Patent ID: 6922470

Claim:
A DC-feed controller for a current-feed subscriber line interface circuit, for controlling voltage on a telephone line, comprising a pair of wires, comprising: a digital summer adapted to receive a predetermined voltage limit digital value as a first input, and to receive a negative digital feedback signal as a second input, and to provide as an output a digital error signal that represents the difference between the voltage limit digital value and the digital feedback signal; a multiplier adapted to multiply the digital error signal by a predetermined digital gain value to provide a scaled digital error value as an output; a digital integrator adapted to integrate the scaled digital error value over time to generate an integrated digital error signal having a first predetermined number n of significant bits; a digital-to-analog converter adapted to receive a modified digital error signal comprising a second predetermined number m of bits, where m<n, of the integrated digital error signal as an input and to provide as an output an error analog signal that is representative of the modified digital error signal; an analog-to-digital converter adapted to receive a sense signal as an input, the sense signal representing a sensed voltage on the telephone line, and adapted to provide as an output a digital sense signal that is a representation of the sense signal; and a first digital low pass filter adapted to receive the digital sense signal, and to provide the digital feedback signal as an output.