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Solutions Search - Analog-to-Digital Converters (ADC)

Reference Filter Increases 32-Bit ADC SNR by 6dB

Guy Hoover - Applications Engineer Sep 26th 2017
Design Note DN568: Introduction Attaining optimal SNR performance from an ADC isn’t just a matter of providing a low noise signal to the ADC’s input. Providing a low noise reference voltage is just as important. While reference noise has no effect at zero-scale, at full-scale any noise on the reference will be visible ...

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LTspice: Simulating SAR ADC Analog Inputs

Kris Lokere - Strategic Applications Manager
Gabino Alonso - Strategic Marketing Engineer
Sep 19th 2017
As resolution and sample rates continue to rise for ADCs, the driver circuitry for the analog inputs, not the ADC itself, has increasingly become the limiting factor in determining overall circuit accuracy. Beyond a simple 1-pole RC lowpass filter (LPF1) for noisy input signals (Figure 1), a coupling ...

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Converting a Low Distortion Single-Ended Sine Source to Fully Differential

Guy Hoover - Applications Engineer Sep 10th 2017
Customers looking for a way to evaluate ADCs with differential inputs will find themselves in need of a low distortion, low noise differential sine source. Single-ended sine sources can be obtained by building a simple Wien-bridge oscillator or by employing any of several readily available audio oscillators. Differential sine ...

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LTC2387 Drivers Part IV: How to Drive the LTC2387 Reference

Derek Redmayne - Staff Scientist Jul 10th 2017
How to Drive the LTC2387 Reference The schematic below shows an external reference filter/buffer that becomes the reference amplifier, “overdriving” REFBUF and producing a 1/f corner that is at least a factor of 50 lower than the internal reference. The internal reference has a 1/f corner at about 15 KHz. With ...

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Low Frequency Noise Analysis for Sensor Signal Chains

Noe Quintero - Application Engineer Jun 7th 2017
Introduction High-resolution, low frequency measurements are easy to implement and perform. All that is needed is an in-depth understanding of everything in the signal chain and a consideration of every aspect of every component. In all seriousness, some considerations are needed in order to get the maximum system performance ...

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Uncompromised Linearity from the LTC2185 and ADA4927-1

Clarence Mayott - Applications Engineer Mar 10th 2017
Introduction The LTC2185 is a 125Msps 16-bit ADC with excellent noise and linearity performance while only consuming 185mW per channel. It is ideal for demanding low power applications that require excellent AC performance. A high performance ADC like the LTC2185 requires a high performance amplifier driving it to maintain ...

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High Linearity, Low Noise LTC2387-18 Drivers for Sinusoidal Signals

Doug Stuetzle - Senior Analog Applications Engineer Jan 10th 2017
Introduction The LTC2387-18 is a high speed SAR (Successive Approximation Register) ADC suited for high linearity, low noise applications. This ADC is capable of sampling at up to 15Msps, which allows it to convert signals at frequencies of several MHz. It is well-suited to convert both pulsed and continuous signals in this ...

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Testing Data Converters with the Arrow / Altera SoCkit FPGA Board

Mark Thoren - Staff Scientist Jan 3rd 2017
Introduction This blog describes how Linear Technology is using the SoCkit Cyclone V SoC FPGA board from Arrow Electronics as a system for evaluating medium- speed data converters: ADCs, DACs with sample rates less than 100Msps. LTC manufactures several evaluation boards for this purpose, including the DC718, DC890, and ...

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LTC2387 Drivers Part II: Drivers for Imaging

Derek Redmayne - Staff Scientist Dec 8th 2016
A Driver for Imaging (short version) The circuit shown below works great. You should try it. This is intended for nominally 0-3V single ended or differential signals, from CCDs, CMOS image sensors, or other similar signal sources. As shown, SNR is 88 dB. With the AD8008, in place of U1, and a few other minor changes, it ...

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Increase Spectral Resolution for the LTC2387-18 Demo Board - Part 2

Doug Stuetzle - Senior Analog Applications Engineer Oct 14th 2016
Introduction In Part 1 we designed and tested a lowpass + downsample structure that increased the spectral resolution of the DC2290A-A demonstration circuit for the LTC2387-18 high speed successive approximation register (SAR) ADC from 114Hz to 0.596Hz per bin. The average noise level per bin was ...

Blog Post PScope 


Increase Spectral Resolution for the LTC2387-18 Demo Board - Part 1

Doug Stuetzle - Senior Analog Applications Engineer Oct 14th 2016
Introduction The LTC2387-18 is a low noise, high speed, 18-bit 15Msps successive approximation register (SAR) ADC. The combination of excellent linearity and wide dynamic range makes the LTC2387-18 ideal for high speed imaging and instrumentation applications. No latency operation provides a unique solution ...

