Analog Devices Global Unlimited Company

Analog Devices Global

Analog Devices International Unlimited Company

Analog Devices,inc.

Sandeep Monangi

Michael C W Coln

Arvind Madan

Maitrey Kamble

Anoop Manissery Kalathil

Mahesh Madhavan

Michael Mueck

Quan Wan

Bhargav R Vyas

Debopam Banerjee

Vinayak Mukund Kulkarni

Archana Patil

A data converter circuit comprises timing circuitry configured to time stages of a conversion performed by the data converter circuit; a level shifter circuit configured to receive a control signal associated with the conversion and provide a level shifted version of the control signal to one or more switch circuits of the data converter circuit; and a time delay circuit element including a replica circuit of the level shifter circuit that adds a circuit delay to a transition of the control signal at the timing circuitry.

Timing methods for SAR ADCs

A successive approximation register analog-to-digital converter (SAR ADC) circuit comprises N weighted bit capacitors, wherein N is a positive integer greater than one; a sampling circuit configured to sample an input voltage onto the N weighted bit capacitors; and logic circuitry. The logic circuitry is configured to enable sampling of the input voltage onto the N weighted bit capacitors in a high-resolution mode; enable sampling of the input voltage onto N&#x2212;M of the weighted bit capacitors in a low-resolution mode and sampling a common mode voltage onto the most significant M weighted bit capacitors, wherein M is a positive integer greater than zero and less than N; and initiate successive bit trials using the weighted bit capacitors to convert the sampled input voltage to a digital value.

SAR ADC with variable sampling capacitor

A successive approximation register analog to digital converter (SAR ADC) is provided in which impact of dielectric absorption is reduced with a correction circuit configured to adjust a present digital code value signal based at least in part upon a previous digital code value signal, an acquisition time and temperature.

Method and apparatus to reduce effect of dielectric absorption in SAR ADC

An electronic circuit comprises a comparator circuit including an input circuit stage and an output circuit stage, and an input stage supply circuit coupled to a circuit supply rail and the input circuit stage. The input stage supply circuit includes a voltage generator circuit and a regulating circuit. The voltage generator circuit includes a replicate circuit of a portion of the input circuit stage to generate a voltage that is less than a voltage of the circuit supply rail and varies with the voltage of the circuit supply rail and device parameters of the replicate circuit. The regulating circuit generates a regulated input stage supply using the generated voltage.

Comparator preamplifier robust to variations in supply and common-mode

A low-noise, low-power reference voltage circuit can include an operational transconductance amplifier (OTA) with inputs coupled to a temperature-compensated voltage, such as can be provided by source-coupled first and second field-effect transistors (FETs) having different threshold voltages. A capacitive voltage divider can feed back a portion of a reference voltage output by the OTA to the inputs of the OTA to help establish or maintain the temperature-compensated voltage across the inputs of the OTA. A switching network can be used, such as initialize the capacitive voltage divider or other capacitive feedback circuit, such as during power-down cycles, or when resuming powered-on cycles. A switch can interrupt current to the OTA during the power-down cycles to save power. The cycled voltage reference circuit can provide a reference voltage to an ADC reservoir capacitor. Powering down can occur during analog input signal sampling, during successive approximation routine (SAR) conversion, or both.

Power-cycling voltage reference

A differential digital-to-analog (DAC) circuit that can include a reservoir capacitor and various switches to couple the bottom plates of the input capacitors, e.g., bit-trial capacitors, to reference voltages, e.g., REF+ or REF&#x2212;. In this manner, the reservoir capacitor can be used to provide any differential charge to the input capacitors, e.g., bit-trial capacitors, and the reference voltages, e.g., REF+ and REF&#x2212;, can be used to provide any common mode charge to the input capacitors.

