a0.35µm1.25vpiezo-resistance digitalroic ...pserra/cnm/2008 - a 0.35um 1.25v piezo... ·...
TRANSCRIPT
ISCAS’08: A Piezo-Resist. Digital ROIC for MEMS Intro Balancing Preamp ADC CMOS Conclusions 1/26
A 0.35µm 1.25V Piezo-ResistanceDigital ROIC
for Liquid Dispensing MEMS
R. Durà1, F. Mathieu2, L. Nicu2, F. Pérez-Murano1
and F. Serra-Graells1
1Centro Nacional de Microelectrónica - CSIC (Spain)2 Laboratoire d’Analyse et d’Architecture des Systèmes - CNRS (France)
May 2008
R. Durà et al. Centro Nacional de Microelectrónica
ISCAS’08: A Piezo-Resist. Digital ROIC for MEMS Intro Balancing Preamp ADC CMOS Conclusions 2/26
1 Introduction
2 Input Gain Balancing
3 Differential Pre-Amplification
4 Integrating A/D Conversion
5 CMOS Integration
6 Conclusions
R. Durà et al. Centro Nacional de Microelectrónica
ISCAS’08: A Piezo-Resist. Digital ROIC for MEMS Intro Balancing Preamp ADC CMOS Conclusions 3/26
1 Introduction
2 Input Gain Balancing
3 Differential Pre-Amplification
4 Integrating A/D Conversion
5 CMOS Integration
6 Conclusions
R. Durà et al. Centro Nacional de Microelectrónica
ISCAS’08: A Piezo-Resist. Digital ROIC for MEMS Intro Balancing Preamp ADC CMOS Conclusions 4/26
Bioplume Scenario
I Liquid dispensing MEMSfor µdroplet patterning
I Integrated piezo-resistive stresssensor to control positioning
I Dummy-based differentialreading to cancel T/M/Edisturbing signals
I Multi channel digital ROICI Low-power to prevent dryingI Low-voltage for single cell
battery operation
microdroplets
referencepipet
digital I/O
battery
ROIC
pipet tip
activepipets
piezo-resistivestresssensor
cantilever
liquid reservoir
R. Durà et al. Centro Nacional de Microelectrónica
ISCAS’08: A Piezo-Resist. Digital ROIC for MEMS Intro Balancing Preamp ADC CMOS Conclusions 5/26
Integratedpiezo-resistance
I Nominal value:5KΩ to 10KΩ100% (±20%)
I Quasi-staticstress signal (9bit):±0.0004%. . .±0.1%
I Technologymismatching: ±2%
I Dynamic disturbingsignals: ±1%
⇓
±0.02% (50LSB) dynamic residual!
Rref
Rsens
nominalvalue
(100%)
mismatching( 2%)§
common disturbingsignals ( )1%§
quasi-static stress signal( )0.0004%... 0.1%§ §piezo-resistance
time1ms0
sampling period
Rsens-Rref
differential disturbingsignals ( 0.02 )%§
offset ( 2 )%§
R. Durà et al. Centro Nacional de Microelectrónica
ISCAS’08: A Piezo-Resist. Digital ROIC for MEMS Intro Balancing Preamp ADC CMOS Conclusions 6/26
Gain BalancingStrategy
I Maximum gaincompensation: ±2%
I Gain accuracy:±0.0002%/2%=±0.01%
I Gain dynamic range:2%/0.01%=(8+1)bit
I Residual dynamicdisturbing: ±0.25LSB
I Residual DC: ±25LSBcompensated bydigital post-processing
Rref
Rsens
nominalvalue
(100%)
mismatching( 2%)§
common disturbingsignals ( )1%§
quasi-static stress signal( )0.0004%... 0.1%§ §piezo-resistance
time1ms0
sampling period
Rsens-Rref
