Contents
What are isolation cells in VLSI?
Isolation cells are additional cells inserted by the synthesis tools for isolating the buses/wires crossing from power-gated domain of a circuit to its always-on domain. The isolation list is a list which consists of all the buses/wires that needs isolation cells.
Where should level shifters be placed?
The level shifter should be placed in the destination domain of the design. There is one disadvantage of inserting the level shifter – it occupies area in design. But, at the same time, inserting the level shifter will help in saving the power of the chip.
Where are isolation cells placed?
Isolation cells are physical only cells which are placed at the interface between the power domain area which are shut down and always on.
How are level shifters used in isolation cells?
Like isolation cells, level shifters are inserted by the synthesis tool. Low to High LS are used for signals crossing from a lower voltage domain to higher voltage domain. It basically amplifies the source signal so that it can be interpreted properly in the destination domain.
How are level shifters used in multi voltage designs?
As Multi Voltage designs have more than one voltage domain, level shifters are used for all the signals crossing from one voltage domain to another voltage domain. Like isolation cells, level shifters are inserted by the synthesis tool.
How are power intent, signal isolation and level shifting controlled?
Power intent, signal isolation and level shifting can all be controlled in a UPF-based multi-voltage IC design through careful coding. A hierarchical design flow offers advantages over a flat approach in part because it enables the problem to be broken down into blocks that can be worked on in parallel.
Where to place a level shifter in an UPF IC?
For example, if a signal is transitioning between two power domains, the required level shifter could be placed in either of the power domains, or on the top-level net connecting them.