February 1, 2010 -- Years ago, systems designers had it relatively easy with respect to system power supplies. Logic ran on 5-V power; hard- and floppy-disk drives needed a 12-V supply; and the rest of the system would operate off those two supply voltages plus perhaps one more negative-voltage supply. Those days are long gone.

Today’s complex logic devices (FPGAs, ASICs, SoCs, ASSPs, etc.) have far more complex power requirements. Just one such chip in a system may need three or four supply voltages. Worse, the order and timing in which these multiple supply voltages come up can be critical to successful system initialization. The order in which these voltages switch off during power-down operations may also be critically important to proper chip shut-down and can also be critical to preventing supply-induced damage to the IC.

Further, power subsystems must actively interact with many of today’s complex systems in real time and must permit real-time reconfiguration based on rapidly fluctuating line and load requirements. In short, power supply subsystem design for today’s complex digital systems calls for far more thought and consideration than ever before, prompting the development of power-management subsystems designed to meet the increasingly complex needs of today’s system designs. System designers have less time to think about these issues than ever because they’re far more concerned with getting their hugely complex systems operational.

By Tim Maloney. (Maloney is with Exar Corp.)