the race to replace quartz - electrical engineering and...

The Race to Replace Quartz

Michael S. McCorquodale, Ph.D.Founder and Chief Technical Officer, Mobius Microsystems, Inc.

University of Michigan, WIMS ERC Seminar Series12:00PM ET April 5, 2007

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Overview

• Quartz applications and specifications• Why replace quartz? Why not?• Emerging technologies

– Si MEMS– FBAR– High-Accuracy Ceramic– RF-TCHO™: Mobius Microsystems

• Measured performance data• RF-TCHO™ technology

– Motivation– Architecture

• ConclusionsQuartz apps. Why? Why not? Emerging Tech. Measurements RF-TCHO Conclusions

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Quartz Applications and Specifications

Quartz apps. Why? Why not? Emerging Tech. Measurements RF-TCHO Conclusions

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Quartz Applications and Specifications

TimingEvery synchronous semiconductor component requires a clock to operate

Carrier synthesisRF systems require precision frequency references for carrier frequency synthesis

Belkin Bluetooth/LANUSB Print Server

• USB XTAL clock reference• Ethernet XTAL clock reference• Processor XTAL clock reference• Bluetooth radio XTAL reference (on flip side)


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Most Relevant Metrics• Frequency and time domain performance

– Short-term frequency stability: Jitter and phase noise– Total frequency accuracy: Accuracy and precision over

• Manufacturing process (P)• Drift over voltage (V) • Drift over temperature (T)• Long-term stability or aging (A)

– Start-up latency, rise/fall time, etc.• Environmental performance

– Sensitivity to microphonics– Storage lifetime/degradation

• Cost– Fabrication process technology– Production trimming requirements– Packaging requirements


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The “Show-Stopper” Metrics for New non-Quartz Technologies

• Accuracy and stability are most significant– Nearly all timing and frequency generation

standards have accuracy and stability requirements

• Other deficiencies may be addressable once sufficient accuracy and stability are demonstrated

• Other benefits may encourage adoption– Reliability– Form factor– Cost


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Common Interface Protocol Reference Frequency and Accuracy Requirements

• Protocol (Application): Rate ± Required Accuracy– CAN/LinBus (Auto): ~kHz ±1500ppm – ±15kppm – USB 2.0 (PC and CE): 12/48MHz ±500ppm– SATA Gen. 1 – Gen. 3 (HDD): 25MHz ±350ppm– PCI/PCIe (PC): 33/66MHz ±300ppm– Embedded µP (PC): ~100MHz ±100 – ±300ppm– Firewire/IEEE1394 (PC and CE): 49.152MHz ±100ppm– Ethernet (Data comm.): 50MHz ±25ppm

• Observations– Most reference frequencies < 100MHz

• Due to power on PCB• Fundamental physical limit to XTAL frequency based on geometry

– Most accuracy requirements > ±100ppmQuartz apps. Why? Why not? Emerging Tech. Measurements RF-TCHO Conclusions

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Observations

• What accuracy does quartz really provide?– ~±50ppm initial error– ~±15ppm insertion error– ~±15ppm TC– ~±10ppm synthesis error– ~±10ppm aging for 5 yrs.

• Total ~±100ppm• Higher accuracy requires expensive TCXO• Not a surprise that most interface protocols

for CE are less accurate than ±100ppmQuartz apps. Why? Why not? Emerging Tech. Measurements RF-TCHO Conclusions

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Common Radio Reference Frequencies and Accuracy Requirements

• Protocol (Application): Freq. ± Required Accuracy– Bluetooth, Zigbee (Network radios): 20MHz ±25ppm– GSM, etc. (Cellular radios): 13MHz ±5ppm– ASK TPMS (Auto): 9.838MHz ±238ppm

• Observations– Most reference frequencies <20MHz– Most accuracy requirements <±25ppm

• Carrier spacing w/ adjacent channels: accuracy must be high• Carrier spacing w/o adjacent channels: accuracy relaxed

• General Observations– Clock/timing generation: >±100ppm at <100MHz– Carrier synthesis: <±25ppm at <50MHz


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Why Replace Quartz? Why not?


