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Optimizing Power for Clocks and other Sensitive Applications

Click here to read the entire article. #noise #Crosstalk #powerintegrity #noisesensitivecircuit #signalanalyzers #decoupling #vrts3 #capacitors #psrr #powersupply #impedancemeasurement #voltagenoise #j2111a #picotest #j2180a #power #impedance #regulator #clockjitter #controlloop

Impedance measurements stabilize op-amp buffers

Figure 1. Op amps are often used as unity gain signal buffers, which are not as simple to use as it may appear. The unity-gain op amp (operational amplifier) buffer circuit is routinely used to transform high-impedance inputs into low-impedance outputs. ADC (analog-to-digital converter) voltage references are also frequently buffered to reduce the voltage reference noise resulting from the ADC sampling current. When implemented well, using an appropriate op amp, the results w

Paultre on Power – Steve Sandler of Picotest on power test and noise (Podcast)

October 31, 2014 In this podcast Steve Sandler of Picotest talks to Alix Paultre of Power Systems Design on the issues of power test, especially in the area of reducing noise. Not only is noise in a system a potential interference hazard, it is also a sign that the system is not operating optimally. Speed, bandwith, and probe considerations are among the many factors involved in performing proper test. More and more application spaces need clean power and more efficient syste

Techniques for accurate PSRR measurements

By John Rice, System Engineer, Texas Instruments and Steve Sandler, Managing Director, Picotest Introduction In theory, measuring the power-supply-rejection ratio (PSRR) is relatively simple. A variable-frequency signal modulates the power-supply input, and the attenuation of that signal is measured at the output. However, the measurement is highly sensitive to setup noise, including noise from the probe-loop area and the layout of the printed circuit board (PCB). This artic

Three Stability Assessment Methods Every Engineer Should Know About

Many engineers are familiar with the Bode plot as an effective stability assessment method. However, some authors suggest and even teach that the Bode plot is the only method needed. This article shows why this thinking is short-sighted. A single, low cost instrument that can produce Bode plots, as well as two other stability assessment methods is discussed providing a more comprehensive stability assessment set of guidelines. A single word illustrates why Bode plots cannot b

Inside the 21st Century Power Test Lab

In this 5-minute video, Steve Sandler of AEi Systems ( and Picotest ( takes you on a tour of an advanced power test lab that contains a wide assortment of instruments for measuring various power supply waveforms and troubleshooting various power-related problems, particularly those encountered in power distribution networks or PDNs. Sandler introduces a number of different test instruments that he has used to make various measurements, and discus

Five Things Every Engineer Should Know About Bode Plots

In 1938 Hendrik Wade Bode, who worked at Bell Labs, published his asymptotic assessment of phase margin and gain margin, bearing his name [2]. The Bode plot is recognized for its simplicity and the simple asymptotic approach makes the method useful for both design and assessment of power system control loops.  There have been many other methods introduced since, including Nathaniel Nichol’s stability charts in 1947 [4] and root locus introduced by Walter Evans in 1948 [5].  I

Troubleshooting Distributed Power Systems: Making Time Domain Measurements (Part 8 – The final

He presents examples of various waveform anomalies and discusses techniques and tips for observing them as well as pitfalls to avoid. Sandler also advises designers on minimum and recommended specifications for oscilloscopes in order to be able to catch the types of waveform anomalies discussed here. Click here to watch the video. #oscilloscopes #vrm #powerintegrity #j2111a #picotest #videos #timedomainmeasurements

Non-Invasively Assess Your Multiple-Loop LDO’s Stability

Some low-dropout regulators (LDOs) use multiple feedback loops to improve output voltage transient response. In many of these cases, some or all of the loops are inside the IC. Designers can assess the stability of these regulators by using the non-invasive stability measurement capability of the OMICRON Lab Bode 100 vector network analyzer (VNA). The simplified schematic in Figure 1 shows traditional error amplifier feedback along with a second loop that connects some functi

Troubleshooting Distributed Power Systems: Measuring Ripple (Part 7 of the ongoing series)

And by taking measurements across all three test domains, designers can trace power supply ripple-related problems back to root causes such as switching frequency, load dynamics, and PCB crosstalk as explained here. Various test setups, which include instruments from Picotest and other vendors, and measurement techniques are described in this video and results of example ripple measurements using different point of load regulators (POLs) are discussed. Along the way, Sandler

Troubleshooting Distributed Power Systems: Using Current Injectors (Part 5 of the ongoing video seri

