Stay ahead of power system challenges with expert guidance on switched-mode power supplies, DC/DC optimization, and high-voltage applications. Learn proven strategies for overvoltage protection, noise reduction, and efficient power module layout. Explore solutions for maintaining power quality in automated systems and implementing effective galvanic isolation for both power and signal lines. Essential reading for power electronics engineers and designers seeking reliable, high-performance solutions.
We get technical
Power | Volume 4
How to address DC/ DC noise, efficiency, and layout issues using integrated power module Maintaining electrical power quality within automated systems How to implement galvanic isolation for power and signal lines in high-voltage systems
we get technical
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Editor’s note Power conversion has always played a major part in the electronics industry. Some of these applications include: ■ Phone charging: A power supply is needed to charge our phones, typically in the form of a wall adapter. ■ Automotive electronics: Vehicles have become more dependent on computer control that requires a clean power source, typically in the form of a DC/DC converter (or a “Voltage Regulator” if you are in that market). ■ Electrical utilities: When looking at the electrical utilities providers, there are electronics deployed at the micro and macro levels to monitor and control the grid. As all of these applications change over time and as new applications emerge, the technologies behind power conversion have needed to evolve as well. Today, GaN and SiC semiconductors are playing a larger role in the evolution of power and are at the leading edge of advancements in power switching technology. These technologies are enabling gains in power conversion efficiency. In a properly designed power supply, efficiency gains can mean a reduction in waste heat, which can reduce thermal stresses on components, which in turn can increase reliability. All of this can enable an increase in power density and a reduction in weight. In addition to the direct impact that efficiency can have on a power supply, many countries have enacted legislation around minimum efficiency levels. So, whether you are designing a power supply or just purchasing one, having higher efficiency power conversion can help to future proof your design.
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Understand and apply supervisory ICS to avoid low-voltage power-up glitch headaches
How to address DC/DC noise, efficiency, and layout issues using integrated power modules
Special feature: retroelectro March 16 – Ohm's Day
How to design effective power supply thermal management in industrial and medical systems
Maintaining electrical power quality within automated systems
How to implement galvanic isolation for power and signal lines in high-voltage systems
How to use ensure electronic circuits and users are protected from excessive voltages, currents, and temperatures to IEC and UL safety standards
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Understand and apply supervisory ics to avoid low-voltage power-up glitch headaches
Experienced engineers know that one of the riskiest times for a system is when power is applied. Depending on time constants and how smoothly and quickly the power rail comes up to nominal, the different ICs and parts of the system may start, lock up, or start in an incorrect mode as they attempt to work with each other. Adding to the challenge is that the timing and slew-related performance of the ICs on power-up can be a function of temperature, associated capacitors, mechanical stress, aging, and other factors. The potential problem is aggravated as operating voltage rails drop to low single-digit values, reducing the amount of “slack” or headroom for functioning with the nominal rail value. All of these factors can lead to inconsistent
What is a glitch? As with many engineering terms such as “buffer” or
“programmable,” the word “glitch” has different meanings depending on the context. A glitch can be: ■ A noise-induced spike on a signal or power line ■ A sudden, brief drop in a power supply rail due to a load transient ■ A microsecond period when both upper and lower MOSFETs in a bridge are inadvertently turned on simultaneously, as a result of different turn on/off times in their gate drivers (a very bad occurrence) ■ A momentary indeterminate
By Bill Schweber Contributed By DigiKey's North American Editors
signal and race condition due to timing tolerances and differences between components.
This article looks at the glitch that can occur during the “power-up” period when power is turned on, and the ICs are transitioning to their normal operating condition, especially in low-voltage systems. Such power-on glitches are especially frustrating because they can cause intermittent, hard-to-debug problems that have no apparent correlation or consistency. As the glitch-inducing conditions are often “on the edge,” their occurrence can vary with temperature, power-rail tolerance (while still within specification),
startup performance and frustrating debug sessions.
For these reasons, analog IC vendors have devised specialized ICs that offer supervisory management features that eliminate the uncertainty and inconsistency of power-up. This article will define and characterize the glitch problem, and then show how it can be avoided through the addition of some small, specialized ICs from Analog Devices.
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Understand and apply supervisory ics to avoid low-voltage power-up glitch headaches
between 0.5 to 0.9 volts, potentially causing system instability. Once the supervisory IC turns on, the reset line is pulled down to prevent the microcontroller from inadvertently turning on. This glitch is common to all previous generations of supervisory ICs. Low-voltage systems magnify the problem This glitch scenario becomes a major concern with the trend toward low-power devices that are operating at ever-lower voltages. Consider systems with three logic levels of 3.3 volts, 2.5 volts, and 1.8 volts ( Figure 3 ). For the 3.3-volt system, the output low- voltage threshold (Vol) and the input low-voltage threshold (Vil) are between 0.4 volts and 0.8 volts. If a glitch occurs at 0.9 volts,
it would potentially cause the processor to become unstable by switching it off and on. The situation for a nominal 1.8-volt system is more sensitive. Now, Vol and Vil are much lower at 0.45 volts and 0.63 volts. A 0.9 volt glitch in this system represents a larger percentage, giving it a higher potential for error. How does this situation play out with the glitch impacting system operation? Consider a power supply voltage VDD which ramps up slowly to 0.9 volts and “lingers” there for a short period of time ( Figure 4 ). Although this voltage is not enough to turn on the supervisory IC, the microcontroller could still be enabled and running in an unstable state. Since the 0.9-volt value is in an indeterminant state, the glitch can be interpreted by the microcontroller RESET input as either a logic 1 or 0, which would erratically enable or disable it.
