present in every major industry for critical monitoring and control applications, are shrinking in size, must consume less power and have higher reliability.

“Sensor-based system designs are time-consuming and complicated to develop, requiring an optimal design for each system,” said Anita Ganti, Precision Systems Business Unit Director at National Semiconductor.  “Until now, designers have developed customized analog solutions that took weeks or even months to develop, but we can now help them get to market more quickly.”

“National's goal is to make that job a little easier and make it so that these tedious tasks can be done a little faster and a little easier which will enable system designers to focus their energies on finding ways of differentiating their sensor system from the competition”.

The first in a family of products, National’s two configurable sensor AFE products are each customized to a specific sensor application and have a variety of features, including programmable current sources, voltage reference options and adjustable sample rates.  

The WEBENCH Sensor AFE Designer features technical specifications for hundreds of temperature, pressure and chemical sensors.  The database features products from Omega Engineering, Inc., Honeywell Sensing & Control, Tempco Electric Heater Corp. and All Sensors Corp.

National Semiconductor says it is offering designers increased flexibility by giving them an alternative to long hardware development cycles by allowing designers to either choose a design online through National's WEBENCH Designer or on the bench with a sensor AFE development system. 

The company claims that its sensor AFE kit configurability means it is able to provide designers with an IC that is tailored to meet the specific needs of the sensor-based system in just a few minutes.  Each sensor signal path is optimized for performance and power.  Depending on the requirements of the sensor application the designer can also configure programmable current sources, multiple reference options and sensor diagnostics. 

National claims the LMP90100 is the industry’s first multi-channel, low power, 24-bit sensor AFE with true continuous background calibration and diagnostics for high performance transmitter and transducer applications.  National’s patented continuous background calibration effectively eliminates offset and gain error over time and temperature.  Offset and gain error are determined without disturbing the measured signal. 

The LMP90100 features a 24-bit sigma-delta ADC with a flexible input (mux) configuration to interface with any combination of differential or single-ended inputs.  Signal gains (1, 2, 4, 8, 16, 32, 64 and 128), sample rate and diagnostics are programmable for each sensor and two matched current drives are available to drive sensors.  The LMP90100 draws less than 0.7 mA on average and is guaranteed over the entire -40°C to 125°C temperature range, making it ideal for temperature transmitter or 4 mA to 20 mA applications.

National’s LMP91000 claims to be the industry’s first fully configurable, low-power potentiostat that provides a complete, integrated signal path solution between a sensor and ADC.  The programmable AFE is well-suited for use in micro-power chemical and gas sensing applications such as three-electrode single gas and two-terminal oxygen sensors. 

The LMP91000 measures current in a potentiostat that is proportional to the gas concentration.  It generates an output voltage proportional to the cell current using a transimpedance amplifier.  Transimpedance gain is user programmable through an I²C compatible interface, allowing the LMP91000 to support toxic gas sensitivities over a range of 0.5 nA/ppm to 9.5 nA/ppm.  The device supports a variety of chemical sensors including: Ammonia, Carbon monoxide, Chlorine, Ethylene oxide, Hydrogen, Hydrogen chloride, Hydrogen cyanide, Hydrogen sulphide, Methane, Nitric dioxide, Nitric oxide, Ozone, Phosphines, Sulphur dioxide.

Ultra-low power makes the LMP91000 optimal for battery-operated systems, as well as 4 mA to 20 mA transmitter applications.  The cell voltage and cell output gain are user-selectable using on-board programmability.  Together, they allow the user to support a wide range of gases and gas concentrations with a total current consumption for the device as low as 10 µA on average.  The I²C interface allows the user to verify sensor performance and an embedded temperature sensor provides an additional output to monitor temperature.  The LMP91000 operates across a voltage range of 2.7 V to 5.5 V.  

National’s new WEBENCH Sensor AFE Designer is a bench-top evaluation tool with a hardware interface that helps to minimize engineering design time and facilitate prototype evaluation.  The tool allows the user to download configuration data from their design to the sensor AFE, attach sensors and start their evaluation.

“We are working on several other sensor AFE products that are targeted at specific industrial instrumentation, automotive and medical applications,” said Ganti.  “The two new products we are now launching already have medical applications.  For example, we have been working with a person who was making an insulin pump and he used the LMP90100 in that application.  We also were working with some people who were working on electrochemical sensors for medical applications.  There will be more products in the pipeline that we will be releasing through the year and then we will have even more targeted applications in the medical sector and other markets”. 

Availability and Pricing

Offered in a 28-pin TSSOP package, National’s LMP90100 is available now and priced at $4.95 in 1,000-unit quantities. Also available now, the LMP91000 is offered in a 14-pin LLP package and priced at $3.95 in 1,000-unit quantities. 

• For more information about the LMP91000 AFE IC visit http://bit.ly/LMP91000
• For more information about the LMP90100 AFE IC visit http://bit.ly/LMP90100
• For more information about National’s sensor AFE products, WEBENCH Sensor AFE Designer and other support tools is available at http://www.national.com/sensorAFE

Watch a video demonstration of the WEBENCH Sensor AFE Designer at http://bit.ly/AFEvideo