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Solutions Search - ADC Driving Solutions

LTspice: Worst-Case Circuit Analysis with Minimal Simulations Runs

Joseph Spencer - Field Applications Engineer
Gabino Alonso - Strategic Marketing Engineer
Jun 8th 2017
When designing a circuit in LTspice, you may wish to assess the impact of component tolerances. For example, the gain error introduced by non-ideal resistors in an op amp circuit. This article illustrates a method that reduces the number of simulations needed, and as a result speeds your time to results. Varying a Parameter LTSpice ...

Blog Post LTspice 


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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Anti-Alias Filter for 24-bit ADC

Guy Hoover - Applications Engineer Aug 3rd 2016
For many ADC applications a simple RC filter at the buffer input will provide adequate anti-alias filtering. For applications that require a higher order filter an active filter is often used. The active component in that filter must have sufficient bandwidth, fast settling, low noise and low offset so that it doesn’t ...

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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 ...

Blog Post 


LTC6363 LTC6363 Used as Lowpass Filter/Driver with 10VP-P Singled-Ended Input, Driving a SAR ADC

Aug 31st 2015
The LTC®6363 is a low power, low noise, fully differential op amp with rail-to-rail outputs optimized to drive low power SAR ADCs. The LTC6363 draws only 1.9mA supply current in active operation and features a shutdown mode which reduces the current consumption to 20μA (VS = 3V). ...



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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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. ...

Blog Post 


Digital Gain Compression (DGC) for SAR ADCs

Mar 11th 2014
The LTC2378-20 offers a digital gain compression (DGC) feature which defines the full-scale input swing to be between 10% and 90% of the ±VREF analog input range. This feature allows the SAR ADC driver to be powered off of a single positive supply since each input swings between 0.5V and 4.5V as shown in the figure below. Needing ...

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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 


DC Accurate Driver for the LTC2377-20 Achieves 2ppm Linearity

Guy Hoover - Applications Engineer Jan 10th 2014
Introduction As resolution and sample rates continue to rise for analog-to-digital converters (ADCs), the driver circuitry for the ADC analog input, not the ADC itself, has increasingly become the limiting factor in determining overall circuit accuracy. First, the driver circuitry must buffer the input signal and provide gain. ...

Blog Post 


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 ...

Blog Post 


Improve S21 Flatness Measurements

Doug Stuetzle - Senior Analog Applications Engineer Dec 16th 2013
An important performance measure of a 2-port network is S21. A 2-port network can be an amplifier or a filter, for example. So what is S21? This parameter is one of several S-parameters that are commonly used to characterize 2-port networks. An S-parameter indicates the amount of power leaving one port of the network, given ...

Blog Post 


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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ADC Driving: Driving Differential ADCs

Guy Hoover - Applications Engineer Sep 10th 2013
For most fully differential applications, it is recommended that the LTC2389-18 be driven using the LT6201 ADC driver configured as two unity-gain buffers, as shown in Figure 1. The LT6201 combines fast settling and good DC linearity with a 0.95nV/√Hz input-referred noise density, enabling it to achieve the full ADC data ...

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ADC Driving: Single-Ended To Differential Conversion

Guy Hoover - Applications Engineer Sep 5th 2013
Figure 1 shows the LT6350 being used to convert a 0V to 5V single-ended input signal to differential for an ADC with differential inputs. In this case, the first amplifier is configured as a unity gain buffer and the single-ended input signal directly drives the high-impedance input of the amplifier. As shown in the FFT of Figure ...

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ADC Driving: Pseudo-Differential Unipolar or Bipolar Inputs

Guy Hoover - Applications Engineer Aug 28th 2013
For most applications, we recommend the low power LT6202 ADC driver to drive the LTC2369-18. With a low noise density of 1.9nV/√Hz and a low supply current of 3mA, the LT6202 is flexible and may be configured to convert signals of various amplitudes to the 0V to 5V input range of the LTC2369-18. To achieve the full ...