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Why replace quartz?

• Benefits to eliminating XTALs/XOs in systems– Reduced cost– Reduced form factor and PCB footprint– Reduced time to market– Reduced start-up latency (possibly)– Reduced EMI (possibly)– Increased reliability– Increased integration (opportunity for multiple instances)

• Quartz is one of the last great hold-outs for microelectronic integration


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Why not?

• Quartz is robust and relatively cheap– Simple and proven “no brainer” technology– Historical traction (original XO from 1927)– Economies of scale with handsets continues to

drive cost down to <$0.15/unit– Supply chain reliability– Volume manufacturability

• The winner of the race will need to contend with these formidable barriers to entry


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Emerging Technologies


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Surface Micromachined Si MEMS• Capacitively-coupled µresonators

– Surface micromachined poly-Si structures with capacitive actuation

• Benefits– Very high-Q (>10,000) demonstrated– Likely low-power due to high-Q

• Challenges– High motional impedance (>kΩ)– Nonlinear transduction causes flicker noise

upconversion in oscillator circuits– Power handling limits– Specialized packaging required– Process difficult to integrate with CMOS– Frequency trimming required– Moderate temperature coefficient– Aging (material fatigue)– Microphonic sensitivity may be high

• Status– Samples available from Discera

Clamped-clamped beam poly-Si microresonator[Nguyen, McCorquodale, et al.]

Disk poly-Si microresonator [Nguyen, et al.]


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Surface Micromachined Si MEMS

• Piezoelectrically-coupled µresonators– ZnO film couples actuation to surface

micromachined poly-Si beam– Remainder of device identical to previous

microresonator• Benefits

– Much lower motional resistance than previous µresonator (~100Ω)

– Same as remaining benefits for previous µesonators

• Challenges– Same as remaining challenges for previous µresonators

• Status– Research area– No commercialization effort yet

Tuning Capacitor

Handle Layer

Oxide

Device Layer

ZnO Film

Sense Electrode

Drive Electrode

Piezoelectric microresonator [Ayazi, et al.]


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Bulk Micromachined Si MEMS• Capacitively-coupled microresonators

– Bulk micromachined Si structures with capacitive actuation

• Benefits– Bulk technology enables hermetic

packaging under CMOS– Same as remaining benefits for previous µresonators

• Challenges– No CMOS over MEMS area (cost)– Same as remaining challenges for

previous µresonators• Status

– Samples available from SiTime– Limited volume production– CMOS over MEMS still not in production

Bulk microresonator [SiTime]

Stacked die assembly [SiTime]Quartz apps. Why? Why not? Emerging Tech. Measurements RF-TCHO Conclusions

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Film Bulk Acoustic Wave Resonators (FBAR)

• Piezoelectric FBAR– Similar to a quartz XTAL, but a film of piezoelectric

material over a Si substrate• Benefits

– High-Q– Very low motional impedance– No specialized packaging required

• Challenges– Some challenges to integrate with CMOS– Low accuracy because film thickness sets frequency

• Status– Now in high-volume production at Agilent for filter

products (>400MU/yr.)– Some research oscillator work with VCOs (Berkeley),

but not reference oscillators

Drive Electrode

Thin Piezoelectric

Film

FBAR [Ruby, et al.]

Sense Electrode


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High-Accuracy Ceramic Resonators

• High-Accuracy Ceramic Resonator– Ceramic, as opposed to quartz, resonators

• Benefits– Cheaper than Quartz– More reliable than quartz, particularly at high-T– Very common in automotive for CAN/LinBus

• Challenges– Initial accuracy and aging compromise total frequency

accuracy– TC also compromises total frequency accuracy– Only cost benefit over quartz – still a macroscopic device

• Status– ±500ppm samples available from Murata though aging

likely puts part out of spec. – typical closer to ±3kppm– Target application is HS-USB – making ceramic a true

quartz replacement tech. if ±500ppm can be achievedQuartz apps. Why? Why not? Emerging Tech. Measurements RF-TCHO Conclusions

