Embedded System for Temperature Control of Large-Scale Integrated Circuits

Abstract

An embedded system is designed for the control of Temperature of VLSI chips during their operation. Due to the very high packing density, VLSI 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 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.

Introduction

With rapid advancements in VLSI technology, modern ICs pack a large number of transistors into very small areas, causing high heat generation and creating serious thermal management challenges. CPU chips now dissipate around 100 W with peak power densities of 400–500 W/cm², and rising temperatures lead to degraded performance, timing issues, and reduced operating frequencies. Effective cooling is therefore essential to maintain reliable chip performance.

Traditional cooling methods such as heat sinks, fans, heat pipes, and clock throttling are commonly used. Fans are effective but noisy, while clock throttling reduces performance. To address these issues, the present work designs a hardware-based automatic fan speed control system using an LM35 temperature sensor and an ARM7-based microcontroller.

The LM35 provides accurate, linear temperature readings, which are fed to the ARM processor’s ADC. Based on this input, the processor generates a PWM signal to control a brushless DC fan through an L293D driver IC. A graphic LCD displays the current temperature and fan speed, while a buzzer alerts in case of overheating or fan failure.

The system is developed using ARM IAR Workbench and programmed via Flash Magic using the LPC2378 microcontroller, which provides extensive communication interfaces, ADC/DAC units, timers, and a PWM module.

Testing with various chips (Pentium processor, FPGA, etc.) shows that fan speed increases automatically with rising temperature, effectively maintaining safe operating conditions.

However, the study highlights challenges such as:

• Temperature measured near the chip may differ from actual die temperature.

• External sensors have thermal delays.

• Low-frequency PWM fan control can cause audible noise.

• Sudden fan speed changes can be annoying in user environments.

It suggests that using on-chip thermal diodes and limiting fan speed change rates can improve accuracy and user comfort.

Conclusion

In recent times, the industry has witnessed rapid developments in VLSI technology, the IC designers are trying to put more transistors in a very small package. So, the ICs run at higher speeds and produce large amount ofheat which creates the problem of thermal management. For example, nowadays the CPU chips arebecoming smaller and smaller with almost no room for the heat to escape. The total power dissipationlevels now reside on the order of 100 W with a peak power density of 400-500 W/Cm2, and are stillsteadily climbing [1,2]. As the chip temperature increases its performance is very much degraded byparameters shift, decrease 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 andover 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 usuallyemployed. 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 varyingthe fans speed based on temperature i.e. the fan can turn slowly when the temperature is low and canspeed up as the temperature increases.

References

[1] Ma Kunquan and Liu Jing, Liquid Metal Cooling in Thermal Management of Computer Chips, FrontiersEnergy Power Engineering China, 2007, Vol.1, No. 4, 2007, pp. 384-402. [2] Narasimha Murthy Yayavaram, Saritha Chappidi, Sukanya Velamakuri,Embedded Processor Based Automatic Temperature Control of VLSI Chips,Sensors & Transducers Journal,Vol.100, Issue1,January 2009 [3] MAXIM Application note 707, Fan speed Control is Cool, Feb. 02, 2001. [4] National Semiconductor’s Temperature Sensor Hand Book. [5] ARM Architecture Reference Manual, Addison-Wesley, 2001. [6] Philips Semiconductors – LPC2378 Manual. [7] Philips ISP Software, LPC 2000 Flash magic, http://www.esacademy.com [8] MAXIM Application Note 3173, Automatic Fan Control Techniques: Trends in Cooling High – SpeedChips, July 08, 2004. [9] http://maxim-ic.com

Copyright

Copyright © 2025 Dr. K.P. Venkateswara Rao, Dr. M. Baba Fakruddin. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.