Common mode rejection in reservoir capacitor analog-to-digital converter

Various examples are directed to a variable speed comparator circuit comprising a first comparator, a second comparator, and a third comparator and a logic circuit. The first comparator may be configured to generate a first comparator output using a first input and a second input. The second comparator may be configured to generate a second comparator output using the first input and the second input. The third comparator may be configured to generate a third comparator output using the first input and the second input. A propagation delay of the second comparator may be less than a propagation delay of the first comparator. Also, a propagation delay of the third comparator may be less than the propagation delay of the second comparator. The second comparator may have an input offset relative to the third comparator. The logic circuit may be configured to determine that the second comparator output and the third comparator output are not equivalent and set a comparator circuit output to the first comparator output.

Variable speed comparator

Techniques to use reservoir capacitors in ADC to supply most of the charge to bit-trial capacitors as bit-trials are performed. An accurate reference voltage source, e.g., a reference buffer circuit, only needs to supply the difference, e.g., an inaccuracy, in the charge supplied by the reservoir capacitors. Instead of having to resettle for each bit-trial, the accurate reference voltage source has only to deliver the initial charge to the reservoir capacitors during acquisition and once more when the ADC is ready to sample onto the residue amplifier. These techniques can ease the demands on the reference buffer circuit and requirement of external decoupling capacitors, for example.

Reservoir capacitor based analog-to-digital converter

Systems and methods to reduce the amount of reference current drawn by a SAR ADC by including an auxiliary or precharge reference source. The ADC can connect the bit trial capacitors of a main digital-to-analog converter (DAC) to an auxiliary or precharge reference source during the loading of the bit trials, and then the ADC can switch to a main reference buffer. After allowing enough time for both phases, the main DAC can proceed with the bit trials to resolve the remaining bits. The rest of the bit trials can be performed directly using the main reference buffer.

Reference precharge techniques for analog-to-digital converters

To reduce the overall reference charge needed to perform operations, analog-to-digital converters can maintain reference voltage connections of the bit trial capacitors of the digital-to-analog converter (DAC) from the end of a current conversion to just prior to the beginning of the next acquisition phase. At the start of the next acquisition phase, the bottom plates of the bit trial capacitors of the DAC can be shorted to generate a common mode voltage. As the conversion phase begins, the bottom plates of the sampling capacitors are disconnected from the input voltage and the bottom plates of each bit trial capacitor are shorted to generate input common-mode voltage. As bit trials progress, the shorts between the bottom plates of the bit trial capacitors are removed and the bit trial results are applied to the bottom plates of the bit trial capacitors.

Reducing reference charge consumption in analog-to-digital converters

A successive approximation routine (SAR) analog-to-digital converter integrated circuit can include multiple analog-to-digital converters (ADCs) sharing a reference voltage that can be perturbed by a capacitor array of a digital-to-analog converter (DAC) sampling the reference voltage, which can limit conversion accuracy. Synchronizing every bit trial across the ADCs can improve accuracy but can slow the conversion. Synchronizing a subset of at least one, but fewer than N, bit trials across ADCs can help obtain both speed and robustness. This selected subset can include bit trials corresponding to pro-defined critical events, such as those events for which a stable reference voltage node is particularly desirable.

SAR analog-to-digital converter selective synchronization

Multichannel successive approximation register (SAR) analog-to-digital converters (ADC), along with methods and systems for multichannel SAR analog-to-digital conversion, are disclosed herein. An exemplary multichannel SAR ADC can include a first SAR ADC for each of a plurality of input channels, and a second SAR ADC, a multiplexer, and a residue amplifier shared among the plurality of input channels. The multiplexer can select an analog residue signal from one of the first SAR ADCs for conversion by the second SAR ADC. The residue amplifier can amplify the selected analog residue signal. The second SAR ADC, multiplexer, and/or residue amplifier may be shared among all of the plurality of input channels. Where the multichannel SAR ADC includes N input channels, the second SAR ADC, multiplexer, and/or residue amplifier may be shared among b channels of the N input channels.

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Srikakulam, India

Sandeep Monangi