individual component variations in a batch of the same device, and other hard-to-determine factors. What is this glitch, and what is its source? Consider a system with a microcontroller and an associated supervisory/protection reset IC. The role of the latter IC is simple and focused: to maintain reliable system operation during power- up, power-down, and brownout conditions ( Figure 1 ). In a typical battery-powered application, the DC-DC converter generates the supply rail from a small, low-voltage battery. The supervisory IC is generally added between the DC-DC converter and the microcontroller to monitor the supply voltage and enable or disable the microcontroller. The supervisory IC ensures reliable operation by accurately monitoring the system power supply and then asserting or de-asserting the microcontroller's enable input. The enabling and disabling of the microcontroller is managed via the supervisory IC’s reset output pin. This pin is typically an open- drain that is connected to a 10 kilohm (kΩ) pull-up resistor. The supervisory IC monitors the power supply voltage and asserts a reset when the input voltage falls below the reset threshold. After the monitored voltage rises above the threshold voltage
This causes the microcontroller to execute partial instructions or incomplete writes to memory, as just two examples of what might happen, likely causing system malfunction and possible catastrophic system behavior. Solving the glitch problem Overcoming this problem does not require a return to higher voltage rails, or demand complicated system-level architectures to eliminate its occurrence or minimize its impact. Instead, it requires a new generation of supervisory ICs that recognize the unique aspects of the problem and prevent glitches from forming, regardless of the voltage level during power-up or brown-out conditions. Figure 4: As the power supply voltage VDD ramps up to 0.9 volts and lingers there, the microcontroller can be turned on and off erratically. (Image source: Analog Devices)
Figure 1: Understanding a glitch source begins with a look at a simple, typical arrangement of a microcontroller and its associated supervisory/protection reset IC, both powered by a battery and its regulator. (Image source: Analog Devices)
to its nominal value, the reset output remains asserted for a reset timeout period and then de-asserts. This allows the target microcontroller to leave the reset state and begin operating.
before the supervisory IC turns on and pulls it low? The answer is found by looking closely at a typical power-up sequence ( Figure 2 ). As supply rail VCC begins to power up, both the microcontroller and the supervisory IC are off. As a consequence, the reset line is floating and the 10 kΩ pullup resistor causes its voltage to track V CC . This voltage rise can be anywhere
But what happens to the reset line
Figure 2: In a typical power-up sequence, the reset line is floating, so its voltage tracks the rise in supply rail VCC. (Image source: Analog Devices)
Figure 3: Logic levels have shrunk from 3.3 volts down to 1.8 volts, and so have associated voltage thresholds. (Image source: Analog Devices)
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Understand and apply supervisory ics to avoid low-voltage power-up glitch headaches
Achieving this result requires a proprietary circuit and IC such as the MAX16162, a nanopower supply supervisor with glitch- free power-up. With this tiny IC— available in four-bump WLP and four-pin SOT23 packages—the reset output is held low whenever VDD is lower than the threshold voltage, preventing a voltage glitch on the reset line. Once the voltage threshold is reached and the delay period is completed, the reset output de-asserts and enables the microcontroller ( Figure 5 ).
N-channel pass gates. Additional supervisory functions include undervoltage and overvoltage monitoring and reporting, as well as microprocessor reset generation. The type and source of faults are reported for diagnosis. Individual channel controls are available to exercise the enable outputs and supervisory functions independently. For systems with more than four rails, multiple LTC2928s can be easily connected to sequence an unlimited number of power supplies. Conclusion Glitches are present in every application, but they have not posed a significant issue for higher voltage applications which dominated until recently. Now, power supply voltages are moving lower, making system turn-on less reliable due to 0.9-volt glitches. As shown, designers can improve reliability using newer supervisory ICs that offer glitch-free operation to provide the highest degree of system protection for low-power/ low-voltage applications.
Figure 6: The MAX16161 and MAX16162 are similar but with a small functional and pinout difference: the MAX16161 has an MR input that asserts a reset when it receives an appropriate input signal, while the MAX16162 has separate VCC and VIN pins. (Image source: Analog Devices)
Figure 7: A circuit using the MAX16161 can be configured so the device not only ensures glitch-free power-up but also manages power-rail sequencing between two rails. (Image source: Analog Devices)
There are also many designs that have multiple rails and more complex sequencing needs. In these situations, the Analog Devices LTC2928 Multichannel Power Supply Sequencer and Supervisor offers a solution ( Figure 8 ). This four-channel cascadable power supply sequencer and high-accuracy supervisor allows designers to configure power-
management sequencing thresholds, order, and timing using just a few external components. It ensures that power rails are enabled in the desired order. In addition to power-on sequencing, it can manage the complementary and often equally critical power- down sequencing. The sequence outputs are used to control supply-enable pins or
Unlike conventional supervisory ICs that are unable to control the reset output state when VCC is very low, the MAX16162 reset output is guaranteed to remain asserted until after a valid VCC level is achieved. The MAX16161 is a close sibling of the MAX16162 with nearly identical specifications, but with one functional difference and some redefining of pin assignments ( Figure 6 ). It features a manual reset (MR) input that asserts a reset when it receives an appropriate input signal, which can be either active-low or active-high, depending on the option selected. In contrast, the MAX16162 has no MR input but instead has separate VCC and VIN pins, allowing threshold voltages as low as 0.6 volts.