Blog Post PScope 


Single-Ended to Differential Driver Circuit for the LTC2387-18 SAR ADC

Doug Stuetzle - Senior Analog Applications Engineer Sep 26th 2016
The LTC®2387-18 is a 15Msps, highly linear, low-noise SAR converter with differential inputs. The combination of excellent linearity and wide dynamic range makes this ADC ideal for high speed imaging and instrumentation applications. No-latency operation provides a unique solution for high speed control loop applications. ...

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LTC2387 Drivers Part III: Trans-Impedance Amplifier/Driver

Derek Redmayne - Staff Scientist Sep 8th 2016
This is unabashedly a classic case of what marketing calls “a solution looking for a problem”. It is an example of how the full SNR of the LTC2387 may be realized for a real world signal. Most signals originating in low level circuitry, in sensors, or in the real world, will require significant gain to develop 8Vp-p ...

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Consequences of Not Following the Data Sheet Bypass Recommendation

Guy Hoover - Applications Engineer Aug 8th 2016
I occasionally get customers who ask me to review their ADC schematics and often I will see that the values for the bypass capacitors for Vdd and Vref are smaller than the data sheet recommendations. Here is an experiment I would like to share to show why it is important to use the suggested bypassing values. The circuit of ...

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How to Drive the LTC2387 (Part 1): Signal Applications to 5MHz that Require Low Inter-Modulation Distortion

Derek Redmayne - Staff Scientist May 13th 2016
The biggest challenge in driving a 15Msps, 18-bit ADC with an 8Vp-p input range is the lack of integrated amplifiers with adequate bandwidth, low noise, and the required output excursion. There are low-noise, high-BW amplifiers than can produce 2VPP. There are low speed amplifiers than can produce 8VPP. For low distortion beyond ...

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A New Era in Space Products - Radiation Tolerant

T.J. Fure - Product Marketing Manager
Gabino Alonso - Strategic Marketing Engineer
Mar 23rd 2016
Recent developments have made doing business in space ever more achievable to a broadening base of companies. A market previously consisting solely of major defense contractors and national governments has been disrupted by a growing list of commercial companies determined to deploy an enterprise beyond the confines of our terrestrial ...

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Low Power, Precision Op Amp Simplifies Driving of MUXed ADCs

Guy Hoover - Applications Engineer Oct 2nd 2015
Design Note 1034: Introduction The high speed op amps required to buffer a modern 16‑/18-bit analog-to-digital converter (ADC) typically dissipate as much power as the ADC itself, often with a maximum offset spec of about 1mV, well beyond that of the ADC. If multiple multichannel ADCs are required, the power dissipation can ...

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Injection-Lock a Wien-Bridge Oscillator

Glen Brisebois - Applications Engineer - Signal Conditioning Sep 22nd 2015
I recently had the opportunity to investigate a new micropower 6-MHz LTC6255 op amp driving a 12-bit, 250k sample/sec LTC2361 ADC. I wanted to acquire the FFT of a pure sinusoid of about 5 kHz. The problem is that getting the FFT of a pure sinusoid requires, well, a pure sinusoid. Most programmable signal generators, however, ...

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Micropower Op Amp Drives 8-Channel 18-Bit Simultaneous Sampling ADC without Compromising Accuracy or Breaking the Power Budget

Guy Hoover - Applications Engineer Jun 23rd 2015
Design Note 541: Introduction The op amps used to drive 18-bit analog-to-digital converters (ADCs) typically draw as much supply current as the ADC itself, often with a maximum offset spec that is well above that of the ADC. If multiple ADC channels are required, the power dissipation from these drivers quickly rises to unacceptable ...

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Sometimes You Need a Little Gain Part 2

Guy Hoover - Applications Engineer Apr 28th 2015
Introduction Part 1 of "Sometimes You Need a Little Gain" dealt with a pseudo-differential ADC driver with gains of one to ten. This time a fully differential ADC driver, again with gains of one to ten will be described. First a brief recap on the LTC2373-18 SAR ADC and a description of the LTC6237 op amp which will be ...

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Sometimes You Need a Little Gain - Part 1

Guy Hoover - Applications Engineer Apr 9th 2015
Introduction The LTC2373-18 is an 18-bit, 1Msps, 8-channel SAR ADC with an integrated high performance reference and programmable sequencer. The LTC2373-18 can be configured to accept both pseudo-differential (unipolar and bipolar) and fully differential input signals. For best performance, an op amp should ...

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Multiple LTC2315-12 ADCs Share SPI Bus

Guy Hoover - Applications Engineer Mar 18th 2015
The data sheet doesn’t always show everything you need to know about using a part. For example, a common application when using multiple serial ADCs is to share the clock and data output lines to simplify the interface to the processor/ FPGA. The data sheet for the LTC2315-12 12-bit 5Msps, SPI compatible ADC with an integrated ...

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Driving the LTC2323-16 with +/-10V Input Signals

Jul 22nd 2014
Here is a driver circuit for the LTC2323-16 dual 16-bit differential input ADC. This circuit accepts a single-ended +/-10V signal and converts it to a differential +/-4.096V signal which is optimal for the LTC2323-16 using a 5V supply. The driver circuit is shown in Figure 1. This circuit has an SNR of 82dBFS (Add full ...

