Date: 25/01/2011
Configurable analog front end ICs enable simple and configurable sensor circuit design
National Semiconductor has introduced two configurable sensor analog front-end (AFE) integrated circuits (ICs). National has enabled its WEBENCH software to help the sensor circuit developer to select a sensor, design and configure the solution and download configuration data to the sensor AFE chip. National says its one chip solution saves cost, time and space compared to other solutions, which may require more boards and up to 25 components.
"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. "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."
The LMP91000 is a configurable, low-power potentiostat that connects between a sensor and analog-to-digital converter (ADC) chip. This chip is suggested 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. 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 ľA 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 over a voltage range of 2.7V to 5.5V.
The LMP90100 is a multi-channel, low power, 24-bit sensor AFE with true continuous background calibration and diagnostics for high performance transmitter and transducer applications. LMP90100 with a flexible input (mux) configuration can accept 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 designed operate in the temperature range of -40 degrees C to 125 degrees C. National suggest this device as a temperature transmitter in 4 mA to 20 mA applications.
Both these chips are customized to a specific sensor application and have features such as programmable current sources, voltage reference options and adjustable sample rates
The WEBENCH Sensor AFE Designer software includes technical specifications for hundreds of temperature, pressure and chemical sensors from companies such as Omega Engineering, Inc., Honeywell Sensing & Control, Tempco Electric Heater Corp. and All Sensors Corp.
Package: Both in 28-pin TSSOP
Availability: Now
Price:
LMP90100: Each $4.95 per 1K pieces
LMP91000: Each $3.95 per 1K pieces
Editorial Product Rating: *** (High Value)