Ceramic Resonators [Murata]

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Radio Frequency Temperature-Compensated Harmonic Oscillator (RF-TCHO™)

• RF-TCHO™– All-CMOS temperature compensated

harmonic (LC) reference oscillator• Benefits

– All CMOS (lowest cost, size, etc.)– Trivial to integrate with host– Suitable for harsh environments– Already achieves sufficient accuracy

• Challenges– Production frequency trimming– Achieving <100ppm accuracy– Power dissipation higher in some apps.

• Status– In volume production as IP for USB from

Mobius Microsystems– Component samples available in Q1 ’07

from Mobius Microsystems 12MHz USB Macro [McCorquodale, et al.]


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Measured Performance Data


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Performance Data

• Measured performance for– CTS 24MHz quartz can oscillator– Ecliptek (SiTime) 25MHz Si MEMS oscillator– Abracon 12MHz ceramic oscillator – Mobius 12MHz RF-TCHO™

• Measured parameters– Total frequency accuracy– RMS period jitter– Phase noise at 10k/100k/1MHz offset from carrier– Power dissipation


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CTS 24MHz Quartz Resonator

• Technology and Architecture– CTS AT-cut quartz crystal– Mated to CMOS reference oscillator in can

• Performance– Measured accuracy: ~±10ppm– Measured RMS period jitter: 8.19ps– Measured phase noise (@10k/100k/1M):

-102/-124/-140dBc/Hz


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CTS 24MHz Quartz Resonator: Accuracy


Frequency Error of AT-Cut XO

-6

-4

-2

0

2

4

6

8

0 10 20 30 40 50 60 70 80

Temperature (°C)

Freq

uenc

y Er

ror

(ppm

)

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CTS 24MHz Quartz Resonator: Period Jitter


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CTS 24MHz Quartz Resonator: Phase Noise


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Ecliptek 25MHz Si MEMS Oscillator

• Technology and Architecture– Bulk micromachined Si MEMS resonator

stacked and bonded on CMOS (SiTime)– Low frequency µresonator + Σ∆-Ring-PLL

• Performance– Measured accuracy: ±25ppm– Measured RMS period jitter: 17.69ps– Measured phase noise (@10k/100k/1M):

-75/-85/-117dBc/Hz


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Ecliptek 25MHz Si MEMS Oscillator: Accuracy


Frequency Error of Si MEMS Oscillator

-25

-20

-15

-10

-5

00 10 20 30 40 50 60 70 80

Temperature (°C)

Freq

uenc

y Er

ror (

ppm

)

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Ecliptek 25MHz Si MEMS Oscillator: Period Jitter


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Ecliptek 25MHz Si MEMS Oscillator: Phase Noise


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Abracon 12MHz Ceramic Resonator

• Technology and Architecture– Ceramic resonator– Mated with Cypress CMOS reference oscillator

• Performance– Measured accuracy: ~±3200ppm– Measured RMS period jitter: 8.96ps– Measured phase noise (@10k/100k/1M):

-110/-129/-130


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Abracon 12MHz Ceramic Resonator: Accuracy


Frequency Error of Ceramic Resonator

-3000

-2000

-1000

0

1000

2000

3000

4000

0 10 20 30 40 50 60 70 80

Temperature (°C)

Freq

uenc

y Er

ror

(ppm

)

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Abracon 12MHz Ceramic Resonator: Period Jitter


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Abracon 12MHz Ceramic Resonator: Phase Noise


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Mobius 12MHz RF-TCHO™

• Technology and Architecture– All-CMOS– RF temperature compensated harmonic (LC)

oscillator• Performance

– Measured accuracy: ±225ppm– Measured RMS period jitter: 7.98ps– Measured phase noise (@10k/100k/1M):

-96/-124/-141dBc/Hz


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Mobius 12MHz RF-TCHO™: Accuracy


