This paper demonstrates the design process and performance prediction of a cryogenic 22 nm FDSOI circuit using a design-oriented model. The simplified EKV model is adopted to capture IV characteristics of short-channel transistors, for which parameters are extracted from cryogenic measurement of commercial FDSOI MOSFETs. When applied to a complete circuit, the model accurately predicts performances at various back-gate voltages and temperatures, achieving less than 1 % average absolute error. This validates the presented analytical approach, even under the stringent requirements of low-temperature operation, paving the way to exploiting rather than enduring cryogenic temperature effects on CMOS designs.