1V Compact Class-AB CMOS Log Filters X. Redondo and F. - - PowerPoint PPT Presentation

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1V Compact Class-AB CMOS Log Filters X. Redondo and F. - - PowerPoint PPT Presentation

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ISCAS05 1V Compact Class-AB CMOS Log Filters Intro Class-A Class-AB Example Conclusions 1/23 1V Compact Class-AB CMOS Log Filters X. Redondo and F. Serra-Graells Circuits and Systems Group Institut de Microelectrnica de Barcelona

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SLIDE 1

ISCAS’05 1V Compact Class-AB CMOS Log Filters Intro Class-A Class-AB Example Conclusions 1/23

1V Compact Class-AB CMOS Log Filters

  • X. Redondo and F. Serra-Graells

Circuits and Systems Group Institut de Microelectrònica de Barcelona Centre Nacional de Microelectrònica - CSIC Spain

25th May 2005

  • X. Redondo and F. Serra-Graells

Institut de Microelectrònica de Barcelona

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SLIDE 2

ISCAS’05 1V Compact Class-AB CMOS Log Filters Intro Class-A Class-AB Example Conclusions 2/23

1 Introduction 2 Basic Class-A Operation 3 New Class-AB Proposal 4 Design Example 5 Conclusions

  • X. Redondo and F. Serra-Graells

Institut de Microelectrònica de Barcelona

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SLIDE 3

ISCAS’05 1V Compact Class-AB CMOS Log Filters Intro Class-A Class-AB Example Conclusions 3/23

1 Introduction 2 Basic Class-A Operation 3 New Class-AB Proposal 4 Design Example 5 Conclusions

  • X. Redondo and F. Serra-Graells

Institut de Microelectrònica de Barcelona

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SLIDE 4

ISCAS’05 1V Compact Class-AB CMOS Log Filters Intro Class-A Class-AB Example Conclusions 4/23

Companding filtering scenario

F

  • 1

Vout Vin G

F

instantaneous compression non-linearintegration instantaneous expansion externallylinearprocessing Iin Iout Vstate C

log-domain: F(x) = ex Low-voltage ? Low-current vs dynamic range ? Low-area vs auxiliary circuitry . . . the answer is compact Class-AB!

MOS log-mapping

VGB VSB VDB ID

D S B G

weak inversion:

VSB,DB ≫ VGB−VT O

n

forward saturation:

VDB − VSB ≫ Ut

ID = ISe

VGB−VT O nUt

e− VSB

Ut

IS = 2nβU 2

t

IC = ID IS

  • X. Redondo and F. Serra-Graells

Institut de Microelectrònica de Barcelona

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SLIDE 5

ISCAS’05 1V Compact Class-AB CMOS Log Filters Intro Class-A Class-AB Example Conclusions 5/23

1 Introduction 2 Basic Class-A Operation 3 New Class-AB Proposal 4 Design Example 5 Conclusions

  • X. Redondo and F. Serra-Graells

Institut de Microelectrònica de Barcelona

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SLIDE 6

ISCAS’05 1V Compact Class-AB CMOS Log Filters Intro Class-A Class-AB Example Conclusions 6/23

Compressor and expander

Iin

K 1

Iref K

Vin Vref Iref Ccomp Cin

Iout

Vout Vref Iref Iref

M1 M2 M10 M11 M3 M6 M7 M8 M9 M12

boxed devices in weak inversion saturation: I = F(V ) = Irefe

V −Vref nUt

I > 0

Note: presented by same authors in ISCAS’00

Vref used to optimize low-voltage: M3,12 do not need saturation! K allows simple frequency compensation ζ = 1

2

  • KCcomp

Cin

K ≥ 2

Cin Ccomp

× Iref limits the full-scale due to log-mapping: Imax ≡ Iref

2

with thermal noise: ∆SNR = +3dB/oct(Iref) . . . poor improvement!