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LTspice: SAR ADC Driver Interface

Kris Lokere - Strategic Applications Manager Apr 3rd 2014
High-performance SAR ADCs can offer amazing dynamic range and linearity at faster and faster sample rates. But how do you design the amplifier and interface at the analog inputs? LTspice IV can help. This video shows how to use LTspice to simulate the analog input interface of high-performance SAR ADCs. We will look at charge ...

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Driver for 14-Bit, 4.5Msps ADC Operates Over a Wide Gain Range

Guy Hoover - Applications Engineer Apr 3rd 2014
Introduction The LTC2314-14 is a 14-bit, 4.5Msps, serial output ADC with an integrated high performance reference. The single-ended input of the LTC2314-14 is easy to drive and in many instances does not require a buffer. A driver, such as the LT6236 op amp, may be required for a signal that is small or has high output impedance. ...

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Alternate Bit Polarity Reduces Digital Feedback in High Speed ADCs

Apr 2nd 2014
Click here for a list of high speed data converters with alternate bit polarity mode Digital feedback occurs when the high speed transitions at the outputs of a high speed ADC are coupled (either capacitely or inductively) through the ground plane back to the sensitive analog input, creating unwanted tones and impairing the ...

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Digital Output Randomizer for High Speed ADCs

Apr 2nd 2014
Click here for a list of high speed ADCs with Digital Output Randomization Interference from an analog-to-digtal converter's digital outputs is sometimes unavoidable. Digital interference may be from capacitive or inductive coupling or coupling through the ground plane. This effect is more pronounced with high speed ADCs where ...

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A Low Jitter Clock is Required to Evaluate High Resolution ADCs

Guy Hoover - Applications Engineer Mar 3rd 2014
“How bad can the ADC clock be and still get good SNR results?” I’ve never been asked this question directly by a customer but I do periodically get asked about using clock sources that are not appropriate for high resolution ADCs. Usually it involves a function generator which can have jitter up to 1nsRMS. ...

Blog Post PScope 


Internal Dither Improves High Speed ADC SFDR Performance

Mar 3rd 2014
Click here for a complete list of analog to digital converters with internal dither The LTC2208 is a 16-bit ADC with a very linear transfer function; however, at low input levels even slight imperfections in the transfer function will result in unwanted tones. Small errors in the transfer function are usually a result of ADC ...

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Generating a ±10.24V True Bipolar Input for an 18-Bit, 1Msps SAR ADC

Guy Hoover - Applications Engineer Dec 17th 2013
Introduction The LTC2338 is an 18-bit fully differential SAR ADC that is remarkably easy to drive. This 1Msps ADC operates from a single 5V supply and achieves ±4LSB INL maximum with –111dB THD and 100dB SNR. Its fully differential ±20.48V true bipolar input range minimizes the need for range scaling, and ...

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Short Ground Leads Make Better Scope Photos

Guy Hoover - Applications Engineer Nov 6th 2013
I often ask customers to send me oscilloscope photos showing the ADC interface timing of their circuits. Occasionally, what I get back is a waveform with large amplitude ringing or even something that resembles a sine wave for what should be a relatively clean square wave. When asked how the scope probe was grounded, they will ...

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36V Input, Low Output Noise, 5A μModule Regulator for Precision Data Acquisition Systems

Jaino Parasseril - Applications Engineer Sep 1st 2013
Introduction Low output noise, fast transient response and high efficiency are just a few of the stringent power supply demands made by applications featuring high data rate FPGA I/O channels and high bit count data converters. The power supply designer faces the difficult task of meeting all of these requirements with as few ...

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A Short Course in PCB Layout for High-Speed ADCs

Derek Redmayne - Staff Scientist Mar 28th 2013
The intention here is to create the most concise layout guide ever.  This goes against our general philosophy of writing to minimize the number of phone calls.  This will likely generate a few phone calls because the reasons for the advice are not given.  They are the subject of a much longer document for those ...

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PScope: High-Speed ADC Data Collection Software

Clarence Mayott - Applications Engineer Jan 4th 2011
When Linear Technology provides a customer with a high speed ADC demo board we also provide PScope, the software to evaluate the demo board. PScope is a simple software package that can collect, and display data from high speed ADC demo boards. It will also provide a simple and easy way to measure the key performance parameters ...

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Reduce Digital Feedback in High Speed Data Conversion Systems - LTC2261

Clarence Mayott - Applications Engineer Mar 15th 2009
Linear Technology's newest high-speed ADC family achieves one third the power consumption of existing solutions without compromising AC performance. Operating from a low 1.8V supply, the 14-bit, 125Msps LTC2261 dissipates 125mW while maintaining 73.4dB SNR and 85dBc SFDR. Digital outputs can be configured as DDR CMOS, DDR LVDS ...

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