Analog Devices,inc.

Analog Devices Global Unlimited Company

Frank M Murden

Michael Ray Elliott

Ahmed Mohamed Abdelatty Ali

John Kevin Behel

Peter Delos

Hajime Shibata

Lawrence A Singer

Carl W Moreland

Yunzhi Dong

David Nelson Alldred

Ralph David Moore, Jr

Sharvil Pradeep Patil

Joseph Michael Hensley

Ed Balboni

Joe Young

An ultra-wideband distributed ADC can be cascaded to build high performance radio frequency (RF) analog electronics integrated with advanced digital complementary metal-oxide-semiconductor (CMOS) electronics on the same wafer. Advantages can include wide spectral coverage, high resolution, large dynamic range, and high information processing bandwidth. Part of an overall system includes a precise, programmable, real-time delay circuit that can achieve picosecond accuracy.

Distributed ADC for enhanced bandwidth and dynamic range

Improved track and hold (T/H) circuits can help analog-to-digital converters (ADCs) achieve higher performance and lower power consumption. The improved T/H circuits can drive high speed and interleaved ADCs, and the design of the circuits enable additive and multiplicative pseudo-random dither signals to be injected in the T/H circuits. The dither signals can be used to calibrate (e.g., linearize) the T/H circuits and the ADC(s). In addition, the dither signal can be used to dither any remaining non-linearity, and to calibrate offset/gain mismatches in interleaved ADCs. The T/H circuit design also can integrate an amplifier in the T/H circuit, which can be used to improve the signal-to-noise ratio (SNR) of the ADC or to act as a variable gain amplifier (VGA) in front of the ADC.

Track and hold circuits for high speed and interleaved ADCs

A multi-input analog-to-digital converter (ADC), i.e., a single ADC, can receive multiple analog input signals and generate multiple digital outputs. To combine multiple analog input signals into a single multi-input ADC, the multi-input ADC would typically include multiple track and hold (T/H) circuits and an adder, which can consume a significant amount of power and incur large cost overhead. An improved approach is to combine multiple inputs through a unique T/H circuit in the front-end of the ADC. The multiple analog input signals can be aggregated using code sequences, without requiring a significant amount of external circuits.

Multi-input data converters using code modulation

Residue generation systems for use in continuous-time and hybrid ADCs are described. An exemplary system includes a filter, e.g. a FIR filter, for generating a filtered analog output based on an analog input, a quantizer for generating a digital input to a feedforward DAC based on the filtered analog output generated by the filter, a feedforward DAC for generating a feedforward path analog output based on the digital input generated by the quantizer, and a subtractor for generating a residue signal based on the feedforward path analog output. Providing a filter that filters the analog input before it is quantized advantageously allows blockers to be attenuated before they are sampled and aliased by the quantizer. At least some of the residue generation systems described herein may be implemented with relatively small design and power dissipation overheads.

Blocker tolerance in continuous-time residue generating analog-to-digital converters

Embodiments of the present invention provide a pipeline ADC front-end sampling structure that provides a continuous time input signal to a flash comparator for sampling. By providing a continuous time input signal to the flash comparator, no delay is introduced from the need to transfer a DC charge representing the sampled input to the flash comparator. Matching sampling networks in the residual generator and the flash comparator are avoided due to the high bandwidth response requirements of the residual generator and the flash comparator when operating on high frequency input signals.

Front-end sampling technique for analog-to-digital converters

Reference network embodiments are disclosed that provide reference signals to, for example, switched-capacitor multiplying digital-to-analog converters (MDACs) in pipelined analog-to-digital converters (ADCs). These embodiments are configured to maintain accuracy of the levels of the reference signals in the presence of high speed charge-injection and charge-extraction currents which are presented by the MDACs.

Converter networks for generation of MDAC reference signals

Signal coupling systems are provided which enhance signal isolation and dynamic range with structures that increase bias voltages in upstream signal amplifiers to guard against transistor saturation that would otherwise increase current drain, reduce response time and possibly cause lock-up of an associated gain-control system. Dynamic range is thus enhanced because these systems can operate over an extended range of source signals. The increased bias voltages also decrease parasitic junction capacitances which increases input impedances and thereby enhances signal isolation and reduces signal distortion.

