Sensor AFE Simplifies Design Work

The LMP91000 analog front end (AFE) takes a bow as the industry’s first fully configurable, low-power potentiostat that provides a complete, integrated signal path between a sensor and ADC.  Also on tap, the LMP90100 assumes position as the industry’s first multi-channel, low-power 24-bit sensor AFE with true continuous background calibration and diagnostics. 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 device to support toxic gas sensitivities over a range of 0.5 nA/ppm to 9.5 nA/ppm. The LMP90100 employs National’s patented continuous background calibration to effectively eliminate offset and gain error over time and temperature.  Offset and gain error are determined without disturbing the measured signal.  The device features a 24-bit sigma-delta ADC with a mux input 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. Prices for the LMP90100 in a 28-pin TSSOP and LMP91000 in a 14-pin LLP are $4.95 and $3.95 each/1,000, respectively. NATIONAL SEMICONDUCTOR CORP., Santa Clara, CA. (800) 272-9959.