In complex mixed-signal ASIC development, Real Number Modeling (RNM) has become an essential tool for fast, high-level verification of analog functionality. These models abstract continuous analog behavior into real-valued signal representations, enabling efficient top-level simulations and integration with digital verification environments.
But abstraction comes with a risk: misalignment.
The schematic and the model might look like they describe the same circuit. But do they behave the same? And more importantly: do they both reflect the original hardware requirements?
The Role of Requirements as the Anchor Point
The hardware requirements define what a block is supposed to do—its functionality, performance targets, signal interfaces, and operating constraints. They serve as the source of truth across design and verification teams.
Both the RNM behavioral model and the schematic (transistor-level or gate-level) should be independently derived from these same requirements. This is what gives the verification process integrity: two representations of the same intent, from different directions.
And yet, discrepancies happen. Without a clear check between abstraction and implementation, errors can slip through unnoticed—until it’s too late.
Where Things Break
The schematic captures physical non-idealities: gain variation, offset, parasitics, startup behavior. The RNM model—by design—is often idealized. Unless there’s structured cross-verification, subtle mismatches can creep in:
- Inverted signal polarity
- Incorrect gain or transfer functions
- Logic-level edge mismatches at mixed-signal interfaces
- Missing enable/disable conditions
- Misaligned timing or handshaking
These are the kinds of issues that don’t always show up in analog regression or digital testbenches—but can still cause silicon bugs, bringup delays, or worse: silent functional violations.
How to Close the Gap
Verifying the schematic against the RNM model (with hardware requirements as the benchmark) is more than a best practice—it’s a necessity for robust mixed-signal signoff.
Here’s how leading teams approach it:
- Mixed-signal co-simulation between RNM models and schematic netlists
- Assertion-based checks at key functional boundaries
- Formal equivalence techniques in cases where logic-level alignment must be guaranteed
- Coverage closure against functional requirements—not just waveforms
This becomes even more critical in automotive, medical, or industrial designs, where precision, traceability, and compliance are non-negotiable.
Final Thoughts
In spec-driven design, alignment across abstraction levels isn’t optional—it’s foundational.
Cross-verifying the RNM model and schematic against the same set of hardware requirements gives teams confidence that their simulation assumptions hold up in silicon.
In short: don’t just trust your model. Verify it against what really matters.
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#ASICVerification #MixedSignalDesign #RNM #BehavioralModeling #SchematicVerification #AnalogDesign #AMSVerification #FunctionalSignoff #AutomotiveASIC #SpecDrivenDesign #TheSiliconJournal #SmartSilicon