A Wide Frequency PLL-less Clock Generator with Fast Intermittent Operation for Low-Power Wearable Medical Applications

A Wide Frequency PLL-less Clock Generator with Fast Intermittent Operation is presented in this paper to replace both the external frequency reference and PLL combination used in current wearable medical devices. The system uses one loop to stabilize the amplitude and the other to stabilize the slope of a saw-tooth signal to generate stable frequency over a wide range. Measurement results from a chip fabricated in 180nm CMOS process gives a linear frequency range of 0.1MHz-10MHz and 7us settling time without using a PLL. The total power consumption is 360uW that includes output buffers and external current sources with ±0.84% variation in frequency from 0-70 degrees. Using the proposed system as a clock generator for microcontrollers used in current wearable medical devices, would result in a one or more order of magnitude reduction in power consumption.