Two different ASIC approaches can be used for signal-conditioning a MEMS piezoresistive silicon pressure sensor. One is based on a digital scheme for applications requiring a low operating voltage and low power consumption. The other involves an analog method for
Two different ASIC approaches can be used for signal-conditioning a MEMS piezoresistive silicon pressure sensor. One is based on a digital scheme for applications requiring a low operating voltage and low power consumption. The other involves an analog method for low-cost, high-volume applications. In both cases, the ASIC is employed to calibrate and compensate the sensor with a total error of less than ±1% of full scale over two different operating-temperature ranges. The total error includes effects due to offset and sensitivity, as well as the offset and sensitivity temperature coefficients (TCs).
Researchers chose ASICs because a typical output signal for a piezoresistive pressure sensor depends on temperature. ASICs also operate in the few-millivolt range. This level is too low for control and interface with microprocessors. Moreover, ASICs offer advantages over traditional approaches. Passive laser trimming of resistor networks, for example, provides high resolution and a wide range of resistor values. But the resistors have to be serially and individually trimmed, so it's capital intensive. It requires complicated and expensive production fixtures, as well.
Researchers at the Electron Device Laboratory of Fujikura Ltd. in Tohoku and Tokyo, Japan, devised a DSP-based circuit that corre