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A CMOS Potentiostatic Delta-Sigma for - - PowerPoint PPT Presentation

Mar 23, 2023 1.03k likes •1.37k views

Low-power potentiostat 2 nd Order CT ADC for ECS 1/26 A CMOS Potentiostatic Delta-Sigma for Electrochemical Sensors Joan Aymerich, Michele Dei, Llus Teres and Francisco Serra-Graells

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SLIDE 1

Low-power potentiostat 2nd Order CT ADC for ECS

  • J. Aymerich Gubern

PRIME 2018

A CMOS Potentiostatic Delta-Sigma for Electrochemical Sensors

Joan Aymerich, Michele Dei, Lluís Teres and Francisco Serra-Graells joan.aymerich@imb-cnm.csic.es

Integrated Circuits and Systems (ICAS) Instituto de Microelectrónica de Barcelona, IMB-CNM(CSIC) July 2018

1/26

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SLIDE 2

Low-power potentiostat 2nd Order CT ADC for ECS

  • J. Aymerich Gubern

PRIME 2018

Sensors Market Vision

Sensors/year Year

56%/year 21%/year 222%/year

Electrochemical sensors are growing exponentially due to potential of miniaturization and mass production

2/26

Several organizations created visions for continued growth to trillion(s) sensors Applications in biosensors, quality control, ...

Expected sensor production growth per year

$15 trillion by 2022 www.tsensorssummit.org Monolithic or hybrid integration

  • nto CMOS platforms
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SLIDE 3

Low-power potentiostat 2nd Order CT ADC for ECS

  • J. Aymerich Gubern

PRIME 2018 3/26

1 Amperometric Electrochemical Sensors Conclusions 2 Potentiostatic Modulator architecture 3 4 5 Low-Power Circuit Implementation 0.18- CMOS Design Example

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SLIDE 4

Low-power potentiostat 2nd Order CT ADC for ECS

  • J. Aymerich Gubern

PRIME 2018 4/26

1 Amperometric Electrochemical Sensors Conclusions 2 Potentiostatic Modulator architecture 3 4 5 Low-Power Circuit Implementation 0.18- CMOS Design Example

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SLIDE 5

Low-power potentiostat 2nd Order CT ADC for ECS

  • J. Aymerich Gubern

PRIME 2018 5/26

Amperometric Electrochemical Sensors

Electrochemical time constant: Measurement independent of the R and C impedances. Three electrodes: Interaction with microorganisms Interaction with microorganisms Selectivity by functionalization Reduced speed and life time Potentiostatic and amperometric

  • perations

Current associated to the electrons involved in a redox process

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SLIDE 6

Low-power potentiostat 2nd Order CT ADC for ECS

  • J. Aymerich Gubern

PRIME 2018 5/26

Amperometric Electrochemical Sensors

Cyclic Voltammetry (CV) Different detection methods are required Chronoamperometry (CA) Sensor performance, rapid location of redox potentials, ... fixed and monitored as a function of time while concentration is swept

1

0.7 0.0 0.1 0.2 0.3 0.4 0.5 0.6

t [s]

[A]

  • 1
  • 1

1 1

  • 1

1

[A]

1

t [s]

1

Sweeping electrode potential and measuring resulting current

Oxidation Reduction

Potentiostat must sink/source current

0.1mM 0.2mM 0.3mM 0.4mM 0.5mM 0.6mM 2mM

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SLIDE 7

Low-power potentiostat 2nd Order CT ADC for ECS

  • J. Aymerich Gubern

PRIME 2018

Classic circuit implementation

A1 establishes the control loop to accomplish potentiostat operation & Requires multiples OpAmps + ADC A2 converts sensor current to voltage for digitization and readout Large area and power consumption Potentiostat Amperometry

6/26

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SLIDE 8

Low-power potentiostat 2nd Order CT ADC for ECS

  • J. Aymerich Gubern

PRIME 2018 7/26

1 Amperometric Electrochemical Sensors Conclusions 2 Potentiostatic Modulator architecture 3 4 5 Low-Power Circuit Implementation 0.18- CMOS Design Example

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SLIDE 9

Low-power potentiostat 2nd Order CT ADC for ECS

  • J. Aymerich Gubern

PRIME 2018

Behaviour similar to low-pass first-order single-bit CT A/D modulator Error current converted into voltage and shaped in frequency by the electrochemical sensor itself High oversampling ratios (OSR>100) can be easly obtained with kHz-range clock frequencies fS

