An ultra low power and small size PLL for wearable and implantable medical sensors

Low-power, low-phase noise and small size PLL is a critical component in wearable and implantable medical sensors. A new ultra-low power, low-phase noise and small size ring VCO on 65 nm IBM CMOS technology for use in PLL is introduced in this paper. This VCO operates in the Medical Implant Communication Service (MICS) frequency band. This ring oscillator VCO doesn't need external inductor and capacitor like other LC oscillators and so requires very small die area. This VCO has two voltage control points. First control point has a wide tuning range from 350 MHz to 450 MHz for the coarse tuning and frequency correction account for process supply voltage and temperature effects. This point has a KVCO and large tuning range but would have higher sensitivity and phase noise for fine tuning as part of a PLL. To decrease the phase noise in fine tuning, another control point is added. The second control point has a narrow tuning range from 399 MHz to 416 MHz for fine tuning within the MICS band frequency. The simulated phase noise of this VCO is -105 dBc/Hz at 1 MHz offset and -91 dBc/Hz at 300 kHz offset from a 400 MHz center frequency. The power consumption of the VCO is 196 micro watt.