Patent ID: 7142142
Filing Date: 2006-11-28
Classification: A61B,H03M

Abstract:
1. A 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 wherein the multi-bit sigma-delta modulator comprises first and second integrators; a first switching circuit, coupled to the input, the first switching circuit being adapted to switch between connecting first and second reference voltages to the input; a feedback circuit, coupled to an output of the multi-bit sigma-delta modulator to receive the digital output signal, the feedback circuit being adapted to control the switching between the first and second reference voltages by the first switching circuit; and a second switching circuit coupled to an input of the second integrator and controlled by the feedback circuit, the second switching circuit being adapted to switch to the second voltage reference when the first switching circuit connects to the first voltage reference, and to switch to the first voltage reference when the first switching circuit switches to the second voltage reference.