A low-latency, HDL-synthesizable dynamic clock frequency controller is presented as a time-efficient alternative to full-custom implementations. Frequency division of a fully integrated hybrid temperature-compensated LC oscillator (TC-LCO) and ring oscillator clock reference avoids PLL locking delays to enable low-latency, hazard-free frequency selection on an actively running CPU. Fabricated in 0.18mum CMOS as part of a low-power SoC microsystem, the circuit dissipates 480muW at 1.8V