  • X. Redondo and F. Serra-Graells

Institut de Microelectrònica de Barcelona

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SLIDE 7

ISCAS’05 1V Compact Class-AB CMOS Log Filters Intro Class-A Class-AB Example Conclusions 7/23

Integrator

◮ ODE in the lineal I-domain:

dIout dt = ±1 τ Iin

◮ ODE in the compressed V -domain:

dVout dt = ±nUt τ e

Vin−Vout nUt

◮ ODE in the circuit Q-domain:

dQout dt = C dVout dt

Icap

= ±Itune

Vin−Vout nUt

τ = nUtC Itun

Vout C Itun Icap Vin

M1 M2 M3 M4 M5

Tunable time constant Single dis/charge due to log mapping (Iin > 0), op ensured at filter level Half integrator shared × SNR issues (Itun ≥ Iref) cause high-value C!

  • X. Redondo and F. Serra-Graells

Institut de Microelectrònica de Barcelona

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SLIDE 8

ISCAS’05 1V Compact Class-AB CMOS Log Filters Intro Class-A Class-AB Example Conclusions 8/23

1 Introduction 2 Basic Class-A Operation 3 New Class-AB Proposal 4 Design Example 5 Conclusions

  • X. Redondo and F. Serra-Graells

Institut de Microelectrònica de Barcelona

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SLIDE 9

ISCAS’05 1V Compact Class-AB CMOS Log Filters Intro Class-A Class-AB Example Conclusions 9/23

Input Splitter and Compressor

◮ Differential signaling:

Iin = Iinp − Iinn Iinp,n > 0

◮ Constant geometric

mean splitting: IinpIinn = I2

ref

Same low-voltage capability as Class-A Full-scale ImaxIref Optimization: Iref ↓ ∆SNR≃+6dB/oct(Imax)

Iin

K 1

Iref K

Vinn Vref Iref Iref Iref Vref

Iinn Iinp

Vinp

M1 M2 M3 M4 M5 M6 M7 M8

  • current multiplier M1-M4
  • I2

ref

Iinp feedback M6-M8

  • M2 shared by TL+compressors
  • X. Redondo and F. Serra-Graells

Institut de Microelectrònica de Barcelona

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SLIDE 10

ISCAS’05 1V Compact Class-AB CMOS Log Filters Intro Class-A Class-AB Example Conclusions 10/23

Differential Integrator with CMFB (1)

◮ ODE in the linear I-domain for multiple-inputs:

dIout dt = 1 τ

  • K

±IinK (even different τK)

◮ High-gain CMFB to ensure geometric-mean common-mode:

dIoutp dt = 1 τ

  • K

±IinpK−IoutpIoutn Iref + Iref

  • dIoutn

dt = 1 τ

  • K

±IinnK−IoutpIoutn Iref + Iref

  • Does not affect Iout

CMFB overhead ∝ filter order filter complexity

  • X. Redondo and F. Serra-Graells

Institut de Microelectrònica de Barcelona

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SLIDE 11

ISCAS’05 1V Compact Class-AB CMOS Log Filters Intro Class-A Class-AB Example Conclusions 11/23

Differential Integrator with CMFB (2)

◮ ODE in the compressed V -domain:

dVoutp dt = nUt τ

  • K

±IinpK Ioutp −Ioutn Iref + Iref Ioutp

  • dVoutn

dt = nUt τ

  • K

±IinnK Ioutn −Ioutp Iref + Iref Ioutn

  • ◮ Finally, ODE in the circuit Q-domain:

dQoutp dt = Itun

  • K

±e

VinpK −Voutp nUt

−e

Voutn−Vref nUt

+ e

Vref −Voutp nUt

  • cross coupled

dQoutn dt = Itun

  • K

±e

VinnK −Voutn nUt

−e

Voutp−Vref nUt

+ e

Vref −Voutn nUt

  • X. Redondo and F. Serra-Graells

Institut de Microelectrònica de Barcelona

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SLIDE 12

ISCAS’05 1V Compact Class-AB CMOS Log Filters Intro Class-A Class-AB Example Conclusions 12/23

Differential Integrator with CMFB (and 3)

◮ Realization:

dQoutp dt = Itun

  • K

±e

VinpK −Voutp nUt

−e

Voutn−Vref nUt

+e

Vref −Voutp nUt

  • dQoutn

dt = Itun

  • K

±e

VinnK −Voutn nUt

−e

Voutp−Vref nUt

+e

Vref −Voutn nUt

  • Low-voltage capability

Most CMFB shared by 1. . . K Half CMFB shared by all C’s Iref ↓ allows Itun ↓, so downscaling C (Si area)

Voutp C Itun Icapp VinpK Vinp1

M1 MK ...

