Platform-dependent, leakage-aware control of the driving current of embedded thermoelectric coolers

One of the biggest stumbling blocks for the successful continuation of the Moore's law is the substrate temperature of VLSI circuits. Thermoelectric cooling is one of the promising cooling methods to combat high die temperatures. This method provides key benefits such as compactness, high reliability, and exceptionally high heat-pumping capability. On the other hand, even with the recent advances in the fabrication techniques, thermoelectric coolers (TECs) are suffering from a poor coefficient of performance (COP), which denotes the ratio of heat removed per second to the power needed to drive the TEC, is rather low. In this paper, different techniques to improve the performance of a TEC, when it is embedded inside a processor package, are investigated. In particular, first the COP of TECs is reformulated to consider the leakage power, which is exponentially dependent on the die temperature. Next it is demonstrated that the TEC driving current that yields the maximum decrease in the die temperature is quite different from the one that runs the TEC in its highest COP state. Based on these observations, a platform-dependent, leakage-aware cooling policy in which the TEC driving current is set based on the target specs (high-performance vs. low-power) and actual conditions of the chip (emergency vs. preventive thermal management) is proposed. Experimental results show that, with this policy, one can reduce the temperature of chip hotspots while achieving a high COP.