Sequencer versus supervisor
Another pair of terms that have some overlap and ambiguity are supervisor and sequencer. A supervisor monitors a single power supply voltage and asserts/ releases reset under defined circumstances. In contrast, a sequencer coordinates the relative resets and “power OK” assertions among two or more rails. The MAX16161 and MAX16162 can be used as simple power supply sequencers ( Figure 7 ). After the output voltage of the first regulator becomes valid, the MAX16161/ MAX16162 insert a delay and generate the enable signal for the second regulator after the reset timeout period. Because the MAX16161/MAX16162 never de- assert reset until the supply voltage is correct, the controlled supply is never incorrectly enabled.
Figure 5: The MAX16162 holds the reset output low whenever VDD is lower than the threshold voltage, preventing a voltage glitch on the reset line. (Image source: Analog Devices)
Figure 8: The LTC2928 power sequencer manages power-up and power-down sequencing among four independent rails, and enables user control over key parameters. (Image source: Analog Devices)
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It doesn’t seem difficult to build a basic step-down (buck) DC/ DC regulator for low voltages of 10 volts (typical) or less and modest current levels of about 2 to 15 amperes (A). The designer just needs to select a suitable switching regulator IC and add a few passive components using the example circuit on the datasheet or application note. But is the design really done and ready to release to pilot run, or even to production? Probably not. While the regulator provides the desired DC rail, it still has several potential problems and issues. First, the efficiency may not meet project objectives or regulatory requirements, thereby adding to thermal impact, as well as shorter battery life. Second, additional components may be needed to ensure proper start-up, transient
performance, and low ripple, which in turn affects size, time to market, and the overall bill of material (BOM). Finally, and perhaps most challenging, the design may not meet the increasingly stringent limitations on electromagnetic interference (EMI) or radio frequency interference (RFI) as defined by the various regulatory mandates, thus requiring a redesign or further additional components and testing. This article describes the gap between expectations and performance between a basic DC/DC regulator design and a superior one that meets or exceeds requirements for efficiency, low radiated and ripple noise, and overall integration. The article then introduces Analog Devices’ Silent Switcher µModules and shows how to use them to solve multiple DC/ DC buck regulator problems.
ICs make it look easy, at first
Step-down DC/DC (buck) regulators are widely used to provide DC rails. A typical system may have tens of these providing different rail voltages or physically separated rails at the same voltage. These buck regulators commonly take a higher voltage, typically between 5 and 36 volts DC, and regulate it down to a single-volt value at a few or low double-digit amperes ( Figure 1 ).
There’s good news and bad news when constructing a
basic buck regulator. The good news is that building one that provides nominally “good- enough” performance is generally not difficult. There are many switching ICs available to do the bulk of the task that need only a single field effect transistor (FET) (or none at all) and a few
How to address DC/ DC noise, efficiency, and layout issues using integrated power modules By Bill Schweber
Contributed By DigiKey's North American Editors
Figure 1: The role of the DC/DC regulator (converter) is straightforward: Take an unregulated DC source which may be from a battery or a rectified and filtered AC line, and provide a tightly regulated DC rail as the output. (Image source: Electronic Clinic)
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How to address DC/DC noise, efficiency, and layout issues using integrated power modules
Quiet: There are two broad classes of noise that concern designers. First, the noise and ripple on the output of the DC/DC regulator must be low enough so that it does not adversely affect system performance. This is an increasing concern as rail voltages drop to low single digits in digital circuits, as well as for precision analog circuits where ripple of even a few millivolts can degrade performance. The other major concern is related to EMI. There are two types of EMI emissions: conducted and radiated. Conducted emissions ride on the wires and traces that connect to a product. Since the noise is localized to a specific terminal or connector in the design, compliance with conducted emissions requirements can often be assured relatively early in the development process with a good layout and filter design. Radiated emissions, however, are more complicated. Every conductor on a circuit board that carries current radiates an electromagnetic
increases real estate, makes thermal management and testing more difficult, and introduces additional assembly costs. Another technique is to slow down the switching edges of the regulator. However, this has the undesired effect of reducing the efficiency, increasing minimum on and off times as well as the required dead times, and compromising the current-control-loop speed. Still another approach is to adjust the regulator design to radiate less EMI by careful selection of the key design parameters. The task of balancing these regulator tradeoffs involves assessing the interaction of parameters such as switching frequency, footprint, efficiency, and resultant EMI. For example, a lower switching frequency generally reduces switch loss and EMI and improves efficiency, but requires larger components with associated increases in footprint. The quest for greater efficiency is accompanied by low minimum on and off times, resulting in higher harmonic content due to the faster switch transitions. In general, with every doubling of switching frequency, the EMI becomes 6 decibels (dB) worse, assuming all other parameters such as switch capacity and transition times, remain constant. The wideband EMI behaves like a first-order high-pass filter with 20 dB higher emissions
