1 A Frequency Synthesizer Using Two Different Delay Feedbacks 班級：積體所碩一 學生：林欣緯 指導教授：林志明 教授 Circuits and Systems, ISCAS IEEE International Symposium on May 2005 page(s): Vol. 3

2 Outline Introduction Architecture Circuit Implementation Simulation Results Conclusion

3 Introduction The large dead zone induced by the PFD, it causes the phase error accumulation at the VCO output. The jitter evoked by the inevitable 1/f and white noise of the circuits, it forces VCO to contribute phase noise toward the output. The clock feedthrough and charge injection motivated by CP switches, it results in the abrupt vibrations on the VCO control line and their corresponding clock jitter even when the loop is locked.

4 Two PFDs with separate dead zones

5 Conventional PLL architecture second-order low-pass filter

6 The proposed PLL architecture with double PFDs scheme

7 The operations of the proposed PLL architecture

8 The schematics of the delay cell PMOS input differential pair cross-coupled feedbacks current source diode-connected transistors

9 The schematics of the ring oscillator

10 The schematic of three-state PFD with delay buffers discard the spurs

11 Charge pump circuit & Switch

12 The schematic of the TSPC divider TSPC True Single Phase Clock 1. simple of structure 2. small dead zone

13 Simulation results when Δt = 90ps

14 Simulation results when Δt = 30ps

15 Simulation results for the ring oscillator

16 Transient responses of the PLLs settling time < 22 μ s

17 The chip layout

18 Performace summary of the proposed PLL

19 Conclusion A fully differential delay cell for the VCO is introduced to achieve wide locking range and low-jitter performance. Two PFDs are combined to provide a less dead zone with a new phase-detecting approach and a less settling time. A tunable delay element is used to suppress the ripple on the VCO control line, and hence a more accurate output clock can be resulted.