Multi-bit ADC with sigma-delta modulation
First Claim
Patent Images
1. A pulse oximeter circuit comprising:
- a multi-bit sigma-delta modulator having an input adapted to receive a first analog signal representative of received red light and a second analog signal representative of received infrared light through a single path, the multi-bit sigma-delta modulator being configured to produce a digital output signal; and
a feedback circuit configured to receive the digital output signal of the multi-bit sigma-delta modulator and generate a pulse width modulated signal (PWM), the PWM signal being directed to a first switching circuit and a D flip-flop, the first switching circuit providing a first or second reference voltage as a feedback signal to the multi-bit sigma-delta modulator, the D flip-flop generating a sample and hold signal, the sample and hold signal controlling a second switching circuit coupled to the input of the multi-bit sigma-delta modulator, the second switching circuit being configured to direct the first and second analog signals to an inverting input of the multi-bit sigma-delta during a sampling period.
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Abstract
There is provided a pulse oximeter circuit including a feedback circuit configured to receive a digital output signal of a multi-bit sigma-delta modulator and generate a pulse width modulated signal (PWM). The PWM signal is directed to a first switching circuit and a D flip-flop. The first switching circuit provides a first or second reference voltage as a feedback signal to the multi-bit sigma-delta modulator. The D flip-flop generates a sample and hold signal. The sample and hold signal controls a second switching circuit coupled to the input of the multi-bit sigma-delta modulator.
45 Citations
20 Claims
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1. A pulse oximeter circuit comprising:
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a multi-bit sigma-delta modulator having an input adapted to receive a first analog signal representative of received red light and a second analog signal representative of received infrared light through a single path, the multi-bit sigma-delta modulator being configured to produce a digital output signal; and
a feedback circuit configured to receive the digital output signal of the multi-bit sigma-delta modulator and generate a pulse width modulated signal (PWM), the PWM signal being directed to a first switching circuit and a D flip-flop, the first switching circuit providing a first or second reference voltage as a feedback signal to the multi-bit sigma-delta modulator, the D flip-flop generating a sample and hold signal, the sample and hold signal controlling a second switching circuit coupled to the input of the multi-bit sigma-delta modulator, the second switching circuit being configured to direct the first and second analog signals to an inverting input of the multi-bit sigma-delta during a sampling period. - View Dependent Claims (2, 3, 4, 5, 6)
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7. An oximetry device comprising:
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a multi-bit sigma-delta modulator having an input adapted to receive a first analog signal from a sensor and a second analog signal from a sensor through a single path, the multi-bit sigma-delta modulator being configured to produce a digital output signal representative of the first and second analog signals;
at least first and second capacitors coupled in parallel to the input of the multi-bit sigma-delta modulator;
a capacitor switching circuit configured to couple to the first capacitor upon receipt of the first analog signal and to couple to the second capacitor upon receipt of the second analog signal, wherein the first and second capacitors are selected to correspond with a quantization error for the corresponding analog signals; and
a feedback circuit coupled about the multi-bit sigma-delta modulator, the feedback circuit comprising a sample and hold circuit configured to enable the input of the multi-bit sigma-delta modulator during receipt of the first or second analog signals and to disable the input during a holding period. - View Dependent Claims (8, 9, 10, 11, 12, 13, 14)
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15. A method for analog-to-digital conversion comprising:
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converting a digital output signal of a multi-bit sigma-delta modulator to an analog pulse width modulated (PWM) signal, the PWM signal having one fixed edge occurring at a constant rate and one variable edge;
controlling a feedback circuit using the PWM signal to provide a first or second reference voltage as a feedback signal;
generating a sample/hold signal by dividing the PWM signal, the sample/hold signal controlling an input switch of the multi-bit sigma-delta modulator;
combining the feedback signal through a resistor with first and second analog signals to generate a combined signal, the first and second analog signals representing a detected red signal and a detected infrared signal; and
alternately coupling the combined signal to an inverting input or a non-inverting input of an operational amplifier of the multi-bit sigma-delta modulator to provide sampling periods or holding periods, respectively. - View Dependent Claims (16, 17, 18, 19, 20)
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Specification