A 0.35-V 240-μW Fast-Lock and Low-Phase-Noise Frequency Synthesizer for Implantable Biomedical Applications

Chung Chih Hung*, Shih Hsing Wang

*Corresponding author for this work

Research output: Chapter in Book/Report/Conference proceedingChapterpeer-review


For implantable frequency synthesizers, realizing ultra-low voltage (ULV) and low power in addition to meeting PLL targets, fast lock and low phase noise, poses a difficult challenge. This chapter presents techniques to achieve PLL targets as well as ULV and low power in the same chip through the use of a regular CMOS technology node. A curvature-PFD technique achieves both faster locking and lower jitter compared with conventional techniques. A two-step switching technique substantially reduces the power consumption in current mirrors and reduce noise when switching from a charge pump. Leakage analysis and subthreshold-leakage-reduction technique reduce reference spur and jitter to the voltage-controlled oscillator (VCO). A dither technique randomizes and averages reference spurs. The proposed chip was implemented in 90-nm CMOS technology; the 0.35-V medical-band frequency synthesizer consumes 238-μW power while generating output clock of 401.8–431.31-MHz and exhibiting a phase noise of −105.7 dBc/Hz at 1-MHz frequency offset with 20 μs locking time.

Original languageEnglish
Title of host publicationAnalog Circuits and Signal Processing
Number of pages26
StatePublished - 2022

Publication series

NameAnalog Circuits and Signal Processing
ISSN (Print)1872-082X
ISSN (Electronic)2197-1854


  • Curvature-PFD (CPFD)
  • Dead zone
  • Dither technique
  • Dynamic power
  • Fractional-N
  • Implantable applications
  • Implantable medical device
  • Leakage mechanisms
  • Leakage reduction
  • Loop filter
  • Low power
  • Medical device radio communication service (MedRadio)
  • MedRadio
  • MICS (Medical Implant Communication Service)
  • Phase noise
  • PLL
  • Reference spur
  • Ring oscillator (RO)
  • SoC (system on chip)
  • Two-step switching (TSS)
  • Ultra-low voltage
  • Ultra-low-power electronics
  • Voltage-controlled oscillator (VCO)


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