8/26

Potentiostatic

Amperometric read-out through the modulation of output bit stream by chemical input

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SLIDE 10

Low-power potentiostat 2nd Order CT ADC for ECS

  • J. Aymerich Gubern

PRIME 2018

From electrochemical only to hybrid/mixed EC/electronic

9/26

Allows precise potentiostatic operation Feed-Forward through Stabilize the loop Electronic time constant

[5] J. Aymerich, M. Dei, L. Terés and F. Serra-Graells, ”Design of a Low-Power Potentiostatic Second-Order CT Delta-Sigma ADC for Electrochemical Sensors, ” 2017 13th Conference on Ph.D. Research in Microelectronics and Electronics (PRIME)

Tones and pattern noise suppression

9/26

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SLIDE 11

Low-power potentiostat 2nd Order CT ADC for ECS

  • J. Aymerich Gubern

PRIME 2018

Direct path from Vr to input the single-bit quantizer Improved architecture Area and power consumption Low-power CMOS circuits Large flexibility on the selection of potentiostatic voltage Wide common-mode voltage range

10/26

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SLIDE 12

Low-power potentiostat 2nd Order CT ADC for ECS

  • J. Aymerich Gubern

PRIME 2018 11/26

1 Amperometric Electrochemical Sensors Conclusions 2 Potentiostatic Modulator architecture 3 4 5 Low-Power Circuit Implementation 0.18- CMOS Design Example

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SLIDE 13

Low-power potentiostat 2nd Order CT ADC for ECS

  • J. Aymerich Gubern

PRIME 2018

Single-bit quantizer: Wide input common-mode voltage range Transconductance : Wide input/output common-mode voltage range Large flexibility on the selection of potentiostatic voltage. Direct path from Vr to input the single-bit quantizer Improved architecture Area and power consumption Low-power CMOS circuits

12/26

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SLIDE 14

Low-power potentiostat 2nd Order CT ADC for ECS

  • J. Aymerich Gubern

PRIME 2018 13/26

Single-bit quantizer

Rail-to-rail complementary latch comparator Combinational logic allows to merge both NMOS-PMOS-input comparators Zero-static power consumption

Comb. logic

High-input impedance

PMOS-input latch NMOS-input latch

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SLIDE 15

Low-power potentiostat 2nd Order CT ADC for ECS

  • J. Aymerich Gubern

PRIME 2018 14/26

Single-bit quantizer

PMOS OFF: Input common-mode > (Vdd-VTHp) Outp nodes remain at the negative rail regardless Rail-to-rail complementary latch comparator Combinational logic allows to merge both NMOS-PMOS-input comparators Zero-static power consumption High-input impedance

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SLIDE 16

Low-power potentiostat 2nd Order CT ADC for ECS

  • J. Aymerich Gubern

PRIME 2018 15/26

Single-bit quantizer

NMOS OFF: Input common-mode < (VTHn) Outn nodes remain at the positive rail regardless PMOS OFF: Input common-mode > (Vdd-VTHp) Outp nodes remain at the negative rail regardless Rail-to-rail complementary latch comparator Combinational logic allows to merge both NMOS-PMOS-input comparators Zero-static power consumption High-input impedance

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SLIDE 17

Low-power potentiostat 2nd Order CT ADC for ECS

  • J. Aymerich Gubern

PRIME 2018

From 1st order to 2nd order

Single-bit quantizer: Wide input common-mode voltage range Transconductance : Wide input/output common-mode voltage range Large flexibility on the selection of potentiostatic voltage. Direct path from Vr to input the single-bit quantizer Improved architecture Area and power consumption Low-power CMOS circuits

16/26

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SLIDE 18

Low-power potentiostat 2nd Order CT ADC for ECS

  • J. Aymerich Gubern

PRIME 2018 17/26

Gm-C Integrator

Constant gm over the input common-mode voltage Sum of the tail currents constant Avoid variations in the electronic integrator time constant M1 - M4 operated in weak inversion Wide output swing Overdrive voltage

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SLIDE 19

Low-power potentiostat 2nd Order CT ADC for ECS

  • J. Aymerich Gubern

PRIME 2018 17/26

1 Amperometric Electrochemical Sensors Conclusions 2 Potentiostatic Modulator architecture 3 4 5 Low-Power Circuit Implementation 0.18- CMOS Design Example

