App note from Coilcraft on the design and construction of common mode filter inductor. Link here (PDF)
Noise limits set by regulatory agencies make solutions to common mode EMI a necessary consideration in the manufacture and use of electronic equipment. Common mode filters are generally relied upon to suppress line conducted common mode interference. When properly designed, these filters successfully and reliably reduce common mode noise. However, successful design of common mode filters requires foresight into the nonideal character of filter components — the inductor in particular. It is the aim of this paper to provide filter designers the knowledge required to identify those characteristics critical to desired filter performance.
Coilcraft’s app note on temperature rise due to losses on inductors and transformers. Link here (PDF)
Core and winding losses in inductors and transformers cause a temperature rise whenever current flows through a winding. These losses are limited either by the allowed total loss for the application (power budget) or the maximum allowable temperature rise.
For example, many Coilcraft products are designed for an 85°C ambient environment and a 40°C temperature rise implying a maximum part temperature of +125°C. In general, the maximum allowed part temperature is the maximum ambient temperature plus temperature rise. If the losses that result in the maximum allowed part temperature meet the power budget limits, the component is considered acceptable for the application.
App note from MAXIM Integrated on very compact PMIC using only single inductor to drive three independent switching regulators. Link here
Small form factor and minimal power loss are key criteria for internet of things (IoT) hardware, particularly wearables. Meeting these criteria typically involves some tradeoffs. For example, to meet a specific power consumption goal, a designer usually would have to compromise with an increase in design size.
Another app note from Holtek this time about their HT66FB574, a USB keyboard device that can support single color LED streamer. Link here (PDF)
The video gaming industry is seeing continual increasing demand for multi-feature keyboards. These can include features such as keys with an individual LED which can display different graphical effects along with variable illumination levels. With each key having an illuminated surrounding area effect along with multiple colour and pattern changes, this allows for a more colourful and stimulating gaming keyboard.
App note from Holtek on using their HT66FB574/572 to develop color effect mice. Link here (PDF)
Demands from the video gaming industry for different types of gaming mouse continue to expand. Adding a large number of RGB LEDs to the mice can produce different colours and brightness changes creating a range of visual special effects. This enhances the colour and stimulating effects of gaming mice. For example, having multiple RGB LEDs to form an outer ring on a gaming mouse can produce a colour changing waterflow effect. These are known as colour effect USB mice.
Another application notes from Richtek this time on LED lamps flickering. Link here
Applying LEDs in offline retrofit lamps seems straightforward, but should be done with care to achieve similar light quality as the conventional lamp that the user is trying to replace. Light flicker is one of the aspects that need to be considered carefully during LED lamp design to avoid customer complaints from the field. This application note explains the LED lamp flicker phenomena in relation to driver topology and LED characteristics, and provides solutions based on several Richtek LED drivers in combination with specific LED strings. A practical flicker measurement method is explained as well, that can be used to measure light flicker in LED lamps.
Richtek app note for Li-ion battery definitions and gauge introduction. Link here
SOC is defined as the status of available energy in the battery and usually expressed as percentages. Because the available energy change depends on different charging/discharging currents, temperatures and aging effects, the SOC could be defined more clearly as ASOC (Absolute State-Of-Charge) and RSOC (Relative State-Of-Charge). Typically, the range of RSOC is from 0% to 100%, a fully charged battery’s RSOC is always 100% and a fully discharged battery has 0% RSOC. The ASOC is a reference calculated by Design Capacity which is a fixed capacity from when the battery is manufactured. A fully charged new battery will have 100% ASOC, but a fully charged aging battery could be less than 100% because of different charge/discharge conditions.
Battery management is part of power measurement. The fuel gauge is responsible to estimate the capacity of battery in the domain of battery management. The basic function of fuel gauge is to monitor the voltage, charge/discharge current and battery temperature, and to estimate the battery’s SOC and Full Charge Capacity (FCC) of battery. There are two classic methods to do the SOC estimation which are Open Circuit Voltage (OCV) and Coulomb Counter, respectively. The other method is dynamic voltage-based algorithm designed by RICHTEK.
Light guide basics app note from OSRAM. Link here (PDF)
Light Guides are used wherever the light of a light source should be distributed homogeneously over a particular area, when there is a spatial distance between light source and the area which is to be illuminated.
App note from OSRAM about different approaches on LED string diagnostic in automotive. Link here (PDF)
One requirement especially in automotive applications is the diagnosis of failures in functions and systems. Therefore light functions realized with LEDs like break light, daytime running light, low and high beam may require a diagnostics function. This application note describes some items which have to be taken into account, when a diagnostic function for a LED string or a multi LED module has to be realized.
Another app note from Maxim Integrated about challenge-response security on 1-wire devices. Link here (PDF)
Challenge-response can be a secure way of protecting access to any privileged material if implemented correctly. In this document, many options for challenge-response access control are discussed but the most secure method given is presenting a different random challenge on each access attempt and having a response that only the host can interpret without giving out any secrets. This document shows why Maxim’s SHA-1 iButtons® and 1-Wire devices are ideal choices when implementing this kind of challenge-response system