Abstract: A stage of a pipeline ADC which uses separate pairs of sampling network and amplifier (in a sample and hold circuit (SHA)) to provide inputs to quantizer (which generates a sub-code) and a switched capacitor network (implementing a DAC, a subtractor and amplification). Due to the use of separate components/paths to provide the input signal, the throughput performance of the ADC is enhanced.

Abstract: Systems and methods are disclosed for providing automatic gain control of a multi-stage system. A method can include defining at least one parameter that is adapted to at least one of maximize hardware capacity of each of a plurality of gain stages and mitigate part-to-part variations of the multi-stage system. An order is selected for training the plurality of stages based on relative noise dominance for the plurality of stage. For a given stage of the plurality of stages, which is selected according to the selected order, output signals of the multi-stage system are measured over a plurality of gain settings for the given stage. A gain setting of the given stage of the multi-stage system also is configured based on the measured output signals relative to the at least one parameter defined for the given stage. The plurality of gain stages can include an analog equalizer as well programmable gain amplifiers connected in series.

Abstract: An integrated circuit provides digital output signals in either single-ended or differential form on a shared set of pins. A control circuit generates signals to ensure that when one form (single-ended or differential) of outputs are being provided, outputs in the other form are disabled. Outputs in differential form may be provided at twice the frequency as compared to the outputs in single-ended form. As a result the same number of pins can be supported for both single-ended and differential outputs for a desired data throughput, and the pin count of the integrated circuit is reduced.

Abstract: According to an aspect of the present invention, samples of an input signal are provided with reduced distortion, when the input signal is received from a lead terminal offering lead inductance on an input path. Such a feature is achieved by charging a energy storage element to a value proportional to the input signal using a portion of charging energy received through a path having less lead inductance compared to the path connecting the input signal to the energy storage element. Thus, the energy drawn through the lead impedance is reduced, thereby reducing the magnitude of the distortion caused.

Abstract: A stage of a pipeline ADC which uses separate pairs of sampling network and amplifier (in a sample and hold circuit (SHA)) to provide inputs to quantizer (which generates a sub-code) and a switched capacitor network (implementing a DAC, a subtractor and amplification). Due to the use of separate components/paths to provide the input signal, the throughput performance of the ADC is enhanced.

Abstract: According to an aspect of the present invention, different reference voltage levels are used for different stages of a multi-stage analog to digital converter (ADC). In one embodiment, the amplification and unity gain bandwidth (UGB) requirements in the first stage is reduced as a result.

Abstract: A technique to attenuate even-order harmonics of an output stage of a multistage nested Miller compensation circuit. In one example embodiment, this is accomplished by using a low-bandwidth low-swing amplifier in the common mode feedback loop to improve the even-order harmonic performance in the signal path. The technique uses a separate multistage loop for the common mode feedback loop to attenuate the even-order harmonics. The common mode feedback loop is the fourth stage and uses the third stage of the nested Miller compensation circuit. The fourth stage of the common mode feedback loop includes a single harmonic and uses a low voltage supply to achieve lower power consumption by the common mode feedback loop.

Abstract: A method of providing an improved transfer function for a Discrete Multitone (DMT) type modulation transmitter with digital filtering after modulation followed by digital to analog converter and analog filtering is provided by sending a test signal to said transmitter and measuring the results of the test signal to determine the transfer function. The inverse of the transfer function that needs to be compensated is determined and the inverse of transfer function to be compensated is truncated to the region of interest (H2). The desired band split component of pre-compensation filter is designed (H3). The desired target frequency response of the pre-compensation filter is determined by H4=H2*H3 where H4 is the multiplication of H2 and H3 Given the target frequency response in H4 Hermetian symmetry is imposed on the frequency response. The inverse Fourier transform (IFFT) is taken to generate a time domain filter, h5. The characteristic of this filter is added at the digital filtering after modulation.

Abstract: Ensuring sufficient bias current is provided to a portion of a circuit containing low voltage transistors operating with a high supply voltage. Such a sufficient bias current may be ensured by generating a primary bias current from a low supply voltage and a backup bias current from a high supply voltage, and providing the backup bias current as the bias current if the primary bias current is not present. The primary bias current may be provided as the bias current when the low supply voltage is available. Thus, the backup bias current is provided as bias current in case of undesirable supply sequencing.

Abstract: A technique to attenuate even-order harmonics of an output stage of a multistage nested Miller compensation circuit. In one example embodiment, this is accomplished by using a low-bandwidth low-swing amplifier in the common mode feedback loop to improve the even-order harmonic performance in the signal path. The technique uses a separate multistage loop for the common mode feedback loop to attenuate the even-order harmonics. The common mode feedback loop is the fourth stage and uses the third stage of the nested Miller compensation circuit. The fourth stage of the common mode feedback loop includes a single harmonic and uses a low voltage supply to achieve lower power consumption by the common mode feedback loop.