... Voutn C Itun Icapn VinnK Vinn1

...

...

  • X. Redondo and F. Serra-Graells

Institut de Microelectrònica de Barcelona

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SLIDE 13

ISCAS’05 1V Compact Class-AB CMOS Log Filters Intro Class-A Class-AB Example Conclusions 13/23

Differential Integrator with CMFB (and 3)

◮ Realization:

dQoutp dt = Itun

  • K

±e

VinpK −Voutp nUt

−e

Voutn−Vref nUt

+e

Vref −Voutp nUt

  • dQoutn

dt = Itun

  • K

±e

VinnK −Voutn nUt

−e

Voutp−Vref nUt

+e

Vref −Voutn nUt

  • Low-voltage capability

Most CMFB shared by 1. . . K Half CMFB shared by all C’s Iref ↓ allows Itun ↓, so downscaling C (Si area)

Voutp C Itun Icapp VinpK Vref Vinp1

M1 MK ...

...

MC1

Voutn C Itun Icapn VinnK Vref Vinn1

...

...

  • X. Redondo and F. Serra-Graells

Institut de Microelectrònica de Barcelona

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SLIDE 14

ISCAS’05 1V Compact Class-AB CMOS Log Filters Intro Class-A Class-AB Example Conclusions 14/23

Differential Integrator with CMFB (and 3)

◮ Realization:

dQoutp dt = Itun

  • K

±e

VinpK −Voutp nUt

−e

Voutn−Vref nUt

+e

Vref −Voutp nUt

  • dQoutn

dt = Itun

  • K

±e

VinnK −Voutn nUt

−e

Voutp−Vref nUt

+e

Vref −Voutn nUt

  • Low-voltage capability

Most CMFB shared by 1. . . K Half CMFB shared by all C’s Iref ↓ allows Itun ↓, so downscaling C (Si area)

Voutp C Itun Icapp VinpK Itun Vref Vref Vinp1

M1 MK ...

...

MC1 MC2

Voutn C Itun Icapn VinnK Vref Vinn1

...

...

  • X. Redondo and F. Serra-Graells

Institut de Microelectrònica de Barcelona

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SLIDE 15

ISCAS’05 1V Compact Class-AB CMOS Log Filters Intro Class-A Class-AB Example Conclusions 15/23

Differential Integrator with CMFB (and 3)

◮ Realization:

dQoutp dt = Itun

  • K

±e

VinpK −Voutp nUt

−e

Voutn−Vref nUt

+e

Vref −Voutp nUt

  • dQoutn

dt = Itun

  • K

±e

VinnK −Voutn nUt

−e

Voutp−Vref nUt

+e

Vref −Voutn nUt

  • Low-voltage capability

Most CMFB shared by 1. . . K Half CMFB shared by all C’s Iref ↓ allows Itun ↓, so downscaling C (Si area)

Voutp C Itun Icapp VinpK Itun Vref Vref Vinp1

M1 MK ...

...

MC1 MC2

Voutn C Itun Icapn VinnK Vref Vinn1

...

...

  • X. Redondo and F. Serra-Graells

Institut de Microelectrònica de Barcelona

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SLIDE 16

ISCAS’05 1V Compact Class-AB CMOS Log Filters Intro Class-A Class-AB Example Conclusions 16/23

Output Expanders

◮ Differential to single-ended:

Iout = Ioutp − Ioutn Iout = Iref

  • e

Voutp−Vref nUt

− e

Voutn−Vref nUt

  • Vref

Iref Voutp Voutn Iout

M1 M2 M3

Low-voltage capability like Class-A Same Iref↓ as compressors M1,2 expanders share half circuitry For multiple outputs, all expanders can share this part. . .

