Welcome to part three of this blog series discussing electromagnetic compatibility (EMC) testing. In parts one and two we discussed the background of certification testing and the specifications for ESD and radiated EMI immunity tests. This time, we’ll continue with the details of electrical fast transient (EFT) and surge testing.
IEC 61000-4-4: EFT (Electrical Fast Transients…
**Click on images to enlarge.
Just about every single-supply application uses a “supply splitter” to create a mid-point reference that is ½*Vcc. Texas Instruments makes an IC dedicated to that purpose called the TLE2426. Now, before you quit reading because you think I am trying to sell you something, hear me out. The below information is valid for the TLE2426
…I regularly respond to questions on the Precision Amplifiers forum attempting to clarify misunderstanding of differences between the specified and operating conditions used in our product datasheet (PDS) for defining various op amp parameters. These differences have great technical implications since PDS limits apply only to specified ranges. Therefore, it is paramount for designers not to use operating conditions as…
Galvanic isolation is a key requirement in many industrial applications. Isolation provides technical advantages such as breaking noisy ground loops, and it also protects the end user and sensitive equipment from potentially dangerous high voltage and transients.
An isolated current-monitoring acquisition system can be constructed as shown in Figure 1: the input current is transformed…
The PowerPad™ is a great package feature that allows operational amplifiers and other linear circuits to deliver otherwise unattainable output power from a device packaged in a small outline (SO) package. The PowerPad™ provides a highly conductive thermal path from the back of the integrated circuit die to an external heat sink, or to a copper PC board plane acting like one. The product datasheet is specific about the…
Part 1:
2-wire 4-20 mA sensor transmitters are very common in industrial control and automation. They are popular because they allow a remote process to be monitored with only two analog signal wires. The two wires carry both the power for the sensor/monitoring circuitry and the analog output signal. Common applications for 2-wire sensor transmitters are pressure sensors, gas sensors, chemical sensors, level sensors,…
This is the second post in our SAR ADC series.
Part 2: A marketing analogy
When a response time of 1 µs is required from the SAR ADC (tRESP-ADC = 1 µs), many engineers would search for a SAR ADC with throughput of 1 Msps (tTHROUGHPUT = 1 us). In reality, the two parameters are actually different. To demonstrate the difference, let’s look at the following analogy:
You are the marketing manager of a major…
I recently performed some tests in the lab and noticed a strange ringing on the output signal. After troubleshooting the problem, I managed to trace the ringing back to the input signal. Figure 1 shows the input signal of my circuit with the ringing boxed in red. I needed to find the cause of the ringing since a clean step response was expected. It turns out that my lab equipment was not properly terminated. This blog…
This post was co-written by Kunal Gandhi and Rahul Prakash.
Engineers may agree that one of the most anxious and stressful moments they face is when his or her design is back from fabrication and ready to be tested. While it is thrilling to see our concept or design work for the first time in the lab, sometimes we have to accept catastrophic failures, too.
In this blog post…
Noise and distortion are two common enemies for engineers designing precision analog systems. But when looking at total harmonic distortion and noise (THD+N) figures in an op amp datasheet, it may not be immediately clear which enemy you’re battling: noise or distortion?
“Noise” describes the random electrical signals produced by the amplifier. “Distortion” refers to unwanted…
This technical article was updated on July 23, 2020.
Part 1:
The objective of many typical control system applications is to effect a control action based on the status of input control variables. Some of these include position, speed, angle, level, temperature and pressure.
And for each of these control variables, you may need to optimize the design for ‘precise’ measurements, ‘precise’ control actions, and/or a fast…
This technical article was updated on July 23, 2020.
In the first ADC Accuracy post, we established the differences between the resolution and accuracy for an analog-to-digital converter (ADC). Now we can dig into the factors that contribute toward total accuracy of the ADC, often referred to as Total Unadjusted Error (TUE).
Ever wondered what “Total” stands for in the TUE specification of ADC? Is it as simple as adding…
Have you ever wondered why a traditional 3-op amp instrumentation amplifier’s offset voltage changes with gain? Figure 1 is an excerpt from the INA333 datasheet that shows an example of the dependence of the offset voltage on device gain. Today, let's walk through how the equation is determined.