Frequency Error of RF-TCHO

-250

-200

-150

-100

-50

0

50

100

150

200

250

0 10 20 30 40 50 60 70 80

Temperature (°C)

Freq

uenc

y Er

ror (

ppm

)

Nominal VDD VDD-10% VDD+10%

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Mobius 12MHz RF-TCHO™: Period Jitter


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Mobius 12MHz RF-TCHO™: Phase Noise


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Performance Comparison

[email protected]@[email protected]@3.3Power (mA@V)

8.19

-102/-124/-140

~±10

24MHzXO

8.96

-110/-129/-130

~±3200

12MHzCeramic

7.9817.69RMS period jitter (ps)

-96/-124/-141-75/-85/-117

SSB phase noise PSD

@10k/100k/1M (dBc/Hz)

~±225~±25Total accuracy(ppm)

12MHzRF-TCHO™

25MHzSi MEMSVariable/Metric


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8.19

-102/-124/-140

~±10

24MHzXO

8.96

-110/-129/-130

~±3200

12MHzCeramic


-96/-124/-141-75/-85/-117

SSB phase noise PSD

@10k/100k/1M (dBc/Hz)


12MHzRF-TCHO™



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Thoughts on Measured Data

• Quartz is lower power because signal is directly synthesized (no PLL)

• Si MEMS– Phase noise is high due to high loop multiplication

factor (low frequency µresonator) and Ring-PLL– Power is higher due to PLL and TC architecture

• RF-TCHO™– Phase noise and jitter are competitive with

quartz/ceramic – how does it work?– Power is higher, though competitive – why?– Accuracy is sufficient for most clock applications


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RF-TCHO™ Technology


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System Observations

• Current XTAL-replacement work focuses too heavily on component-Q– Component-Q is compromised by frequency multiplication– Component-Q only affects reference oscillator performance– Component-Q is only loosely related to jitter– High component-Q increases start-up latency– However, high component-Q may imply lower power, though that

lower power may be lost in PLL• Should consider metrics relevant to the output signal, not

the reference signal or reference device– Jitter (period, cycle-to-cycle, long-term)– Phase noise– Frequency accuracy/precision – Start-up latency– Reliability


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System Observations

dtdφ

=ω

Phase and frequency are related by a linear operator

Frequency mult./div. results in phase noise mult./div.:

))(cos()( ttVtv noon φ+ω= ))(cos()(, tNtNVtv noomultn φ+ω=

Using narrowband FM approximation:

)log( 2

./.,

NPN

PN

mm fo

o

divmultfo

o ±⎟⎟⎠

⎞⎜⎜⎝

⎛=⎟⎟

⎠

⎞⎜⎜⎝

⎛

Linear freq. trans. results in quadratic change in noise power


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System Observations

• The relationship between phase noise and period jitter (σRMS)– ωo = fundamental radian frequency– To = fundamental period– fm = offset frequency from fundamental– Sφ(fm)= phase noise at offset fm from fundamental

• Key observations– Phase noise is masked by a trigonometric function with period To/2– Far-from-carrier phase noise contributes significantly to σRMS

( )∫∞

φ πω

=σ0

22 sin8

mommo

RMS dfTffS


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Pha

se n

oise

PS

D (d

Bc/

Hz)

System Observations

• Component-Q of the reference is degraded by frequency multiplication

• Frequency division can enhance a low component-Q reference

• Can introduce the concept of an “effective” Q or an “output” Q which accounts for frequency translationfm (Hz)

+20log10(N)

×NReference ÷N

-20log10(N)

Decrease noisewith freq. division


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Pha

se n

oise

PS

D (d

Bc/

Hz)

fm (Hz)

System Observations

• Reference signal component-Q matters only within the PLL loop BW

• The ring VCO has high far-from-carrier phase noise so jitter is high

• Remember:

PLL ring VCO (unlocked)

XOreference

Period jitter integration mask+20log10(N)

