High-Speed Serial InterfaceCircuits and Systems

Project1 –

Phase-Locked Loop (PLL)

High-Speed Circuits and Systems Lab., Yonsei University

Goals

High-Speed Circuits and Systems Lab., Yonsei University2

PFDLoop

Filter

LC VCO

Divider

(÷16)

Charge

Pump

Ref.

clockOutput

clock

Schematic designed

Full PLL simulation-PFD, Divider: Verilog-A model-Charge pump, Loop filter, VCO: schematic model

Loop bandwidth optimization-Low-jitter PLL can be achieved

Copy Verilog-A Models

Account> cd TSMC180nm

Account> cd [저장할디렉토리] ex)cd tsmc18rf

Account> cp ~/../PFD ./ -rf

Account> cp ~/../Divider ./ -rf

File Refresh

High-Speed Circuits and Systems Lab., Yonsei University3

Verilog-A Models

PFD(Phase Frequency Detector)-vin_if: reference clock-vin_lo: feedback clock-sigout_inc: 𝑈𝑃-sigout_dec: Down

ref) www.designers-guide.org

Divider-in: input clock-o: output clock-Threshold: 1.75V-Output swing: 0~1.8V

High-Speed Circuits and Systems Lab., Yonsei University4

PLL TOP Schematic

Ref. clock-1.8V swing

(0.9V offset)

-93.75MHz frequency

Charge-Pump-200uA current

(as designed before)

-0.9V bias

Loop filter-R=6k Ohm

-C1=200 pF

-C2=13 pF

LC VCO-1.5GHz target

(as designed before)

-0.8V bias

High-Speed Circuits and Systems Lab., Yonsei University5

Reference ClockNoise-Freq1(Hz)

Noise BW

:10G

-Noise1(V2/Hz)

Noise Magnitude

:1f

Frequency-0.9V offset

-1.8V swing

-93.75MHz

White noise f

PSD

(V2/Hz)

fnoise

Noise

BW

Noise

Magnitude

High-Speed Circuits and Systems Lab., Yonsei University6

Bias & Terminal

LC VCO(Differential output)

-Add Instance basics

noConnPlace

Bias

-Charge pump bias: 0.9V-VCO bias: 0.8V

VDD Pulse

(0V -> 1.8V)

High-Speed Circuits and Systems Lab., Yonsei University7

Simulation Setup (Transient)Time: 20us

Accuracy: conservative(mandatory!!)

Transient noise

-Noise Fmax: 10G

-Noise Fmin: 1K

-Noise Seed:1

-Noise Scale:1

-Noise Tmin:1/Fmax=100p

-Noise Update: fmax

Noise Contribution: on

-Input sine source

-LC VCO

Initial Condition

-Vcont(0V) Step-response

High-Speed Circuits and Systems Lab., Yonsei University8

Simulation Result

Vcont

Vout

Output Frequency

High-Speed Circuits and Systems Lab., Yonsei University9

Eye Diagram

Eye Diagram

High-Speed Circuits and Systems Lab., Yonsei University10

Jitter

Period jitter: ∆ = 𝑇0 − 𝑡𝑖+1′ − 𝑡𝑖

′

Cycle-to-cycle jitter: ∆ = (𝑡𝑖+2′ − 𝑡𝑖+1

′ ) − (𝑡𝑖+1′ − 𝑡𝑖

′)

Absolute jitter: ∆ = 𝑡𝑖 − 𝑡𝑖′ Commonly used

Phase noise

(Frequency domain)

Jitter

(Time domain)

. . .timet0 t1 t2 t3 ti-1 ti

T0

. . .timet0

't1

't2

't3

'ti-1

'ti

'

High-Speed Circuits and Systems Lab., Yonsei University11

Loop BW Optimization

Low-pass Filtered High-pass Filtered

Wider BWWider BW

High-Speed Circuits and Systems Lab., Yonsei University12

Jitter Measurement (Jabs)

Clip wave from 15us to 20us Calculate jitter with given period

Absolute Jitter

(From 15us to 20us)Peak-to-peak jitter

-calculator

(peakToPeak)

:767.3fs

RMS jitter

-calculator

(rms)

:310.8fs(0.4 mUI)

High-Speed Circuits and Systems Lab., Yonsei University13

Project

Design 2.5GHz PLL with LC VCO(Input reference noise: 1f V2/Hz PSD, 10GHz BW)

Use schematic level circuits for CP, LF, VCO and Verilog-A models for PFD, Divider-Design each block for better performance(schematic level circuits)

-Recommend to set C2 as C1/15

Show schematic(size), Vcont(transient result), output clock, eye diagram, rms jitter

(minimum 5us interval).

Explain how you come up with your circuit design and loop filter design.

Compare and analyze the step-response of theoretical second-order system(approximation)

and simulation result with your design parameters(ICP, KVCO, R & C).

Due date: 1 Nov. in class

PFD

LC VCO

Divider

(÷16)

Charge

Pump

Ref.

clock

(156.125MHz)

Output

clock

(2.5GHz)

Loop

Filter

R1

C1

C2

Vcont

High-Speed Circuits and Systems Lab., Yonsei University14