  • X. Redondo and F. Serra-Graells

Institut de Microelectrònica de Barcelona

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SLIDE 17

ISCAS’05 1V Compact Class-AB CMOS Log Filters Intro Class-A Class-AB Example Conclusions 17/23

1 Introduction 2 Basic Class-A Operation 3 New Class-AB Proposal 4 Design Example 5 Conclusions

  • X. Redondo and F. Serra-Graells

Institut de Microelectrònica de Barcelona

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SLIDE 18

ISCAS’05 1V Compact Class-AB CMOS Log Filters Intro Class-A Class-AB Example Conclusions 18/23

Second-Order Band-Pass Log-Filter

C Itun Vref Vref Itun C Itun Voutp Voutn Vref Itun Iout

Iin

K 1

Iref K

Vinn Vref Iref Iref Iref Vref Vinp C Itun C Itun

2

Itun Vref

2

Itun

◮ fcenter = 42KHz ◮ Q = 1

  • X. Redondo and F. Serra-Graells

Institut de Microelectrònica de Barcelona

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SLIDE 19

ISCAS’05 1V Compact Class-AB CMOS Log Filters Intro Class-A Class-AB Example Conclusions 19/23

Class-A versus New Class-AB

◮ 0.35µm CMOS

technology

◮ Designed for the

same full-scale

◮ IMD analysis

through periodic steady-state

(PSS) simulations:

fin1 = 40KHz fin2 = 44KHz

Frequency[KHz] 100 10 1 Iout Iin / [dB]

  • 20

1000

  • 10
  • 30
  • X. Redondo and F. Serra-Graells

Institut de Microelectrònica de Barcelona

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SLIDE 20

ISCAS’05 1V Compact Class-AB CMOS Log Filters Intro Class-A Class-AB Example Conclusions 20/23

Class-A versus New Class-AB

◮ 0.35µm CMOS

technology

◮ Designed for the

same full-scale

◮ IMD analysis

through periodic steady-state

(PSS) simulations:

fin1 = 40KHz fin2 = 44KHz

InputAmplitude[ ]

peak

¹A 100 10 1 0.1 IMD [%] 1 0.1 0.01 0.001 10

Class-A Class-AB

  • X. Redondo and F. Serra-Graells

Institut de Microelectrònica de Barcelona

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SLIDE 21

ISCAS’05 1V Compact Class-AB CMOS Log Filters Intro Class-A Class-AB Example Conclusions 21/23

Overall Results

Class-A Class-AB Units Supply voltage 1 V VT ON+|VT OP | 1.2 V Vref 0.5 V Iref (and Itun) 10 2.5 µA C 1000 250 pF Boxed-MOSFET ratios 50× 40

1.5

21× 40

1.5 µm µm

Signal full-scale ∼10 µAp IMD @ half full-scale 0.15 0.3 % DR (10KHz-100KHz) 68 >68 dB Quiescent power 150 85 µW Total capacitance 2000 1000 pF Total boxed-MOS area 0.033 0.037 mm2

  • 40% overall power
  • 50% capacitance area
  • X. Redondo and F. Serra-Graells

Institut de Microelectrònica de Barcelona

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SLIDE 22

ISCAS’05 1V Compact Class-AB CMOS Log Filters Intro Class-A Class-AB Example Conclusions 22/23

1 Introduction 2 Basic Class-A Operation 3 New Class-AB Proposal 4 Design Example 5 Conclusions

  • X. Redondo and F. Serra-Graells

Institut de Microelectrònica de Barcelona

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SLIDE 23

ISCAS’05 1V Compact Class-AB CMOS Log Filters Intro Class-A Class-AB Example Conclusions 23/23

Conclusions

◮ Very low-voltage Class-AB CMOS log filters ◮ Complete set of basic building blocks:

splitting, compression, expansion, integration and CMFB

◮ Quiescent low-power consumption ◮ Compact area with reduced circuit overhead ◮ 0.35µm CMOS Class-A/AB comparative example

  • X. Redondo and F. Serra-Graells

Institut de Microelectrònica de Barcelona