Most of today's CPLDs (com-plex programmable-logic devices) feature reduced-power operating modes, but, when the system is not in use, a complete shutdown that conserves battery power remains the ultimate power-reduction goal of many designers. Figure 1 shows how you can add a few discrete components to a CPLD—in this example, an Altera EPM570-T100—to implement a battery-powered system's power-down circuit. An external P-channel MOSFET, Q_1, an International Rectifier (www. irf.com) IRLML6302 or equivalent, serves as a power-control switch for the CPLD, IC_1, and other components in the system.
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