Mixed signal systems and Integrated Circuits signal_Lecture2_071009... · Mixed signal systems and...

51
2007/10/4 Mixed signal A. Matsuzawa, Tokyo Tech. 1 Mixed signal systems and Integrated Circuits Akira Matsuzawa Tokyo Institute of Technology

Transcript of Mixed signal systems and Integrated Circuits signal_Lecture2_071009... · Mixed signal systems and...

Page 1: Mixed signal systems and Integrated Circuits signal_Lecture2_071009... · Mixed signal systems and Integrated Circuits ... dt dV ∆V = σ V sig. 2007/10 ... DCS1800 WCDMA Blocker

2007/10/4 Mixed signal A. Matsuzawa, Tokyo Tech. 1

Mixed signal systems and Integrated Circuits

Akira Matsuzawa

Tokyo Institute of Technology

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2. High speed ADC and DAC

1. Characterization of data converters

2. Overview of high-speed A/D converters

3. Overview of high-speed D/A converters

4. Basic design considerations

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1. Characterization of data converters

• Basic functions of ADC and DAC• Static performance

– INL, DNL, monotonicity– Quantization noise

• Dynamic performance– SNR, SFDR, THD, SNDR, ENOB– Sampling Jitter– ERB– Glitch

• Figure Of Merit• Performances and applications

– Needed performances for wireless systems

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Basic functions of ADC

Sampling: Sampling the analog signal with accurate timing.Quantization: Express the converted data with certain accuracy.

Sampling Quantization

Volta

ge

Volta

geTime Time

ADCCodingSam

pling

Quantization

Coding 00

0100

1001

1110

0010

0110

0001

1101

0100

1100

1001

00

0111

0111

0111

0110

0110

0110

0110

Analog Digital

CLK

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Static performanceINL and DNL are the major static performance indicators of ADC and DAC.

DNL: Differential Non-LinearityIDEAL

IDEALj,ACTUALj Width

WidthWidthDNL

−≡

INL: Integrated Non-Linearityj,IDEALj,ACTUALj fuctionTransferfunctionTransferINL −≡

j1jj

jk

0kkj

INLINLDNL

DNLINL

−=

=

+

=

=∑

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DNL and INL

DNL profile INL profile

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Monotonicity in DACBinary coded DAC often degrades monotonicity. The monotonicity stands for the qualitative characteristics of data converters of which transfer function keep the monotonic increase or decrease.

If the converter can not guarantee the monotonicity, The feedback loop doesn’t work properly and results in backrush.

At the change of MSB bit

01111->10000

Keep monotonic

In

Out

Large DNL

Degrade monotonicity

In

Out

1/2

1/4

1/81/161/32

1/2

1/4

1/8

1/161/32

Binary weight

→ 1/2

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Quantization noise

Quantization causes noise Higher SNR needs higher resolution

Quantization noise

Transfer characteristics( )

( )

76102610

2511222

22

22

21

21

.N.PPlogSNR

.PPSNR

P

n

sdB

NN

n

s

N

s

+⋅=⎟⎟⎠

⎞⎜⎜⎝

⎛=

⋅=⋅⋅

=≡

⋅=

∆∆

20

112

1 22

2

22

2

2

∆∆

∆∆

<⎪⎩

⎪⎨⎧

=

=== ∫∫ −−

e,eotherall,

)e(P

deede)e(PeP/

/

/

/n

Q

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Dynamic performance

Dynamic performance indicates the ratio between signal and noise or distortion.

We should use the suitable terms depending upon the type of application.

026761

10

10

10

10

..SNDR

ENOB

powerdistortionandNoisepowerSignal

logSNDR

powerSignalpowerdistortionharmonicTotal

logTHD

powerspuriousestargLpowerSignal

logSFDR

powernoisefloorTotalpowerSignal

logSNR

-=

=

=

=

=

Fc=40MHz, fin=4MHzSFDR=49.8dBSNDR=44.9dB, ENOB=7.17-bit2ndHD=-49.8dB, 3rdHD=-56.7dB

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Sampling jitter effect

Sampling jitter is converted to noise.When the input frequency becomes higher, the SNR becomes lower.

