App note: Gate drive characteristics and requirements for HEXFET power MOSFETs

an_infineon_AN-937

App note from International Rectifier on driving their Power MOSFETs. Link here (PDF)

The conventional bipolar transistor is a current-driven device. A current must be applied between the base and emitter terminals to produce a flow of current in the collector. The amount of a drive required to produce a given output depends upon the gain, but invariably a current must be made to flow into the base terminal to produce a flow of current in the collector.

The HEXFET®is fundamentally different: it is a voltage-controlled power MOSFET device. A voltage must be applied between the gate and source terminals to produce a flow of current in the drain. The gate is isolated electrically from the source by a layer of silicon dioxide. Theoretically, therefore, no current flows into the gate when a DC voltage is applied to it though in practice there will be an extremely small current, in the order of nanoamperes. With no voltage applied between the gate and source electrodes, the impedance between the drain and source terminals is very high, and only the leakage current flows in the drain.

App note: Microcontroller Clock – crystal, resonator, RC Oscillator, or silicon oscillator?

an_maxim_an2154

App note from Maxim Integrated on clock sources of microcontrollers and their strengths and weaknesses. Link here

The majority of clock sources for microcontrollers can be grouped into two types: those based on mechanical resonant devices, such as crystals and ceramic resonators, and those based on electrical phase-shift circuits such as RC (resistor, capacitor) oscillators. Silicon oscillators are typically a fully integrated version of the RC oscillator with the added benefits of current sources, matched resistors and capacitors, and temperature-compensation circuits for increased stability.

App note: Clearing Xilinx FPGA configuration to allow boundary scan testing

Another application note from XJTAG on preparing Xilinx FPGA for proper boundary scan testing. Link here

When Xilinx FPGAs are configured it can restrict the boundary scan access to some signals on the device. One work-around for this problem is to configure the FPGA with a ‘blank’ image that closely matches its unconfigured state, allowing boundary scan testing to occur without any problems.

A second issue that can affect boundary scan testing with FPGAs is that they contain pull resistors. Depending on the design, these may be enabled when the FPGA is unconfigured as well as when it is configured. If these internal resistors are enabled on nets that contain pull resistors mounted on the board, two potential problems can occur:

1. If the internal resistor and external resistor pull in opposite directions, the boundary scan tests may not be able to test the external pull resistor if it is weaker than the internal pull resistor.
2. If the internal and external resistors pull in the same direction, a fault with the external resistor may not be detected because the internal resistor may mask the fault.

By setting the correct configuration options it is possible to disable these internal pull resistors when generating a ‘blank’ FPGA image.

App note: Using a test reset section to initialise JTAG devices

an_xjtag_test_rst

An app note from XJTAG about applying test reset to put some devices to JTAG compliant mode. Link here

Some JTAG devices require a specific sequence of states to be applied to some signals in order to put the device into a JTAG-compliant mode. This application note describes how a Test Reset section can be used to describe the required sequence and control its application.

App note: Linear power MOSFETS basic and applications

an_IXYS_IXAN0068

Some examples of power MOSFETS application from this app note from IXYS Corporation. Link here (PDF)

Applications like electronic loads, linear regulators or Class A amplifiers operate in the linear region of the Power MOSFET, which requires high power dissipation capability and extended Forward Bias Safe Operating Area (FBSOA) characteristics. Such mode of operation differs from the usual way of using Power MOSFET, in which it functions like an “on-off switch” in switched-mode applications. In linear mode, the Power MOSFET is 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 device to fail

App note: Depletion-Mode power MOSFETs and applications

an_IXYS_IXAN0063

IXYS Corporation’s N-Channel power MOSFET selection and application. Link here (PDF)

Applications like constant current sources, solid-state relays, telecom switches and high voltage DC lines in power systems require N-channel Depletion-mode power MOSFET that operates as a normally “on” switch when the gate-to-source voltage is zero (VGS=0V). This paper will describe IXYS latest N-Channel Depletion power MOSFETs and their application advantages to help designers to select these devices in many industrial applications.

App note: Infrared (IR) Spectroscopy with the SFH 473X – Background & technology

an_osram_infrared_spectroscopy_SFH473X

Infrared spectroscopy by OSRAM and their SFH 473X broadband light emitters. Link here (PDF)

Imagine you can check if the mangos on the market are sweet – without even touching them…

Imagine you can verify if your prescribed medical tablets contain the life-saving compound – or if they are counterfeits…

Imagine you can check the calories of your favorite cheese dish – before eating…

Imagine all this is possible with one fingertip on your smartphone…

The SFH 473X series is precisely designed to support this innovation. This note covers briefly the background of spectroscopy and the case for the SFH 473X series.

App note: Ambient light sensors – General application note

an_osram_ambient_light_sensors_gen

Different ambient sensors differs on their ability to sense specific wavelength and introduce different ambient levels compared to human eye, here’s a general application note from OSRAM. Link here (PDF)

This application note introduces discusses ambient light sensing. The different types of ambient light sensors are described and related to specific applications.