A 10-bit Linearity Current-Controlled Ring Oscillator with Rolling - - PowerPoint PPT Presentation

10-bit Linearity CCRO with Rolling Regulation

• M. Dei et al.

IEEE ISCAS 2017 1/19

A 10-bit Linearity Current-Controlled Ring Oscillator with Rolling Regulation for Smart Sensing

M.Dei1, J.Sacristán1, E.Marigó2, M.Soundara2,L.Terés1,3 and F.Serra-Graells1,3

paco.serra@imb-cnm.csic.es

1Instituto de Microelectrónica de Barcelona, IMB-CNM(CSIC), Spain 2Silterra Malaysia Sdn. Bhd., Malaysia 3Universitat Autònoma de Barcelona, Spain

May 2017

Intro CCRO Rolling-Regulation Example Conclusions

10-bit Linearity CCRO with Rolling Regulation

• M. Dei et al.

IEEE ISCAS 2017 2/19

Introduction 1 CCRO Non-Linearity Issues 2 Rolling Regulation Proposal 3 Design Example in 0.18µm CMOS Technology 5 Conclusions 6

Intro CCRO Rolling-Regulation Example Conclusions

10-bit Linearity CCRO with Rolling Regulation

• M. Dei et al.

IEEE ISCAS 2017 3/19 Intro CCRO Rolling-Regulation Example Conclusions

Introduction 1 CCRO Non-Linearity Issues 2 Rolling Regulation Proposal 3 Design Example in 0.18µm CMOS Technology 5 Conclusions 6

10-bit Linearity CCRO with Rolling Regulation

• M. Dei et al.

IEEE ISCAS 2017 4/19

Introduction

Time-domain processing for low-voltage digital-like ADCs Current-controlled ring oscillator (CCRO) to interface with current-mode sensors (e.g. optical, chemical) Coarse/fine architectures for low-power operation

Intro CCRO Rolling-Regulation Example Conclusions

10-bit Linearity CCRO with Rolling Regulation

• M. Dei et al.

IEEE ISCAS 2017 5/19

Introduction

Time-domain processing for low-voltage digital-like ADCs Signal dependency of CCRO rail voltage (VOSC) causes I-to-F non-linearity Current-controlled ring oscillator (CCRO) to interface with current-mode sensors (e.g. optical, chemical) Coarse/fine architectures for low-power operation Current steering to improve uniformity of fine quantization Classic current-starving circuit implementation

Intro CCRO Rolling-Regulation Example Conclusions

10-bit Linearity CCRO with Rolling Regulation

• M. Dei et al.

IEEE ISCAS 2017 6/19 Intro CCRO Rolling-Regulation Example Conclusions

Introduction 1 CCRO Non-Linearity Issues 2 Rolling Regulation Proposal 3 Design Example in 0.18µm CMOS Technology 5 Conclusions 6

10-bit Linearity CCRO with Rolling Regulation

• M. Dei et al.

IEEE ISCAS 2017 7/19

CCRO Non-Linearity Issues

Differential latch (M1,2) with symmetrical load capacitance (Cstage)

Intro CCRO Rolling-Regulation Example Conclusions

10-bit Linearity CCRO with Rolling Regulation

• M. Dei et al.

IEEE ISCAS 2017 8/19

CCRO Non-Linearity Issues

Differential latch (M1,2) with symmetrical load capacitance (Cstage) PMOS transistors define rail voltage:

EKV model in strong inversion forward saturation

Intro CCRO Rolling-Regulation Example Conclusions

10-bit Linearity CCRO with Rolling Regulation

• M. Dei et al.

IEEE ISCAS 2017 9/19

CCRO Non-Linearity Issues

Differential latch (M1,2) with symmetrical load capacitance (Cstage)

1 2 3 4 5 6 7 8 9 10 1 2 3 4 5 6 7 8 9 10

Strong non-linearities for high-current full scale or low-voltage operation

Intro CCRO Rolling-Regulation Example Conclusions

PMOS transistors define rail voltage:

10-bit Linearity CCRO with Rolling Regulation

• M. Dei et al.

IEEE ISCAS 2017 10/19 Intro CCRO Rolling-Regulation Example Conclusions

Introduction 1 CCRO Non-Linearity Issues 2 Rolling Regulation Proposal 3 Design Example in 0.18µm CMOS Technology 5 Conclusions 6

10-bit Linearity CCRO with Rolling Regulation

• M. Dei et al.

