A Sub-0.75RMS-Phase-Error Differentially-Tuned Fractional-M Synthesizer with On-Chip LDO Regulator and Analog-Enhanced AFC Technique Lei Lu,Lingbu Meng,Liang Zou, Hao Min and Zhangwen Tang Fudan University,Shanghai,China
A Sub-0.75°RMS-Phase-Error Differentially-Tuned Fractional-N Synthesizer with On-Chip LDO Regulator and Analog-Enhanced AFC Technique Lei Lu, Lingbu Meng, Liang Zou, Hao Min and Zhangwen Tang Fudan University, Shanghai, China
Outline 。Motivation ·System Architecture Level Shifter for Symmetrical Tuning Curves High-PSR LDO Regulator Digital AFC with Monitor 。Measured Results 。Conclusions 2
2 Outline • Motivation • System Architecture • Level Shifter for Symmetrical Tuning Curves • High-PSR LDO Regulator • Digital AFC with Monitor • Measured Results • Conclusions
Motivation Symmetrical tuning curves Level Shifters eliminate threshold voltage Large noise from power supply deteriorates VCO severely High-PSR LDO Regulator Frequency drift due to temperature variation Control Voltage monitor to restart AFC 3
3 Motivation • Symmetrical tuning curves – Level Shifters eliminate threshold voltage • Large noise from power supply deteriorates VCO severely – High-PSR LDO Regulator • Frequency drift due to temperature variation – Control Voltage monitor to restart AFC
Single-Ended Tuned Synthesizer ZF(s) Kvco=△fvcol△Ve PFD Charge Pump Filter Divider DSM IcpZF(S)Kvco open-loop gain三 2TTN Advantage:Single-ended CP and VCO Disadvantage:Susceptible to CM noise, large LPF area
4 Single-Ended Tuned Synthesizer • Advantage: Single-ended CP and VCO • Disadvantage: Susceptible to CM noise, large LPF area Divider PFD Charge Pump DSM fref fvco Icp Kvco =Δ fvco/Δ Vc Loop Vc Filter Z F(s) N 2 π N open-loop gain Icp Z F(s) Kvco VCO
Differentially Tuned Synthesizer 0.5lcp ZF(s) Loop KvCo=AfvCoA(Vcp-Vcn) Charge Filter cp PFD Pump cn Filter -0.5Icp Divider DSM open-loop gain I0.51cp（-0.5p】☑(s)Kvco 2TTN Advantage:Immune to CM noise,small LPF area (differential LPF) Disadvantage:differential CP and VCO 5
5 Differentially Tuned Synthesizer Kvco = Δ fvco/Δ ( Vcp – Vcn ) Divider PFD Charge Pump DSM fref fvco Vcp Z F(s) N Loop Filter Loop Filter Vcn 0.5 Icp –0.5 Icp Z F(s) [0.5 Icp–(–0.5 Icp)] ZF(s) Kvco 2 π N open-loop gain VCO • Advantage: Immune to CM noise, small LPF area (differential LPF) • Disadvantage: differential CP and VCO