Abstract: An apparatus for offloading power includes a power offload element providing a supply drop from a first supply level to a second supply level. The supply drop varies in response to a control signal. A signal processor of a subscriber line interface circuit provides the control signal. A linefeed driver of the subscriber line interface circuit is coupled to receive the second supply level for driving a subscriber line.

Abstract: In one embodiment, a subscriber line interface circuit includes circuitry to generate metering pulses for insertion onto a subscriber line. The circuitry includes a cascaded digital-to-analog converter (DAC) structure including a first DAC to convert a digital sine wave into an analog representation, a second DAC to multiply the analog representation with a ramp value to obtain an unscaled output, and a third DAC to multiply the unscaled output with a gain value to generate a metering pulse.

Abstract: A subscriber line interface circuit apparatus includes indicating circuitry indicating a change between a first state and a second state of subscriber equipment coupled to a subscriber line. Common mode control circuitry transitions a common mode variable of the subscriber line from a first value to a distinct second value, wherein the transition is slew-rate limited. In one embodiment, a method includes ramping a common mode variable from a first value to a second value upon initiation of a state change of subscriber equipment coupled to a subscriber line.

Abstract: In one embodiment, a subscriber line interface circuit includes circuitry to generate metering pulses for insertion onto a subscriber line. The circuitry includes an audio path and a pulse metering path, where the pulse metering path includes a metering generator to generate a digital sine wave from a plurality of stored values, a first interpolator to interpolate the digital sine wave, a filter to filter the interpolated digital sine wave, and a second interpolator to interpolate the filtered interpolated digital sine wave.

Abstract: In one embodiment, a subscriber line interface circuit includes circuitry to generate metering pulses for insertion onto a subscriber line. The circuitry includes a cascaded digital-to-analog converter (DAC) structure including a first DAC to convert a digital sine wave into an analog representation, a second DAC to multiply the analog representation with a ramp value to obtain an unscaled output, and a third DAC to multiply the unscaled output with a gain value to generate a metering pulse.

Abstract: A power offload network has a node for receiving at least one supply V1. The power offload network includes at least one switch and a power offload element providing a supply drop of VR. The switch is configurable for selecting a linefeed supply level from the set including {V1, V1?VR}. A subscriber line interface circuit receives the selected linefeed supply level for driving a subscriber line.

Abstract: Methods and apparatus for coupling outgoing analog audio signals to a subscriber line are described. One method includes the step of receiving the outgoing audio signal. The outgoing audio signal is coupled to the subscriber line through a plurality of transistors coupled in a common base configuration. In one embodiment, linefeed driver control signals for controlling battery feed to the subscriber line are received on the same signal lines as the outgoing audio signal. A subscriber line interface circuit apparatus includes a first circuit for coupling a received outgoing audio signal to a subscriber line. The first circuit couples the received outgoing audio signal to the subscriber line through a common base isolation stage. In various embodiments, the common base isolation stage comprises a plurality of bipolar junction transistors coupled in a common base configuration or a plurality of field effect transistors coupled in a common gate configuration.

Abstract: A linefeed on a subscriber loop is generated to generate a current on the subscriber loop. Whether a relationship between a voltage on the subscriber loop and a threshold voltage for an identified range of voltages satisfies a condition is identified. The linefeed on the subscriber loop is controlled to modify the current on the subscriber loop in response to identifying that the relationship between the voltage on the subscriber loop and the threshold voltage for the identified range of voltages satisfies the condition to help generate the voltage on the subscriber loop in the identified range of voltages. The identifying and controlling are continued to help generate and maintain the voltage on the subscriber loop in the identified range of voltages.

Abstract: A power offload network has a node for receiving at least one supply V1. The power offload network includes at least one switch and a power offload element providing a supply drop of VR. The switch is configurable for selecting a linefeed supply level from the set including {V1, V1-VR}. A subscriber line interface circuit receives the selected linefeed supply level for driving a subscriber line.

Abstract: A subscriber line interface circuit apparatus includes tip/ring sense circuitry generating a tip sense signal and a ring sense signal from three sensed currents, wherein the tip sense signal and the ring sense signal correspond to subscriber loop tip and ring currents, respectively. In one embodiment, the tip/ring sense circuitry includes a current mirror generating first and second mirrored sense currents from a first sense current proportional to a battery feed node voltage of a subscriber loop. Current differencing circuitry provides the tip sense signal from a difference between the first mirrored sense current and a second sense current associated with a tip line of the subscriber loop. The current differencing circuitry provides the ring sense signal from a difference between the second mirrored sense current and a third sense current associated with a ring line of the subscriber loop.

Abstract: A subscriber line interface apparatus includes a switching core generating a negative subscriber line battery supply voltage (VBAT) for supplying at least one of a tip line and a ring line of a subscriber line from a positive first supply voltage. The apparatus includes voltage control circuitry driving the switching core in accordance with a tracked signal corresponding to a sensed one of the tip and ring lines.

