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Analog Dialogue

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Engineers that must design for very high temperature environments -- such as down-hole oil and gas, avionics, heavy industrial, and under-hood automotive -- face quite a challenge when it comes to making high precision circuits that are also reliable, compact and low power.  After all, 210°C/410°F is a great temperature to cook a pizza, but standard electronic circuits are not going to fare very well!  At these temperatures there are multiple physical phenomena working against you when it comes to the performance and reliability of integrated circuits.  Gustavo.Castro and I described many of these factors in our 2012 article  "High-Temperature Electronics Pose Design and Reliability Challenges", which I would recommend reading for a good overview of the applications, challenges, solutions and best practices.

 

Since 2012 a lot of progress has been made in this space.  Analog Devices has released several new products for high temperature environments, enabling a signal chain for "sensor-to-bits", including sensor signal conditioning, analog-to-digital conversion and MEMS inertial sensors.  To that end, we are excited to introduce our first reference design for high temperature precision data acquisition, based around the new AD7981 High Temperature 600 kSPS SAR ADC:

 

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In the August 2015 edition of Analog Dialogue, Maithil Pachchigar (maithil) and I present a new reference design for high temperature data acquisition, characterized from room temperature to 175°C. This circuit is intended to be a complete data acquisition circuit building block that will take an analog sensor input, condition it, and digitize it to an SPI serial data stream. It is versatile enough to be used as a single channel, or it can be scaled for multiple channel simultaneous sampling applications. Recognizing the importance of low power consumption, the power consumption of the ADC scales linearly with the sample rate. The ADC can also be directly powered from the voltage reference, eliminating the need for an additional power rail and the associated power conversion inefficiencies. This reference design is available off the shelf (CN0365) to facilitate testing by designers and includes all schematics, bill of materials, PCB artwork, and test software.  You can read the full text of the article at "A Low Power Data Acquisition Solution for High Temperature Electronics Applications"

 

You can see this board in action in a demo that we made that incorporates the data acquisition reference design along with the eval board for our high temp MEMS gyroscope, the ADXRS645:

 

 

For more information on high temperature products from Analog Devices, visit www.analog.com/hightemp.

One of the more difficult aspects of PLL synthesizer applications is dealing with spurious signals and using frequency planning to avoid unwanted interference. This article details a simple, yet very effective optimization technique for avoiding spurious signals from the Analog Devices family of integrated PLLVCO products. The article also introduces our new, free frequency planning software: ADIsimFrequencyPlanner.

 

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For more information on this application, please read, Analyzing, Optimizing, and Eliminating Integer Boundary Spurs in Phase-Locked Loops with VCOs at up to 13.6 GHz, which was recently published in the August 2015 issue of Analog Dialogue. We hope that you find this useful and look forward to your feedback.

Some of the most interesting applications for MEMS IMUs involve a purposeful blend of multiple inertial observers, in addition to the IMU.  While this article was published a few years ago, it serves as a relevant reminder of how combining independent sensing technologies can create exciting, life-changing functions.  In this case, GPS, Laser, wheel-based odometers and the MEMS IMU combine to provide very accurate, autonomous robot operation.

 

 

For more information on this application, please read, Inertial Sensors Facilitate Autonomous Operation in Mobile Robots, which was originally published in the August 2010 issue of Analog Dialogue. We hope that you find this useful and look forward to your feedback.

Highly integrated, fully specified sensor systems, such as the ADIS16209 tilt sensor, allow system developers to readily use sensor technologies with which they may have little experience—with minimal investment and risk. Since accuracy is fully specified at a given power level, it might appear that the developer's ability to reduce power consumption is constrained. However, the use of power cycling techniques provides a useful trade space in applications where energy use must be tightly managed. This article focuses on the key behaviors in smart sensor products, which may impact power cycling and how effectively this technique can reduce power.

ADIS1620x_PowerCyclingRessponse.PNG

The concepts and analysis techniques presented in this article provide a good starting point for engineers who value highly integrated sensor products but are also under pressure to reduce power consumption where possible. More importantly, the thought process associated with identifying and analyzing behaviors that can impact overall power goals will be even more important, as each system design offers new opportunities and risks.

 

For more information, click on the following link to access, Power Cycling 101: Optimizing Energy Use in Smart Sensor Products, which originally published in the August 2010 Issue of Analog Dialogue. We hope that this helps and look forward to your feedback.

 

Sincerely,

NevadaMark

Sensor misalignment is often a key consideration for high performance motion control systems that use MEMS inertial measurement units (IMUs) in their feedback loops. For the gyroscopes in the IMU, sensor misalignment describes the angular difference between each gyroscope’s axis of rotation (solid blue lines) and the system defined inertial reference frame, also known as the global frame (gray dotted lines).

ADIS1648x_Alignment.PNG

ADIS16485 Inertial Misalignment Angles

 

Managing the impact that misalignment has on sensor accuracy can require unique packaging, special assembly processes, or even complex inertial testing in the final configuration. All of these things can have a major impact on important project management metrics such as schedule, investment, and the total cost associated with the IMU in each system. To start learning how to understand and manage sensor misalignment, check out The Basics of MEMS IMU/Gyroscope Alignment in Analog Dialogue.


We hope that this article helps you as early as possible in your design cycle, so that you can avoid surprises that impact critical system objectives (schedule, cost, power....) and exceed all of your performance objectives.  We look forward to your feedback on this!

Can you explain why the minimum and maximum gain errors specified by my ADC differ so much? Learn more in "Isn’t that gain specification a bit lopsided?" as published in the March 2015 issue of Analog Dialogue.

 

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We welcome your feedback. Has this article helped you in your design? Would you like more information on this topic?

