Tag Archives: app notes

App note: How to protect mobile devices from ‘USB Kill’ threats

via Dangerous Prototypes

Great read from Bourns about USB killer devices and port protection solutions. Link here (PDF)

Researchers have long warned about the security risks of inserting other users’ USB drives into your PC, even those from whom you trust. If the threat of malware infections isn’t cause enough for concern, there have been stories of malicious USB thumb drives that have “fried” laptops. Does this seem like a far-fetched occurrence? Hearing of the threats, PC World documented the work of an electronics engineer who set out to create a prototype that could actually kill a mobile device’s USB port.

App note: Protecting USB Type-C Cable connectors featuring higher power & tighter pin spacing

via Dangerous Prototypes

Bourns’ built-in thermal cut-off devices adds extra protection from faults directly on USB Type-C cables. Link here (PDF)

The now ubiquitous Universal Serial Bus (USB) standard was initially developed in 1994 with the intent of providing a communication standard to improve and simplify communication between the PC and peripheral devices. An updated version of the USB interface standard is the USB 3.1 Superspeed+, which doubles the data rate to 10 Gbps – a 2x improvement of the previous generation USB 3.0 Superspeed. USB 3.1 Superspeed+ is backwards compatible with USB 1.1, 2.0 and 3.0 with a power delivery projected at 100 W. This gives users enhanced data encoding for more efficient data transfer offering higher throughput and improved I/O power efficiency.

In addition to the increased power capability and bandwidth achieved in this updated USB standard, the connector has been changed. The original simple 4 pin D+/ D- Power and GND format has been upgraded and now combines multiple connector functions into one. The new USB Type-C connector features 24 pins in a smaller form factor.

A downside to this combination of increased power and the extremely tight pin spacing is heightened concern about potential safety and fire hazards due to the possibility of thermal runaway at the connector. To deal with these potential threats, it is recommended that electronic equipment manufacturers and connector and cable manufacturers integrate overcurrent and overtemperature protection into the Type-C connector.

App note: Offline non-isolated flyback converter protection

via Dangerous Prototypes

A white paper from Bourns about thermal protection PTCs on flyback converters. Link here (PDF)

This paper examines the use of resettable polymer fuses for protecting offline flyback converters. Using a thermal model of the resettable fuse surrounding solder pads and copper to optimize the trip time so that the converter is protected during overloads, there are two potential positions considered for polymer Positive Temperature Coefficient (PTC) resettable fuses in the circuit. One position is directly on the winding and the other position is beyond the control loop. Results are taken from the converter and compared with a simulation.

App note: Assembly guidelines for QFN (quad flat no-lead) and SON (small outline no-lead) packages

via Dangerous Prototypes

NXP’s app note about the internals and how to’s footprint design and solder their leadless dual and quad flat packages. Link here (PDF)

The small outline no-lead (SON)/quad flat no-lead (QFN) is a small size, lead-less plastic package with a low profile, moderate thermal dissipation, and good electrical performance. It is a surface mount package with metallized terminal pads located at the bottom surface of the package. SON have terminal pads along two opposite edges of the package versus QFN with terminal pads along the four edges of the bottom surface. SON is sometimes also referred as DFN: Dual flat no-lead package.

App note: Emitters and detectors for infrared (IR) touchscreens

via Dangerous Prototypes

App note from OSRAM about IR LEDs and IR detectors used on touchscreen technologies. Link here (PDF)

Touchscreens as a popular user interface are more and more common. Applications span from public information systems to customer self-service terminals. Thus, as a logical step, more and more devices today feature this kind of user interface, e.g. bank automatic teller machines (ATMs), personal digital assistants (PDAs), mobile phones and PC displays. The widespread popularity is actively supported by standard computer based operating systems, such as e.g. Windows® 7.

The rapid development of CMOS imaging sensors and the development of high power infrared (IR) emitters in slim packages have led to a series of new optical touchscreen technologies. Many of them contain proprietary technology and solutions.