Tag Archives: app notes

App note: Low temperature soldering

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A study and actual test using LTS (Low Temperature Soldering) on SMT devices from Nexperia. Link here (PDF)

New generation Low Temperature Solder (LTS) pastes for Surface Mount Technology (SMT) is proposed for low temperature applications such as computing. LTS pastes are commonly build on near-eutectic SnBi alloying system and therefore show reduced melting temperatures which reduces the reflow temperatures as well as the energy consumption during SMT by up to 40%. This translates into reduced CO2 emissions and reduced manufacturing cost. Additionally, such effect can improve the yield impact created by high temperature (HT) warpage. HT warpage is widely recognized seen as main driver to reduce the reflow temperature for SMT. New product markets such as ultra-mobile computing and the Internet of Things (IoT) drive the need for smaller and thinner packages and boards which can suffer warpage by reflow temperatures of current solder systems like SAC. By lowering the peak temperature during reflow, warpage is reduced, resulting in higher SMT yields.

App note: Resistor Equipped Transistors (RETs)

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Introduction and application of resistor equipped transistors from Nexperia. Link here (PDF)

Bipolar transistors are controlled via the base current applied. Because of high temperature dependency of the voltage drop across the base-emitter path, it is required to add at least a series resistors at the base for stable and safe operation of a transistor in most applications This is required to keep base current at a desired level.
To reduce the number of components and to make board designs less complex, Resistor-Equipped Transistors (RET) have been introduced. These are single or dual transistors with resistors integrated on the same die. The integrated resistors have higher tolerances than commonly used external resistors. This fact makes RETs most suitable for switching applications where the transistor operates either in on-state or off-state. This is the reason also, why RETs are often referred to as digital transistors.

App note: Protecting charger interfaces and typical battery charging topologies

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Nexperia’s app note presenting ideas to protect USB port on devices. Link here (PDF)

This application note describes a complete solution for battery charging in mobile devices. This includes how to charge a Li-Ion battery with typical battery charger topologies, particularly with external bypass transistors and ways to effectively protect against overvoltage and overcurrent from the charger connector.

App note: Discrete LED driver

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Simple discrete LED driver application from Nexperia. Link here (PDF)

This application note describes a 300 mA discrete LED driver, based on a buck-converter principle, with a cycle-by-cycle current control. It includes a proposal for a BOM and layout of a low cost, low component count solution.
Key applications for the driver are lighting applications, where constant LED brightness, high efficiency and low cost are important features. For example, automotive lighting applications require that general illumination and signage should not consume too much power when the motor is not running. The input voltage of +6 V to +18 V supports automotive requirements, too.
Additionally, battery driven handhelds such as flashlights or headlamps will benefit from the
topology and efficiency the driver delivers.

App note: Power MOSFETs in linear mode

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App note from Nexperia about MOSFET characteristics in linear mode within their SOA. Link here (PDF)

Power MOSFETs are extensively used as switches due to the very low RDSon and thus low conduction losses. However, in many applications MOSFETs are used in their saturated state, with certain cases requiring both these modes to be robust and performant within the same device.

App note: How Litz wire maximizes offline multi-output flyback transformer efficiency for battery charger applications

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This app note from Bourns presents improvement in efficiency and reduce thermal rise using Litz wire for multi-output flyback transformers. Link here (PDF)

Flyback transformers are a robust, highly efficient and versatile option for AC-DC and DC-DC power supplies. Their wide input voltage range makes them an optimal choice for multiple designs while their use of minimal additional components makes them a cost-effective power conversion solution. Typically, flyback converter applications offer power levels up to 100 W allowing flyback transformers to be used for battery charger applications in EV (Electric Vehicle) and industrial ESS (Energy Storage System) solutions.
It is important that the size of the transformer be minimized in a power supply design as it is usually the biggest component on the PCB. However, minimizing the size of the transformer can lead to increased winding and core losses. A plus with flyback transformers is that they often offer multiple outputs, which can boost efficiency and provide more design flexibility. Conversely, this benefit can make it hard for the designer to minimize the size of the transformer while also balancing winding losses.
Litz wire is becoming more and more popular for flyback transformers as it can reduce power loss and boost power efficiencies. Litz wire is constructed using multiple fine wires that are woven together to replicate a typical copper wire. The benefit of Litz wire is that by having multiple conductors bunched together, the skin effect is greatly reduced. Reducing the skin effect has been shown to reduce AC resistance and boost the efficiency of power conversion designs.