Part 4 of this series discussed the issues and requirements involved in the design of a 2-wire sensor transmitter that accepts inputs from an externally powered sensor/source. In this installment, I’ll expand on the concepts presented in that p...

Last week, I posted a short quiz so readers could test their analog knowledge. Take a look at the quiz here if you missed it. All answers are found in the Analog Engineer's Pocket Reference, a new book of commonly used precision signal chain equations...

Often in high-power motor drives or industrial controllers, designers use closed-loop current sensors when their application requires a highly accurate representation of either AC or DC current. Also used in energy and hybrid electric vehicle (HEV) applications, a closed-loop current sensor can utilize a special sensor signal conditioning chip like the DRV411 that includes a Hall effect…

In the first two posts of the delta-sigma (ΔΣ) analog-to-digital converter (ADC) basics blog series, we have discussed the two basic building blocks used in ΔΣ ADCs: the modulator and the digital filter. You’ll encounter many other integrated circuits as you work with these devices, however. The available functional blocks and the many variations of each one are why there are so many different ΔΣ ADCs customized…

As an analog applications engineer, much of my problem-solving involves recommending application circuits for customers to use as subcircuits in their overall product design. Thus, I understand the need for standard values, formulas, printed circuit board (PCB) characteristics and shortcuts for predicting performance.

A colleague of mine, Tim Green, has about 32 years of experience, of which 16 are in board-/system-level…

In the first two parts of my ADC accuracy series, I established the differences between resolution and accuracy for an analog-to-digital converter (ADC) and explained the factors that contribute to total unadjusted error (TUE) of the ADC. Most of these errors are static errors that can be calibrated under ambient conditions. System performance can continue to drift even after calibration, however, due to a change in temperature…

The previous three parts of this blog series focused on 2-wire 4-20mA sensor transmitter designs composed completely of analog components. While analog signal conditioning is practical for linear sensors, many sensors have nonlinear outputs that can only be modestly corrected with analog compensation. Examples of non-linear sensors include pressure sensors, gas and chemical sensors and many temperature sensors.

In my previous post, I explained how to design 2-wire, or loop-powered, analog outputs for industrial automation. In this post, with the design and operation of the transmitter in mind, I will talk about how to design circuits to protect these systems. For reference, Figure 1 shows the basic 2-wire transmitter design.

In Part 2 of this series, I explained a serial interface in which a conversion result for sample S is transferred to the host controller after the conversion is complete but before the start of the next conversion. I also noted that with this type of interface, both the throughput and response time of the analog-to-digital converter (ADC) degrade when using lower clock speeds.

In my previous blog post, I explained a simple serial interface in which each data bit is transferred as it is resolved. I also noted that this type of interface is usually restricted to lower resolution or lower speed. Most of the modern, high-resolution (>12 bits) successive approximation register (SAR) analog-to-digital converters (ADCs) employ redundancy and error-correction techniques to improve the performance…

Designing with a delta-sigma analog-to-digital converter can help achieve the highest possible resolution in your system. But to maximize this architecture’s benefits, it helps to understand how the delta-sigma modulator and digital filter in t...

Welcome to the final installment of this blog series discussing electromagnetic compatibility (EMC) testing. In Parts 1, 2 and 3 we discussed the background of certification testing, as well as the specifications for electrostatic discharge (ESD)...

Many applications, such as motor drives and power inverters, require isolated measurements of both current and voltage. Although optimized for current sensing applications, TI’s isolated delta-sigma modulators enable high-performance voltage measurements.

The most prevalent TI E2E™ Community forum question concerning instrumentation amplifiers (IAs) revolves around common-mode voltage (Vcm) vs. output-voltage (Vout) plots. There are typically only a few of these plots in a data sheet based on commonly used power supply and reference voltage configurations. The issue is that the plots depend on the device’s supply voltage, gain and reference voltage. Therefore, if the final…

In the previous posts in the Industrial DACs series we’ve been looking at how to build and protect 3-wire industrial analog outputs. Today, we will change gears and look at 2-wire analog outputs.

The delta-sigma (ΔΣ) analog-to-digital converter (ADC) is a mysterious construct to many engineers, shrouded in mathematical descriptions and defying clear explanations. This complexity can deter circuit designers from using this ADC topology and taking advantage of its many benefits. These converters are used in a wide variety of applications, including weigh scales, temperature measurements and seismic monitors for…

In my previous blog post, I explained the differences between a SAR ADC’s throughput and response time. Today, let’s see how an interface topology affects the throughput and response time of a SAR ADC.

Part 2 of this blog series derived the basic transfer function for a typical two-wire transmitter, commonly used in industrial control and automation, and explained the currents flowing inside it. It also explained that connecting the transmitter return (IRET) to the loop supply ground (GND) prevents proper operation of the transmitter. Today’s post discusses the current consumption limits of the circuitry that is…

Many applications, such as motor drives and power inverters, require isolated measurements of both current and voltage.  Although optimized for current sensing applications, TI’s isolated delta-sigma modulators enable high-performance volt...

Three… two…one…happy New Year! As the fond memories of 2014 give way to the exciting possibilities of 2015, many people begin the New Year by making resolutions: some modulate their junk food intake; others filter out a bad habit; a few even integrate exercise into their daily routine. And while these are all great ideas, I propose we ring in the New Year with a different kind of resolution – delta-sigma (ΔΣ) analog…

If you missed Part 1 in this series, here’s the background:

While working on a low-noise amplifier circuit I found that the ceramic capacitors on my printed circuit board (PCB) were exhibiting piezoelectric effects and ruining the otherwise extremely low noise of the circuit. This behavior is common in non-C0G type ceramic capacitors, and to remedy the situation, I decided to test three alternative capacitor types…

While working on a low-noise amplifier circuit for an upcoming TI Designs reference design, I was caught off-guard by some interesting behavior. Casually moving the printed circuit board (PCB) on my workbench caused the output voltage to jump! F...

This technical article was updated on July 23, 2020.

Arguably the most important parameter that will determine the accuracy of your SAR ADC is settling error associated with the input and reference signals. “Well, what about the noise and linearity errors of the ADC?” you might ask. Good question, but if you’ve already picked a high-resolution ADC, then chances are these intrinsic ADC errors will be tiny compared to the…

Part 1 of this blog series provided an overview of the operation and uses of 2-wire 4-20 mA field sensor transmitters and provided a basic example system. The post also introduced the current transmitter compliance voltage, which when violated prevents the transmitter from properly regulating the current loop.

Today we’ll discuss the circuitry that regulates the output current of a 2-wire transmitter by deriving the basic…

This technical article was updated on July 23, 2020.

As with any complex analog circuit, designing SAR ADC circuits involves multiple tradeoffs and is thus an iterative process. Thanks to SPICE simulation tools, such as TINA-TI and TI's Precision SAR ADC models, accurate computer-based performance estimation after each design iteration is relatively quick and painless.

The most…