1 3 Microsyst Technol DOI 10.1007/s00542-015-2475-x TECHNICAL PAPER A complete analytical model for clamped edge circular diaphragm non-touch and touch mode capacitive pressure sensor Sumit Kumar Jindal · Ankush Mahajan · Sanjeev Kumar Raghuwanshi Received: 5 February 2015 / Accepted: 19 February 2015 © Springer-Verlag Berlin Heidelberg 2015 modes: normal mode and touch mode. In normal mode deflection of the plate is smaller than the height of cavity and in touch mode the plate touches the electrode placed at bottom. To achieve linearity characteristic, pressure sens- ing at high range and overload protection touch mode is designed. To clearly understand deflection of diaphragm, capacitance of electrode at each stage, sensitivity variation and linearity characteristic a step by step solution has been discussed and analyzed for both normal and touch mode capacitive pressure sensor. Various aspect depends on the fact as to how we apply uniform pressure and the manner in which absolute capac- itance is developed. It should be noted that we only deal with the case of linear elastic deformation of the circular plate. Previous work shows the mathematical modelling for capacitive sensor being dealt with different approach such as power series solution (Meng and Ko 1999) and pseudo spectral method (Lee et al. 2013). In both the case large deflection theory has been utilized. In this study, we for- mulate the expressions for different performance parameter based on small deflection theory. Here we deal with three different sections. At first a general theory has been discussed and then the approach has been to develop the mathematical formulation for the key parameters involved. Finally well supported MAT- LAB simulation has been discussed to validate the theory evaluated. 2 Theory To describe the behaviour of micromachined touch mode capacitive pressure sensor (TMCPS) a capacitive pressure curve can be used which shows three different zones as Abstract Capacitive pressure sensor have become good substitute for piezoresistive pressure sensor because of low power consumption. In order to evaluate the characteristic profile for touch mode micro pressure sensor an accurate and simple model needs to be designed. Hence preferable analytical model is necessary to design and characterize the device. Lot of study has been done on touch mode capaci- tive sensing but no elaborate work has been presented to clearly understand the underlying expressions and the role of key performance parameters. With this step by step theo- retical evaluation model the key performance parameter such as deflection, capacitance and sensitivity can be easily studied for both non-touch and touch mode capacitive pres- sure sensor. The next aspect has been to simulate the find- ings in order to validate the results and hence MATLAB has been introduced. It also eliminates the need for design using FEM and hence the study becomes lot easier. 1 Introduction Among the most successful MEMS developed in last four decades has been capacitive and piezoresistive microma- chined pressure sensor. Pressure sensors are required in high performance application such as automotives, power station, biomedical, industrial and environmental monitor- ing. To achieve high pressure sensitivity, low turn on tem- perature drift, low noise and less dependence on side stress, capacitive pressure sensor is used (Fragiacomo et al. 2010; Daigle et al. 2007). These sensors can be designed for two S. K. Jindal (*) · A. Mahajan · S. K. Raghuwanshi Department of Electronics Engineering, Indian School of Mines, Dhanbad, Jharkhand, India e-mail: sumitjindal08@gmail.com