 

Best regards,

Scott

Do I really need to match the impedance between both inputs of my amplifier? Learn more at "Muntzing can save cost, components, and even your sanity" as published in the April 2015 issue of Analog Dialogue.

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We welcome your feedback. Has this article helped you in your design? Would you like more information on this topic?

 

Best regards,

Scott

Choosing References

Posted by analogkidr Feb 6, 2015

How do I choose a voltage reference? Learn more at "Choosing References" as published in the February 2015 issue of Analog Dialogue.

 

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We welcome your feedback. Has this article helped you in your design? Would you like more information on this topic?

 

Best regards,

Scott

 

My amplifier doesn’t behave properly when multiplexing channels. What could be the cause? Find out in "Don't Get Caught Speeding" as published in the January 2015 issue of Analog Dialogue.

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We welcome your feedback. Has this article helped you in your design? Would you like more information on this topic?

 

Best regards,

Scott

How can a high-performance analog-to-digital converter have numerous power connections but only a couple of grounds? Find out at "Exposed Paddles and Downbonds Improve Performance and Reduce Pin Count" as published in the December 2014 issue of Analog Dialogue.

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We welcome your feedback. Has this article helped you in your design? Would you like more information on this topic?

 

Best regards,

Scott

Choosing Analog ICs

Posted by analogkidr Feb 6, 2015

You’ve told us that we need not be too careful when choosing discrete transistors. What about analog ICs? Learn more in "Choosing Analog ICs", as published in the November 2014 issue of Analog Dialogue.

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We welcome your feedback. Has this article helped you in your design? Would you like more information on this topic?

 

Best regards,

Scott

What should concern me when testing my heart-rate monitor prototype? Find out in "I Grew Up in the 80s and Survived! " as published in the October 2014 issue of Analog Dialogue.A-D 48-10 RAQ.jpg

We welcome your feedback. Has this article helped you in your design? Would you like more information on this topic?

 

Best regards,

Scott

I need 100-dB dynamic range for a medical imaging application. Can you help me choose between successive-approximation and sigma-delta ADC architectures? Find out more in ADCs for High Dynamic Range – Successive-Approximation or Sigma-Delta? as published in the September 2014 issue of Analog Dialogue.

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We welcome your feedback. Has this article helped you in your design? Would you like more information on this topic?

 

Best regards,

Scott

We live in an interconnected world where we get a cup of coffee, listen to music, heat our lunch, all on a push of a button. The millenials have taken over! The world of instant gratification is here, where we want things to happen instantaneously. So that got me thinking......what would it feel like to have this instant gratification when a systems architect is designing a heterodyne receiver with an ADC and some associated components. Now, that is a different cup of coffee y'all.

 

Analog Devices Inc. (ADI) has always prided itself in providing industry leading performance in Analog-Digital Conversion. There are two ways to see this in action:

  1. Read the datasheet and blindly "trust" the numbers, or
  2. Get an evaluation system for yourself and find it out (if you are the old school type where "seeing is believing")

 

Now, what if.......just what if the hardware you bought was not what you were looking for. Now you have hundreds of dollars worth of boards in your lab, that you essentially don't want. Try explaining that your boss.

 

There however, exists a third method. This method is behavioral modeling and it is gathering steam. ADI has been providing behavioral models for ADCs and other products for a long time, but this in my opinion has been under-utilized. In order to utilize the behavioral models for ADCs one only needs to download and install our free tool VisualAnalog. VisualAnalog is a versatile tool that helps systems architects determine which ADC they would want in their system. VisualAnalog is usually marketed as a tool to evaluate ADCs, which is true. An added benefit to VisualAnalog is that you really do not need to buy hardware to evaluate ADC performance. This is because of the behavioral modeling tool within VisualAnalog called ADISIMADC. See below for a comparison of ADISIMADC and actual performance of AD9467, our highest dynamic range ADC to date. Figures 1 and 2 show the measured and simulated performance of the AD9467 evaluation board when clocked using a Rohde & Schwarz SMA100A with B22 low phase noise option.

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Figure 1: Measured performance from Evaluation Board of AD9467 at 97MHz analog input

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Figure 2: Simulated performance of AD9467 at 97MHz analog input

 

Now if you choose to use an ADI clocking solution, the combined performance can be simulated by spending a grand total of $0! This is because there is a behavioral modeling tool called ADISIMCLK that can simulate clock performance. The information from ADISIMCLK can be passed on to the ADISIMADC model within VisualAnalog and the performance of the AD9467 (for example) can be simulated with the AD9523 (for example) clocking it. If you dont like what you see, you can select another ADC, or clocking device. For free! How about that!

 

Figure 3 below shows how closely ADISIMADC predicts the SNR performance of the AD9467 across input frequency when driven using the AD9523.

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Figure 3: Simulated vs. measured performance of AD9467 + AD9523 across frequency


I have always wondered if modeling tools will gain the trust of systems designers in helping them choose the appropriate ADC and clocking chip. I think the suite of tools from ADI is definitely a step in the right direction to help him make that decision without a major investment in evaluation boards. Here is where I discuss this problem in detail.

ADC Modeling Tools Speed Up Evaluation

 

We can learn a thing or two from a millenial after all......

 

Ciao

Umesh

 

11/08/2014 Edit:

- changed figure 2 to match the same conditions as figure 1

- provided link to VisualAnalog

The Diamond Plot

Posted by analogkidr Jul 10, 2014

Your signal is within the instrumentation amplifier's specified input voltage range, but the output is saturated. Find out what's happening in The Diamond Plot, as published in the July 2014 issue of Analog Dialogue.


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We welcome your feedback. Has this article helped you in your design? Would you like more information on this topic?

 

Best regards,

Scott

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