( )2tinf21log10)dB(SNDRσπ

−=

1 .10 13 1 .10 12 1 .10 1120

40

60

80

100

120

SNDR 10 106⋅ σt,( )SNDR 20 106⋅ σt,( )SNDR 50 106⋅ σt,( )SNDR 100 106⋅ σt,( )SNDR 200 106⋅ σt,( )

σtTime

Inpu

t sig

nal

t0t

V∆

tsig

dtdV

V σ∆ =

sigV

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Effective Resolution Bandwidth

ERB is the input frequency where the SNDR has dropped 3dB (or ENOB 0.5 bit)EN

OB

(bit)

Input frequency (MHz)300200100

3

4

5

6

SNR

SNDR

3dB (0.5bit) down

ERB

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GlitchGlitch is the spiky signal at code transition.

I/2 I/4 I/8 I/16

I/2 I/4 I/8 I/16

I/2 I/4 I/8 I/16

State 1: [1000]=8

State 2: [0111]=7

Intermediate: [1111]=15 8

15

7

Glitch

Caused by overlapping of signalsThis appears within a few psec,However, energy is not negligible.Glitch causes the distortion of signal

Tg

Xg

N2s

g

2

QNmax,g

s

g22N2max,g

23TT

12PP

TT

2P

⋅<∴

=<

⋅⋅= −

Cur

rent

Time

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Figure Of Merit

Figure of merit shows energy efficiency for data conversion.

H igh Speed A DC[Sam pling Freq. VS Pow er]

1

10

100

1000

10000

1 10 100 1000 10000

Sampling Freq.[MSps]

Power[mW]

12Bit(Paper)

10Bit(Paper)

12Bit Products

10Bit Products.

JSSC,ISSCC,VLSI,CICC,ESSCC

& Products

(≧10Bit,≧

10MSps)1995-2006

conv/pJ5.0MHz/mW3.0

bit10

conv/pJ8.0MHz/mW1

bit12

10b12b

BW22Poweror

f2Power

stepConversionEnergyFOM

ENOB

sENOB

×=

×=

=

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Performance and application

Needed resolution and conversion rate depending upon the application.

6 8 10 12 14 16

Resolution (bits)

Con

vers

ion

Rat

e (M

Hz)

0.1

1

10

100

1000

5

3050

300500

0.5

0.05

HDD/DVDGraphics

Audio

GeneralPurpose

DVC/DSC/Printer

Video/Communication

Servo

(µ-Computer)

Automobile

Meter

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Needed SNR for certain BER in wireless system

Lower Bit Error Rate in the digital modulation needs higher SNR.

Q

I

16QAM

10A2

“1”“0”

BER

Noise distribution

( ) ⎟⎟⎠⎞

⎜⎜⎝

−⋅

⎟⎟⎠

⎞⎜⎜⎝

⎛−≈

1n2SNR2erfc

n112BER

⎟⎠⎞

⎜⎝⎛≈

nsinSNRerfcBER π

n-PSK

n-QAM

0 10 20 30 401 .10 10

1 .10 9

1 .10 8

1 .10 7

1 .10 6

1 .10 5

1 .10 4

1 .10 3

0.01

0.1

1

BERq SNR 16,( )

BERq SNR 64,( )

BERq SNR 256,( )

BERp SNR 4,( )

SNR

16QAM

64QAM

256QAMQPSK

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BER requirementThe lower the bit error rate the higher the required ADC/DAC resolution.

Resolution (quantization noise) affects BER.

DAC requirement for QAM ADC requirement for digital read-channel

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Signal intensity in wireless system

Amp. ADC

Filter

A B CA

Thermal noise Thermal noise

Wantedsignal

Adjacentsignal

FarsignalFilter

> Needed dynamic range to the blocker

Thermal Noise+ Quantization noiseFrequency

Inte

nsity

(dB

)

B C

Due to aliasing

Due to distortion of ADC

> Needed SNR

Wireless system has strong unwanted signals. Also, electric circuits generate distortion and noise.

