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A Single-Chip CMOS Pulse Oximeter with On-Chip Lock-In Detection.

He D, Morgan SP, Trachanis D, van Hese J, Drogoudis D, Fummi F, Stefanni F, Guarnieri V, Hayes-Gill BR - Sensors (Basel) (2015)

Bottom Line: The experimentally measured AC and DC characteristics of individual circuits including the DC output voltage of the transimpedance amplifier, transimpedance gain of the transimpedance amplifier, and the central frequency and bandwidth of the analogue band-pass filters, show a good match (within 1%) with the circuit simulations.With modulated light source and integrated lock-in detection the sensor effectively suppresses the interference from ambient light and 1/f noise.The single-chip sensor enables a compact and robust design solution that offers a route towards wearable devices for health monitoring.

View Article: PubMed Central - PubMed

Affiliation: Electrical System and Optics Research Division, Faculty of Engineering, University of Nottingham, University Park, Nottingham NG7 2RD, UK. diwei.he@nottingham.ac.uk.

ABSTRACT
Pulse oximetry is a noninvasive and continuous method for monitoring the blood oxygen saturation level. This paper presents the design and testing of a single-chip pulse oximeter fabricated in a 0.35 µm CMOS process. The chip includes photodiode, transimpedance amplifier, analogue band-pass filters, analogue-to-digital converters, digital signal processor and LED timing control. The experimentally measured AC and DC characteristics of individual circuits including the DC output voltage of the transimpedance amplifier, transimpedance gain of the transimpedance amplifier, and the central frequency and bandwidth of the analogue band-pass filters, show a good match (within 1%) with the circuit simulations. With modulated light source and integrated lock-in detection the sensor effectively suppresses the interference from ambient light and 1/f noise. In a breath hold and release experiment the single chip sensor demonstrates consistent and comparable performance to commercial pulse oximetry devices with a mean of 1.2% difference. The single-chip sensor enables a compact and robust design solution that offers a route towards wearable devices for health monitoring.

No MeSH data available.


(a) Block diagram of the sensor. (Photodiode, I/V—Current to Voltage Converter, ADC—analogue to digital converter, Digital signal processor, DAC—digital to analogue converter, LED—light emitting diode)—Items inside dotted region are all “CMOS on-chip”; (b) Layout of the CMOS sensor.
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sensors-15-17076-f001: (a) Block diagram of the sensor. (Photodiode, I/V—Current to Voltage Converter, ADC—analogue to digital converter, Digital signal processor, DAC—digital to analogue converter, LED—light emitting diode)—Items inside dotted region are all “CMOS on-chip”; (b) Layout of the CMOS sensor.

Mentions: Figure 1a illustrates a block diagram of the pulse oximeter sensor. It consists of a 1 mm × 2.5 mm n-well-p-substrate photodiode, a linear transimpedance amplifier having an 8 M Ohm feedback resistor and 30 KHz bandwidth, two Sallen-Key band-pass filters having 2 KHz (band-pass1) and 4 KHz (band-pass2) filter bandwidths respectively, two 10-bit successive approximation register (SAR) ADCs running at a sampling rate of 640 KHz. The digital signal processor includes a quadrature demodulator and LED timing control unit generating 10 KHz and 20 KHz square waves. The LEDs shown in the figure are off-chip components whilst all other components illustrated inside the dotted line are all integrated into a single semi-custom CMOS chip.


A Single-Chip CMOS Pulse Oximeter with On-Chip Lock-In Detection.

He D, Morgan SP, Trachanis D, van Hese J, Drogoudis D, Fummi F, Stefanni F, Guarnieri V, Hayes-Gill BR - Sensors (Basel) (2015)

(a) Block diagram of the sensor. (Photodiode, I/V—Current to Voltage Converter, ADC—analogue to digital converter, Digital signal processor, DAC—digital to analogue converter, LED—light emitting diode)—Items inside dotted region are all “CMOS on-chip”; (b) Layout of the CMOS sensor.
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Related In: Results  -  Collection

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getmorefigures.php?uid=PMC4541923&req=5

sensors-15-17076-f001: (a) Block diagram of the sensor. (Photodiode, I/V—Current to Voltage Converter, ADC—analogue to digital converter, Digital signal processor, DAC—digital to analogue converter, LED—light emitting diode)—Items inside dotted region are all “CMOS on-chip”; (b) Layout of the CMOS sensor.
Mentions: Figure 1a illustrates a block diagram of the pulse oximeter sensor. It consists of a 1 mm × 2.5 mm n-well-p-substrate photodiode, a linear transimpedance amplifier having an 8 M Ohm feedback resistor and 30 KHz bandwidth, two Sallen-Key band-pass filters having 2 KHz (band-pass1) and 4 KHz (band-pass2) filter bandwidths respectively, two 10-bit successive approximation register (SAR) ADCs running at a sampling rate of 640 KHz. The digital signal processor includes a quadrature demodulator and LED timing control unit generating 10 KHz and 20 KHz square waves. The LEDs shown in the figure are off-chip components whilst all other components illustrated inside the dotted line are all integrated into a single semi-custom CMOS chip.

Bottom Line: The experimentally measured AC and DC characteristics of individual circuits including the DC output voltage of the transimpedance amplifier, transimpedance gain of the transimpedance amplifier, and the central frequency and bandwidth of the analogue band-pass filters, show a good match (within 1%) with the circuit simulations.With modulated light source and integrated lock-in detection the sensor effectively suppresses the interference from ambient light and 1/f noise.The single-chip sensor enables a compact and robust design solution that offers a route towards wearable devices for health monitoring.

View Article: PubMed Central - PubMed

Affiliation: Electrical System and Optics Research Division, Faculty of Engineering, University of Nottingham, University Park, Nottingham NG7 2RD, UK. diwei.he@nottingham.ac.uk.

ABSTRACT
Pulse oximetry is a noninvasive and continuous method for monitoring the blood oxygen saturation level. This paper presents the design and testing of a single-chip pulse oximeter fabricated in a 0.35 µm CMOS process. The chip includes photodiode, transimpedance amplifier, analogue band-pass filters, analogue-to-digital converters, digital signal processor and LED timing control. The experimentally measured AC and DC characteristics of individual circuits including the DC output voltage of the transimpedance amplifier, transimpedance gain of the transimpedance amplifier, and the central frequency and bandwidth of the analogue band-pass filters, show a good match (within 1%) with the circuit simulations. With modulated light source and integrated lock-in detection the sensor effectively suppresses the interference from ambient light and 1/f noise. In a breath hold and release experiment the single chip sensor demonstrates consistent and comparable performance to commercial pulse oximetry devices with a mean of 1.2% difference. The single-chip sensor enables a compact and robust design solution that offers a route towards wearable devices for health monitoring.

No MeSH data available.