We present a spread spectrum clock generator for EMI reduction, where the modulating signal is generated by a suitably designed chaotic map. With respect to past solutions, the map has been designed to achieve a specific short-term behavior of the generated sequences, which allows to optimize the electromagnetic interference peak reduction not only for the theoretical spectrum, but also in the measurement setting prescibed by CISPR norms. In the latter case, we are able to achieve a 3.8dB improvement in EMI reduction with respect to the triangular modulation when using the peak detector, which increases to 6.9 dB when switching to the quasi-peak detector. Results are measured on a prototype which has been designed and fabricated in a 0.18 μm CMOS technology. © 2011 IEEE.