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Needed ADC dynamic range Existence of strong blockers results in the need for high dynamic range ADC.

DCS1800 WCDMA-26dBmBlocker

signal

-97dBm

Quantizationnoise

Wantedsignal

15dB15dB

ADC dynamic range=86dB (14b)

Adjacentchannel

-52dBm

-93dBm

Quantizationnoise

Wantedsignal

8dB

-33dB

-85dB

Filter attenuation

Thermal noise

20dB

ADC dynamic range=36dB (6b)

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2. Overview of high-speed A/D converters

• Performance and ADC architecture• Integrating ADC• Successive approximation ADC• Flash ADC• Sub-ranging ADC• Interpolation method• Folding ADC• Pipelined ADC

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ADC performance and architecturesThere are many conversion architectures with varying performance parameters.

4 6 8 10 12 14 16

10M

1M

100k

10k

100M

1G

10G

20184 6 8 10 12 14 16

10M

1M

100k

10k

100M

1G

10G

2018

Con

vers

ion

freq

uenc

y (H

z)

Resolution (bit)

Successiveapproximation

Integrating

Flash

Sub-range

Multi-bitsigma-delta

Pipeline

Single-bit sigma-delta

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Integrating ADC

+ vx +

S1

vref

-vin Comparator

T

vx

R

C

vref

-vin

vref

-vin

0Time

vin大

Going to 0 -> 1, when Vx becomes negative.

PhaseⅠ PhaseⅡ

( ) TRCvd

RCv)T(v inT

0in

x =−

−= ∫ τ

・High resolution (20bit and more)・Very low speed (DC measurement)・Small DNL・Can realize zero offset voltage・Small analog elements and area

Water clock

Integrating ADC achieves high resolution, but at low speed.Recently it has been used as column-ADC in CMOS imager.

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Successive-approximation ADCSuccessive-approximation method is based on a binary search.

b1 b2 b3 b4 b5 b6

MSB LSBVFS

V0

Binary search

Vin

VDACVin

VFS21

VFS21 VFS4

1+

VFS21 VFS8

1+

VFS21 VFS8

1+ VFS161+

b1=1b1=1b2=0

b1= b3= 1b2=0

b1= b3= b4= 1b2=0

S/HVin Successive-approximation resistor and control logic

b1 b2 b3 Bout

DAC Vref

VDAC

ComparatorBalance

CMPin

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Charge-redistribution ADC

C C2

C4

C8

C16

C16

Vin Vref

Vx=0Q=-2CVin

1) Sampling

Binary weighted Capacitor array

Charge-redistribution ADC draws attention as a suitable ADC in the nano-meter CMOS era. Because it needs no OP-Amp, but just needs capacitors and comparator.

C C2

C4

C8

C16

C16

Vx=-VinQ=-2CVin2) Hold

Vin Vref

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Charge-redistribution ADC

C C2

C4

C8

C16

C16

Vref

Vx=-Vin+Vref/2Q=-2CVin

3) Charge redistribution

Vref

If neededDetermine from MSB Vin Resistor ladder for

higher resolution

Higher resolution

Ultra low power

Low conversion rate

Easy calibration

No OP amp

Needs multi clock

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Flash ADC

Flash ADC is very fast, but area and power increase exponentially with resolution.

R

R

R

R

R

R

R

VDD

+

+

+

+

+

+

+

+

R/2

R/2

vin

Encoder

Comparator

Φ

Digitalout

Ultra fast operation: Several GHzNo sample and holdLow resolution: <8 bitLarge input capacitance difficult to drive

10001

01011

D1D2D3D4D5

0

1

Inputvoltage

NrefV

2

refV

Scale

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Sub-ranging ADC

GND

0

8

1 6

2 4

0

2

4

6

Input voltage

Upperconversion

Lowerconversion

Multi-step conversion can reduce the # of comparators.However, it needs high precision comparators.As a result, small power and area.

