Patent ID: 7337026
Filing Date: 2008-02-26
Classification: H03G

Abstract:
1. A digital audio volume control circuit comprising: a serial interface having an input for receiving a digital audio signal, and an output for serially outputting bits of the digital audio signal; a shift register having a serial input connected to the output of the serial interface for storing bits of the digital audio signal; a first-in-first-out (FIFO) buffer having a parallel input connected to a parallel output of the shift register; a volume controller connected to the FIFO, the volume controller initiating loading of bits in the shift register into the FIFO according to a volume control signal; a digital-to-analog processor connected to a parallel output of the FIFO; and an analog amplifier connected to an output of the digital-to-analog processor, the analog amplifier comprising an operational amplifier having a feedback variable resistance and an input variable resistance, wherein the volume controller delays or speeds loading of bits in the shift register into the FIFO according to a coarse component of the volume control signal, and the volume controller adjusts the feedback variable resistance or the input variable resistance according to a fine component of the volume control signal.