On digital power management

Tony Armstrong, Linear Technology



Tony Armstrong, Linear Technology

The use of a standard serial digital bus, for example I2C, enables simple and efficient communications to and from digitally equipped DC/DC converters, and emerging standards like PMBus facilitate component interoperability. Important regulator parameters, including startup characteristics and timing, output voltages and current limits, margining specifications and over- and undervoltage supervisory limits can all be directly programmed digitally instead of set with resistors and space-consuming sequencing and monitoring products. Further, critical operating parameters such as temperature and input and output voltages and currents can be routinely monitored and used to optimize system performance and reliability.

A principal benefit of digital power system management (PSM) is reduced design cost and faster time to market. Complex multi-rail systems can be efficiently developed using a comprehensive development environment with intuitive graphical user interface (GUI). Such systems also simplify in-circuit testing (ICT) and board debug by enabling changes via the GUI instead of soldering in “white wire” fixes. Another benefit is the potential to predict power system failures and enable preventive measures, thanks to the availability of real-time telemetry data. Perhaps most significantly, DC/DC converters with digital management functionality allow designers to develop “green” power systems that meet target performance (compute speed, data rate, etc.) with minimum energy usage at the point of load, board, rack and even installation levels, reducing infrastructure costs and the total cost of ownership over the life of the product.

Linear Technology’s has developed a growing PSM product line that incorporates all of these capabilities and more. This includes synchronous step-down DC/DC controllers with integrated power FET gate drivers and comprehensive power management features accessed via the I2C-based PMBus. These include precision references and temperature-compensated analog current-mode control loops offering ±0.5% DC accuracy, easy compensation that is calibrated to be independent of operating conditions, cycle-by-cycle current limit, and fast and accurate current sharing and response to line and load transients without any of the ADC quantization-related errors found in products utilizing “digital” control.

Some of these systems also incorporate 16-bit data acquisition systems that provide digital read back of input and output voltages and currents, duty cycle and temperature. Also include is a fault logging capability via an interrupt flag along with a “black box” recorder that stores the state of the converter operating conditions just prior to a fault. Finally, multi-rail system development is facilitated though a Linear developed LTpowerPlay™ free software program that also includes an easy-to-use GUI interface.

Furthermore, we continue to invest in PSM products and will continue to release new products in this area on an annual basis. It is now evidently obvious that digital power system management holds the promise of enabling higher performance with lower energy usage in next generation green electronic systems. Although the initial applications were in high-end Enterprise computing systems, there are clear indications that PSM is migrating into many other market segments including industrial and medical systems.