A Design of 0.7-V 400-MHz Digitally-Controlled Oscillator

We present a low-voltage digitally-controlled oscillator (DCO) with the third-order Delta Sigma modulator utilized in the medical implant communication service (MICS) frequency band. An optimized DCO core operating in the subthreshold region is designed, based on the g(m)/I-D methodology. Thermometer coder with the dynamic element matching and Delta Sigma modulator are implemented for the frequency tuning. High frequency resolution is achieved by using the Delta Sigma modulator. The Delta Sigma-modulator-based LC-DCO implemented in a 130-nm CMOS technology has achieved the phase noise of -115.3 dBc/Hz at 200 kHz offset frequency with the tuning range of 382 MHz to 412 MHz for the MICS band. It consumes 700 mu W from a 0.7-V supply voltage and has a high frequency resolution of 18 kHz.