Figure 1: INA333 offset voltage specification
Traditional 3-op amp instrumentation…
This technical article was updated on July 23, 2020.
In talking to system designers using analog-to-digital converters (ADCs), one of the most common questions that I hear is:
“Is your 16-bit ADC also 16-bit accurate?”
The answer to this question lies in the fundamental understanding of the difference between the concept of resolution and accuracy. Despite being two completely different concepts, these two…
This technical article was updated on July 23, 2020.
Today, we continue our series on successive approximation register (SAR) analog-to-digital converters (ADCs) input types. Previously, I reviewed input considerations and pnoise performance comparisons between SAR ADCs. In this post, we will look at the source for Total Harmonic Distortion (THD) in a SAR ADC and how it differs between various input types.
THD Impact
…To simulate, or not to simulate, that is the question-
Whether it is wiser in the Engineer’s mind to suffer
The ridicules of colleagues and wrath of management,
Or to hasten accuracy and time to market,
And by using SPICE, end all doubt?
The use, or overuse, of SPICE simulation is an age old controversy. Many engineers rely heavily on simulation and do relatively little hand calculation. Other engineers have distain…
In the last two posts in this series I talked about how to build 3-wire analog outputs and how to protect them from transient overstress. This post will finish off the discussion of 3-wire analog outputs with some solutions to one more application-specific problem.
A growing trend in the industrial application space is for analog output modules to provide both voltage and current outputs on a single terminal block. This…
In this three-part series, I discussed the solutions for generating two well-matched, low-drift voltage references. We started with three topologies in Part 1, we compared and contrasted the differences in terms of performance in Part 2. Now, let’s take a look at other design considerations of these solutions: space consumption and cost.
Space Consumption and Cost
Apart from system performance, PCB real estate…
This technical article was updated on July 23, 2020.
My previous blog Input considerations for SAR ADC's, introduced various input types for Successive Approximation Register (SAR) analog-to-digital converters (ADCs): single-ended, pseudo-differential, fully differential input and true differential input.
Some of the key specifications considered when selecting a SAR ADC include resolution, channel count, sampling…
In my previous post, we talked about three topologies for generating two high-accuracy voltage reference outputs. Today, we’ll compare the performance of these solutions from three perspectives: total error, drift tracking and matching between outputs.
Total error
Equation (1) converts specifications given as a percentage (%) to parts per million (ppm).
(Equation 1)
The Total Error performance metric of each…
Developing a low-drift system can be very difficult, especially with a bipolar input signal. Applications such as bidirectional current sensing shown in Figure 1, require the use of two well-matched, low-drift reference voltages. The first voltage, VREF, defines the full-scale range of the ADC. A bias voltage, VBIAS, is necessary in order to level shift the bipolar signal. It is desirable to have VBIAS = VREF/2 so that…
Welcome to part two of this blog series discussing electromagnetic compatibility (EMC) testing. In part one, we discussed the need for certification testing, who performs the tests, and what constitutes a pass or fail condition. This time, we’re going to dive right into the technical specifications of some of the most common tests.
IEC 61000-4-2: ESD (Electrostatic discharge)
ESD (Electrostatic discharge) is one…
Calculating the total error of a system can be tricky, especially when the specifications units vary widely. When calculating the total error, all specifications must be converted into a common unit before combining. This blog will show you how to convert between units of volt, percentage and parts per million (ppm) to ensure proper calculation of total system error.
Most errors…
In my last post, I talked about how integration has simplified 3-wire analog output design. In this post, I’ll show you one way to protect these designs against dangerous industrial transients that can cause electrical overstress.
Part 2 of 2:
Two commonly asked questions when designing an operational amplifier into a new application are:
1. What is its “typical” power dissipation? Covered in my first post.
2. What is its “maximum” power dissipation?
The op amp’s maximum power should be evaluated in the intended circuit. Let’s assume the first case where the amplifier is being operated…