62122;steptwo

102312;Flash:bits10

2N

N

=⎟⎟⎠

⎞⎜⎜⎝

⎛−

=− Slide gauge

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Interpolation methodInterpolation can generate accurate intermediate references which are between two references. Thus step sizes are almost equal, even though mismatch voltages are large.

Mismatchvoltage

SmallDNL

K. Kusumoto and A. MatsuzawaJSC, pp. 1200-1206, 1993.

Step sizeStep size Step size

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Folding ADC

Upper bitsADC

Lower bitsLogic

Comp

Comp

Comp

Comp

Folding Circuits

Folding Circuits

Folding Circuits

Folding Circuits

vin

Analog signal

Input signal

Parallel

Folded signalsFold

ed s

igna

ls

Input signal is folded to the compressed signals of which phases are different.Lower bits are obtained by comparing between these folded signals.

Low power and small size, yet still high speed.However, not suitable for higher resolution. <10bit

The signal is compressedThe signal is compressed→→The # of comparators can be reduced

Digital signalThe # of comparators can be reduced

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Folding circuits

Composing the folding characteristics by the summation of currentsfrom differential transistor pairs.

VDD

vin

V1 V2 V3 V4

V1 V2 V3 V4 Input voltageO

utpu

t vol

tage

vout

VDD

Current summation

V1Vin

VDD

V1 VinInput voltage

Out

put v

olta

ge VDD

Vout

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Pipelined ADCPipelined ADC is the centerpiece of embedded ADCs for many applications,such as digital cameras, digital TVs, ADSLs, VDSLs, and wireless LANs.

Suitable for CMOS High resolution(<15bit)Moderate speed(<200MHz)Low power consumption

Switched capacitor operation

M-bitDAP DAP DAP DAP

MSBLSB

vin

+ ×2M

Amplifier

S/H

Digital Approximater(DAP)ADC

(M bit)

DAC(M bit)

-Vref

+Vref

-Vref

+Vref

0 1

X2

-Vref

+Vref

-Vref

+Vref

0 1 0 1

X2

MSB 2nd

Conventional M is 1 or 1.5

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1.5-bit/stage Pipeline ADC

Amplification at each stage reduces the input referred thermal noise.1.5b/stage architecture reduces the requirement for the comparator offset drastically.

MUX

+VR -VR

LATC

H4RV

+

4RV

SUB-ADC DAC 2X GAIN

Vi

Vo

Cf

Cs

S2

S3+

-+-

-+

+VR-VR

+VR

-VR

reff

ii

f

s VCCV

CC1 +⎟

⎟⎠

⎞⎜⎜⎝

⎛+

if

s VCC1 ⎟

⎟⎠

⎞⎜⎜⎝

⎛+

reff

ii

f

s VCCV

CC1 −⎟

⎟⎠

⎞⎜⎜⎝

⎛+

4V

Vi ref−<if

if4

VV

4V ref

iref ≤≤−

if 4V

V refi >

=oV

Transfer characteristics

Unit conversion stage for 1.5-bit/stage pipeline ADC

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Pipelining

-

-+

+

Op amp

CMPDAC

-

-+

+

Op amp

CMPDAC

-

-+

+

Op amp

Sample & Hold 1st stage 2nd stage

Cf

Cs

Cf

Cs

1st stageSample

Amp.Sample

Amp.

Pipeline action relaxes settling time requirement.

Sample Amp. Sample Amp.2nd Stage

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3. Overview of high-speed D/A converters

• Basic two concepts of DAC• Binary method

– R-2R based DAC– Capacitor array DAC

• Decoder method– Resistor string DAC– Current steering DAC

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Basic two concepts of DAC

1. Binary method 2. Decoder method

111110101100011010001000

Decoder

Sw

itch

mat

rix

Vref

Small DNLSmall glitchLarge area

Bin

ary

Wei

ght c

kt.

Vref

Not small DNLLarge glitchSmall area i

N

1iireflgana D

21VV ⋅= ∑

=

i

1N

0i

iqlgana D2VV ∑

=

⋅⋅=

AnalogD3D2D1

Analog

Digital

D3D2D1

Digital

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R-2R based DACBinary method

R-2R resistor ladder can generate binary weighted current easily.