Abstract: An apparatus for interfacing an integrated circuit with external circuitry includes a transistor having an emitter coupled to a node for receiving a control current (IP) from the integrated circuit. A beta compensator disposed within the integrated circuit provides a compensating current (IM) to the node. The compensating current IM is proportional to a base current (IB) of the transistor. A method of interfacing the integrated circuit with external circuitry includes the step of providing the control current (IP) from the integrated circuit to a node coupled to a transistor emitter. A compensating current (IM) is provided to the node in response to the transistor base current (IB). The net node current provided to the emitter is IP+IB so that the transistor collector current is substantially the same as the control current. The transistor collector is coupled to the external circuitry.

Abstract: An apparatus for powering a plurality of devices sharing a supply line includes a supply control and a variable supply associated with the supply line. The supply control varies the supply level of the supply line to accommodate the supply level request representing a greatest magnitude supply level of any requests communicated from the devices. Another apparatus includes a plurality of supply controls each coupled to control a supply level provided by an associated supply line. Each device is capable of selectively coupling itself to an exclusive one of the supply lines. At least one device communicates a supply level request to a selected supply control that adjusts the supply level of its associated supply line to accommodate the supply level request representing the greatest supply level magnitude of any other supply level requests. If necessary, the selected device switches to the supply line associated with the selected supply control.

Abstract: A common mode feedback circuit includes first and second nodes defining a differential node pair. A collective plurality of transconductors includes a first plurality of transconductors associated with the first node and a second plurality of transconductors associated with the second node. Each plurality, for example, may consist of 2 transconductors such that one may be serve as a common mode current sink and the other may be operated as a current source during calibration. At least one transconductor of the collective plurality has an adjustable transconductance. In various embodiments, each node has at least one transconductor with an adjustable transconductance. The common mode feedback circuit includes a calibration engine. The calibration engine adjusts at least one adjustable transconductor until a sensed differential voltage across the differential node pair is substantially zero without the use of external current sources.

Abstract: A linefeed on a subscriber loop is generated to generate a current on the subscriber loop. A relationship between a voltage on the subscriber loop and a threshold voltage is identified. A current limit for the subscriber loop is modified in response to the identifying. The linefeed on the subscriber loop is controlled to modify the current on the subscriber loop in response to the modifying.

Abstract: An apparatus for interfacing an integrated circuit with external circuitry includes a transistor having an emitter coupled to a node for receiving a control current (IP) from the integrated circuit. A beta compensator disposed within the integrated circuit provides a compensating current (IM) to the node. The compensating current IM is proportional to a base current (IB) of the transistor. A method of interfacing the integrated circuit with external circuitry includes the step of providing the control current (IP) from the integrated circuit to a node coupled to a transistor emitter. A compensating current (IM) is provided to the node in response to the transistor base current (IB). The net node current provided to the emitter is IP+IB so that the transistor collector current is substantially the same as the control current. The transistor collector is coupled to the external circuitry.

Abstract: A method of controlling a DC feed from a subscriber loop interface circuit (SLIC) includes the steps of switching from a normal mode DC feed following a first characteristic curve to a modified mode DC feed following a second characteristic curve when the metallic voltage (VM) meets or falls below a first threshold voltage. The SLIC switches back from the modified mode to the normal mode when VM meets or exceeds a second threshold voltage. In one embodiment the first and second characteristic curves are linear and have the same pre-determined slope.

Abstract: A common mode feedback circuit includes first and second nodes defining a differential node pair. A collective plurality of transconductors includes a first plurality of transconductors associated with the first node and a second plurality of transconductors associated with the second node. Each plurality, for example, may consist of 2 transconductors such that one may be serve as a common mode current sink and the other may be operated as a current source during calibration. At least one transconductor of the collective plurality has an adjustable transconductance. In various embodiments, each node has at least one transconductor with an adjustable transconductance. The common mode feedback circuit includes a calibration engine. The calibration engine adjusts at least one adjustable transconductor until a sensed differential voltage across the differential node pair is substantially zero without the use of external current sources.

Abstract: A signal generator 600 includes oscillator circuitry for generating first and second signals having a selected phase relationship and an interpolator 610 for interpolating between a phase of the first signal and a phase of the second signal to generate a third signal having a phase between the phases of the first and second signals.

Abstract: A system and method is disclosed for calibrating comparators of an ADC. Individual comparators may be calibrated at random or psuedo-random times while the ADC is performing conversions without the addition of extra "proxy" or replacement comparators. More particularly, at periodic intervals a psuedo-random one of the comparators may be disconnected from the standard ADC circuitry for calibration. In order to prevent a significant degradation in the conversion quality, the digital logic downstream of the comparators may be designed to provide the necessary adjustments to accommodate for the removal of one of the comparators. Thus, a calibration technique is provided in which individual comparators are removed from the data conversion path during conversion and the downstream logic adjusts to accommodate for the removal of the comparator. The calibration technique is particularly advantageous for use with optical data storage systems.