Module 51 min
Power Domains & Voltage Islands
A power domain is a group of logic that shares the same power supply and can be independently powered on/off or operated at different voltages. Modern SoCs have
A power domain is a group of logic that shares the same power supply and can be independently powered on/off or operated at different voltages. Modern SoCs have 5–20 power domains enabling fine-grained power management.
| Concept | Definition | Purpose |
|---|---|---|
| Power Domain | Group of logic sharing one supply rail | Enable independent power control |
| Voltage Island | Power domain at a different voltage from neighbors | Run some blocks slower/cheaper to save power |
| Always-On (AON) | Domain that never powers down | Retains critical state - PMU, RTC, wake logic |
| Switchable Domain | Domain that can be fully powered off | Zero leakage when block unused |
| Level Shifter | Cell that translates signal between voltage domains | Required at every domain boundary with different VDD |
| Isolation Cell | Cell that clamps output to known value when domain is off | Prevents floating signals from corrupting always-on logic |