PLLoutputpath

PLLloop BW


( )∫∞

φ πω

=σ0

22 sin8

mommo

RMS dfTffS

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System Observations Summary

• Frequency div./mult. can improve/degrade “signal-Q” of output signal– PLLs with high loop multiplication factors have severely degraded

jitter, despite the high component-Q reference– LCOs have low component-Q but division can improve signal-Q

• Far-from-carrier phase noise is a significant contributor to jitter– Far-from-carrier phase noise in ring PLLs is very high– LC-VCOs have low far-from-carrier phase noise– In an LC-PLL, low jitter performance originates from the

LC-VCO, not the high component-Q reference• Component-Q of the reference is marginally important to relevant metrics

– Effects above dominate signal integrity– These effects can be exploited to introduce RF-TCHO– Still implies low power, though must add power of PLL


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RF-TCHO™ Architecture

• Architectural concept– Free-run an LCO at RF and compensate for

temperature, bias, etc. – Frequency-divide by a large ratio– Architecture ensures low jitter, low phase noise– Architecture enables low start-up latency

• Challenges– Initial frequency accuracy– Maintaining frequency accuracy via compensation for

bias and temperature variation as well as aging– Maintaining low power


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RF-TCHO™ Architecture

Signal Conditioning

Output

LCSustaining Amp.Bias Stability

Temp. Comp.

Process Comp.

Freq. Division Output


Digital ControlProduction Trimming Logic

RF-TCHO Reference oscillator

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Reference Oscillator

-gm

+ _

+_v+

_

Transconductanceamplifier + I(T) bias

I(T)generation

RL

L Cf

RC

Resonant tank, LC

vctrl(T)generation

fo(T) compensation module, Cv+f(T)

Cv+f(vctrl)

Cv+f(vctrl)

Process variation comp. module, Cf(bp-1,…,b0)

Resonantfrequencycorrection, Cf(bp-1,…,b0)

bp-1,…,b0generation

Automatic frequency calibration macro

fref


On tester load board

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Resonant Tank, LC

LTCR

LTCRLTCRT L

oC

Lo

2

2

2

1)(1

)()()( −ω≅−−

ω=ω

• Due to the parasitic RL & RC present in a monolithic implementation:

• RL(T) & RC(T) cause a temp. induced frequency drift:

• Where: • Temperature drift is highly linear and

dominated by coil loss

RL

L C

RC LC1

≠ω

LCo 1=ω


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• Complementary cross-coupled –gmamplifier

• pMOS tail to minimize flicker noise upconversion

• Cascode to minimize bias sensitivity

4nH

vctrl(T)

R

+vout -vout

MRn

MRp

R

½Cf ½Cf

Cv(vctrl) Cv(vctrl)Ibias

VDD

x

x

11x

11x


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Transconductance Amplifier + I(T) Bias

RL

L Cf

RC

Resonant tank, LC

-gm

+ _

+_v+

_


I(T)generation


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Transconductance Amplifier

⎟⎟⎠

⎞⎜⎜⎝

⎛−

−ω=ω ∑∞

=2

2)(2

2

21 1211

nnio h

nn

Q

• Sustains oscillation by injecting energy (current) into the resonant tank

• Causes harmonic work imbalance which leads to frequency drift

• Frequency drift due to harmonic work imbalance function of normalized Fourier coefficients hi(n) of current waveform

• Note, as Q → ∞, drift due to harmonic work imbalance approaches 0

1 1.5 2 2.5 3 3.5 4-15

-10

-5

0

5

10

15

t (ns)

i C(t)

(mA

)

1 1.5 2 2.5 3 3.5 4-600

-400

-200

0

200

400

600

v C(t)

(mV

)

gm-amp injects current onto net capacitance

Waveform is distorted


voltagecurrent

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Frequency Drift Mechanisms

• PVTA frequency drift originates from– Initial inaccuracy due to process variation (P)– Harmonic work imbalance due to bias changes (V)– TC due to coil loss (T)– Aging due to package and common mode variation

from hot carrier and tunneling effects (A) – not discussed in this seminar (but terribly interesting)

