1、基于嵌入式处理器的vlsi芯片的温度自动控制英文翻译大学本科毕业论文Embedded Processor Based Automatic Temperature Control of VLSI ChipsAbstractThis paper presents embedded processor based automatic temperature control of VLSI chips, using temperature sensor LM35 and ARM processor LPC2378. Due to the very high packing density, VLSI
2、chips get heated very soon and if not cooled properly, the performance is very much affected. In the present work, the sensor which is kept very near proximity to the IC will sense the temperature and the speed of the fan arranged near to the IC is controlled based on the PWM signal generated by the
3、 ARM processor. A buzzer is also provided with the hardware, to indicate either the failure of the fan or overheating of the IC. The entire process is achieved by developing a suitable embedded C program. Keywords: Temperature sensor, ARM processor, VLSI chips, Brushless DC motor1.IntroductionWith t
4、he phenomenal developments in VLSI technology, the ambitious IC designers are trying to put more transistors in to smaller packages. So, the ICs run at higher speeds and produce large amount of heat which creates the problem of thermal management. For example, nowadays the CPU chips are becoming sma
5、ller and smaller with almost no room for the heat to escape. The total power dissipation levels now reside on the order of 100 W with a peak power density of 400-500 W/Cm2, and are still steadily climbing. As the chip temperature increases its performance is very much degraded by parameters shift, d
6、ecrease in operating frequencies and out-of specification of timings. So the high speed chips 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
7、 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 als
8、o generate a great deal of acoustic noise. This noise can be reduced significantly by varying ,the fans speed based on temperature i.e. the fan can turn slowly when the temperature is low and canspeed up as the temperature increases.The other prominent method is clock throttling i.e. reducing the cl
9、ock speed to reduce power dissipation. But it also reduces the system performance and the systems functionality is lost.So, 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
10、by the sensor LM35.The LM35 series are precision integrated-circuit 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
11、 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 14C at room temperature and 34C over a full 55 to +150C temperature range. Low cost is assured by trimming and calibration
12、 at the wafer level. The LM35s 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 A from its supply, it has very low se
13、lfheating, less than 0.1C in still air. The LM35 is rated to operate over a 55 to +150C temperature range, while the LM35C is rated for a 40 to +110C range (10 with improved accuracy). The LM35 series is available packaged in hermetic TO-46 transistor packages, while the LM35C, LM35CA, and LM35D are
14、 also available in the plastic TO-92 transistor package. The LM35D is also available in an 8-lead surface mount small outline package and a plastic TO-220 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 c
15、hanged in accordance to the output of the LM35temperature sensor. So the important component of this entire project is the temperature sensor.2. DescriptionIn ARM processor based automatic temperature control system, the output of the temperature sensor is fed to the on chip ADC and the output of th
16、e 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 whic
17、h 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.Fig. 1. Block diagram.Fig. 2. Circuit Diagram.3. Software DescriptionThe present work is implemented using ARM IAR Workbench IDE and the necessary embe
18、dded C program is developed and dumped into the embedded processor using Flash magic ISP Utility. The ARM IAR Workbench IDE is a very powerful Integrated Development Environment (IDE) that allows you to develop and manage complete embedded application projects. In-System Programming is programming o
19、r reprogramming the on-chip flash memory, using the boot-loader software and a serial port. The LPC2387 microcontroller is based on a 16-bit/32-bit ARM7TDMI-S CPU with real-time emulation that combines the microcontroller with 512 kB of embedded high-speed flash memory.A 128-bit wide memory interfac
20、e and unique accelerator architecture enable 32-bit code execution at the maximum clock rate. For critical performance in interrupt service routines and DSP algorithms, this increases performance up to 30 % over Thumb mode. For critical code size applications, the alternative 16-bit Thumb mode reduc
21、es code by more than 30 % with minimal performance penalty.The LPC2387 is ideal for multi-purpose serial communication applications. It incorporates a 10/100 Ethernet Media Access Controller (MAC), USB full speed device with 4 kB of endpoint RAM,four UARTs, two CAN channels, an SPI interface, two Sy
22、nchronous Serial Ports (SSP), threeI2C interfaces, and an I2S interface. This blend of serial communications interfaces combined with an on-chip 4 MHz internal oscillator, 64 kB SRAM, 16 kB SRAM for Ethernet, 16 kB SRAM for USB and general purpose use, together with 2 kB battery powered SRAM makes t
23、his device very well suited for communication gateways and protocol converters. Various 32-bit timers, an improved 10-bit ADC, 10-bit DAC, one PWM unit, a CAN control unit, and up to 70 fast GPIO lines with up to 12 edge or level sensitive external interrupt pins make this microcontroller particular
24、ly suitable for industrial control and medical systems.The LPC2378 Microcontroller provides on-chip boot-loader software that allows programming of the internal flash memory over the serial channel. Philips provides a utility program for In-System programming called Flash magic Software.4. Results a
25、nd ConclusionsEmbedded ARM processor based automatic speed control DC motor fan is designed and implemented.To test the validity of the design, the temperature sensor is kept inside a small oven and its temperature is increased beyond the room temperature. Now the fan is operated to run with full sp
26、eed and the temperature is found to comeback to normal temperature. This is repeated with various VLSI chips like Pentium processor, FPGA chips etc. Now the temperature sensor is kept very near to the Pentium processor of the computer and it is observed that, as the time lapses the speed of the fan
27、is automatically increased and the temperature of the chip is found to be controlled. These results are displayed on LCD panel. Though the present system is working well in the given environment, still it is worthwhile to highlight the following conclusions. Normally, controlling fan speed or clock
28、throttling based on temperature requires that the temperature of the high speed chip should be first measured. This is done by placing a temperature sensor close to the target chip either directly next to it or in some cases, under it or on the heat sink. The temperature measured in this way corresp
29、onds to that of the high speed chip, but can be significantly lower and the difference between measured temperature and the actual die temperature increases as the power dissipation increases. So, the temperature of the circuit board or heat sink must be correlated to the die temperature of the high
30、 speed chip. Of course a better alternative is possible with a number of high speed chips. Many CPUs, FPGAs and other high speed ICs include a thermal diode which is actually a diode connected bipolar transistor, on the die. Using a remote diode temperature sensor connected to this thermal diode, th
31、e temperature of the high speed ICs die can be measured directly with an excellent accuracy. This not only eliminates the large temperature gradients involved in measuring temperature outside the target ICs package, but it also eliminates the long thermal time constants,from several seconds to minut
32、es, that cause delays in responding to die temperature changes.There is also a drawback in fan speed control. Normally the fan speed is controlled by adjusting the power supply voltage of the fan. This is done by a low-frequency PWM signal, usually in the range of about 50 Hz, whose duty cycle is va
33、ried to adjust the fans speed. This is inexpensive and also efficient. But the disadvantage of this method is that it makes the fan somewhat nosier because of the pulsed nature of the power supply. The PWM waveforms fast edges cause the fans mechanical structure to move, which is easily audible.In some systems, it is al
