App note: Interfacing AT84AD001B dual 8-bit 1 Gsps ADC and AVR ATmega128L

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e2v’s application note interfacing their 1 Gsps 8-bit ADC to AVR. Link here (PDF)

With its smart feature (3-wire serial interface), e2v’s AT84AD001B dual 8-bit 1 Gsps ADC provides you with digital control over various functions offered with the dual ADC: calibration, gain and offset adjustments, DMUX ratio selection, analog and clock input mode, and partial or full standby mode.

This digital control via the 3-wire serial interface can be managed using Atmel’s ATmega128L AVR. The aim of this application note is to provide you with the relevant information for interfacing these two devices.

App note: WM8731 Suggested power-On/Off sequence

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Interesting app note from Cirrus Logic on how to minimize popping sound on the output when turning on/off the DAC on their WM8731 digital to analog converter. Link here (PDF)

As with any consumer audio product, it is important that any on/off power noise be kept to a minimum. Generally, this is done with some sort of external mute circuit at the output socket of the application. Although effective, this does increase the BOM (bill of materials) cost, which in many cases is a critical factor.

With this in mind, the WM8731 DAC signal path may be powered-on in such a way that power on/off noise is kept to a minimum with no need for an external muting circuit, reducing the BOM cost.

App note: CS3001/2/11/12 & CS3003/4/13/14 Chopper-stabilized Operational Amplifiers

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Cirrus Logic’s app note, discussing their own designed chopper amps. Link here (PDF)

The chopper-stabilized amplifiers designed at Cirrus Logic are unique. These amplifiers offer performance benefits that combine the best features of bipolar amplifiers with the best features of chopper amplifiers. The intent of this application note is to understand Cirrus Logic’s unique technology and to see how it can be applied in various measurement applications.

App note: WM9712 Jack plug auto-detection, hookswitch detection and microphone headset detection

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App note on Cirrus Logic’s WM9712 jack plug auto-detection by monitoring the connected headphone resistance. Link here (PDF)

This application note describes two operations associated with using headset. The first is the facility to automatically switch between a mono ear speaker and stereo headphones for use in a Smartphone, PDA etc. The second operation is a method which can be used to detect if stereo headphones have been attached or if a mono headset with microphone has been attached.

App note: An Introduction to MEMS Microphone Specifications

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An application note from Cirrus Logic on their MEMS microphones, which are small and perfect for wearables devices. Link here (PDF)

MEMS microphones are small form factor microphones, which translate acoustic sound pressure input into an electrical output response. They utilise the silicon wafer processes from the microelectronic industry to create high performance microphones of increasingly smaller geometries.

These processes give MEMS microphones a number of advantages over conventional electret condensing microphones (ECM), which has resulted in a general market transition to MEMS technologies for many of the latest consumer applications, including those requiring multi-microphone support or high quality capture.

The aim of this applications note is to enlighten readers with little or no experience of MEMS microphones to a point that they are confident in basic terminology and able to understand datasheet information to make product selections.

App note: Iris Recognition SFH 4780S

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This application note from OSRAM describes the use of the SFH 4780S in iris recognition (iris scanning) as illumination module. Link here (PDF)

Personal authentication is becoming a key requirement for various electronic devices. Besides of the pin number, today most systems are based on so called biometric “properties”. Biometrics can include fingerprints, facial features, retina, iris, voice, fingerprint, palmprints, vein structures, handwritten signatures and hand geometry. All these biometrics have various pros and cons. However, only iris recognition claims to be a ‘hard-to-spoof’ system in combination with an ultra-low false acceptance rate (i.e. one in a million). Additionally, it also features greater speed, simplicity and accuracy compared to other biometric systems. The traits of iris recognition systems rely on the unique patterns of the human iris which are used to identify or verify the identity of an individual.