field: every board trace is an antenna, and every copper plane is a mirror. Anything other than a pure sine wave or DC voltage generates a wide signal spectrum. The difficulty is that even with careful design, a designer never really knows how bad the radiated emissions are going to be until the system gets tested, and radiated emissions testing cannot be formally performed until the design is essentially complete. Filters are used to reduce EMI by attenuating the levels at specific frequencies or over a range of frequencies using various techniques. Some of the energy radiating through space is attenuated by using sheet metal as a magnetic shield. The lower frequency part that rides on pc board traces (conducted) is controlled using ferrite beads and other filters. Shielding works but brings a new set of problems. It must be well-designed with good electromagnetic integrity (often surprisingly difficult). It adds cost,
passive components to complete the job. The task is made even easier as the datasheet for the regulator IC almost always shows a typical application circuit with a schematic, a board layout, and a BOM that may provide component vendor names and part numbers. The engineering dilemma is that a “good” level of performance may not be adequate with respect to some non-obvious regulator performance parameters. While the output DC rail may deliver enough current with adequate line/load regulation and transient response, those factors are only the beginning of the story for power rails. The reality is that in addition to those basic performance criteria, a regulator is also assessed by other factors, some of which are driven by external imperatives. The three critical issues which most regulators must address are not necessarily apparent, solely from the simplistic perspective of a functional block that accepts an unregulated DC input and provides a regulated DC output. They are ( Figure 2 ): ■ Cool: High efficiency and associated minimal thermal impact. ■ Quiet: Low ripple for error-free system performance, plus low EMI to meet radiated noise standards (non-acoustic).
■ Complete: An integrated solution that minimizes size, risk, BOM, time to market, and other “soft” concerns. Addressing these issues brings a set of challenges, and solving them can become a frustrating experience. This is in line with the “80/20 rule”, where 80% of the effort is devoted to getting the last 20% of the task done. Looking at the three factors in more detail: Cool: Every designer wants high efficiency, but exactly how high, and at what cost? The answer is the usual one: it depends on the project and its tradeoffs. Higher efficiency is important for three main reasons: ■ It translates into a cooler product that enhances reliability, may allow for operation at a higher temperature, may eliminate the need for forced air (fan) cooling, or may simplify setting up effective convection cooling if feasible. At the high end, it may be needed to keep specific components that run particularly hot below their maximum allowed temperature and within their safe operating area. ■ Even if these thermal factors are not a concern, efficiency translates to longer run time for battery-operated systems or a reduced burden on the upstream AC-DC converter.
Quiet
Success
Cool
Complete
Figure 2: A DC/DC regulator must do more than just deliver a stable power rail; it must also be cool and efficient, be EMI “quiet,” and be functionally complete. (Image source: Math.stackexchange.com; modified by author)
■ There are now many regulatory standards mandating specific efficiency levels for each class of end product. While these standards do not call out efficiency for individual rails in a product, the designer’s challenge is to ensure that the overall aggregate efficiency meets the mandate. This is easier when each contributing rail’s DC/DC regulator is more efficient, as that provides for headroom in the summation with the other rails and other sources of loss.
when the switching frequency increases by a factor of ten.
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How to address DC/DC noise, efficiency, and layout issues using integrated power modules
To overcome this, experienced pc board designers will make the regulator’s current loops (“hot loops”) small, and use shielding ground layers as close to the active layer as possible. Nevertheless, pinout, package construction, thermal design requirements, and package sizes needed for adequate energy storage in decoupling components dictate a certain minimum hot-loop size. To make the layout problem even more challenging, the typical planar pc board has magnetic or transformer-style coupling between traces above 30 megahertz (MHz). This coupling will attenuate the filtering efforts since the higher the harmonic frequencies, the more effective unwanted magnetic coupling becomes.
These standards are complex and define the test procedures, probes, instrumentation, data analysis, and more. Among the many limits defined by the standard, the Class B radiated emission limit is often of most interest to designers. Complete: Even when the design situation is fairly well understood, selecting and employing the needed support components in just the right way is a challenge. Slight differences in component placement and specifications, pc board grounds and traces, and other factors can adversely affect performance. Modeling and simulation are necessary and can help, but it’s very difficult to characterize the parasitics associated with these components, especially if their values shift. Further, a change in vendors (or unannounced change by the preferred vendor) may induce a subtle shift in second- or third-tier parameter values (such as inductor dc resistance (DCR)),
which could have significant and unanticipated consequences. Further, even slight repositioning of the passive components or adding “just one more”, can change the EMI scenario and result in emissions exceeding allowable limits. SilentSwitcher µModules resolve the issues Anticipating and managing risk is a normal part of a designer’s job. Reducing the number and intensity of these risks is a standard end- product strategy. A solution is to use a functionally complete DC/ DC regulator that, through good design and implementation, is cool, quiet, and complete. Using a known device reduces uncertainty while addressing size, cost, EMI, BOM, and assembly risks. Doing so also accelerates time to market and reduces regulatory compliance angst.
