Tag Archives: app notes

App note: HT45F3420 LED flashlight application

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Holtek’s HT45F3420 MCU provide LED flashlight application all in with minimal external components. Link here (PDF)

In traditional LED flashlight application circuits, the battery is used to directly drive the LED which will cause uneven brightness levels and the possibility of damaged LEDs due to changing battery conditions. Using the HT45F3420 for LED flash application, both buck and constant current techniques are used.

App note: BH45F0031 Earphone jack communication

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Holtek’s App note about their audio to digital signal converter chip BH45F0031 that together with an phone app, communication via audio phone jack is possible. Link here (PDF)

The BH45F0031 is a Flash type 8-bit high performance RISC architecture microcontroller, which is designed for smart phone headset interface applications that can directly transmit data and communicate with the microcontroller using their audio earphone interface.

The BH45F0031 can convert the analog audio signals from mobile phones into digital data and transmit them to a master external MCU. The device can also convert the digital data from the master MCU into analog audio signals and transmit them to mobile phones.

App note: Charging batteries using USB power

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Fairly old application note from MAXIM Integrated about getting out power from USB ports. Link here (PDF)

Many devices with rechargeable batteries use USB power to recharge the batteries while they are connected. This application note describes the power available from USB and how it can be used to charge batteries, including circuits and some hints.

App note: Improve flicker performance of direct AC driven LED fixtures with self valley fill

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Application note from ON Semiconductors on LED lighting flicker caused by its own AC supply by adding an improved self valley fill circuit. Link here (PDF)

To provide power to LED loads from AC input, SwitchMode Power Supplies (SMPS) are generally used since LED need to be driven by regulated current. Consequently, LED lighting solution have to inherit the design complexity of a typical SMPS which includes designing the magnetic component, handling of Electromagnetic Interferences (EMI) as well as implementing Power Factor Correction (PFC). Direct-AC Drivers (DACD) for LEDs provides a new way to drive the LED load from an AC input with much simpler system architecture while satisfying EMI and power factor (PF) requirements with minimal effort. However, its drawback is flickering of light output at the zero crossing of AC line voltage due to loss of current to the LED load.

Though flicker is not always obvious, it can still cause headaches for a small percentage of people exposed to flickering lights for long periods. This is a major issue for offices, schools, stores and other brightly lit commercial and industrial spaces where people spend a lot of time.

App note: Using touch interface in harsh environments

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Tough design and software reference from NXP of touch interface. Link here (PDF)

The touch-sensing method is used to replace most of traditional tact switch inputs as a new type of human-machine interface used in home-appliance applications. However, using such kind of detection method in harsh environment is still a challenge for most of product designers. A good balance of fast response and no false trigger in key detection is always an essential factor for the user-interface design. The touch-sensing input (TSI) module in Freescale MCUs provides capacitive touch detection with high sensitivity and durability, which can help customers to adapt this kind of human touch-sensing technology quicker.

This application note describes how to use the S08PT family MCU features in applications with emphasis on both touch-sensing interface and safety aspect. Different techniques in circuit design, intelligent software control and reliable mechanical structure are illustrated in this application note to show how to achieve a product design with protection features for handling faults and fast TSI response without any false trigger in extreme conditions. Most of the critical scenarios and unexpected use cases from the end-user point of view must be fully studied and well-covered in advance to prevent any serious flaw persisting in the final design stage which causes significant delay in the whole project schedule.

App note: Water level monitoring

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A reference design from NXP about water level detection using pressure sensor. Link here (PDF)

Many washing machines currently in production use a mechanical sensor for water level detection. Mechanical sensors work with discrete trip points enabling water level detection only at those points. The purpose for this reference design is to allow the user to evaluate a pressure sensor for not only water level sensing to replace a mechanical switch, but also for water flow measurement, leak detection, and other solutions for smart appliances. This system continuously monitors water level and water flow using the temperature compensated MPXM2010GS pressure sensor in the low cost MPAK package, a dual op-amp, and the MC68HC908QT4, eight-pin microcontroller.