IEEE ISCAS 2017 11/19

CCRO with Rolling Regulation

Series transistor (M3) to regulate rail voltage independently from signal current Second generation current conveyor (CCII+) as common control Rail voltage regulation + signal current steering Control of M3 transistors is ROLLING along the ring like Isens

Intro CCRO Rolling-Regulation Example Conclusions

10-bit Linearity CCRO with Rolling Regulation

• M. Dei et al.

IEEE ISCAS 2017 12/19

CMOS Circuit Implementation

3-stage CCII+ circuit:

Intro CCRO Rolling-Regulation Example Conclusions

+ X-branch to supply

low input impedance and to sense error current

+ Y-branch to bias M4

for any PVT condition so Vosc=Vref when Ierr=0

+ Z-branch to apply

negative-feedback control using error current

10-bit Linearity CCRO with Rolling Regulation

• M. Dei et al.

IEEE ISCAS 2017 13/19

CMOS Circuit Implementation

3-stage CCII+ circuit:

Intro CCRO Rolling-Regulation Example Conclusions

Better stability compared to OpAmp-based solutions: + X-branch to supply

low input impedance and to sense error current

+ Y-branch to bias M4

for any PVT condition so Vosc=Vref when Ierr=0

+ Z-branch to apply

negative-feedback control using error current dominant pole

Rail-voltage low sensitivity respect to signal current

10-bit Linearity CCRO with Rolling Regulation

• M. Dei et al.

IEEE ISCAS 2017 14/19

Introduction 1 CCRO Non-Linearity Issues 2 Rolling Regulation Proposal 3 Design Example in 0.18µm CMOS Technology 5 Conclusions 6

Intro CCRO Rolling-Regulation Example Conclusions

10-bit Linearity CCRO with Rolling Regulation

• M. Dei et al.

IEEE ISCAS 2017 15/19

Application Example

MEMS temperature monitoring

Intro CCRO Rolling-Regulation Example Conclusions

CMOS PTAT reference

• perating in weak inversion

as temperature sensor 10-bit 100-kS/s ADC specifications Design parameters: + 5-bit/5-bit coarse/fine

quantization splitting

+ Vosc = 1.4V

Cstage = 20fF Iptat = 5µA at 300K fosc<4MHz

10-bit Linearity CCRO with Rolling Regulation

• M. Dei et al.

IEEE ISCAS 2017 16/19

Application Example

MEMS temperature monitoring

Intro CCRO Rolling-Regulation Example Conclusions

CMOS PTAT reference

• perating in weak inversion

as temperature sensor 10-bit 100-kS/s ADC specifications Design parameters: + 5-bit/5-bit coarse/fine

quantization splitting

70-µW (at 1.8-V) power consumption

2.6 2.8 3 3.2 3.4 3.6 Frequency [MHz] −40 −30 −20 −10 10 20 30 40 50 60 70 80 90 −1 −0.75 −0.5 −0.25 0.25 0.5 0.75 1 Temperature [C] DNL [LSB]

10-bit linearity for the 125-C temperature span none digital calibration nor post-compensation technique required

+ Vosc = 1.4V

Cstage = 20fF Iptat = 5µA at 300K fosc<4MHz

10-bit Linearity CCRO with Rolling Regulation

• M. Dei et al.

IEEE ISCAS 2017 17/19

Application Example

MEMS temperature monitoring

Intro CCRO Rolling-Regulation Example Conclusions

CMOS PTAT reference

• perating in weak inversion

as temperature sensor 10-bit 100-kS/s ADC specifications Design parameters: + 5-bit/5-bit coarse/fine

quantization splitting

70-µW (at 1.8-V) power consumption ...currently being integrated in 0.18-µm 1P6M CMOS technology.

250µm x 200µm (0.05mm2)

+ Vosc = 1.4V

Cstage = 20fF Iptat = 5µA at 300K fosc<4MHz

10-bit Linearity CCRO with Rolling Regulation

• M. Dei et al.

IEEE ISCAS 2017 18/19

Introduction 1 CCRO Non-Linearity Issues 2 Rolling Regulation Proposal 3 Design Example in 0.18µm CMOS Technology 5 Conclusions 6

Intro CCRO Rolling-Regulation Example Conclusions

10-bit Linearity CCRO with Rolling Regulation

• M. Dei et al.

IEEE ISCAS 2017 19/19

Conclusions

A highly linear I-to-F current-steering CCRO has been presented for ADC

Intro CCRO Rolling-Regulation Example Conclusions

Partially funded by Silterra Malaysia Sdn. Bhd. and supported by CSIC-201650E019 and 2014-SGR-1452

Based on rail-voltage distributed regulation concept Usage of current conveyors to improve loop stability Performance achieved without digital calibration nor post-compensation 10-bit 100-kS/s ADC example in 0.18-µm 1P6M CMOS technology

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