Making digital power control viable for high-current DC-DC designs

January 28, 2014 // By Ben Dowlat
Ben Dowlat, Senior Product Director (Linear and Power), Micrel explains how technology improvements can make digital power control viable for high-current DC-DC designs.

Digital power control has, in the past, been one of those technologies that appears superficially attractive, but that fails to gain a toehold in the market because of a single, deal-breaking drawback. In the case of digital power, this drawback has been latency – the time between the acquisition of the feedback signal and the generation of the subsequent modulated output.
This latency has resulted in slower transient response than equivalent analog controllers. In high-performance systems that require an instantaneous response to a change in load, the use of a slow digital power controller is out of the question.
Now two changes are serving to swing the balance decisively in favor of digital power control in high-performance computing and networking applications such as data centers and server farms. Here, the demand for improved energy efficiency and energy cost reduction is leading to new and innovative uses of granular and real-time power consumption data – information that is easily available from a digitally-controlled power architecture.
At the same time, incremental improvements in the implementation of digital power control designs have recently led to reductions in latency in the digital control loop, resulting in transient response times even better in some cases than equivalent analog controllers can offer.

Telemetry in large server installations
One of the great advantages of a digital power controller is that intelligence is an inherent feature of the device’s mode of operation – it comes, as it were, for free, in the same IC that implements power control. This intelligence supports the provision of attractive features that digital system designers can readily appreciate. At the simplest level, these will typically include output voltage margining, and telemetry of key parameters such as voltage, current and temperature.
The digital architecture also enables the easy configuration of these and many other operational parameters in a software design environment normally hosted on a PC. The straightforward selection

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