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Matsuzawa& Okada Lab.

Matsuzawa& Okada Lab.

A Fully Synthesized Fractional-NIL-PLL Using Only Digital Library

Dongsheng Yang, Wei Deng, Kengo Nakata,Teerachot Siriburanon, Kenichi Okada, and Akira Matsuzawa

Tokyo Institute of Technology, JapanIEICE General Conference 2016

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Matsuzawa& Okada Lab.

Outline

• Motivation• Concept of Injection Locking• Fractional-N Implementations• Performance Comparison• Conclusion

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Matsuzawa& Okada Lab.

Motivation

[1] W. Deng, et al., ISSCC2014

• Why High Performance PLL– Clock generation/distribution

• Key Specifications for SoC Clocking– Small area– Low power consumption– Low jitter– Insensitive over environment variations– Scalable with technology advancement

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Matsuzawa& Okada Lab.

Injection Locking Technique

JitterTDC-PLL=6.4ps JitterIL-PLL=1.5ps

Frequency Offset [Hz]

Phas

e N

oise

[dB

c/Hz

]

10M 100M1M100k

-70

-90

-110

-130IL-PLL

TDC-PLL

Free-running oscillator

BW=2MHz

BW=40MHz

𝒇𝒇𝐢𝐢𝐢𝐢𝐢𝐢 =⁄𝟔𝟔 (𝑵𝑵(𝑵𝑵− 𝟏𝟏))

𝟐𝟐𝝅𝝅· 𝒇𝒇𝐫𝐫𝐫𝐫𝐫𝐫

REF Injection locked

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Integer-N Operation

Reference

VCO

Reference

D D D D...

e.g. N=3

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Sub-Integer-N Operation

[P. Park, et al., ISSCC 2012]

Reference

D D D D...

...

P0 P1 P2

e.g. N=3+(1/M)

Reference

VCO

P0

P1

P2...

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Matsuzawa& Okada Lab.

Time Domain (Fractional-N)

• Injection at the same phase two times

Reference

VCOP1

P2

... ...

[2] W. Deng, et al., ISSCC2015

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Phase Domain (Fractional-N)

P0 P0 P1 P1 P2 P2 P3 …

fPLL=(N+0.5/M)·fref

N·2π

2·Tref 3·TrefTref 4·Tref 5·Tref

φPLL

t

(2·N+1/M)·2π

(3·N+1/M)·2π

(4·N+2/M)·2π

P0

P1

P1

P2

P0

[2] W. Deng, et al., ISSCC2015

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Fractional-N Controller

DSM

FCW

Deglitching

Mapping

SubIntegerDither

MDLL

Retimer

REFGating Array

[2] W. Deng, et al., ISSCC2015

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Matsuzawa& Okada Lab.

Design Procedure

Verilog netlist(gate-level)

Verilog RTL

Verilog netlist(gate-level)

DCO DAC

Logic

Logic

Logic Synt. Tool

GDSII

P&R Tool

Netlist

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Chip Microphotograph

CMOS 65nm technology

275µm

175µ

m

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Comp. of State-of-art PLLs

This work [1] [4] [5]

CMOS 65nm 65nm 65nm 65nm

TopologySoft

Injectionlocking

Injection locking

DTC-basedMDLL

Injection locking

Type Frac-N Int-N Frac-N Sub-Int-NFrequency

[GHz] 0.8-1.7 0.39-1.41 1.6-1.9 0.25-1.65

Power[mW]

3@1.5222GHz

0.78@0.9GHz

3@1.7GHz

10.5@0.58GHz

FoM[dB] -224.2 -236.5 -232 -221.9

Synthesizable ? Yes No

*FOM is calculated based on RMS jitter.

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Conclusion

• A fully synthesizable fractional-N IL-PLL is presented.

• Only digital library is used in the whole design.

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Matsuzawa& Okada Lab.

Thank you for your attentionQ & A