Power Intent

Power intent is the formal specification of a chip's power architecture — defining all power domains, voltage levels, power switches, isolation requirements, retention strategy, level shifters, and power state transitions in a structured, machine-readable format that drives the entire low-power design and verification flow.

What Power Intent Specifies

• Power Domains: Which logic blocks belong to which power domain — each domain has its own supply voltage and power management capability.
• Supply Networks: The VDD and VSS connections for each domain — real (always-on) vs. virtual (switchable) supplies.
• Power States: The set of valid power modes the chip can be in — e.g., all-on, core-off, deep-sleep, hibernate — and the allowed transitions between them.
• Power Switches: Which domains can be gated, what switch cells to use, and the control signals.
• Isolation: At each domain boundary, the type of isolation (clamp-0, clamp-1, latch), the isolation control signal, and which direction (input/output) requires isolation.
• Retention: Which flip-flops in a switched domain need retention, the save/restore control signals, and the retention cell type.
• Level Shifters: Where voltage level conversion is needed between domains at different voltages — the type and location of level shifter cells.
• Power Sequencing: The order in which domains are powered up/down, when isolation and retention signals are asserted/de-asserted.

Why Power Intent Is Needed

• Modern SoCs have 10–50+ power domains with complex interactions — manually tracking all requirements is error-prone and unscalable.
• Power intent provides a single source of truth that all EDA tools consume:
• Synthesis: Inserts isolation cells, level shifters, retention flops.
• Place and Route: Places power switches, routes multiple supply networks, places special cells at domain boundaries.
• Verification: Checks that all power intent rules are correctly implemented — no missing isolation, correct level shifting, proper sequencing.
• Simulation: Power-aware simulation models domain shutdowns and their effects on functionality.

Power Intent Formats

• UPF (Unified Power Format): IEEE 1801 standard. Industry-standard, supported by all major EDA vendors. Synopsys-originated.
• CPF (Common Power Format): Si2/Cadence format. Alternative to UPF, primarily used in Cadence flows.
• Both specify the same concepts — power domains, switches, isolation, retention, level shifters — in different syntax.

Power Intent in the Design Flow

1. Architecture: Architect defines the power domain structure and power states.
2. UPF/CPF Authoring: Write the power intent file describing all domains and requirements.
3. Synthesis: Tool reads UPF/CPF, inserts special cells, implements power structure.
4. P&R: Physical implementation with power switches, dual-rail routing, special cell placement.
5. Verification: Power-aware simulation and formal checks validate correctness.
6. Sign-Off: Final power integrity and low-power verification.

Power intent is the blueprint of low-power design — it transforms the power architect's vision into a precise, verifiable specification that drives every step of the implementation flow.