Power Management

Which is NOT a reason chips need margin in their supply voltage?

  1. AWhen circuits switch together, supply wiring resistance and inductance cause momentary voltage drops (supply noise)
  2. BHigher voltage always reduces power consumption
  3. CManufacturing variation, temperature and aging change circuit speed
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Answer: B. Higher voltage always reduces power consumption

Circuits slow down with even a slight voltage drop and can miss timing. When many circuits switch at once, resistive drop in the supply wiring (IR drop) and inductive voltage from rapid current changes momentarily lower the voltage. Speed also varies with process, temperature and aging, so some margin is needed. But margin also wastes power, so it is reduced through stronger power delivery networks, AVS and similar techniques.

  • A. This is a reason margin is needed.
  • B. Correct. Raising voltage increases power.
  • C. This is a reason margin is needed.
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More Power Management questions

  1. What is an advantage of placing the regulators that generate CPU supply voltages inside the chip or package rather than on the motherboard (integrated regulators)?
  2. Why is the energy-delay product (EDP) sometimes preferred over energy alone in evaluating low-power designs?
  3. What is the closest efficiency of a linear regulator (LDO) producing 1.0 V from a 1.8 V input (ignoring the regulator's own quiescent current)?
  4. A device drawing 300 mA on average runs from a 3000 mAh battery. Roughly how many hours does it run (ignoring voltage drop and similar)?
  5. What is the difference between power and energy?