A ±0.15% RH Inaccuracy Humidity Sensing System With ±0.44 °C (3σ) Inaccuracy On-Chip Temperature Sensor

This article describes a high accurate humidity sensing system. The humidity sensor and the interface circuit of our system-in-package (SiP) are 3-D stacked to optimize integration density with small foot print. A single reconfigurable ADC is utilized for both 3- D stacked humidity and onchip temperature sensors. An incremental Delta Sigma ADC with a reconfigurable Delta Sigma modulator is employed with dual input stages. With the combination of chopping, correlated double sampling (CDS), dynamic element matching (DEM), and system-level chopping techniques, high accuracy sensing system is achieved. The interface circuit, implemented in a standard CMOS 0.18 mu m CMOS technology, occupies an area of 1.24mm2. The SiP sensing system dissipates only 146.5 mu Aand 25 mu A from3.3 V supply and 1.8 V supply, respectively. Its humidity inaccuracy is 0.15 %RH with a resolution of 0.012 %RH, while a temperature inaccuracy is 0.44 degrees C (3 sigma) with a resolution of 0.015 degrees C.