Although not quite as accurate as the two-port VNA impedance measurement, the current injection technique has advantages including wide range (approx. 1 milli-ohm to thousands of ohms), the ability to measure in-system, and a suitability for measuring low-power devices such as op amps, voltage references and voltage regulators. In addition, current injectors can be used to carry out other types of tests such as non-invasively measuring PSRR, determining power integrity and si

How to Solve 8 of 10 Design Issues

The vast majority of design issues are directly or indirectly attributable to control loop stability. The most common offenders: Linear regulators Voltage references Op-amps The control loop stability of these devices can propagate through an entire system. Symptoms include: EMI Increased circuit noise Clock jitter These are all simple circuits, so why is this a common issue? We are not clear on the definition of stability In the high-reliability world, including satellite sy

Troubleshooting Distributed Power Systems: Measuring Impedance Using Vector Network Analyzers (One-P

This video focuses on single-port measurements, describing how they can be applied to low power circuits such as linear regulators, voltage references and op amps as well as semiconductors, capacitors, and inductors. Test set up requirements are discussed and example measurements are presented. Click here to watch the video. #spicemodelling #sifet #powerintegrity #opamp #e5061b #bode100 #impedancemeasurement #j2111a #bsmcimpedanceadapter #picotest #videos #pdn #stability #bjt

Troubleshooting Distributed Power Systems: Why Stability Matters (Part 1 of the ongoing video series

In this 5-minute video presentation, Steve Sandler discusses how stability impacts circuit performance, offering examples that demonstrate the effects of stability problems on both power supply and system performance. Click here to watch the video. #phasemargin #gainmargin #design #j2110a #j2100aj2101a #powerintegrity #nyquist #bode100 #nism #j2111a #picotest #videos #pdn #noninvasivemeasurement #stability #converter #bodeplots #controlloop

Clock Power Optimization Depends On Jitter Control

Clock-jitter performance has become a top priority among clock, analog-to-digital controller (ADC), and power-supply manufacturers. Why? Simply, it interferes with the performance of digital circuits, particularly high-speed ADCs. High-speed clocks can be quite sensitive to input power “cleanliness,” though quantifying the relationship takes some effort. New lines of regulators (predominantly low-dropout regulators, or LDOs) coming from voltage-regulator manufacturers promise

Assessing Point-Of-Load Regulators Using Non-Invasive Techniques

Evaluating the stability of a Point-Of-Load (“POL”) regulator can be performed using both traditional Bode plot and output impedance measurement techniques. Measuring output impedance has an advantage over the Bode plot in some cases as the output impedance test can be non-invasive.3 With the right equipment, the non-invasive measurement does not require access to the control loop, such as an injection resistor or transformer. The test techniques used to make these measuremen

FAQ #22: So how does this non-invasive measurement relate to phase margin and gain margin?

We can equate the stability to an equivalent phase margin by assuming the magnitude of the gain vector to be 1 and solving for the Q. In our simple example below, the measured Q from the output impedance is 5.77 and we can equate that with 1/(1-T). Click here to read the entire article. #phasemargin #gainmargin #faq #nism #j2111a #picotest #noninvasivemeasurement

New Injector Supports Testing of POLs

High Fidelity POL Testing with the J2112A The J2112A: Faster, Non-Invasive, and High Fidelity POL Step Load Testing Testing the step load performance of Point of Load (POL) regulators and Low Dropout linear regulators (LDOs) requires an electronic load that is non-invasive, easily controlled, has fast edge speeds and is capable of providing large current steps. The J2112A is just such an electronic load. The J2112A is also known as a Current Injector for its ability to sink c

FAQ #21: How do you use the Picotest injectors and the Agilent analyzer to measure output impedance

How do you use the Picotest injectors and the Agilent analyzer to measure output impedance and/or non-invasive step loading? For the output impedance measurement you need to connect the output of the J2111A current injector and a scope probe (preferably 1X for best sensitivity) to the output of the LM117. You would connect the scope probe to the “T” input (terminated into 1MOhm) and the current monitor from the current injector to the “R” input (terminated into 50 Ohms). The

Essential Test Adapters for Your Network / Impedance Analyzer

The network analyzer, sometimes referred to as a Frequency Response Analyzer (FRA) is a common piece of equipment in most of our labs today. Analyzers are used for a variety of tasks including stability analysis, component characterization and of course frequency response measurements. They can vary in features but regardless of the analyzer being used, the analyzer oscillator signal must be injected into the circuit being tested in order for a measurement to be made. As desi

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