I finally got to watch the critically acclaimed sci-fi movie “Inception” last weekend and life has not been the same since. Without giving away too much detail for the benefit of those who have not watched it yet, the main plot involves dreams within dreams within dreams – three levels to be precise—to “incept” an idea into someone’s subconscious mind. Are you still with me? Never mind, the first thing that came to my mind when I was exposed to the concept of dreams within dreams was – nested domains in multi-voltage (MV) designs. Blame the nerd gene for triggering this reaction, but the truth remains.
One thought led to another and before long I was dreaming about nested multi-voltage domains with donut shaped domains, which happens to be reality. The donut shaped nested domains is one of the new emerging flavors for nested multi-voltage designs and it brings a new set of requirements and challenges for the MV flow. Some of the key considerations for the donut shaped nested domains are:
• Number of levels of nested hierarchy
• Defining donut domains in the UPF
• Hierarchy and netlist management for the top level and the donut domains
• Placement of cells based on connectivity in the donut hole and the top level
• Handling of level shifters based on connectivity (need to be placed in the donut hole or the top level)
• Handling of isolation cells if the donut domain has a switching supply
• Power routing to the donut hole if the donut domain has a switching supply
• Power supply routing to the donut domain if the top level has a switching supply
• Handling power switches if either the donut or the top level has a switching supply
• Building a balanced clock tree for the donut domain
• Signal Routing within the donut domain boundary and meeting timing requirements
• Always-on buffer handling for the donut hole or the top level
• Ensuring power integrity for all the domains, etc.
Nested Donut Domains in Multi-Voltage Designs
If there are more than two levels of nesting with donut shapes this list will get even longer and much more complex. Why exactly a designer would need a donut domain is beyond me but whoever planted the idea is playing a cruel practical joke. Now, if you will excuse me I need to go and spin my top.
–Arvind Narayanan, Product Marketing Manager, Place and Route Product Line