• To achieve desired accuracy, must develop analog open-loop compensation circuitry


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Temp. Comp., Cv+f(T)

-gm

+ _

+_v+

_


I(T)generation

RL

L Cf

RC

Resonant tank, LC

vctrl(T)generation


Cv+f(vctrl)

Cv+f(vctrl)


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Temp. Comp., Cv+f(vctrl)

• fo(T) compensation is programmable

• x-bit bank of AMOS varactors in parallel with fixed capacitance

• Control varactors with a temperature-dependent control voltage, vctrl(T)creating a temperature-dependent capacitance, Cv+f(T)


1Cv 1Cf

b0

2x-1Cv 2x-1Cf

bx-1

To one side of the

resonant tank

VDD

VDD

vctrl(T)

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Temp. Comp., vctrl(T)

• Create a temperature-dependent current, I(T), using a combination of temperature-dependent current generators

• Source I(T) into a resistor with a known TC generating a temperature-dependent control voltage, vctrl(T)

• Include the ability to switch resistor types to allow vctrl(T) to be finely tuned

I(T)

I(T)

b0

CR0(T)

To vctrl(T) of C(vctrl)calibration module vctrl(T)

bt-1

Rt-1(T)


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Effects of Cf+v(vctrl) & vctrl(T) on fo(T)

T

foTank is mostly

variable capacitance, Cv

Tank is mostly fixed

capacitance, Cf

Tank is a combination of

variable and fixed cap.,

Cv+Cf


AMOS varactors enable coarse tuningResistor TC bank enables fine tuning

Linear negative fTCas predicted previously

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Process Variation Comp., Cf(bp-1,…,b0)

-gm

+ _

+_v+

_

Transconductanceamplifier + I (T) bias

I(T)generation

RL

L Cf

RC

Resonant tank, LC

vctrl(T)generation


Cv+f(vctrl)

Cv+f(vctrl)




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Process Variation Comp., Cf(bp-1,…,b0)

1Ctrim

b0

2p-1Ctrim

bp-1

1Ctrim

b0

2p-1Ctrim

bp-1

Parallel binary-weighted fixed capacitor banks

To resonant tank

Binary-weighted capacitor array adds or subtracts capacitance adjusting the oscillation frequency

Simple concept; complicated details


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Automatic Frequency Calibration

-gm

+ _

+_v+

_


I(T)generation

RL

L Cf

RC

Resonant tank, LC

vctrl(T)generation


Cv+f(vctrl)

Cv+f(vctrl)





fref


On tester load board

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Automatic Frequency Calibration

RF-TCHO

MSB

x-bitREF

counterRESET

CLK_REF

CLK_IN

TC

x-bitCLK

counterRESET Bus

N

REF_MSB

REF_RESET

CLK_RESET

S

Register

0

1

P

N

P

Up/downcounter

+State

machineCLK_TC

EC


A digital frequency locked loop (FLL) that runs counting “races” between a precision reference and the RF-TCHO™

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-gm

+ _

+_v+

_

Transconductanceamplifier + I1(T) bias

I(T)generation

RL

L Cf

RC

Resonant tank, LC

vctrl(T)generation


Cv+f(vctrl)

Cv+f(vctrl)



fref


• TCHO is core technology• Other portions of design

– Bandgap reference– Voltage regulator– Custom logic– NVM– etc.

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USB IP Implementation of RF-TCHO™

• USB to RS-232 bridge controller for cables and thumb drives

• RF-TCHO replaced the XTAL + PLL with an all-Si clock generator and reduced the clock module cost to pennies and size by over 1,000X

• 100kunits/month

• RF-TCHO™ is first commercial quartz replacement

• 0.18mm2 in 0.35µm CMOS


[McCorquodale, et al., JSSC, Feb. 2007]

400µm

450µ

m

This is a custom IP macro

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Mobius 12MHz RF-TCHO™: Temp. Comp.