By looking at a complete family of such regulators, such as the Silent Switcher µModules from Analog Devices, designers can choose a DC/DC regulator matched to the needed voltage and current rating, while being assured that EMI mandates will be met, size and cost will be known, and there will be no surprises. These regulators incorporate much more than innovative schematics and topologies. Among the techniques they use are: ■ Technique #1: The switching of the regulator acts as an RF oscillator/source and combines with the bond wires, which act as antennas. This turns the assembly into an RF transmitter with undesired energy that may exceed allowed limits ( Figures 3, 4, and 5 ). ■ Technique #2: The use of symmetrical input capacitors bounds EMI by creating balanced, opposing currents ( Figure 6 ). ■ Technique #3. Finally, the use of opposite current loops to cancel magnetic fields ( Figure 7 ).
Figure 4: The Silent Switcher assembly begins by replacing the wire bonds with flipchip technology, thus eliminating the energy-radiating wires. (Image source: Analog Devices)
Which standards are relevant?
Figure 5: The flipchip approach effectively eliminates the antennas and minimizes radiated energy. (Image source: Analog Devices)
There is no single guiding standard in the EMI world, as it is largely determined by the application and relevant governing mandates. Among the most cited ones are EN55022, CISPR 22, and CISPR 25. EN 55022 is a modified derivative of CISPR 22 and applies to information technology equipment. The standard is produced by CENELEC, the European Committee for Electrotechnical Standardization, and is responsible for standardization in the electrotechnical engineering field.
Figure 6: Dual, mirrored input capacitors are also added to constrain EMI. (Image source: Analog Devices)
Figure 3: The bond wires from the IC die to the package function as miniature antennas and radiate undesired RF energy. (Image source: Analog Devices)
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How to address DC/DC noise, efficiency, and layout issues using integrated power modules
These Silent Switcher µModules represent the evolution of step- down regulator design and packaging from an IC with support components to an LQFN IC with integral capacitors to a µModule with requisite capacitors and inductors ( Figure 8 ). Broad offering addresses needs, tradeoffs The Silent Switcher µModules comprise many individual units with different ratings for input voltage range, output voltage rail, and output current. For example, the LTM8003 is a 3.4 to 40-volt input, 3.3-volt output, 3.5 A continuous (6 A peak) µModule that meets CISPR 25 Class 5 limits, yet measures just 9 × 6.25 millimeters (mm) and 3.32 mm high ( Figure 9 ). It is offered in a pinout which is failure mode effects analysis (FMEA) compliant (LTM8003-3.3), meaning that the output stays at
Figure 7: An internal layout with current loops in opposite directions also cancels undesired magnetic fields. (Image source: Analog Devices)
or below the regulation voltage during an adjacent-pin short circuit or if a pin is left floating. The typical quiescent current is just 25 microamperes (µA), and the H-grade version is rated for 150°C operation. The DC2416A demonstration (demo) board is available for designers to exercise the regulator and assess its performance for their application ( Figure 10 ). Two nominally similar Silent Switcher µModule family members, the LTM4657 (3.1 to 20-volt input; 0.5 to 5.5 volt @8 A output) and the LTM4626 (3.1 to 20-volt input; 0.6 to 5.5 volt at 12 A output), show the nature of the tradeoffs that the
devices offer. The LTM4657 uses a higher value inductor than the LTM4626, allowing it to operate at lower frequencies to decrease switching loss.
The LTM4657 is a better solution for high switching losses and low conduction losses, such as in applications where the load
Figure 8: By incorporating capacitors and an inductor in the package, the Silent Switcher µModules are the third stage in the advancement of IC- centric switching regulators. (Image source: Analog Devices)
Figure 9: The LTM8003 Silent Switcher is a tiny, self-contained package that easily meets the CISPR 25 Class 5 Peak Radiated energy limit from DC to 1000 MHz. (Image source: Analog Devices)
Figure 10: The DC2416A demo board simplifies connection with and evaluation of the LTM8003 Silent Switcher device. (Image source: Analog Devices)
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How to address DC/DC noise, efficiency, and layout issues using integrated power modules
current is low and/or the input voltage is high. Looking at the LTM4626 and LTM4657 operating at the same switching frequency, and with the same 12-volt input and 5-volt output, the superior switching loss of the LTM4657 can be seen ( Figure 11 ). Additionally, its higher-value inductor reduces the output voltage ripple. However, the LTM4626 can supply more load current than the LTM4657. Users can assess the performance of the LTM4657 using the DC2989A demo board ( Figure 12 ), while for those who need to evaluate the LTM4626, the DC2665A-A board is available (Figure 13). The Silent Switcher µModules are not restricted to single- output modules. For example, the LTM4628 is a complete, dual 8 A
Figure 14: The LTM4628 can be configured as a dual-output, 8 A per channel switching DC/DC regulator, or in a single-output, 16 A output configuration. (Image source: Analog Devices)
output switching DC/DC regulator that can be easily configured to provide a single 2-phase 16 A output ( Figure 14 ). The module is offered in 15 mm × 15 mm × 4.32 mm LGA and 15 mm × 15 mm × 4.92 mm BGA packages. It includes the switching controller, power FETs, inductor, and all supporting components. The module operates over an input voltage range of 4.5 to 26.5 volts and supports an output voltage range of 0.6 to 5.5 volts, set by a single external resistor. Users can investigate its performance as a single or dual- output device using the DC1663A demo board ( Figure 15 ). Conclusion Designing a functioning DC/ DC regulator is fairly easy with available ICs. However, designing
a regulator that simultaneously excels in efficiency, is functionally complete, and meets the often various confusing and stringent regulator mandates is not. The Silent Switcher µModules from
Analog Devices simplify the design process. They eliminate risk by meeting the goals for cool and efficient operation, EMI emissions below allowed limits, and drop-in completeness.
