Inrush Currents Tamed – Part 3

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17 June 2018

In part 1 and part 2 of my blog, we looked at the capabilities that the EDA tools provided in the area of supply network analysis as well as the different methods of power shut off control. In this third blog, we will look at inter-domain switch control and role it plays in further taming the inrush currents.

Inter-Domain Switching Control

We must also consider the inter-domain switching control methods during our supply network analysis. Here each method provides a way to control the simultaneous switching of multiple logic domains.

  • No control – logic domains may all transition at the same time. This can cause higher peak inrush currents to occur and require longer switch control delays, additional decoupling capacitance or larger physical power rails.
  • Sequential domain list – reduces the simultaneous transitions to one by following a fixed sequence for the domain transitions. This limits the inrush current to a single domain at a time, but increases total transition time.
  • First level grouping based on state followed by a sequential domain list – reduces the simultaneous transitions to one by processing the domains in a series of groups defined by the operating point state then, within each group following a fixed sequence for the domain transitions. This allows the transition order to be modified per operating point state. The inrush current is again limited to a single domain at a time, but increases total transition time.
  • Cost model per supply – reduces the simultaneous transitions to a smaller number based on a cost model per domain and a limit per supply. Domains with a small cost may transition if the supply remains under a limit. Domains with a large cost may have to wait until other transitions complete. This reduces the total time to transition a series of domains and still maintain an acceptable inrush current.

Read the full blog here

Greg Ehmann

Greg Ehmann is EPU Architect at Sonics.