Tag Archives: app notes

App note: MOSFETs withstand stress of linear-mode operation

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App note from IXYS talking about MOSFET operating in linear region in application like electronic load. Link here (PDF)

Power MOSFETs are most often used in switchedmode applications where they function as on-off switches. But in applications like electronic loads, linear regulators or Class A amplifiers, power MOSFETs must operate in their linear region. In this operating mode, the MOSFETs are subjected to high thermal stress due to the simultaneous occurrence of high drain voltage and current, resulting in high power dissipation.
When the thermo-electrical stress exceeds some critical limit, thermal hot spots occur in the silicon causing the devices to fail. To prevent such failure, MOSFETs operating in the linear region require high power dissipation capability and an extended forward-bias safe operating area (FBSOA).

App note: Digital inrush controller

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App note from IXYS about their unique digital inrush controller using Zilog’s 8-bit Z8F3281 MCU. Link here (PDF)

Digital control allows distinctive solutions to control inrush current in typical AC-DC rectifier with capacitive load by limiting capacitor pre-charge current to a predetermined value at each half sine-wave cycle. Capacitor charge is spread over a number of cycles until capacitor is charged proportion of peak value of AC voltage source. Capacitor is charged according to timedependent pulse train. The pulses are designed in a way to provide substantially equal voltage increment applied to capacitor to keep peak of charging current about the same value at each cycle. Number of cycles depends on capacitor value and charge current. For a given capacitor value which is selected depending on desired ripples amplitude, the charge current is a function of number of pulses and its timing position with respect to rectified sine wave. Detailed algorithm of creating pulse train for Digital Inrush Control is described in the Principles of Operation section.

App note: Bipolar transistors maximum ratings

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Deep dive on to the maximum ratings of bipolar transistors presented in this app note from Toshiba. Link here PDF!

For transistors, the maximum allowable current, voltage, power dissipation and other parameters are specified as maximum ratings.
The absolute maximum ratings are the highest values that must not be exceeded during operation even instantaneously. When two or more ratings are specified, two ratings can not be applied to the transistor at the same time.
Exposure to a condition exceeding a maximum rating may cause permanent degradation of its electrical characteristics. Care should be exercised as to supply voltage bounces, variations in the characteristics of circuit components, possible exposure to stress higher than the maximum ratings during circuit adjustment, changes in ambient temperature, and input signal fluctuations.

App note: Comparison of SiC MOSFET and Si IGBT

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App note from Toshiba on the advantages of Silicon carbide (SiC) MOSFET over silicon (Si) IGBT. Link here PDF!

Silicon carbide (SiC) comprises silicon (Si) and carbon (C) atoms. Each atom is surrounded by four different atoms in the form of a regular tetrahedron. SiC is a compound semiconductor with the densest tetrahedral arrangement. SiC has many crystalline structures called polytypes that exhibit different physical properties because of periodic differences in the overlap of tetrahedrons.
Compared to silicon, SiC has a wider energy gap where no electron states can exist (called a bandgap) between the valence band (i.e., an energy band filled with valence electrons) and the conduction band (i.e., an empty energy band in which electrons can be present). A wide bandgap provides a strong chemical bond among atoms and therefore a high electric breakdown field. SiC has an electric breakdown field roughly ten times that of silicon. Because of a strong atomic bond, SiC has greater lattice vibration and consequently conducts energy more easily than silicon. Therefore, SiC is a semiconductor material with good thermal conduction.

App note: Driving solenoids in automotive applications

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App note from Nexperia about various solenoid driver used in automotive. Link here (PDF)

There are a wide variety of solenoid drive circuit topologies. Most of them use MOSFETs in various configurations and driving modes. In this application note four of them will be discussed: solenoid driver with free-wheeling diode, solenoid driver with MOSFET avalanching, solenoid driver with active clamp and solenoid driver with auxiliary boost circuit.

App note: Power Battery Charger Calibration Fixture

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Automated battery charger calibration fixture using Holtek’s ASSP MCUs. Link here (PDF)

Power chargers for electric bicycles, electric motorcycles and power tools, etc., are all calibrated before delivery, thereby correcting any charging parameter drifts due to external component tolerances. This will ensure the output voltage and current conform to their specifications. However, traditional applications are calibrated manually in production by using variable resistors, which reduces production efficiency as well as increasing manpower, thus increasing manufacturing costs.