+vout

2R 2R 2R 2R

A0 A1 A2 A3

Resolution: 12bLarge DNLSmall area at high resolutionModerate speedLarge power consumption

RF

Virtual ground

-vref

R 2RR R

Rv

I

AIAIAIAIRv

refr

rrrrFout

2

222 131210

=

⎟⎠⎞

⎜⎝⎛ ⋅+⋅+⋅+⋅=

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Capacitor array DACBinary method

16C

vref

+ vout8C 4C 2C C

[ ]

CQv

ACACACACvQ

out

ref

16

842 3210

−=

⋅+⋅+⋅+⋅=

+ vout8C 4C 2C C

16C

vref

A0A1A2A3

Q

Reset

Enable

Virtual ground

Ai= 0 or 1

Capacitor array DAC is widely used in CMOS technology.

Low power and no sample & Hold

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Resistor string DACDecoder method

Vref

+Vout

Decoder

Decoder method can realizes small DNL, however needs large area at high resolution.

Resolution limit: 10bGood DNLLow speedSmall glitch

R

R

R

R

R

R

R

R

large parasitic capacitance: 2N

Digital value

111

110

101

100

011

010

001

000

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2007/10/4 Mixed signal A. Matsuzawa, Tokyo Tech. 38

Current steering DACDecoder method

Widely used for high speed DAC. Graphics, communications, etc.

VDD

Bias

Vout

Di Di

Current source

High speed, -- 1 GHzResolution – 14 bSmall DNLSmall glitch

Conventionally large area

R

VoutDi=1

Row

dec

oder

Di=0

Column decoderCurrent cell with switch

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2007/10/4 Mixed signal A. Matsuzawa, Tokyo Tech. 39

4. Basic design considerations

• Accuracy– Current mismatch and DAC accuracy– VT mismatch– Capacitor mismatch

• Comparator– Offset compensation

• Op-Amp– Gain and GBW– kT/C noise

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2007/10/4 Mixed signal A. Matsuzawa, Tokyo Tech. 40

Current mismatch and DAC accuracy

Larger resolution requires smaller mismatch.

6 8 10 12 141 .10 3

0.01

0.1

sigma 3.0 N,( )

sigma 2 N,( )

sigma 1.3 N,( )

sigma 0.8 N,( )

N

90%50%

10%

99.7%

Van den Bosch,.. Kluwer 2004

INL yield

0iI ∆+ 1iI ∆+ 2iI ∆+ 1N2iI −+ ∆

N2C2

1I

)I(≈

σ

N: resolution

C: constant determined by INL yield

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2007/10/4 Mixed signal A. Matsuzawa, Tokyo Tech. 41

VT mismatch

Larger gate area is needed for smaller VT mismatch.Technology scaling reduces VT mismatch if the gate area is equal.

1 10 100 1 .1030.1

1

10

100

δVT LW( )0

δVT LW( )1

δVT LW( )2

LW

LWTV ox

T ∝∆

0.4um Nch

0.13um Nch In w/o Halo*

0.13um Nch Boron, w. Halo

)mV(VT∆

)m(LW 2µ

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2007/10/4 Mixed signal A. Matsuzawa, Tokyo Tech. 42

Mismatch current and transistor size

Smaller mismatch requires larger L and W.

( )2Tgsds VVL

W'KI −=

⎟⎠⎞

⎜⎝⎛

⎟⎠⎞

⎜⎝⎛∂

∂+

∂∂

+∂∂

=L

W

LWI'K

'KIV

VII dsds

TT

dsds ∆∆∆∆

⎟⎠⎞

⎜⎝⎛

⎟⎠⎞

⎜⎝⎛

++−

−=

LW

LW

'K'K

VVV2

II

Tgs

T

ds

ds∆

∆∆∆22WL

'K

VTT

L1

W1A

LW

LW

LWA

'K'K

LWAV

+=⎟⎠⎞

⎜⎝⎛

⎟⎠⎞

⎜⎝⎛

⎟⎠⎞

⎜⎝⎛

=−

LW'K

IVV dsTgs

Mismatch

2

222WL

2K

ds2

2VT

2

ds

ds

L1

W1A

WLA

ILA'K4

II

⎟⎠⎞

⎜⎝⎛ +++=⎟⎟

⎞⎜⎜⎝

⎛ ∆

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2007/10/4 Mixed signal A. Matsuzawa, Tokyo Tech. 43

