App note: Eye safety for proximity sensing using infrared light-emitting diodes

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A guide to human eye safety for designers of consumer products, app note from Renesas. Link here (PDF)

Active Proximity Sensing for Consumer products requires the use of a light-emitting component to illuminate the target object to be detected at some distance from the sensor. Typically, product designers do not want the illumination to interfere with the other functions of the product, or to distract the user during normal use. Therefore, Infrared Light-emitting Diodes (IR-LEDs) are used as the light-emitting components for proximity sensing. To further reduce the user awareness of the proximity function, the IR-LED and the proximity sensor are located under heavily tinted – but, infrared-transmitting – glass. While remaining unaware of any illuminating light source, the consumer indeed is exposed to low-levels of infrared radiation. All consumer products that emit light radiation – whether visible, ultraviolet, or infrared – must adhere to international standards that specify exposure limits for human eye safety.

App note: Basics on decoupling

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See AVX technical note on how capacitors filter out transients in high speed digital circuits. Link here (PDF)

This paper discusses the characteristics of multilayer ceramic capacitors in decoupling applications and compares their performance with other types of decoupling capacitors. A special high-frequency test circuit is described and the results obtained using various types of capacitors are shown.

App note: Hand soldering tutorial for fine pitch QFP devices

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No SMD tools removal and soldering of QFP packages tutorial from Silicon labs. Link here (PDF)

This document is intended to help designers create their initial prototype systems using Silicon Lab’s TQFP and LQFP devices where surface mount assembly equipment is not readily available. This application note assumes that the reader has at least basic hand soldering skills for through-hole soldering. The example presented will be the removal, cleanup and replacement of a TQFP with 48 leads and 0.5 mm lead pitch.

App note: 3V DACs used in ±10V applications

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Boosting DAC’s output to drive larger voltage tackled in this app note from MAXIM Integrated. Link here (PDF)

Many modern systems have the majority of their electronics powered by 3.3V or lower, but must drive external loads with ±10V, a range that is still very common in industrial applications. There are digital to analog converters (DACs) available that can drive loads with ±10V swings, but there are reasons to use a 3.3V DAC and amplify the output voltage up to ±10V.

App note: Tire pressure monitor system

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NXP Semiconductor’s implementation of Tire pressure monitor (TPM) system. Link here (PDF)

The Tire Pressure Monitoring System Reference Design consists of five modules: four tire modules and a receiver module. The tire modules consist of the MPXY80xx, the RF2, a battery, several discrete components, and a printed antenna. The receiver module has the MC33954, the KX8, five LEDs to display the status, a battery, a power supply connection, and an RS-232 serial interface.

App note: Crystal oscillator troubleshooting guide

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App note from NXP Semiconductors dealing with oscillators in microcontrollers. Link here (PDF)

Most microcontrollers can use a crystal oscillator as their clock source. Other options include external canned oscillators, resonators, RC oscillators, and internal clocks. The main advantages of a crystal oscillator are frequency accuracy, stability, and low power consumption. However, high reliability is needed to fully benefit from these advantages.

App note: Active cell balancing in battery packs

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Cell balancing implementation from NXP Semiconductors. Link here (PDF)

Batteries made of multiple cells connected in series are often used as a power source for common electronic devices. In multicell battery chains, small differences between the cells (due to production tolerances or operating conditions) tend to be magnified with each charge or discharge cycle. In these situations, weaker cells are overstressed during charging, causing them to become even weaker, until they eventually fail and cause a premature failure of the whole battery. Cell balancing is a way of compensating for these weaker cells by equalizing the charge on all the cells in the chain, thus extending the battery life.

App note: Reduced power dissipation of relay loads

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Another app note from ON Semiconductors on using PWM technique to reduce power consumed when latching mechanical relays. Link here (PDF)

Integrated circuit driver circuits often use relay loads in their application. Output drivers are a source of power dissipation on the IC. Latching relays can be used to keep sustaining load current at a minimum by engaging and removing drive current, but a PWM system can also preserve reduced power conditions by engaging and reducing duty cycle using standard type relays.

By considering the Maximum Turn−On Voltage and Minimum Turn−Off Voltage specifications typically quoted in the relay electrical specification, your system design can utilize a signal to pull−in and activate the relay followed by a reduced power PWM sustaining signal.

App note: The load switch – Selection and use of ecoSWITCH(TM) products

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ecoSWITCH(TM) from ON Semiconductors offers space saving solution on power distribution system. Link here (PDF)

Load switches play an important part in the management of supply domains and the protection of the loads they supply. Loads switches are often used for power sequencing, standby load leakage reduction, and inrush current control. Integrated ecoSWITCH products deliver an area reducing solution, offering over current protection, load soft start, and extremely low on series resistances of sub − 20 milliohm. This article discusses the primary benefits of load switches, application considerations, and how ecoSWITCH differs from other types of integrated switch offerings. A generic cloud system application and USB power delivery example are presented to demonstrate how the addition of ecoSWITCH solves design challenges such as achieving low quiescent current, local load protection, and startup sequencing.

App note: The behavior of electro-magnetic radiation of power inductors in power management

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Würth Elektronik app note on EM radiation emission from power inductors. Link here (PDF)

DC-DC converters are widely used in power management applications and the inductor is one of the key components. The usual focus is on electrical performance characteristics such as RDC, RAC and core losses. But, the electro-magnetic radiation characteristics can often be overlooked.

Due to the switching action in SMPS, AC voltage/current is produced over the inductor. Since, an inductor can, in effect, operate as a transmitting loop antenna, the electromagnetic radiation depends on a number of factors. These include the source properties such as core material, shielding material and the orientation of the start of the winding amongst others.

Electromagnetic radiation of an inductor in the low frequency spectrum range (100 kHz to 30 MHz), which is caused by the switching frequency and harmonics, is dependent on whether the inductor is shielded and the winding properties. Whereas, in the high frequency spectrum range (30 MHz to 1 GHz), where emissions are caused by ringing frequencies and their harmonics, the electromagnetic radiation is more dependent on the shielding characteristics of the core material, switching frequency and transitions of the switching converter.