differential disturbingsignals ( 0.02 )%§
offset ( 2 )%§
R. Durà et al. Centro Nacional de Microelectrónica
ISCAS’08: A Piezo-Resist. Digital ROIC for MEMS Intro Balancing Preamp ADC CMOS Conclusions 7/26
ROIC ArchitectureI Parallel processing to
reduce noise bandwidthI Overall programmable
sensitivity (Icom)I Differential gain
balancing through sensorbias (∆Icom)
I OTA pre-amplificationI Integrating A/D
conversionI Digital only
read-out/program-inI Independent references
to avoid crosstalk
Rsens2
Rsens1
Rref
Vcom
ADC
I/O
DAC
Vsens
Icom
Ieff
Rsens3
Rsens4
Icom
Vref
¢Icom
S11-0
C8-0
R. Durà et al. Centro Nacional de Microelectrónica
ISCAS’08: A Piezo-Resist. Digital ROIC for MEMS Intro Balancing Preamp ADC CMOS Conclusions 8/26
1 Introduction
2 Input Gain Balancing
3 Differential Pre-Amplification
4 Integrating A/D Conversion
5 CMOS Integration
6 Conclusions
R. Durà et al. Centro Nacional de Microelectrónica
ISCAS’08: A Piezo-Resist. Digital ROIC for MEMS Intro Balancing Preamp ADC CMOS Conclusions 9/26
Input Gain Balancing
I Calibration throughDAC: ∆Icom(C8-0)
I Gate tuning:
∆Vtun = C2C1+C2
(Vprog − VDD2 )
I Compensation ofpiezo mismatch +OTA unbalance
I Repeated before everyacquisition
I Design parameters:C1=9pF, C2=0.5pF
Rsens
Vcom
Rref
IeffVref
Vsens
25
Icom
phasegenerator
ADC
2225 3
Á1 Á2
Á3Á4
Á5 Á7
Á6
0
1
2
3
4
5
6
7
8
Á1 Á7
Á7
C1
C2
C2 C2 C2 C2
M2 M1
Icom Icom§¢Icom
Vtun
Vprog
gain preset gain calibration refresh A/D conversion
Á1
Á2
Á3
Á4
Á5
Á6
Á7 0 1 2 3 4 5 6 7 8
Tint
C
Vsens−Vref = Icom[Rsens
(1± ∆Icom
Icom
)− Rref
]
R. Durà et al. Centro Nacional de Microelectrónica
ISCAS’08: A Piezo-Resist. Digital ROIC for MEMS Intro Balancing Preamp ADC CMOS Conclusions 10/26
1 Introduction
2 Input Gain Balancing
3 Differential Pre-Amplification
4 Integrating A/D Conversion
5 CMOS Integration
6 Conclusions
R. Durà et al. Centro Nacional de Microelectrónica
ISCAS’08: A Piezo-Resist. Digital ROIC for MEMS Intro Balancing Preamp ADC CMOS Conclusions 11/26
OTA PreamplifierI Differential V to
single ended I
Ieff = Gm (Vsens −Vref )
I Equivalent inputlow-noise
I Large diff. gain(in subthreshold):
Gm = IbiasnnUt
I High commonrejection ratio
I Design parameters:Ibiasp,n = 56µA, 44µA
M2
2Ibiasn
M1
Rsens
Vcom
Rref
IeffADC
Vref
Vsens
Icom
M6M5
M7 M8
M4M3
Ibiasp
Icom Icom§¢
DR(Vsens) ∼ 1mV/4µV
(Rsens ∼ 5kΩ and Icom ∼ 200µA)
R. Durà et al. Centro Nacional de Microelectrónica
ISCAS’08: A Piezo-Resist. Digital ROIC for MEMS Intro Balancing Preamp ADC CMOS Conclusions 12/26
OTA PreamplifierI Differential V to
single ended I
Ieff = Gm (Vsens −Vref )
I Equivalent inputlow-noise
I Large diff. gain(in subthreshold):
Gm = IbiasnnUt
I High commonrejection ratio
I Design parameters:Ibiasp,n = 56µA, 44µA
Frequency [Hz]
1
processcorners
0.1
0.01100 1k101
rms
Vneq ' 2µVrms up to 1kHz