Figure 11: The efficiency comparison of the LTM4626 and LTM4657 at 1.25 MHz with the same configuration on a DC2989A demonstration board shows modest but tangible differences. (Image source: Analog Devices)
Figure 15: Evaluation of the single/dual- output LTM4628 is accelerated with the use of its DC1663A demo board. (Image source: Analog Devices)
Figure 12: The DC2989A demo board is designed to speed the evaluation of the LTM4657 Silent Switcher. (Image source: Analog Devices)
Figure 13: For the LTM4626 Silent Switcher module, the DC2665A-A demo board is available to facilitate exercise and evaluation. (Image source: Analog Devices)
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retroelectro
Ohm's Day By David Ray Cyber City Circuits March 16
1840s - The dashes and dots of the telegraph With the dissolution of the Holy Roman Empire in the recent past, Europe was quickly becoming full of unrest and military action. The superpowers of the time knew that fast and reliable communication would win the upcoming conflicts for territory. By the 1840s, the electrical telegraph had become the cutting edge of technology. Quickly, all over Europe, telegraph lines were installed on overhead poles, along railways and highways, and through mountains and fields. Overhead cable only required little in the way of planning or measurement. In 1843, Sir Charles
March 16: Ohm’s Day March 16, 2024 marks Georg Ohm’s 235th Birthday. As you
already know, the ohm is the unit of electrical resistance in a conductor such that a constant current of one ampere produces a potential difference of one volt. The international standardization of the 'ohm' to denote the practical unit of electrical resistance dates to the first International Electrical Congress of 1881 in Paris. It was here that the units we are all fond of today… amperes, volts, farads… were all etched in stone. That is the ending of this story. It started many years earlier.
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retroelectro
"The science of electricity, and the art of telegraphy, have both now arrived at a stage of progress at which it is necessary that universally received standards of electrical quantities and resistance should be adopted, in order that precise language and measurement may take the place of the empirical rules and ideas now generally prevalent” – Latimer Clark, 1861
Wheatstone used a copper wire of ‘one foot in length and weighing one hundred grains’ as an electrical resistance standard. In the same building, an engineer designing telegraph cables used a standard of ‘a mile of copper wire with a diameter of one-sixteenth inch’ . Early telegrapher manuals may list the length and weight of the copper used as the only useful measurements. The cable manufacturing industry experienced a surge during this period. With numerous players joining the market, there was a buzz of innovation and competition, driving the new electrical industry forward. You could go to any cable manufacturer, and they all sold ‘the best and purist of copper cable’, but there was no established standard to measure this claim against. At the time, this wasn't a big issue because telegraph messages could be sent through almost any length of overhead lines without difficulty.
(charge). Domestically, each country had its own ‘standard.’ Some countries used iron wire in their standard, some used copper wire, and others used gold- alloy wire. It became clear that standardizing the measurement of electrical resistance would be necessary to figure out how to solve the trans-Atlantic cable problem.
1850s - The trans-Atlantic cable By the mid-1850s, man’s telegraphy hubris became an insurmountable obstacle. Between 1850 and 1853, submarine cables were laid from France to Britain and then from Britain to Ireland. In 1854, the concept of a trans-Atlantic cable was becoming trivial in the minds of some. Several attempts were made to connect the New World to the Old World, but their limited understanding of electrical theory and measurements caused one issue after another. Running two thousand miles of heavy conductors through three- mile-deep ocean water at very low temperatures and shoveling two thousand volts of electricity through them may cause problems. Ohm’s Law had been recognized as accurate and practical, so they knew that if they could reckon an absolute measure of resistance, they could model voltaic currents (amperes), electromotive force (voltage), and electrical quantity
by Sir Charles Bright, he starts down the path that will lead to the immortalization of Georg Ohm in the minds of designers, on the tongues of electricians, and within the hearts of every high school physics teacher in the time since by proposing a new committee to study and standardize the measurement of electrical resistance. The following year, the British Association for the Advancement of Science (BAAS) appointed ‘The Committee on Standards of Electrical Resistance’. Members of this committee included Sir
William Thomson (Lord Kelvin), James Clerk Maxwell, Carl Siemens, Sir Charles Wheatstone, and Sir Charles Bright, along with people instrumental in metallurgy, mineralogy, and the design of cable-laying ships. After three years of extensive experimentation, the 1865 Report of the Committee on Standards of Electrical Resistance starts with ‘The Committee has the pleasure of reporting that the object for which they were first appointed has now been accomplished.’ By 1867, the committee had completed the bulk of their work,
and these new standards for resistance revolutionized the entire supply chain, top to bottom. They could now determine the purity of copper based on the length, weight, temperature, and resistance, thus could better model and predict how wire will act in different environments. In 1873, after twelve years of working on this problem, a committee of the British Association for the Advancement of Science formally proposed the ‘ohm’ as the standard unit of measure for electrical resistance.
1860s - The British Association for the Advancement of Science
The year was 1861.
