Power Management

What is the role of the isolation cells placed between a powered-off block and running blocks?

  1. ATo pass a fixed value (0 or 1) to the running side even when the powered-off block's outputs become undefined
  2. BTo convert supply voltages between the two blocks
  3. CTo cool the powered-off block
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Answer: A. To pass a fixed value (0 or 1) to the running side even when the powered-off block's outputs become undefined

Outputs of a powered-off block float at undefined intermediate voltages, which could make receiving circuits malfunction or draw shoot-through current in their input stages. Isolation cells clamp those outputs to fixed values while the block is off. Which signals are clamped to which values is conveyed to design tools in a file describing the power intent.

  • A. Correct. It keeps undefined values from spreading.
  • B. Voltage conversion is the level shifter's job.
  • C. It has nothing to do with temperature.
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More Power Management questions

  1. What is the role of a level shifter inserted when passing signals between two blocks running at different supply voltages?
  2. What is the main purpose of dividing an SoC into multiple power domains?
  3. What is the break-even time used to decide whether powering off an idle block pays off?
  4. Which describes CPU C-states?
  5. Which describes CPU P-states?