(Vnres ∼ 0.4µVrms for Rsens = 10kΩ)
R. Durà et al. Centro Nacional de Microelectrónica
ISCAS’08: A Piezo-Resist. Digital ROIC for MEMS Intro Balancing Preamp ADC CMOS Conclusions 13/26
OTA PreamplifierI Differential V to
single ended I
Ieff = Gm (Vsens −Vref )
I Equivalent inputlow-noise
I Large diff. gain(in subthreshold):
Gm = IbiasnnUt
I High commonrejection ratio
I Design parameters:Ibiasp,n = 56µA, 44µA
Diffe
rential
tra
nsc
onduct
ance
[m
S]
1
Frequency [Hz]
0.1
0.01
10
0.01100 10k 1M 100M
processcorners
Gm ≥ 0.8mS
DR(Ieff ) ∼ 1µA/4nA
R. Durà et al. Centro Nacional de Microelectrónica
ISCAS’08: A Piezo-Resist. Digital ROIC for MEMS Intro Balancing Preamp ADC CMOS Conclusions 14/26
OTA PreamplifierI Differential V to
single ended I
Ieff = Gm (Vsens −Vref )
I Equivalent inputlow-noise
I Large diff. gain(in subthreshold):
Gm = IbiasnnUt
I High commonrejection ratio
I Design parameters:Ibiasp,n = 56µA, 44µA
1CMRR = ∆Gm
Gm
(1− 1
1 + 12nGmRtail
)CMRR→∞ for ∆Gm → 0 or Rtail →∞
MOSFET mismatching + Ibiasn finite impedance
50
10
0
2
4
6
8
Fre
quen
cy [%
]
CMRR(DC) [dB]
100 150
1%0.0002%
=75dB
R. Durà et al. Centro Nacional de Microelectrónica
ISCAS’08: A Piezo-Resist. Digital ROIC for MEMS Intro Balancing Preamp ADC CMOS Conclusions 15/26
1 Introduction
2 Input Gain Balancing
3 Differential Pre-Amplification
4 Integrating A/D Conversion
5 CMOS Integration
6 Conclusions
R. Durà et al. Centro Nacional de Microelectrónica
ISCAS’08: A Piezo-Resist. Digital ROIC for MEMS Intro Balancing Preamp ADC CMOS Conclusions 16/26
A/D Conversion
I Spike counting:PDM+digital filter
I CDS forlow-frequency noisesuppression
I Low-voltageswitching ⇒large reset times
I Design parameters:Cint = 4pF,Vth = 312mV
X Classic PDM:reset-timenon-linearity
Vint
up
V Vref th-
digitalcounter
init
event
V Vref th+
down
Cint
Vref
IeffCCDS
init+event
init+event
Time
Vint
event
Vth
Vref
Upper range saturation of the A/D curve!
R. Durà et al. Centro Nacional de Microelectrónica
ISCAS’08: A Piezo-Resist. Digital ROIC for MEMS Intro Balancing Preamp ADC CMOS Conclusions 17/26
A/D Conversion
I Spike counting:PDM+digital filter
I CDS forlow-frequency noisesuppression
I Low-voltageswitching ⇒large reset times
I Design parameters:Cint = 4pF,Vth = 312mV
X New insensitive PDM
S11-0 = ± IeffTint
CintVth= ±GmTint
CintVthIcom[
Rsens
(1± ∆Icom
Icom
)− Rref
]
Vint
up
V Vref th-
digitalcounter
init
event
V Vref th+
down
Cint
Vref
init
Creset/CDS
event
Ieff
Vint
event
Vth
Vref
Time
R. Durà et al. Centro Nacional de Microelectrónica
ISCAS’08: A Piezo-Resist. Digital ROIC for MEMS Intro Balancing Preamp ADC CMOS Conclusions 18/26
Low-Voltage CMOS Blocks
I Compact CTIA with CDSVint
Cint Vref
Ieff
init
Creset/CDS
event
M1 M2
R. Durà et al. Centro Nacional de Microelectrónica
