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Union Semiconductor Application Notes



Union Semiconductor

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ESD Protection
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Portable Systems Demand Properesd Protection


Portable product designers are constantly challenged to make smaller devices with increased functionality. Doing so calls for more complex semiconductors, requiring submicron processes. In turn, these semiconductors become increasingly more sensitive to the effects of electrostatic discharge (ESD). Portable systems are constantly exposed to ESD. An unsuspecting user can inject a hazardous charge during normal device operation, and then perceive the resulting system failure as poor product quality...

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ESD Protection & Solution in Portable Design


Integrating simple protection on complex ICs is expensive and it is low level

  • IC gate oxides are thinner and are more sensitive to ESD events
  • Protector are most effective when placed farther from the major ICs
  • Designing in ESD/EMI protection up front is cost effective…..
  • Avoid re-designs after a failure during certification tests
  • Avoid cost of returned product from end customers

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ESD Protection for High Speed IO Data Lines


These days, our modern society has rapidly come to fully depend on electronics. And modern computers are based increasingly on low power logic chips, all with ESD sensitivity due to MOS dielectric breakdowns and bipolar reverse junction current limits. The ICs that control I/O ports (USB, Ethernet, etc.) are not an exception since the majority of them are designed and manufactured based on CMOS processes which make them extremely sensitive to damage from ESD conditions...

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EMI ESD Filters for Cellular Phones


Cellular phones, as with all handheld and wireless devices are susceptible to the damaging effects of Electrostatic Discharge (ESD) transients. As much as 40KV of ESD can be generated by the human body or through air discharge. In addition, cellular phones, because of their higher operating frequencies, are more sensitive to EMI/RFI interference. Global authorities are now imposing very strict regulations to ensure that cellular phones are electrically 'clean' before being released to the market...

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Interface
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Level Translator For SPI and I²C Bus Signals


A serial interface is often used for board-level communication between different integrated circuits, especially in space-constrained applications at low-to-medium data rates. The most popular serial interfaces are I²C and SPI. If a system has different supply voltages for the μP and for peripheral devices, suitable level translators are required to be able to use one of these serial interfaces. There are several reasons why today’s systems have two or more supply-voltages....

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Choosing the Right RS-485 Transceiver


At some time during the design of an RS-485 system, a maximum data rate appropriate for that system is determined. Then it becomes necessary to choose the physical RS-485 devices that are capable of running at this speed. Devices are selected that are rated for speeds equal to or greater than the required data rate...

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Choosing the Right RS-232 Transceiver


The RS-232 standard requires signal levels of +5V (minimum) for a low and -5V (minimum) for a high. A higher voltage swing ensures greater noise immunity after the signals travel through lossy cables to RS-232 receivers. Early RS-232 transceivers required dual power supplies. Most circuit boards included a negative power supply solely to power these devices...

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Interface Primer


Line drivers and receivers are commonly used to exchange data between two or more points on a network. Typically, this communication takes place between a personal computer or controller and a local peripheral (e.g. printer). Reliable data communications can be difficult in the presence of induced noise, ground level differences, impedance mismatches, failure to effectively bias for idle line conditions, and other hazards associated with installation of a network....

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Analog Switch &
Multiplexer
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Selecting the right CMOS Analog Switch


First developed about 30 years ago, integrated analog switches often form the interface between analog signals and a digital controller. This tutorial presents the theoretical basis for analog switches and describes some common applications for them. In recent years, integrated analog switches have offered better switching characteristics, lower supply voltages. Because so many performance options and special functions are available, the well-informed product designer can usually find the right part for a particular application...

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Low-Icct Analog Switches for Ultra-portable Designs


Union Semiconductor has revolutionized and enhanced the design of analog switches to meet the demand for ultra-portable products, such as cell phones. Greater integration and improvements in the process technology involves using different voltage rails to power and control the analog chipset. To solve this problem, Union, a leading analog switch supplier, has introduced new analog switches and begun to offer modified versions of existing products. This new generation of analog switches offers an expanded control input range, while maintaining low current consumption and rail-to-rail signaling...

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Balanced modulator demodulator employing UM4684


The UM4684 can be used as a balanced modulator/demodulator at carrier frequencies up to 500kHz. Higher frequencies are possible, but as frequency increases, small imbalances in the UM4684’s internal capacitance and resistance gradually impair performance. Input signal is fed into common node of UM4684, carrier is applied as a logiclevel square wave to analog switch control terminal, for best carrier suppression, the square wave should have a precise 50% duty cycle, and both the input and output signals should be symmetrical about ground...

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Low Resistance Analog Switches Permit Speaker Switching


Cellular phones, as with all handheld and wireless devices are susceptible to the damaging effects of Electrostatic Discharge (ESD) transients. As much as 40KV of ESD can be generated by the human body or through air discharge. In addition, cellular phones, because of their higher operating frequencies, are more sensitive to EMI/RFI interference. Global authorities are now imposing very strict regulations to ensure that cellular phones are electrically 'clean' before being released to the market...

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Low-Voltage Fault Protection


The standard supply voltages for today's systems (unipolar 3.3V or 5V, or bipolar ±3.3V or ±5V) are usually the highest voltages available on a board. The board's input terminals may be exposed to voltages higher than the supply voltages. When power to the board is off, voltages may remain at the input terminals. The first element to be affected by over-voltage is often a multiplexer or a switch, so they must protect downstream circuitry...

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