App note: Thermal management in surface-mounted resistor applications


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.

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Teardown of a Philips dimmable LED bulb


Kerry Wong did a teardown of a Philips dimmable LED bulb:

One of the first things you will notice about this light bulb is that the compact construction. Most noticeably the lack of the telltale heatsink fins. As a result however, the heat dissipation capability is greatly sacrificed. During normal operation when mounted pointing downwards without any airflow obstruction, the case temperature raised to above 60°C within a few minutes. I could only imagine what the temperature would be like when the light bulb is mounted facing upwards in a semi-enclosed light fixture.
So I decided to take it apart to see the what the construction looks like inside.

See the full post on his blog.

Check out the video after the break.

App note: Minimizing the temperature dependence of digital potentiometers


Application notes from NIDEC COPAL Electronics Corp. about digital potentiometer’s temperature dependence. Link here (PDF)

The digital potentiometers (DP) has two temperature dependent parameters, the TC of the end-to-end resistance Rpot and the ratiometric TC. The temperature dependence of the parameters of an analog circuit using a digital potentiometers is reduced if the performance of the circuit is shifted from the TC of the end-to-end resistance of the pot to the ratiometric TC.

App note: Potentiometers and trimmers


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.