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8/20/2019 asdf asdf asdf asdf

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Fischer 08 1

Analog to Digital Converters

Nyquist-Rate ADCs

Flash ADCs

Sub-Ranging ADCs

Folding ADCs

Pielined ADCs

Successive Aro!i"ation #Algorith"ic$ ADCs

%ntegrating #serial$ ADCs

&versa"ling ADCs

Delta-Sig"a based ADCs


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Fischer 08 '

Conversion Princiles


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Fischer 08 (

ADC Architectures

Flash ADCs: )igh seed* but large area and high o+er dissiation,Suitable or lo+-"ediu" resolution #.-10 bit$,

Sub-Ranging ADCs: Require e!onentially e+er co"arators than

Flash ADCs, )ence* they consu"e less silicon area and less o+er, Pipelined ADCs: /ediu"-high resolution +ith good seed, he trade-

os are latency and o+er,

Successive Approximation ADCs: /oderate seed +ith "ediu"-

high resolution #8-1 bit$, Co"act i"le"entation,

Integrating ADCs or Ramp ADCs: 2o+ seed but high resolution,Si"le circuitry,

Delta-Sigma based ADCs: /oderate band+idth due to oversa"ling*

but very high resolution than3s to oversa"ling and noise shaing,


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Fischer 08

Peror"ance 2i"itations 1

n

Quant P 223

1 −=

≤

conveq f kTRn

6

1log

2log2

1

conveq N f kTR P TH 2=

her"al Noise 2i"itation Cloc3 4itter #Aerture$ 2i"itation

Normalized Noise Powers:

TH N Quant

P P ≥

2)(2

1 Jitter conv N t f P Jitter π =

LimitingCondition:

Jitter N Quant

P P ≥

≤

Jitter conv t f n

π 5.1

1log

2log

1

n-5it ADC Sinusoidal %nut S+ing6 719:

"a!; < conv

System Defnitions

MaximumResolution:

in;


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Fischer 08 =

Peror"ance 2i"itations '

Selection o ADC Architecture is driven by Alication

Displays

Audio

Sonar

Ultra Sound

Video

Wireless

Communications

Seismology


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Fischer 08 .

Parallel or Flash ADCs

Concetual Circuit


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Fischer 08 >

Sub-Ranging ADCs

)al-Flash or +o-Ste ADC


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Fischer 08 8

Folding ADCs

Princile Coniguration

…

2n1 Su!Ranges


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Fischer 08 ?

Folding Processor

"xam#le: 2!$it %olding Cir&uit

'2n-1+1)Io for n-Bit

2(o


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Fischer 08 10

Successive Aro!, ADCs

Concet %"le"entation


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Fischer 08 11

DAC Reali@ation 1

#9oltage /ode$


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Fischer 08 1'

DAC Reali@ation '

Sread Reduction through R-'R 2adder


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Fischer 08 1(

DAC Reali@ation (

C)arge!Redistriution Cir&uit

Pros %nsensitive +,r,t, &-a" ain &set #1B Noise$ co"ensated

Cons Requires non-overlaing Cloc3 )igh le"ent Sread Area &utut requires S)

valid only during φ'


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Fischer 08 1

DAC Reali@ation

S#read Redu&tion t)roug) &a#a&iti*e +oltage Di*ision

+= ∑ ∑

= =

−−3

0

7

4

)8()4( 2216

1

i i

i

i

i

iref out bbV V

valid only during φ'

Sread;'nB'

!a"le6 8-5it ADC


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Fischer 08 1=

DAC Reali@ation =

C)arge!Redistriution Cir&uit wit) ,nity!-ain .m#lifer

Pros 9oltage divider reduces sread 5uer lo+ outut i"edance No cloc3 required

Cons Parasitic ca causes gain error )igh &-a" co""on "ode inut required No a"liier oset co"ensation

A"liier %nut Ca/

C ain rror6 E;-CB1.C

1.B1=C

+= ∑ ∑= =−−

3

0

7

4

)8()4( 2216

1

i i

i

i

i

iref out

bbV V Sread;


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Fischer 08 1.

DAC8 +ith nity-ain A"liier

Su!range ut#ut ' LS$s3

0 0,=u 'u1,=u ',=u (,=u ,=u =,=u .,=u(u u =u .u1u

.m#lifer ut#ut

.,=u0 0,=u 'u1,=u ',=u (,=u ,=u =,=u(u u =u .u1u


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Fischer 08 1>

DAC Reali@ation .

Current Mode (m#lementation


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Fischer 08 18

Current Cell Floor Plan

Unit Current Cell

Sy""etrical Current Cell Place"ent

Current summing RailIout

Cascode

Current

Source

Switching

Devices

Array o '=. CellsR


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Fischer 08 1?

DAC %"le"entation

2ayout o 10-5it Current-/ode DAC '0,=µ" C/&S$

Current su""ing Rails


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Fischer 08 '0

/odiied SA Algorith" 1

%dea6 Relace DAC by an Accu"ulator

Consecutively divide Re by '


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Fischer 08 '1

/odiied SA Algorith" '

First cycle only

Accu"ulator

%dea6 /aintain Co"arator Reerence #< FS;nd$

Double revious Accu"ulator &utut


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Fischer 08 ''

SC %"le"entation

SC (m#lementation o4 modifed S. .DC


23/42

Fischer 08 '(

i"ing Diagra"


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Fischer 08 '

&set Co"ensated Circuit

5set Com#ensated SC (m#lementation


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Fischer 08 '=

5uilding 5loc3s 1

DC -ain 66 d$

-ain!andwidt)

17 M8z9

CL 1/;#%

Power 1/< m=

ut#utSwing

+ #!#

ransconductance A"liier


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Fischer 08 '.