Capacitor mismatch

)(

4106)3(pFCC

C −×=

∆ σ

)3( σCC∆

Capacitance (pF)

10bit, ¼ LSB

12bit, ¼ LSB

14bit, ¼ LSB

10bit: 0.4pF12bit: 4pF14bit: 40pF

Smaller capacitor mismatch requires larger capacitanceCoefficient depends on the Fab.

Typical MIM capacitor

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2007/10/4 Mixed signal A. Matsuzawa, Tokyo Tech. 44

CMOS comparators

There are many types of comparator circuits

Page 45: Mixed signal systems and Integrated Circuits signal_Lecture2_071009... · Mixed signal systems and Integrated Circuits ... dt dV ∆V = σ V sig. 2007/10 ... DCS1800 WCDMA Blocker

2007/10/4 Mixed signal A. Matsuzawa, Tokyo Tech. 45

Low power CMOS comparatorA CMOS comparator is low power because of no need of static current.

VSS

VDD

Vin1+

m2

m7

m9 m10

m3 m4m1

m5 m6

m8

m11 m12

Out+Out-

CLK

W1 W2 W1 W2

( ) ( )

( ) ( )⎥⎦⎤

⎢⎣⎡ −++−=

⎥⎦⎤

⎢⎣⎡ −++−=

−−

++

thinthinp

thinthinp

VVL

WVVL

WKG

VVL

WVVL

WKG

22

11

2

22

11

1

Vin2+ Vin1- Vin2-

( ) ( ) −−++ +−=+−

−=

2121

21

inininin nVVnmnVVnm,thenmn:

mnmW:Wif

No static currentDifferential comparisonInterpolation actionHigh speed

T.B.Cho., et al., J.S.C., Vol.30,No.30, pp.166-172, Mar. 1995.

Interpolation action

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2007/10/4 Mixed signal A. Matsuzawa, Tokyo Tech. 46

Design rule and Speed in Comparator

Gain bandwidth (=Speed) is inversely proportional to the L2 (channel length).Technology scaling is still effective to increase the comparator speed, if we don’t take care of the signal dynamic range.

Isink

R R

Isink

R R

effoxj

ksin

oxj

m

VLWC32WC2

I

LWC32WC2

gGBW⎟⎠⎞

⎜⎝⎛ +

=⎟⎠⎞

⎜⎝⎛ +

=ππ

2eff

oxksin V

LW

2CI µ

=L

Coxκ

=

⎟⎟⎠

⎞⎜⎜⎝

⎛+

=

kC

32L2

VGBW

j2

eff

π

µ

0

5

10

15

20

0.1 0.2 0.3 0.4 0.5

Rel

ativ

e ba

ndw

idth

Feature size ( )mµ

0

5

10

15

20

0.1 0.2 0.3 0.4 0.5

Rel

ativ

e ba

ndw

idth

Feature size ( )mµFeature size ( )mµ

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2007/10/4 Mixed signal A. Matsuzawa, Tokyo Tech. 47

Offset compensationTwo ways for suppressing offset voltage.

CLK

LatchVin1

Vin2

A Vout

+

-

-

+Va Vo

Store the offset voltage in capacitors and subtract it from the signal.

( )

osAao

aoosAa

VA1

AVV

VV)A(VV

+=

==−−

=∴

Feedback= High gain type

VosA: Offset of the amplifiera) Offset cancel at input nodes VosL: Offset of the latch

CLK

Latch VoutA+

-

-

+

Feed forward =Low gain type

Vin1

AVV osl

in_os =Vin2

b) Offset cancel at output nodes

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2007/10/4 Mixed signal A. Matsuzawa, Tokyo Tech. 48

Operational amplifier

Sampling

Higher resolution requires higher open loop gain.Higher conversion frequency requires higher closed loop GBW.

