Abstract

Advances in integrated circuit (IC) technology and packaging have led to the rapid growth of speed and integration of diverse functions in mobile devices. Three dimensional packaging of ICs allows for a high density of circuits and interconnects to fit into ever shrinking battery operated devices. Power optimization is especially important in these devices in order to preserve battery life. The increased functionality in devices comes with an increase in the interconnects between the ICs. Current electrical interconnect standards are not optimized for the characteristics of the interconnect it operates on. The work described in this dissertation explores a methodology for optimizing the transmitter power consumption for high-speed electrical links based on link performance measurements that takes fully into account the link characteristics.

Using link performance measurements, specifically the bit error rate (BER) or the signal interference ration (SIR), for dynamically controlling transmitter power has been applied by others to wireless communication links. Electrical links have much higher performance requirements, with BER values up to eight orders of magnitude lower than wireless links, and correspondingly large increase in the time to measure the link BER from seconds to days. This work presents a new accelerated BER testing technique that reduces the time to measure the link BER to seconds instead of days. This technique is integrated into the dynamic power optimization methodology for electrical interconnects.

The proposed methodology is applied to a current-mode transceiver operating over short links, similar to those that would be encountered in mobile and stacked environments. Two ASICs have been implemented, with the first designed to test as proof of concept the proposed methodology and the second designed to test the methodology when the number of links are scaled. Test systems have been built for the purpose of testing the ASICs. Experimental results from the test system show the ability of the accelerated BER technique to give an accurate extrapolation to the actual link BER. This confirms the presented dynamic transmitter power optimization methodology incorporating the accelerated technique is applicable to electrical interconnects.