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Different electrical requirements for different applications
Because the requirements that a semiconductor device must satisfy vary according to the application, so do the device's specifications, electrical characteristics, and noise countermeasures. To illustrate these differences, three types of devices - communication, microprocessing units, and consumer applications - are compared. To prevent the user's having to scroll too much, hyperlink the words shown above to the appropriate sections below. |
Communication devices |
| The main aim in the case of communication devices is acceleration of the transfer rate. The conventional approach has been to use parallel transmission, increasing the transfer rate by expanding the width of the bus to several signal lines. However, raising the clock frequency to increase the speed makes signal synchronization difficult, and both simultaneous switching noise and cross-talk noise are likely to be generated. Given these disadvantages, the main trend these days is to use serial transfer whereby one signal line with a narrow bus width is used to make it difficult for noise to be generated, and to raise the transfer rate by increasing the clock frequency. In this case, however, jitter and attenuation may pose problems. To solve these problems from the viewpoint of the signal characteristics of the package, the extent to which the characteristic impedance differences from one constituent to another can be averaged is important. The TBGA, which uses coplanar wiring, can be cited as a package type that lends itself to such averaging. Further, as the number of channels increases, power supply stability becomes increasingly important. The package must therefore be selected taking into consideration the power characteristics, in addition to the signal characteristics. |
| MPU devices |
| The main aim in the case of microprocessing unit (MPU) devices is increasing the processing speed. Increasingly high clock frequencies have been used for this purpose. At the same time, however, the voltage must be lowered, resulting in a lower noise margin, and making the device more susceptible to noise. The package type best suited for solving this problem is the FCBGA, which supports the placement of power pins on the entire surface and features the shortest connection distance between the chip and solder balls. This package, however, is still expensive. If cost is a priority, a lower-priced package should be selected and components that stabilize the supply voltage, such as capacitors, should be connected to the chip, keeping the connection distance as short as possible. |
| Consumer devices |
| The main aim for many consumer devices is low cost. Therefore, the cheapest possible package should be selected. If the size of the package can be reduced, the cost can be lowered even further, so it is effective to decrease the number of power and ground pins as much as possible. An aspect that may be overlooked by old-timers with many years of experience in consumer devices is that, even in the case of low-cost devices, the trend has been toward ever higher clocks speed and lower voltage. This has resulted in low-cost devices becoming increasingly susceptible to noise, so that noise levels that could safely be ignored in the past may now be a problem that requires the implementation of countermeasures. |
Electrical Design Characteristics Supported by Various Packages |
Transfer Clock Frequencies and Bus Widths Supported by Various Packages  |
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