App note: Power factor correction with ultrafast diodes

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Vishay’s app note in keeping the power supplies’ power factor in check with their ultrafast diodes. Link here (PDF)

More and more switched mode power supplies (SMPS) are being designed with an active power factor correction (PFC) input stage. This is mainly due to the introduction of regulations aimed at restricting the harmonic content of the load current drawn from power lines. However, both the user and the power company benefit from PFC, so it just makes good sense.

App note: Limiting inrush current

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Aimtec’s app note on inrush current on power converters and their solution. Link here

Inrush currents can be problematic in circuits that utilize overload protection devices such as fuses and circuit breakers. The selection of overcurrent protection devices is made more complicated when high inrush currents are present. False overload conditions can trigger unwanted protection events.

App note: Forced air convection and heat sinking for power supplies

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Application note from Aimtec discusses about two ways for taking away heat on power supplies. Link here

When evaluating the operating temperature ranges of power supplies one must consult component’s datasheets. Datasheets state a “usable” operating temperature range typically given at full output load. In order to reach the upper limit of the temperature ranges without derating the load, some additional heat dissipation may be required.

App note: Method to reduce the output ripple & noise of power supplies

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Another app note from Aimtec on power supplies and how to minimize their output noises. Link here

The switching power supplies have the fundamental advantage of high efficiency i.e. low power dissipation when compared to linear voltage regulation. However, there exists an important consideration concerning the presence of ripple and noise at their outputs. If the ripple and noise are left unfiltered their levels may be sufficiently high to adversely affect other devices connected to the same power supply. Fortunately there exists methods to cost effectively reduce the impact of ripple and noise.

App note: Best design and layout practices for SiTime oscillators

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SiTime’s app note about how to properly route an oscillator’s PCB traces. Link here

Proper decoupling, bypassing, and power supply noise reduction is important in many applications to ensure optimal performance for oscillators. A common strategy is to place capacitors near high speed devices on a printed circuit board (PCB). These capacitors serve important functions:
– Provide instantaneous current to the component
– Reduce noise propagation through the system
– Shunt the power supply noise to GND
The following sections describe decoupling, bypassing, noise rejection, and power supply condition recommendations for SiTime’s single-ended and differential timing devices.

App note: Frequency measurement guidelines for oscillators

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Application note from SiTime about frequency measurements and how some methods may not gauged accurately. Link here

Every digital electronic device requires a reference clock and oscillators are widely used to serve that purpose. Verifying frequency characteristics of high performance devices requires accurate frequency measurement. This document contains an overview of various frequency measurement methods and instruments and is intended to help the users of SiTime MEMS oscillators take accurate frequency measurements.

App note: Alkaline battery low-voltage indicator

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Battery low-voltage indicator made from two new comparators TSM9118 and TMS9119 from Silicon Labs. Link here (PDF)

In many battery-powered systems, a user would like to know when it is time to replace the batteries before they are completely discharged, causing the device being powered to fail completely. Alkaline batteries have an open cell voltage of about 1.5 V. As they are discharged, the voltage slowly drops. When the cell voltage reaches about 1.25 V, they have delivered about 90% of their stored energy.

App note: A practical look at current ratings

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An app note from Alpha & Omega Semiconductors about proper way of evaluating MOSFET’s power handling capability based on how much loss it will generate based on the application conditions. Link here (PDF)

System designers are often faced with the task of selecting the most suitable power device from a wide array of products from different manufacturers with very similar ratings. While a detailed parameter by parameter comparison is technically the most correct way of selection, it is not the most practical and designers resort to making their first cut based on 3-4 simple parameters. Among these are package, voltage and current ratings, Rdson etc. In this article we will take a close and practical look at the current rating. For purposes of illustration we will focus on Mosfets in low and medium power packages, but the considerations can be applied to other technologies as well.

App note: Performance capability of the SO8-FL package

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MOSFET SO8-FL package app note from ON Semiconductors provide same thermal performance as metal top package with heat sink attached. Link here (PDF)

The SO8−FL package can deliver high power density and provides excellent thermal dissipation to create a high efficiency, cool design environment when properly cooled. Metal−top devices attempt to remove heat easier through direct contact to the source. This application note provides a comparison of an SO8−FL device with a metal top device of comparable die parameters, and will show that the SO8−FL and metal top devices have comparable thermal performance. Furthermore, it will be shown that while the package itself influences thermal performance, the use of a heat sink provides the largest improvement to thermal dissipation, regardless of package.