App note: Eye safety of IREDs used in lamp applications

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This application note from OSRAM describes the possible hazards of infrared LEDs (IREDs) used for lamp applications with respect to the IEC-62471 standard and how to classify IREDs according to different risk groups. Link here (PDF)

As the radiated optical power of light emitting diodes (LEDs) has increased in recent years, the issue of eye safety has received an ever-increasing amount of attention. Within this context there has been much discussion about the right safety standard either the laser standard IEC-60825 or the lamp safety standard IEC-62471 to apply to the classification of LEDs. Before mid 2006 all LED applications were covered by the IEC-60825. Today most of the LED applications are covered by the lamp standard. Other than lasers, lamps are only generally defined in this standard as sources made to produce optical radiation. Lamp devices may also contain optical components like lenses or reflectors. Examples are lensed LEDs or reflector type lamps which may include lens covers as well. The status quo is, that for different applications of LEDs, like data transmission or irradiation of objects, different standards have to be used: data transmission IEC-60825 & lamp applications IEC-62471. Both safety standards do not cover general exposure scenarios and are not legally binding.

App note: Enhancing workplace safety in hazardous locations with PICO® 259-UL913 intrinsically safe fuse

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Application note from Littelfuse about their (IS) intrinsically safe fuse which doesn’t produce sufficient heat that could trigger sparks which are dangerous in an explosive environment. Link here (PDF)

Gases, petroleum products, and airborne dusts tend, by their very nature, to be explosive if sources of sparks or excess heat are present. Over the years, these hazards have led to some catastrophic losses of life and property. In response to this hazardous potential, regulatory bodies around the world, including Underwriters Laboratories, Inc., have worked to establish and refine a standard that will minimize the hazards associated with these working environments. UL 913, which was originally issued in 1971, establishes the standard for “Intrinsically Safe Apparatus and Associated Apparatus for Use in Class I, II, and III, Division 1, Hazardous (Classified) Locations.”

The purpose of this standard is to specify requirements for the construction and testing of electrical apparatus, or parts of such apparatus, having circuits that are not capable of causing ignition in Division 1 Hazardous (Classified) Locations as defined in Article 500 of the National Electrical Code, ANSI/NFPA 70. Limiting exposure to high surface temperatures and requirements for dust-tight enclosures are key aspects of the UL913 standard.

App note: Controlling LED lighting using triacs and quadracs

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Solid State device and circuits for controlling LEDs lighting, replacing conventional incandescent lamps, an App note from Littlefuse. Link here (PDF)

Light Emitting Diodes (LEDs) are fast becoming the most popular lighting option. Industry forecasts anticipate the market will continue to expand at an annual rate of 20% from 2011 to 2016, with the greatest growth coming in the commercial and industrial lighting sectors. As incandescent lamps have been made largely obsolete, given the U.S. government’s mandate to save energy, they have frequently been replaced by LEDs due to their long life (typically 25,000 hrs.) and the ease of adapting them to many different socket and shape requirements. However, LED lighting control presents a few problems not encountered with incandescent lamps. For example, with much less current from the LED load, normal types of triacs may be challenged in terms of latching and holding current characteristics.

Triacs make up the heart of AC light dimming controls. Triacs used in dimmers have normally been characterized and specified for incandescent lamp loads, which have high current ratings for both steady-state conditions and initial high in-rush currents, as well as very high end-of-life surge current when a filament ruptures.

Because they are diodes, LEDs have much lower steady-state current than incandescent lamps, and their initial turn-on current can be much higher for a few microseconds of each half-cycle of AC line voltage. Therefore, a spike of current can be seen at the beginning of each AC half-cycle. Typically, the current spike for an AC replacement lamp is 6–8 A peak; the steady-state follow current is less than 100 mA.

Designing an AC circuit for controlling LED light output is very simple when using the new Q6008LH1LED or Q6012LH1LED Series Triacs because only a few components are required. All that is needed is a firing/triggering capacitor, a potentiometer, and a voltage breakover triggering device.

App note: Microcontroller-based serial port interface (SPI®) boot circuit

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Simple circuit for sending command upon boot to the target device sortof boostraping hardware tachnique, an app note from Analog Devices. Link here (PDF)

This application note describes the operation of a general purpose, microcontroller-based Serial Port Interface (SPI) boot circuit. This is a low cost solution for users who need to modify some of their device’s parameters at power up. This circuit addresses a 3-wire SPI application for programming converters, or any device that has a SPI option, and sends commands to user-defined SPI registers.