We present a two-stage cascaded clock multiplier with roughly constant energy consumption across 2.5-5.0GHz frequency range. The proposed clock multiplier consists of a reconfigurable delay-locked loop and edge combiner in the first stage while generating a 156.25-312.5MHz clock from 39.0625MHz reference clock frequency. An injection-locked clock multiplier with a frequency tracking loop in the second stage implements a 2.5-5.0 GHz output clock. The clock generation architecture is optimized for the clock multiplication ratio in the two stages and overall power consumption. Designed in TSMC 65nm CMOS process and characterized with post-layout simulations, the first-stage clock multiplier achieves an integrated jitter 1.396-0.607ps _{rms} across 156.25-312.5MHz frequency range at 1.15-2.82mW power consumption. The two-stage clock multiplier gives the total output jitter 1.5-0.9ps _{rms} across 2.5-5.0 GHz output frequency with 0.98-1.06mW/GHz power dissipation. © 2004-2012 IEEE.