Abstract: A technique for providing coarse and fine switching on digital-to-analog converter output for a more refined analog output signal. In a digital-to-analog converter utilizing a switched capacitor low-pass filter, the last stage of the filter implements a two phase charging scheme to ensure distortion reduction.

Abstract: A communication system is provided which draws virtually no loop current during a ringing burst and only draws on-hook loop current during the caller ID field. More particularly, ringer burst circuitry may be powered from the user powered circuitry by the transmission of power across the isolation barrier rather than being powered from the phone line. Thus, loop current need not be drawn from the TIP/RING lines during ringer bursts. The isolation barrier may be a capacitive isolation barrier which allows bidirectional communication and extraction of power from signals transmitted across the barrier.

Abstract: A technique for detecting and suppressing overload conditions in an analog-to-digital converter which uses a delta-sigma modulator. In order to prevent overloading in modulator, a detection unit is used to detect a preset amplitude level associated with an input signal and when such level is detected, the performance of the modulator is degraded in order to prevent the overload condition from occurring. The degrading is achieved by changing the coefficients of operation of the integrator(s) in the modulator.

Abstract: A technique for resetting state variables of a delta-sigma modulator of an analog-to-digital converter. A switched capacitor impedance is placed in the reset feedback path of an integrator to ensure that the integrator tracks to the proper reset voltage, when reset is initiated in a third-order or higher delta-sigma modulator.

Abstract: A stereo digital-to-analog converter is able to operate in an 8 pin package yet to operate under a variety of serial data input formats. The normal de-emphasis pin can be used for receiving a static de-emphasis signal, an external serial clock, or programming data for the serial data formats. In addition metal and wire bond options are used to provide more flexibility in the manufacturing process.

Abstract: A low precision Finite Impulse Response filter (FIR) is provided for filtering in a digital interpolation operation. The interpolation operation is comprised of two steps, a sampling rate conversion operation for interspersing zeroes between samples in an input sequence and a filtering step of filtering out images that result from this operation. The filtering operation utilizes a FIR filter that utilizes a low precision set of filter coefficients that are selected to tune the frequency response such that the low end frequency response including the pass band, the transition band, and the portion of the stop band immediately after the transition band provides a response equivalent to that commensurate with substantially higher precision FIR filter coefficients. A second, low pass filter section is provided for filtering the high frequency image energy at the output of the FIR filter to provide an overall filter response commensurate to that utilizing substantially higher precision FIR coefficients.