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ADC Drivers & Filters: Single Ended Buffer

Guy Hoover - Applications Engineer Aug 28th 2013
Figure 1 shows a recommended single ended buffered drive circuit using the LT1818 in unity gain mode. The 47pF capacitor from AIN to ground and 50Ω source resistor limits the input bandwidth to 68MHz. The 47pF capacitor also acts as a charge reservoir for the input sample-and-hold and isolates the LT1818 from sampling ...

Blog Post 


SAR ADC Input Types

Alison Steer - Product Marketing Manager Jul 24th 2013
Single Ended Inputs An ADC with single-ended inputs digitizes the analog input voltage relative to ground. Single-ended inputs simplify ADC driver requirements, reduce complexity and lower power dissipation in the signal chain. Single-ended inputs can either be unipolar or bipolar, where the analog input on a single-ended ...

Blog Post 


Can You Use the Voltage Reference to Power Your ADC Driver?

Kris Lokere - Strategic Applications Manager Jul 11th 2013
Linear Technology’s family of 16-, 18-, and 20-Bit SAR ADCs (LTC2378-20 family) operates with an external reference voltage of up to 5V. The largest input voltage that you are then supposed to put on each ADC input pin is equal to that 5V reference voltage. It seems logical to use an opamp on a 5V supply with rail-to-rail ...

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Psuedo-Differential Unipolar Inputs: Driving The LTC2369-18

Guy Hoover - Applications Engineer Apr 8th 2013
For most applications, we recommend the low power LT6202 ADC driver to drive the LTC2369-18. With a low noise density of 1.9nV/√Hz and a low supply current of 3mA, the LT6202 is flexible and may be configured to convert signals of various amplitudes to the 0V to 5V input range of the LTC2369-18. To achieve the full distortion ...

Blog Post 


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 ...

Blog Post 


Can a Slow, Precision Op Amp Drive a Fast 18-bit SAR ADC?

Kris Lokere - Strategic Applications Manager Mar 4th 2013
Many times the reference designs for high-speed high-resolution SAR ADCs show a relatively high-speed opamp in front of the ADC to drive it. There are good reasons for that: A low output impedance at high frequencies helps absorb the charge kick-back from the ADC’s sample capacitor, and the opamp’s high loop gain ...

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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 ...

Blog Post Video 


Wideband Receiver

Nov 13th 2008
The LTC5551 is a 2.5V to 3.6V mixer optimized for RF downconverting mixer applications that require very high dynamic range. The LTC5551 covers the 300MHz to 3.5GHz RF Frequency range with LO frequency range of 200MHz to 3.5GHz. The LTC5551 provides very high IIP3 and P1dB with low power consumption. A typical application is ...



LTC6406: 133MHz Differential Amplifier with External Gain Set, Impedance Matching to a 75Ω Source and Level Shifting

Aug 3rd 2007
This circuit shows an example of a single-ended-to-differential amplifi er matching a 75Ω source and level shifting from a 2.5V input common mode to a 1.25V output common mode voltage (typical level shifting required from a 5V single-ended circuit to a 3V differential circuit to drive a high speed ADC). The singleended- ...

Circuit LTspice 


The LT1993-2 Driving an LTC2255 ADC Sampling at 96.12Msps with a 70MHz, 4-Channel WCDMA Signal

Mar 29th 2005
70MHz IF signal driver into ADC. Four to one transformer on input with capacitive coupling into input of LT1993-2, LC filter on output provides Out of Band Filtering. ...



Bipolar, Ground Referenced, Single-Ended Signal Interface To Unipolar, Differential Input ADC

Aug 17th 2001
Differential amplifiers are useful for providing the input to a single supply differential ADC from a bipolar ground referenced input source. All of the signal level shifting and gain requirements can be adjusted with external resistors. ...



Single Supply 16-Bit ADC Driver

Aug 17th 2001
This circuit shows the LT6203 driving an LTC1864 unipolar 16-bit, 250ksps A/D converter. The bottom half of the LT6203 is in a gain of 1 and buffers the 0V negative fullscale signal VLOW into the negative input of the LTC1864. The upper half of the LT6203 is in a gain of 10, referenced to the buffered voltage VLOW and drives ...