自动化专业毕业设计外文翻译--基于嵌入式处理器的vlsi芯片的温度自动控制(编辑修改稿)

自动化专业毕业设计外文翻译--基于嵌入式处理器的vlsi芯片的温度自动控制(编辑修改稿)内容摘要：

hips must be cooled to maintain good performance for the longest possible operating time and over the widest possible range of environmental conditions. The maximum allowable temperature for a high speed chip to meet its parametric specifications depends on the process and how the chip is designed. Among the various cooling techniques, heat sinks, heat pipes, fans and clock throttling are usually employed. Among these techniques, fans can dramatically reduce the temperature of a high speed chip,but they also generate a great deal of acoustic noise. This noise can be reduced significantly by varying ,the fans speed based on temperature . the fan can turn slowly when the temperature is low and canspeed up as the temperature other prominent method is clock throttling . reducing the clock speed to reduce power dissipation. But it also reduces the system performance and the systems functionality is , the objective of the present work is, to design a hardware system consisting of a brushless DC motor fan whose speed is controlled based on the temperature of the chip, sensed by the sensor LM35 series are precision integratedcircuit temperature sensors, whose output voltage is linearly proportional to the Celsius (Centigrade) temperature. The LM35 thus has an advantage over linear temperature sensors calibrated in Kelvin, as the user is not required to subtract a large constant voltage from its output to obtain convenient Centigrade scaling. The LM35 does not require anyexternal calibration or trimming to provide typical accuracies of 177。 1⁄4176。 C at 8 room temperature and 177。 3⁄4176。 C over a full −55 to +150176。 C temperature range. Low cost is assured by trimming and calibration at the wafer level. The LM35’s low output impedance, linear output, and precise inherent calibration make interfacing to readout or control circuitry especially easy. It can be used with single power supplies, or with plus and minus supplies. As it draws only 60 μA from its supply, it has very low selfheating, less than 176。 C in still air. The LM35 is rated to operate over a −55176。 to +150176。 C temperature range, while the LM35C is rated for a −40176。 to +110176。 C range (−10176。 with improved accuracy). The LM35 series is available packaged in hermetic TO46 transistor packages, while the LM35C, LM35CA, and LM35D are also available in the plastic TO92 transistor package. The LM35D is also available in an 8lead surface mount small outline package and a plastic TO220 package. To monitor the voltage at the terminals of the DC motor fan, the PWM signal is generated by the ARM7TDMI processor. This PWM signal is changed in accordance to the output of the LM35temperature sensor. So the important ponent of this entire project is the temperature sensor. 2. Description In ARM processor based automatic temperature control system, the output of the temperature sensor is fed to the on chip ADC and the output of the ADC is given to the L293D driver IC which in turn is fed to DC motor fan as shown in the block diagram in Fig. 1. A graphic LCD (128x64 pixels) is interfacedto the ARM LPC 2378 processor to display the temperature of the IC and the speed of the fan. A buzzer is also connected to the processor which gives an indication, in case of the failure of the fan or overheating of the chip beyond some level. The entire circuit diagram is shown in Fig. 2. 9 Fig. 1. Block diagram.。