-10000

-8000

-6000

-4000

-2000

0

2000

4000

6000

0 10 20 30 40 50 60 70 80

Temperature (°C)

Freq

uenc

y Er

ror (

ppm

)

Uncompensated Compensated

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Mobius 12MHz RF-TCHO™: Temp. Comp.



-250

-200

-150

-100

-50

0

50

100

150

200

250

0 10 20 30 40 50 60 70 80

Temperature (°C)

Freq

uenc

y Er

ror (

ppm

)

Nominal VDD VDD-10% VDD+10%

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Component Implementation: Programmable XO-Replacement


• After proven IP implementation, Mobius transitioned to component model

• RF-TCHO™ now implemented as stand-alone device

Mobius’ 0.25µm wafer leaving foundry Mobius’ die micrograph

Logo: the really important part

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Packaged Component Implementation


Abracon 50MHz 4-Pin Can XO

Technology: Quartz + CMOS

Mobius’ 12 – 75MHz Programmable TSSOP-8 RF-TCHO™

Technology: All-CMOS

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Mobius Component RF-TCHO™: Temp. Comp. Limits


Frequency Error of 30MHz RF-TCHO

-25

-20

-15

-10

-5

0

5

10

15

20

25

0 10 20 30 40 50 60 70 80

Temperature (°C)

Freq

uenc

y Er

ror (

ppm

)

Nominal VDD

Sub-20ppm feasible!

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8.19

-102/-124/-140

~±10

24MHzXO

8.96

-110/-129/-130

~±3200

12MHzCeramic


-96/-124/-141-75/-85/-117

SSB phase noise PSD

@10k/100k/1M (dBc/Hz)


30MHzRF-TCHO™



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Conclusions


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Technical Conclusions

• Takeaways in clock generation– Most reference clocks are at <100MHz ±>100ppm

• Power limits maximum frequency that touches PCB• Device physics limits quartz scaling

– Most carrier synthesis refs. are at <20MHz ±<25ppm• System observation takeaways

– In a PLL, the output performance is dictated largely by the output VCO, thus reference oscillator component Qbecomes much less significant

– Frequency multiplication and division degrade and enhance phase noise and jitter substantially

– For clock jitter, far-from-carrier phase noise is more important than close-to-carrier phase noise


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RF-TCHO™ Observations and Future Work

• RF-TCHO™ Takeaways– RF-TCHO™ is essentially a stabilized free-running LCO which is

equivalent to an LC-PLL– Architecture guarantees low jitter and phase noise– Close-to-carrier phase noise will still likely be higher as compared

to high-Q references, though not by much– Frequency inaccuracy dominated by TC, not VDD or trimming

inaccuracy– Seek to develop compensation techniques to achieve lowest

possible inaccuracy• Thought-provoking comments on RF-TCHO™

– What will the start-up latency of a RF-TCHO™ be? So what?– Can RF-TCHO™ be applied to RF?– Can RF-TCHO™ be integrated to replace the channel-rate (as

opposed to reference) clock generator?


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Final Conclusions

• Quartz is likely to be replaced in the near term– Several viable technologies now sampling commercially– FBAR and RF-TCHO™ on market in volume production– Si MEMS sampling

• Likely fragmentation of applications based on performance (accuracy + jitter / phase noise)– Si MEMS: ±25ppm – ±50ppm, but phase noise too high

for RF– FBAR: Filters – already in production– Ceramic: ±500ppm – ±5kppm – still not a quartz

replacement technology– RF-TCHO™: ~±100ppm – ±500ppm, low jitter and

sufficient accuracy for clocking – and maybe moreQuartz apps. Why? Why not? Emerging Tech. Measurements RF-TCHO Conclusions

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Acknowledgements

• WIMS ERC for Invitation– Tzeno Galchev and WIMS SLC– Ruba Borno– WIMS Staff

• Mobius Staff– Particularly Detroit Design Team: O’Day,

Pernia, Kubba, Carichner, Marsman, Kuhn• Attendees


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The Race to Replace Quartz

Thank you for your attentionand enjoy the race!

Questions are welcome


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