A compact low voltage high current power supply for digital applications

In order to reduce power consumption and improve device performance, the current trend in digital electronics is toward reduced operating voltages. While these reduced voltages of 3.3 V or 1.9 V are ideal for the digital system, this trend possesses great difficulties for power supply designers. This problem is only exacerbated by the increased system complexity and therefore power requirements of the system. The result is a dramatic increase in the current levels which must be provided. In addition, in order to save power, many of these systems utilize sleep states which are highly effective in reducing the overall power usage, however, the instantaneous current that is required to bring the system out of sleep mode adds a further complication to the power supply design. This paper seeks to address some of the issues related to the physical design and fabrication of high reliability, high current power supplies for digital systems applications. A low voltage high reliability power supply has been fabricated using direct bond copper and ceramic MCM technology. The module is intended to provide local power to a processor card, and its low profile design allows direct mounting to the card. Input voltages of 60-70 Volts DC are converted to 3.3 Volts DC with a maximum power rating of 100 watts. With its compact size, the power density of this circuit exceeds 157 watts/in(3). This paper will discuss the issues related to the design and fabrication of high current supplies in general as well as the techniques used for this prototype supply.