Exar Corporation

Intersil Americas Inc.

Nvidia Corporation

Bhupendra K Ahuja

Richard Leigh Gower

Hoa Vu

J Antonio Salcedo

Teck-Boon Serm

Eric Glen Hoffman

Carlos A Laber

Charles Andrew Rogers

Ken Evans

A phased lock loop (PLL) including a retimer unit, rotator unit, and clock selection unit. The retimer unit is configured for sampling a divided clock generated by a divide-by-N unit with a plurality of phases of an oscillator clock generated by a ring oscillator to generate a plurality of phase shifted divide-by-N clocks. The rotator unit is configured for selectively rotating through the plurality of phase shifted divide-by-N clocks based on a constant phase shift interval, wherein the rotator unit controls a clock selection unit to produce a single output phase selected from a plurality of generated divide-by-N clock phases.

Method and system for quantization-free and phase-dithered fractional-N generation for phase-locked-loops

An automatic temperature compensated real-time clock (RTC) chip includes a clock portion having a crystal oscillator block including crystal compensation circuitry adapted to be coupled to a crystal. The crystal compensation circuitry includes a non-linear capacitor DAC including a plurality of load capacitors, wherein the load capacitors have respective switches which switch respective ones of the load capacitors to change a parallel resonance frequency (fp) generated by the oscillator block. The capacitor DAC is arranged so that Analog Trimming (ATR) bits received cause an arrangement of the switches to provide a non-linear change in overall load capacitance to result in a linear relationship between fp and the ATR bits. A temperature sensor block is coupled to the crystal for measuring a temperature of at least the crystal. An A/D converter is coupled to the temperature sensor for outputting a digital temperature signal representative of the temperature of the crystal. A DSP engine receives the digital temperature signal and calculates frequency correction needed to correct for frequency inaccuracy and determines a bit sequence including the ATR bits appropriate to achieve the frequency correction.

Automatic circuit and method for temperature compensation of oscillator frequency variation over temperature for a real time clock chip

A circuit and corresponding method for a precision floating gate voltage reference that uses a feedback loop, conduction of tunnel devices, and a bandgap cell to accurately program a desired charge level on a floating gate and provide a predictable and programmable temperature coefficient parameter for such voltage reference. In one embodiment, a bandgap cell is coupled through a capacitor to the floating gate storage node for providing a voltage source for canceling the temperature coefficient (TC) of the storage capacitor. The circuit and method enables TC to be minimized by either choosing the proper voltage source characteristics or alternatively, by choosing the proper ratio of two capacitors. The bandgap cell can alternatively be designed to have positive TC (PTAT voltage sources) or negative TC (VBE junction).

Precision floating gate reference temperature coefficient compensation circuit and method

A bandgap reference voltage generator includes, in part, a first closed-loop circuit having a first operational amplifier and adapted to generate a first current with a positive temperature coefficient and a second closed-loop circuit having a second operational amplifier and adapted to generate a second current with a negative temperature coefficient. The bandgap reference voltage generator is further adapted to include a multitude of output stages. Each output stage may be independently scaled to sum any selected multiple of the first current to any selected multiple of the second current to generate an output voltage having either a nearly zero, a positive or a negative temperature coefficient. For example, the first output stage may be scaled to generate a reference output voltage with a nearly zero temperature coefficient. Similarly, the second output stage may be scaled to generate a reference output voltage with a negative temperature coefficient.

CMOS bandgap reference with low voltage operation

A method and apparatus for adjusting, on a pixel-by-pixel basis, the gain and offset in an AFE as the pixels are sequentially processed. Although the method can be used for any purpose, it is directed in particular to light source non-linearity, such as edge effects of a scanner. A unique clocking method clocks the gain and offset values into the register at a higher clock rate than the image sampling rate.

Pixel-by-pixel digital control of gain and offset correction for video imaging

A programmable gain amplifier having three separately programmable amplifiers. A programmable transconductance amplifier is followed by a programmable transimpedance amplifier, then a programmable switched capacitor amplifier. In one embodiment, this programmable gain amplifier is implemented in an analog front-end (AFE) circuit. One AFE embodiment provides a coarse pre-gain offset a black reference level sampler, and a fine post-gain offset in the programmable switched capacitor amplifier. In one embodiment, an ADC reference is sampled, and is subtracted directly from the video signal in the switched capacitor amplifier so that the zero level of the video signal is made to correspond to the zero level of the ADC. In another embodiment, a piece-wise linear approximation of an exponential gain function is implemented by programming the transconductance and transimpedance amplifiers to provide exponential jumps in gain, while the switched capacitor amplifier is programmed to interpolate as needed between the exponential gain levels.

Image sampling circuit with a blank reference combined with the video input

A method and circuitry for implementing programmable gain. More particularly, embodiments of the present invention provide an amplifier circuit which can be used as a CDS-amp or an instrumentation amplifier. Included is a two-stage amplifier, each stage having a few as one transistor. A current source biases one stage of the two-stage amplifier. A load resistor network couples to the two-stage amplifier and is configured to set gain values for the two-stage amplifier.

Low power wide bandwidth programmable gain CDS amplifier/instrumentation amplifier

A method and circuitry for implementing low-power analog-to-digital converters. More particularly, embodiments of the present invention provide an amplifier circuit for pipeline ADCs having multiple stages, some in sample mode, some in hold mode. The stages include residue amplifiers which include a pre-amp and a current source. The current source is turned off during the sample mode. Some embodiments include a second current source that provides a bleeder current during the sample phase so that the pre-amp remains in steady state.

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Freemont, CA, United States of America

Bhupendra K Ahuja