Complex model description and main capacitor sizing for the cross-coupled charge pump synthesis process

Jan Marek – Jiri Hospodka – Ondrej Subrt

   This paper presents a dynamic part of the pump stage model of the cross-coupled charge pump. The complex model has been used for both the estimation of the N-stage pump properties in a wide range of the input parameters and derivation of equations for synthesis process, as the main capacitor sizing, which is also mentioned in the article. Dynamic part of the model (pump stage capacitances) is determined from Warďs capacitance piece-wise model through the BSIM MOSFET model equations. Main capacitor and load capacitor sizing are based on the time response characteristics fulfilling the system behavior in time. Guideline on the MOS transistor sizing as the nonlinear main pump capacitor and specification of the diode transistor for the design process are also clarified. The characteristics of the proposed circuit have been verified in the professional design environment Mentor graphics and analysis algorithm based on the state-space description of the inner complex model was programmed in Maple SW. The main benefit is to offer the alternative way of the charge pump synthesis by using the complex model and symbolic description of all formulae to find the required pump parameters without long-time simulation process.

Keywords: time response characteristics, dynamic properties, cross-coupled charge pump, complex model, BSIM equations, pump capacitances

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