ISCAS’08: A Piezo-Resist. Digital ROIC for MEMS Intro Balancing Preamp ADC CMOS Conclusions 19/26
Low-Voltage CMOS Blocks
I Compact CTIA with CDS
I Class-AB window comparator
Vint
V Vref th+
down
V Vref th-
up
M1 M2
M3
M4
R. Durà et al. Centro Nacional de Microelectrónica
ISCAS’08: A Piezo-Resist. Digital ROIC for MEMS Intro Balancing Preamp ADC CMOS Conclusions 20/26
Low-Voltage CMOS Blocks
I Compact CTIA with CDS
I Class-AB window comparator
I Modular and floatingthreshold generator
∆Vth = Ut ln[
(W/L)B(W/L)A
(1 + IB
IA
)+ 1]
MA : weak inversion conductionMB : weak inversion saturation
MA1
MB1 ¢VthMA2
MB2
Vref
init V Vref th+
V Vref th-
Vth
MA3
MB3
IB
IA
R. Durà et al. Centro Nacional de Microelectrónica
ISCAS’08: A Piezo-Resist. Digital ROIC for MEMS Intro Balancing Preamp ADC CMOS Conclusions 21/26
1 Introduction
2 Input Gain Balancing
3 Differential Pre-Amplification
4 Integrating A/D Conversion
5 CMOS Integration
6 Conclusions
R. Durà et al. Centro Nacional de Microelectrónica
ISCAS’08: A Piezo-Resist. Digital ROIC for MEMS Intro Balancing Preamp ADC CMOS Conclusions 22/26
ROIC Integration
I 0.35µm 2P 4M CMOS technology 2.4mm × 1.3mm = 3.1mm2
R. Durà et al. Centro Nacional de Microelectrónica
ISCAS’08: A Piezo-Resist. Digital ROIC for MEMS Intro Balancing Preamp ADC CMOS Conclusions 23/26
ROIC Integration
I 0.35µm 2P 4M CMOS technology 2.4mm × 1.3mm = 3.1mm2
Singlechannel
Sensorbias
Preamp
DAC
ADC
DigitalI/O
R. Durà et al. Centro Nacional de Microelectrónica
ISCAS’08: A Piezo-Resist. Digital ROIC for MEMS Intro Balancing Preamp ADC CMOS Conclusions 24/26
Results
I MEMS + ROIC integrationnot completed yet. . .
I Meanwhile, results frompost-layout simulation
I 4 channel power supply:1.5mW at 1.25V
I Ideally:
∣∣∣∣ S11-0
∆Rsens/Rsens
∣∣∣∣ = GmTint
CintVthIcomRsens ≡
0.8mS× 1ms4pF× 312mV×189µA×5kΩ ' 6kLSB/%
Vth PTAT and Gm 1/PTAT. If Icom,bias PTAT ⇒ S11-0 6= f (T)
S11-0
[LSB
]
600
400
200
0
-200
-400
-6000.02 0.04 0.06 0.08 0.1-0.02-0.04-0.06-0.08-0.1 0
Rsens=5k−
Icom=189 A¹
C '100001000'8-0
=
Tint=1ms
R. Durà et al. Centro Nacional de Microelectrónica
ISCAS’08: A Piezo-Resist. Digital ROIC for MEMS Intro Balancing Preamp ADC CMOS Conclusions 25/26
1 Introduction
2 Input Gain Balancing
3 Differential Pre-Amplification
4 Integrating A/D Conversion
5 CMOS Integration
6 Conclusions
R. Durà et al. Centro Nacional de Microelectrónica
ISCAS’08: A Piezo-Resist. Digital ROIC for MEMS Intro Balancing Preamp ADC CMOS Conclusions 26/26
Conclusions
I Quad-channel ROIC for integrated piezo-resistive sensors.I Sensor balancing by digital gain tuning.I Robust built-in A/D conversion.I Low-voltage and low-power CMOS circuit realization.I Integration in 0.35µm 2-poly 4-metal technology.I Post-layout electrical simulation results.
R. Durà et al. Centro Nacional de Microelectrónica