5uilding 5loc3s '

Power 7/; m=

Resolution > 7/; m+

Settling ?ime

< ns

Lat&)ed CMS Com#arator


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Fischer 08 '>

2ayout o 8-5it ADC

1.= µm #0,= µ" C/&S$


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Fischer 08 '8

Sice Si"ulation #5si"($

8-5it ADC6 cl3;10/)@ conv;1,'=/)@


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Fischer 08 '?

Pielined ADCs

Pielined "odiied SA or Algorith"ic ADC

Pros &set #1B Noise$ co"ensated /ini"u" C-sread &ne conversion every cloc3 eriod

Cons /atching errors digital correction or nG8 Cloc3 eed-through very critical )igh a"liier sle+ rate required


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Fischer 08 (0

%ntegrating or Serial ADCs

Dual Sloe ADC Concet

Constant Ram#Pro#/ to (n#utRam#

Using 2N/k samples requires ef ! F"/k re#uce# Integrator Constant

$%lement "prea#)

N represents #igital

equi&alent of analog Input


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Fischer 08 (1

SC Dual-Sloe ADC

10-5it Dual-Sloe ADC


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Fischer 08 ('

ADC esting

yes o ests

Static esting

Dyna"ic esting

%n static testing* the inut varies slo+ly to reveal the actual codetransitions, Hields %N2* DN2* ain and &set rror,

Dyna"ic testing sho+s the resonse o the circuit to raidly

changing signals, his reveals settling errors and other dyna"ic

eects such as inter-"odulation roducts* cloc3-eed-trough* etc,

Circuit

nder est

&utut%nut

Cloc3


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Fischer 08 ((

Peror"ance /etrics 1

rror yes

&set

ain

DN2

%N2

/issing Codes

%DA2 ADC

Stati& "rrors


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Fischer 08 (

Peror"ance /etrics '

2log2

)2

3(log

10

][

10

10max −

=

dBSNDR

ENOB

Noise

Signal

P

P SNR 10log10=

Frequency Do"ain Characteri@ation

%deal n-5it ADC6

SNR ; .,0' ! n I 1,>. d5:

Har Noise

Signal

P P

P SNDR

+= 10log10

fsig

A m p l i t u d e


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Fischer 08 (=

ADC rror Sources

Static rrors le"ent or Ratio /is"atches

Finite &-a" ain

&-a" Co"arator &sets Deviations o Reerence

Dyna"ic rrors Finite #A"liier$ 5and+idth

&-a" Co"arator Sle+ Rate Cloc3 Feed-through

Noise #Resistors* &-a"s* s+itched Caacitors$

%nter"odulation Products #Signal and Cloc3$


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Fischer 08 (.

Static esting

Servo-loo echnique

Co"arator* integrator* and ADC under test are in negative eedbac3 looto deter"ine the analog signal level required or every digital code transition,

%ntegrator outut reresents equivalent analog value o digital outut,

ransition values are used to generate inutBoutut characteristic o ADC*

+hich reveals static errors li3e &set* ain* DN2 and %N2,


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Fischer 08 (>

Dyna"ic esting

yes o Dyna"ic ests )istogra" or Code-Density est

FF est

Sine Fitting est

?est Set!u#


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Fischer 08 (8

)istogra" or Code-Density est

DN2 aears as deviation obin height ro" ideal value,

(ntegral nonlinearity '(NL3is &umulati*e sum 'integral3o4 DNL/

&set is "aniested by a

hori@ontal shit o curve,

ain error sho+s ashori@ontal co"ression or

deco"ression o curve,


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Fischer 08 (?

)istogra" est

Pros and Cons o )istogra" est

8istogram test #ro*ides in4ormation on ea&)&ode transition/

DN2 errors "ay be concealed due to rando" noise incircuit,

%nut requency "ust be selected careully to avoid

"issing codes # cl3B in "ust be non-integer ratio$,

%nut S+ing is critical #cover ull range$

Requires a large nu"ber o conversions #o 'n ! 1*000$,


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Fischer 08 0

Si"ulated )istogra" est

0!$it S. .DC wit) 7/;@Ratio "rror and ;m+A+Com#arator 5set


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Fischer 08 1

FF est

Pros and Cons o FF est

&ers quantitative %nor"ation on outut oise* Signal-to-Noise Ratio #SR$* Surious Free Dyna"ic Range

#SFDR$ and )ar"onic Distortion #SDR$,

FF test requires e+er conversions than histogra"

test,

Co"lete characteri@ation requires "ultile tests +ith

various inut requencies,

Does not reveal actual code conversions


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Si"ulated FF est

0!$it S. .DC wit) 7/;@ Ratio "rror and ;m+A+ Com#arator 5set

SFDR=! d"

S#DR=$% d"

'"=()*+

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