Signal coupling systems with enhanced isolation and dynamic range

Digitally-controlled, variable-gain mixers and amplifiers are provided which couple transconductance cells to receive respective tap signals from a fixed attenuator that receives a first input signal. A gain interpolator provides first and second control currents with amplitudes that correspond to a segment of a control word and a multiplexer responds to another control-word segment by routing the control currents to a selected pair of adjacent transconductance cells. In response, the transconductance cells provide amplifier current signals which can also be routed to a transistor switch that mixes them with a second input signal to generate a mixer output signal whose amplitude corresponds to the control word.

Digitally-controlled, variable-gain mixer and amplifier structures

Feedback control systems and methods are provided for correcting residue signal offset errors in subranging ADCs. The systems and methods eliminate clock-to-clock offset changes and reduce noise generation. An exemplary control system includes a feedback loop around a residue sampler and a residue amplifier that includes a) a feedback sampler that resamples the output signal of the residue sampler to produce a resampled residue signal, and b) an offset current generator that delivers an offset current to the residue amplifier with a current magnitude that is responsive to the resampled residue signal. The sampling of the residue and feedback samplers is time shifted to block the propagation of spurious signals that are typically generated in DACs of the subranging structure.

Control systems and methods for reducing residue signal offset in subranging analog-to-digital converters

Integrated-circuit structures and methods are provided for generating an error signal that represents temperature and process-induced signal changes in transistor parameters. In particular, a reference transistor and a sense transistor are biased to each generate a substantially temperature-insensitive minority-carrier current. The reference transistor is provided with a substantially constant voltage across its current terminals to convert its minority-carrier current into a substantially temperature-insensitive reference current I,. In contrast, the sense transistor is provided with a temperature-varying voltage across its current terminals to convert its minority-carrier current into a temperature-varying sense current I,. The reference current and the sense current are then differenced to realize an error signal I,that contains information that describes temperature and process-induced signal errors in integrated-circuit transistor stages. The error signal is especially useful for correcting signal errors in circuits that cannot accommodate conventional signal-stabilizing circuitry because that circuitry would degrade circuit operation.

Integrated-circuit structures and methods for correction of temperature and process-induced parameter errors

Structures and methods are provided that linearize and stabilize the gain of adjustable-gain folding amplifiers. Accordingly, these folding amplifiers are suited for use in various compound ADCs where they improve the performance of subsequent folding amplifier stages, increase the number of allowed subsequent stages and replace the functions of other portions of compound ADCs (e.g., subranging ADCs).

Linearizing structures and methods for adjustable-gain folding amplifiers

A serial-type A/D converter uses magnitude amplifiers('magamps') and comparators for effecting the conversion of analog signals to Gray scale code signals that are then converted to binary digital signals by a Gray scale code-to-binary portion of the serial-type A/D converter. More specifically, a serial-type A/D converter uses an n-bit converter that has n-1 magamps and n-comparators. The n-1 magamps are cascaded such that the V.sub.OL and V.sub.OH outputs of a stage are the inputs to the next stage. The output of the comparators are input to the Gray scale code-to-binary portion of the serial A/D converter. The latching of the comparators occurs outside of the magamps. This allows for the parallel latching of the n comparators. The speed of the serial-type A/D converter is determined by the bandwidth of the magamps. The serial-type A/D converter includes an offset method that significantly reduces the effects of early voltage, V.sub.A, on the output waveforms. Each stage of the serial-type A/D converter may have any desired gain and not limited to a particular gain.

n-bit analog-to-digital converter with n-1 magnitude amplifiers and n

A differential amplifier operating as a magnitude amplifier may be used in a serial-type A/D converter. The differential amplifier uses complementary differential emitter pairs for folding and aligning a differential input signal. The differential input signal has a first signal and a second signal each of which is fed to one of two input circuits. One input circuit includes a bipolar npn transistor and a current sink and the other includes a bipolar pnp transistor and a current source. The outputs of the input npn transistors feed a differential pair of output pnp transistors. The emitters of the output pnp transistors are coupled, with the signal on the emitters following the lower of the differential input signals. The outputs of the input pnp transistors feed a differential pair of output npn transistors. The emitters of the output npn transistors also are coupled, with the signal on the emitters following the inputs in a predetermined manner. The results are folded signals at the outputs of the output transistors that are aligned by offset circuits.

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Greensboro, NC, United States of America

Frank M Murden