Cadence Design Systems, Inc.

Stephen T Williams

Eric Harris Naviasky

Michael M Hufford

William Pierce Evans

Michelle LeRoux Williams

Tony L Caviglia

John Matsuzaki

Timothy Henricks

A multiple-input follower amplifier is coupled through a configuration of switching devices to an upper reference voltage at a number of its inputs and to a lower reference voltage at the remaining number of its inputs to form a voltage interpolator. The output of the voltage interpolator is a voltage between the upper and lower reference voltages proportional to the number of inputs coupled to each reference voltage. The voltage interpolator may be constructed so that the interpolated voltage may be selected through a reduced number of signal lines, such as by a row/column selection scheme. A voltage reference circuit providing the upper and lower reference voltages may also implement a row/column selection mechanism, thereby allowing a decoding scheme common to both a voltage reference circuit and a voltage interpolator in a digital-to-analog converter.

Voltage interpolation in digital-to-analog signal conversion

A self-tuning 3order type III phase-locked loop (PLL) is disclosed. In one aspect, the PLL provides frequency control that is implemented in three (3) parallel paths. The PLL provides frequency response tracking using a number of elements including a triple control voltage-controlled oscillator (VCO), a frequency-to-current (F2I) converter, and a switched capacitor loop filter. In addition to compensation for feedback ratio variation, near constant F2I gain over process variations and switched capacitor filters synchronized to a reference signal, near constant VCO gain over process variations allows the open loop frequency response to be tailored to track the reference signal. A high-speed locking technique is employed which significantly reduces acquisition time in low bandwidth cases. This PLL may be fabricated in a 0.18 &#x3bc;m CMOS logic process.

Wideband phase-locked loop with adaptive frequency response that tracks a reference

A gain adjustment circuit for maintaining the overall gain of a multi-component apparatus at a relatively constant level is disclosed. A multi-component apparatus in which the gain adjustment circuit may be implemented includes a first component and a second component. The first component has a variable gain, and receives as input a control signal which determines the gain of the component. The second component has an adjustable gain, and provides as output an output signal which affects the control signal fed to the first component. The gain adjustment circuit adjusts the adjustable gain of the second component based upon the control signal fed to the first component to maintain the overall gain of the components at a relatively constant level. More specifically, if the control signal is at a level which causes the variable gain of the first component to be high, then the gain adjustment circuit sets the adjustable gain of the second component to a low level. On the other hand, if the control signal is at a level which causes the variable gain to be low, then the gain adjustment circuit sets the adjustable gain of the second component to a high level. By doing so, the gain adjustment circuit maintains the overall gain of the components at a relatively constant level. Thus, even though the gains of the individual components may vary greatly, the overall gain of the components does not.

Mechanism for maintaining relatively constant gain in a multi-component apparatus

A charge pump having an automatic compensation capability comprises a current source and a current sink. The current source is selectively coupled to the output of the charge pump by a sourcing control. The sourcing control receives an input control signal and responds by controlling the sourcing current flowed from the current source to the output. Likewise, the current sink is selectively coupled to the output of the charge pump by a sinking control. The sinking control receives a second input control signal and responds by controlling the sinking current flowed from the output to the current sink. The charge pump further comprises a sensing circuit and a compensating circuit. The sensing circuit determines whether, given substantially identical input control signals, there is a difference between the sourcing current and the sinking current generated by the charge pump. If so, the sensing circuit provides at its output an indication of the current difference. In turn, the compensating circuit receives as input the indication of the current difference, and adjusts the sinking current in accordance with the indication of the current difference such that the sinking current equalizes the sourcing current. In an alternative embodiment, the compensating circuit adjusts the sourcing current rather than the sinking current to equalize the sourcing current with the sinking current. In either embodiment, a substantially zero net current is produced at the output of the charge pump when the input control signals are substantially identical.

Automatically compensated charge pump

A voltage to current (V-I) converter includes a low pass filter, a first converting element, a second converting element, and an output. The low pass filter receives an input voltage signal and outputs a filtered voltage signal. The output of the low pass filter is fed to the first converting element, which converts the filtered voltage signal into a corresponding output current which is fed to the output of the V-I converter. Preferably, the voltage to current gain of the first converting element is high. The low pass filter and the first converting element form a low frequency or DC signal path. The V-I converter further includes a second converting element, which receives the input voltage signal and converts it into a corresponding output current which is also fed to the output of the V-I converter. This current is combined with the output current from the first converting element to produce an overall output current. Preferably, the second converting element has a substantially flat frequency response and a low voltage to current gain relative to the voltage to current gain of the first converting element. The second converting element forms the high frequency or alternating current (AC) signal path. By implementing a high gain on the low frequency path and a low gain on the high frequency path, the high frequency noise components are insignificant relative to the low frequency components. Thus, a relatively mall input voltage range is converted into a relatively large output current range without suffering increased sensitivity to noise.

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Laurel, MD, United States of America

Stephen T Williams