After years of work as a cable engineer, including efforts that lead to improvements on the trans-Atlantic cable, Latimer Clark found himself in front of the British Association for the Advancement of Science in Manchester. Being accompanied
Fun Fact: The first transatlantic cable weighed 1,600 tons, used over 26,000 nautical miles of wire, and took 250 workers a year to make.
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Article Name retroelectro
The ‘ohm,’ as represented by the original standard coil, is approximately 109 C. G. S. units of resistance; the ‘volt’ is approximately 108 C.G.S. units of electro-motive force; and the ‘farad’ is approximately 1/109 of the C.G.S. unit of capacity.” - The Committee for the Selection and Nomenclature of Dynamical and Electrical Units, 1873
This was a watershed moment for civilization. Never could a manufacturer take a specification and be assured that a comparable piece could be found, tested, and verified before running it through a mountain range or putting it miles below the ocean. 1881 - The first international electrical congress Even though the British Association for the Advancement of Science mostly completed their work for a standard unit of electrical resistance, some nations did not accept the standard at first. It took a concerted effort to create an international consensus. In 1881 the world’s greatest minds converged on Paris for the First International Electrical Congress. From the fifteenth of September through the fifth of October, a jury of one hundred forty-four representatives from fifteen different countries came together to standardize electrical units for measurement, but also discuss business at hand concerning machines, motors, weights, coils, electrical lamps, sewing machines, etc.
1827
Ohm’s principal work, ‘The Galvanic Circuits Investigated Mathematically,’is published.
1854
The work on the Transatlantic Cable begins.
1861
The International Electrical Congresses in the late 19th and early 20th centuries established electrical standards that drove the Second Industrial Revolution's growth and innovation. These meetings brought together the brightest minds in electrical engineering and were instrumental in propelling rapid technological advancements and industrial expansion.
The news reached London the last week of September and was first published in the London Week News, where it was said: “the passing of these resolutions by the Congress today unanimously, and their acceptance as international decisions by the most distinguished assemblage of physicists which have ever met together in the world’s history, i s quite as remarkable as it is satisfactory.”
An immortal legacy Two hundred years after he first published ‘The Galvanic Circuit Investigated Mathematically,’ Georg Ohm is still in the back pocket of every engineer and technician worldwide. Latimer Clark honored Ohm by proposing a unit of measure for him, immortalizing his work in ways that very few people ever could be. This year, on Ohm’s Day, while you’re celebrating with your friends and loved ones, let us not forget the people like Sir William Thomson (Lord Kelvin), James Maxwell, Sir Charles Wheatstone, Latimer Clark, and Sir Charles Bright, who lifted him above the pantheon of the giants who made our understanding of the movement of electrons possible.
Latimer Clark reads his proposal in Manchester.
1865
The committee creates the first standardized system for measuring electrical resistance.
1873
The B.A.A.S announces the ‘ohm’ as the standard unit of measure for electrical resistance.
1881
The ‘ohm’ is formalized for international use by the First International Electrical Congress.
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How to design effective power supply thermal management
Efficient and cost-effective thermal management for power supply units (PSUs) is important when designing industrial and medical systems to ensure reliability. Designing an effective thermal management system for a PSU is a complex activity, and much depends upon whether the PSU is enclosed or open frame. If an enclosed PSU is used, the type of enclosure has an impact on airflow and thermal dissipation. While fans help, designers need to consider fan reliability as well as the back pressure caused by system fans that can significantly reduce the effectiveness of the PSU fan(s), potentially increasing PSU operating temperatures. PSUs often have lower efficiencies at low input line voltage conditions. As a result, units that are operated for extended periods under low input line conditions can result in higher thermal dissipation and the need for additional cooling. Finally,
PSUs often require derating if operated at elevated temperatures that can be experienced in industrial and medical systems. To speed the implementation of effective thermal management systems, designers can turn to PSUs specifically designed for use in industrial and medical applications that offer a range of thermal management options. This article reviews the thermal management challenges when designing industrial and medical systems and offers guidance for designing effective thermal management solutions. It then presents options when integrating PSUs into industrial and medical equipment using PSUs from Bel Power Solutions as real-world examples, and closes with some practical steps designers can follow when integrating a PSU into the overall system thermal design.
Power supply thermal management challenges PSU thermal management challenges include system airflow and the impact that system fans can have on the performance of any fans integrated into PSUs, the ambient operating temperature, the need for peak power delivery, and the impact the input voltage range can have on power dissipation. These are first-order considerations; this article does not touch on second-order thermal management considerations related to rack mount systems or special environments such as data centers. One of the first considerations is the direction of PSU airflow; normal airflow creates positive pressure exiting the system and reverse airflow creates positive pressure entering the system ( Figure 1 ).
in industrial and medical systems
By Jeff Shepard Contributed By DigiKey's North American Editors
Figure 1: In normal airflow, positive pressure exits the system (left). With reverse airflow, positive pressure enters the system (right). (Image: Bel Power Solutions)
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How to design effective power supply thermal management in industrial and medical systems
performance of the system fan(s) results in a lower (negative) pressure inside the chassis, thereby reducing PSU fan effectiveness. ■ The PSU fan(s) produce reverse airflow and the system fan(s) are helping the PSU cooling, not fighting it. However, if the air entering the PSU is coming from the system exhaust plenum, that can create issues that include a reduction in net airflow, as well as recirculation issues that cause the accumulation of heat in the PSU. ■ The air entry to the PSU is isolated from the main chassis airflow protecting the PSU fans from interference from the system fan(s). To realize the maximum benefit, the airflow channel for the PSU should have a low resistance.