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SLIDE 20

Low-power potentiostat 2nd Order CT ADC for ECS

  • J. Aymerich Gubern

PRIME 2018 18/26

Gm-C integrator occupy most of the area

Low-power 0.18- CMOS Design

to minimize offset, i.e potentiostatic error (Vr - Vpot) slow integrator time constant (sampling frequency @ 1kHz) Large Feedback DAC To minimize low-frequency noise. (DAC noise added directly to the input, it is not shaped by the delta-sigma loop-filter) Ongoing run XFAB-XH018

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SLIDE 21

Low-power potentiostat 2nd Order CT ADC for ECS

  • J. Aymerich Gubern

PRIME 2018

Post-Layout Simulations

19/26

Output spectrum comparison w/ and w/o electronic transient

40dB/dec

70-dB dynamic range for 1.25uA current full scale. (280pA RMS, noise) Higher resolution is achievable enlarging the area of the feedback DAC

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SLIDE 22

Low-power potentiostat 2nd Order CT ADC for ECS

  • J. Aymerich Gubern

PRIME 2018

Post-Layout Simulations

Cyclic Voltammetry Triangular waveform is applied to the reference electrode while the sensor current is measured simultaneously VerilogA model: Vrw-Isens DC look-up tables based on two experimental measurements of ferricyanide CVs

23/26

0.7 0.0 0.1 0.2 0.3 0.4 0.5 0.6

t [s]

Vpot-Vref [V]

0.9 1.8

V p

  • t
  • V

r e f [ V ]

0.7 0.2 0.4 0.6 0.5 0.1 0.3

Ferricyanide Cyclic Voltammetry

20/26

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SLIDE 23

Low-power potentiostat 2nd Order CT ADC for ECS

  • J. Aymerich Gubern

PRIME 2018

Simulation Results

21/26

Performance simulation results Power consumption mainly determined by feedback current DAC Rest of circuit blocks

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SLIDE 24

Low-power potentiostat 2nd Order CT ADC for ECS

  • J. Aymerich Gubern

PRIME 2018 22/26

1 Amperometric Electrochemical Sensors Conclusions 2 Potentiostatic Modulator architecture 3 4 5 Low-Power Circuit Implementation 0.18- CMOS Design Example

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SLIDE 25

Low-power potentiostat 2nd Order CT ADC for ECS

  • J. Aymerich Gubern

PRIME 2018 23/26

Conclusions

High resolution with kHz-range clock frequencies: Compact architecture thanks to the electrode-electrolyte interface used as an integrator stage in the structure Minimalist analog circuits fully integrable in purely digital CMOS technologies Low-power ( ) operation compared to sensor consumption

Conclusions

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SLIDE 26

Low-power potentiostat 2nd Order CT ADC for ECS

  • J. Aymerich Gubern

PRIME 2018 24/26

Conclusions

High resolution with kHz-range clock frequencies: Compact architecture thanks to the electrode-electrolyte interface used as an integrator stage in the structure Minimalist analog circuits fully integrable in purely digital CMOS technologies Low-power ( ) operation compared to sensor consumption

Conclusions

Energy storage Electrochemical sensor <1mm2 ASIC: Potentiostat RF antennas Smart tags for food quality control Wireless contact lens for health monitoring

Future work

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SLIDE 27

Low-power potentiostat 2nd Order CT ADC for ECS

  • J. Aymerich Gubern

PRIME 2017 10/26

Single-bit quantizer

PMOS and NMOS ON Vint > Vr Rail-to-rail complementary latch comparator Combinational logic allows to merge both NMOS-PMOS-input comparators Zero-static power consumption

slide-28
SLIDE 28

Low-power potentiostat 2nd Order CT ADC for ECS

  • J. Aymerich Gubern

PRIME 2017 10/26

Single-bit quantizer

PMOS and NMOS ON Rail-to-rail complementary latch comparator Combinational logic allows to merge both NMOS-PMOS-input comparators Zero-static power consumption Vint > Vr Vint < Vr

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SLIDE 29

Low-power potentiostat 2nd Order CT ADC for ECS

  • J. Aymerich Gubern

PRIME 2017 26/26

Single-bit quantizer

PMOS and NMOS ON Rail-to-rail complementary latch comparator Combinational logic allows to merge both NMOS-PMOS-input comparators Zero-static power consumption Vint > Vr Vint < Vr

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SLIDE 30

Low-power potentiostat 2nd Order CT ADC for ECS

  • J. Aymerich Gubern

PRIME 2017 26/26

Power Consumption Comparison