App note: MELF resistors – The world’s most reliable and predictable, high-performing film resistors

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App note from Vishay on why MELF resistors are so successful and has no alternative in today’s application. Link here (PDF)

For more than 25 years, Vishay’s MELF resistors have successfully met the demanding requirements of the automotive industry. They offer superior SMD resistor performance in terms of accuracy, stability, reliability, and pulse load capability. The cylindrical construction of MELF devices provides an optimal power rating and pulse load capability related to the mounting space. Continuous development has led to improved long-term stability and moisture resistance, and allows high-temperature operation to + 175 °C.

App note: Increasing accuracy in feedback circuits and voltage dividers with thin film chip resistor arrays

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App note from Vishay on using chip resistors to achieve long-term stability. Link here (PDF)

Thin film chip resistor arrays consist of several resistors of equal or different values combined in one package. During the manufacturing processes and the device’s lifecycle, all the particular resistors virtually experience identical conditions, which allow the specification of their relative tolerances, relative temperature coefficients, and even a relative resistance drift. These relative parameters provide precise and stable resistance ratios and far better long-term stability of feedback circuits and voltage dividers compared to discrete resistors.

App note: Custom magnetics – What are they and when do you need them?

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Consideration factors before going to custom magnetic request from manufacturer, an app note from Vishay. Link here (PDF)

There are many manufacturers that claim they build custom magnetics. However, there is often confusion as to what constitutes custom magnetics and whether or not a designer actually needs them or can afford them. This article will clarify what custom magnetics are, help designers determine if they are needed, and explain how to engage with a custom magnetics supplier.

App note: How to avoid chipLEDs sticking to cover tape during automated tape-and-reel assembly

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Investigative app note from Vishay on preventing too light components from sticking on the cover tape of their reel. Link here (PDF)

Customers have informed Vishay that 0603 LEDs (ChipLEDs) supplied in tape and reel format sometimes stick to the PSA cover tape that is peeled off from the carrier tape during the assembly process. This application note describes the problem and provides a summary of precautions that can be used to prevent this unwanted effect from happening.

App note: AC ripple current calculations solid tantalum capacitors

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Application note from Vishay on power and voltage limitations of solid tantalum capacitors for both low and high frequency applications. Link here (PDF)

Solid tantalum capacitors are preferred for filtering applications in small power supplies and DC/DC converters in a broad range of military, industrial and commercial systems including computers, telecommunications, instruments and controls and automotive equipment. Solid tantalum capacitors are preferred for their high reliability, long life, extended shelf life, exceptional stability with temperature and their small size. Their voltage range is 4 to 50 volts for the most common types. Tantalum chip capacitors for surface mount applications are manufactured in very small sizes and are compatible with standard pick-and-place equipment.

App note: Power management solution – Constant Voltage (CV) pulse charging of hybrid capacitors

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App note from Vishay about constant voltage (CV) pulse charging as the most cost-efficient solution to use on Hyrid capacitors. Link here (PDF)

Rechargeable energy storage solutions are of high interest because of their flexibility, low maintenance requirements, and reduced cost over their life-cycle.

For compact applications, classic electrolytic capacitors are environmentally friendly alternatives and available for a wide range of rated voltages. However, they soon reach their energy storage limit with output requirements exceeding a few 100 mWs.

Electric double-layer capacitors (EDLC) offer high power and energy density, as well as long working life, but are limited to low working voltages in the same range as batteries. Electronic systems require a compromise between these technologies, namely solutions that combine the advantages of classic batteries and double-layer capacitors without the limitations.

 

App note: Capacitance change with applied DC voltage

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Tantalum comparison to other types of capacitors shows stable capacitance in this app note from Vishay, Link here (PDF)

Tantalum capacitors in general – and Vishay’s 298D/TR8/TM8 MicroTan tantalum capacitors in particular – demonstrate very stable performance over the DC voltage (bias) applied in an application. At the same time, the majority of capacitors utilizing ceramic or polymer dielectrics (monolithic ceramic, disc ceramic, MLCC, polyester, film, etc.) demonstrate significant shift in both directions – sometimes 40 % to 50 % or higher

App note: Through-Hole versus SMD components

App note from Vishay on the advantages of using Through-Hole mounting. Link here (PDF)

Most electronic gadgets are designed to interface with humans, and we humans are very abusive to most electronic devices. We drop them, poke them, open and close them, and in general feed stuff into and out of them.

It is well understood that a through-hole connection to the PCB is mechanically stronger than most surface-mount connections. By comparison, the strength of the bond that holds a surface-mount component to the PCB is limited to the strength of the solder joint that holds it to the surface of the laminate. As parts get smaller, so does the amount of solder and thus the strength of the bond.

App note: Thermal management in surface-mounted resistor applications

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App note from Vishay on PCB thermal management specifically on components like SMD resistors, where if allowed a design change (e.g. change in SMD size or change in more heat tolarant ones) must be implemented in order to squeeze more thermal capability. Link here (PDF)

Thermal management is becoming more important as the density of electronic components in modern printed circuit boards (PCBs), as well as the applied power, continues to increase. Both factors lead to higher temperatures of individual components and of the entire assembly. However, every electrical component in an assembly has to be used within its prescribed operating temperature limits due to its material properties and reliability aspects. In this application note, experimental results are provided in order to prevent overheating of electronic devices such as surface-mount resistors.

App note: Potentiometers and trimmers

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App note from Vishay on variable resistors primer. Link here (PDF)

A potentiometer is a mechanically actuated variable resistor with three terminals. Two of the terminals are linked to the ends of the resistive element and the third is connected to a mobile contact moving over the resistive track. The output voltage becomes a function of the position of this contact. Potentiometer is advised to be used as a voltage divider.