of 24, 28, 36, or 48 volts direct current (VDC). For example, the ABC601-1T48 has a 48 VDC output. These PSUs are rated for 600 watts of continuous power or peak power up to 800 watts for up to 10 seconds at up to 60°C for the enclosed front-mounted fan models ( Figure 3 ). They have
a 5 VDC standby power output rated for 1.2 amperes (A) for U chassis models and 1.5 A for front-mounted fan models, and a 12 volt, 1 A, fan output. The ABC601 series comes in two packages, U-frame chassis or enclosed with a front-mounted
fan ( Figure 4 ). The ABC601 series features an internal current share circuit for parallel operation between units to enhance total power. The EOS Power VPS600 series of open frame PSUs from Bel Power Solutions feature a narrower input range of 85 to 264 V AC and deliver
A fan is not enough Many PSUs include a cooling fan. Rather than simplifying the thermal design, a PSU with a fan can complicate thermal design with considerations of airflow direction as well as the system or chassis airflow impedance and pressure. Complications include: ■ System fans can compete with and reduce the effectiveness of PSU fans, reducing airflow through the PSU. ■ The entry to the PSU fan can have an unexpectedly high impedance, reducing airflow through the PSU. ■ Cables or other obstacles can block the PSU airflow, reducing the effectiveness of the fans. There are several ways that system and PSU fans can interact, examples are shown in Figure 2 below: ■ The PSU fan(s) produce normal airflow, but the higher
Peak vs. nominal power rating and derating Derating is often different for peak power versus nominal power. Peak power needs vary widely from a few milliseconds (ms) up to 10 seconds or more, and it’s an important consideration in many industrial and medical systems. Consider two 600-watt PSU series optimized for different peak power delivery; the ABC601 series of industrial and medical AC-DC power supplies from Bel Power Solutions that is rated for 10 seconds of peak power delivery, and the VPS600 series that’s rated for 1 ms of peak power. The ABC601 series provides up to 600 watts of regulated output power over an input voltage range from 85 to 305 volts alternating current (VAC) in single outputs
Figure 2: Thermal design must take into consideration the direction of airflow in the PSU and the relative strengths of the PSU and system fans. (Image source: Bel Power Solutions)
Figure 3: The enclosed front-mounted fan models of the ABC601 series deliver 600 watts of continuous power (red line on top graph) or up to 800 watts for up to 10 seconds (red line on bottom graph) at up to 60°C. (Image source: Bel Power Solutions)
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How to design effective power supply thermal management in industrial and medical systems
up to 600 watts of continuous output power and peak power of 720 watts for 1 ms ( Figure 5 ). These PSUs are available with output voltages of 12, 15, 24, 30, 48, and 58 V DC . For example, the VPS600-1048 has an output of 48 VDC. These units include a 5 V DC , 500 milliamperes (mA), standby power output and a 12 volt, 500 mA, fan output. While the ABC601 series is offered in two package styles, the VPS600 series is available in three with different power ratings: convection cooled U channel rated for 600 watts, slotted cover units rated for 420 watts, and plain cover units rated for 360 watts.
The various output voltage options and package styles have different derating curves. For example, the derating for 24 V DC output units is: ■ Open frame - Convection load, 600 watts continuous up to 30°C ■ Slotted cover - Convection load, 420 watts continuous up to 30°C ■ Plain cover - Convection load, 360 watts continuous up to 30°C ■ For all cover styles - Derate between 30 and 50°C by 0.833% per °C - Derate above 50°C by 2.5% per °C to a maximum of 70°C
Figure 6: The ABE1200/MBE1200 PSUs deliver 1200 watts with input voltages from 180 to 305 VAC and 1000 watts with input voltages from 85 to 180 VAC. (Image source: Bel Power Solutions)
Figure 4: ABC601 PSUs are available with fan cooling (top) or convection cooling (bottom). (Image source: Bel Power Solutions)
The input voltage effect PSU efficiency can be reduced at lower input voltages, resulting in derating of the nominal output power. For example, the ABE1200/MBE1200 series of AC-DC power supplies provide 1200 watts with an input of 180 to 305 V AC , and 1000 watts with an input range of 85 to 180 V AC ( Figure 6 ). These nominal ratings are from 0 to 60°C. At 70°C, they derate linearly from 1200 to 1100 watts and from 1000 to 900 watts, respectively. These PSUs include a fan speed control to minimize audible noise when maximum airflow is not needed. They are available in three 1U height compatible packages, including an enclosed model with two fans (24 V DC models only), and a U-shaped chassis with two protective cover options ( Figure 7 ).
Figure 5: The VSP600 series is available in three package configurations with different nominal power ratings; 600-watt convection cooled U channel units, 420-watt slotted cover units, and 360 watt plain cover units. (Image source: Bel Power Solutions)
Figure 7: The ABE1200 PSUs are available with dual fans (24 VDC models only), and two choices of protective covers. (Image source: Bel Power Solutions)
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