-

-+

+

Op amp

Cf

Cs

VinVn

Vn

Amplify

βGCC

GG

f

perror

121−≈⎟

⎟⎠

⎞⎜⎜⎝

⎛+−≈

DC gain

⎟⎟⎠

⎞⎜⎜⎝

⎛+

f

p

CC

2

1MN2G1

+−≤β

N:ADC resolutionM:Stage resolution

106)( +> NdBG for 1.5b pipeline ADC

Closed loop gain-bandwidth

pisf

f

CCCC

++=β

( )pisf

pisfoLpoL CCC

CCCCCC

++

+++=

3fcN

C2gGBW

L

mclose_

⋅>=

π

β

Cf

Cs Cpi gm Cpo COLRL2

1

1

p

+

Equivalent circuit

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2007/10/4 Mixed signal A. Matsuzawa, Tokyo Tech. 49

kT/C noise

Larger SNR requires larger capacitance and larger signal swing.Low signal swing increases required capacitance.

R

CL

CL

vout

φ

vn

0.1 1 10 10050

60

70

80

90

10095.918

51.938

SNRC 1 2, C,( )

SNRC 2 2, C,( )

SNRC 3 2, C,( )

SNRC 5 2, C,( )

1000.1 C

14bit

12bit

10bit

0.1 1 10 100

VFS=5VVFS=3V

VFS=2V

VFS=1V

n=2

SN

R (d

B)

Capacitance (pF)

( ) CkT

2d

CR11kTR4v 2

2n =

+= ∫ π

ωω

CnkTv 2

n = n: configuration coefficient

⎟⎟⎠

⎞⎜⎜⎝

⎛=

nkT8CVlog10)dB(SNR

2FS

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2007/10/4 Mixed signal A. Matsuzawa, Tokyo Tech. 50

Basic design consideration

Very tough tradeoffs, so let’s keep up the design effort.

Small mismatch Solutions 1) ArchitecturePipeline, Parallel

2) Redundancy3) Error compensation4) Circuit design

NFS

off

21

VV

orCC

∝∆∆

Increase Capacitance

goff C

1LW1Vor

C1

CC

∝∝∝ ∆∆However, kT/C issue remains

N22sig 2CVSNR ∝∝

2

sig

N

V2C ⎟

⎟⎠

⎞⎜⎜⎝

⎛∝

N22C ∝ Results in

Decrease speed and Increase Power

N2mm

s 2g

CgGBWf ∝∝∝ N2

dd

2I

CIGBW ∝∝

N2ssddd 2fCfIVP ⋅∝⋅∝∝

Solutions1) Increase signal swing2) Increase OSR

N2d

s 2If ∝ N2

sd 2fP ⋅∝ OSRSNR ∝

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2007/10/4 Mixed signal A. Matsuzawa, Tokyo Tech. 51

Study-aid books• B. Razavi, “Data conversion system design,” IEEE press.

• P. E. Allen and D. R. Holberg, “ CMOS Analog Circuit Design,” 2nd

Edition, OXFORD University Press.

• D. A. Johns and K. Martin, “Analog integrated circuit design,” John Wiley & Sons.

• R. J. Baker, “ CMOS mixed-signal circuit design,” IEEE Press.

• R.van de Plassche, “CMOS Integrated Analog-to-Digital and Digital-to-Analog Converters,” 2nd Edition, Kluwer Academic Publishers.

• M. Gustavsson, J. J. Wikner and N. N. Tan, “CMOS data converters for communications,” Kluwer Academic Publishers.

• C. Shi and M. Ismail, ”Data converters for wireless standards,”Kluwer Academic Publishers.

• A. Rodriguez-Vazquez, F. Mederio, and E. Janssens, “CMOS Telecom Data Converters,” Kluwer Academic Publishers.