Abstract: Systems and methods are disclosed for providing automatic gain control of a multi-stage system. A method can include defining at least one parameter that is adapted to at least one of maximize hardware capacity of each of a plurality of gain stages and mitigate part-to-part variations of the multi-stage system. An order is selected for training the plurality of stages based on relative noise dominance for the plurality of stage. For a given stage of the plurality of stages, which is selected according to the selected order, output signals of the multi-stage system are measured over a plurality of gain settings for the given stage. A gain setting of the given stage of the multi-stage system also is configured based on the measured output signals relative to the at least one parameter defined for the given stage. The plurality of gain stages can include an analog equalizer as well programmable gain amplifiers connected in series.

Abstract: A cost-effective filter consuming low power and occupying minimal space. The filter may be used in a ADSL modem (or CPE) to filter the signal components other than the ADSL signals. A high pass filter first filters the low frequency components to attenuate (or remove) lower frequency components such as that caused by ADSL transmit echo signals and that used for voice transmission. The high pass filter may be modified by adding a few resistors to limit the voltages of the high frequency signals also. The output of the high pass filter is amplified and passed through a low pass filter to filter the high frequency components (HPNA included). Due to earlier filtering operation of the high pass filter, the signal can be amplified substantially before being sent to the low pass filter. The implementation of the low pass filter is simplified due to the prior amplification.

Abstract: A filter circuit with two 2nd order stages cascaded in sequence. The first stage is implemented with high quality (Q) factor, and the second stage is implemented with a low Q factor and an imaginary zero. The first stage is designed to further eliminate the unwanted frequency components. The imaginary zero in the second stage eliminates the noise present in the output of the first stage due to the requirement of high Q in the first stage. Any additional noise introduced by the second stage is minimal due to the low Q of the second stage. Each stage may be implemented using only a single operational amplifier when the first stage generates a differential output signal.

Abstract: A filter circuit with two 2nd order stages cascaded in sequence. The first stage is implemented with high quality (Q) factor, and the second stage is implemented with a low Q factor and an imaginary zero. The first stage is designed to further eliminate the unwanted frequency components. The imaginary zero in the second stage eliminates the noise present in the output of the first stage due to the requirement of high Q in the first stage. Any additional noise introduced by the second stage is minimal due to the low Q of the second stage. Each stage may be implemented using only a single operational amplifier when the first stage generates a differential output signal.

Abstract: A method of providing an improved transfer function for a Discrete Multitone (DMT) type modulation transmitter with digital filtering after modulation followed by digital to analog converter and analog filtering is provided by sending a test signal to said transmitter and measuring the results of the test signal to determine the transfer function. The inverse of the transfer function that needs to be compensated is determined and the inverse of transfer function to be compensated is truncated to the region of interest (H2). The desired band split component of pre-compensation filter is designed (H3). The desired target frequency response of the pre-compensation filter is determined by H4=H2*H3 where H4 is the multiplication of H2 and H3 Given the target frequency response in H4 Hermetian symmetry is imposed on the frequency response. The inverse Fourier transform (IFFT) is taken to generate a time domain filter, h5. The characteristic of this filter is added at the digital filtering after modulation.

Abstract: A T-network containing three impedances is provided between two terminating ends connected to a non-fixed voltage level. Two impedances are connected in series between the two terminating ends. A third impedance is connected between the junction of the first two impedances and a fixed voltage. Switches may be used to trim the third impedance, thus obtaining a desired voltage between the two terminating ends. A terminal of any switches used for trimming can be connected to the fixed voltage node, thereby ensuring that the impedance introduced by the switches does not change substantially during different operating situations.

Abstract: A T-network containing three impedance is provided between two terminating ends not connected to ground. Two impedances may be connected in series between the two terminating ends. A third impedance may be connected between the junction of the first two impedances and a fixed voltage (e.g., ground). Switches may be used to trim the third voltage, thus obtaining a desired voltage between the two terminating ends. A terminal of any switches used for trimming can be connected to the fixed voltage node, thereby ensuring that the impedance introduced by the switches does not change substantially during different operating situations.

Abstract: A modem operating in a narrow voltage range while maintaining a high signal to noise ratio during reception. The modem may contain a coder-decoder (CODEC) and a transformer. The CODEC receives data using more windings of a primary coil than the number of windings used for transmitting. As a result, the turns ratio is higher during transmission, leading to a correspondingly high amplification during transmission. The high amplification in the transmit direction enables the modem to operate in a narrow voltage range. As more windings of the primary coil are used for receiving, a signal of interest received from the telephone line is attenuated to a corresponding lesser degree, which leads to a high signal to noise ratio.