Differential mixed-signal architecture

Fig. 6.7. Block diagram of the differential mixed-signal architecture. AAF Anti-aliasing filter BF Buffer MUX Multiplexer...

Fig. 6.11. Performance of the digital PID temperature controller of the differential mixed-signal architecture in the tracking mode...

The tracking mode performance of the on-chip digital temperature controller of the differential mixed-signal architecture is shown in Fig. 6.11. The measurement was done at room temperature, and the digital code of the reference temperature of microhotplate 1 was increased in steps of 100 digits. Microhotplates 2 and 3 were switched off during the measurement. The resolution of the digital temperature controller was better than 2 °C. 

This chapter includes two different sensor system architectures for monolithic gas sensing systems. Section 5.1 describes a mixed-signal architecture. This is an improved version of the first analog implementation [81,91], which was used to develop a first sensor array (see Sect. 6.1). Based on the experience with these analog devices, a complete sensor system with advanced control, readout and interface circuit was devised. This system includes the circular microhotplate that has been described and characterized in Sect. 4.1. Additionally to the fabrication process, a prototype packaging concept was developed that will be presented in Sect. 5.1.6. A microhotplate with a Pt-temperature sensor requires a different system architecture as will be described in Sect. 5.2. A fully differential analog architecture will be presented, which enables operating temperatures up to 500 °C. 

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