How to place macros?

 o   Analyze Connectivity (Flylines) – all fanin, all_fanout.

o   Use trace macro feature of Innovus.

o   Group by Hierarchy/Connectivity

o   Consider Data Flow:

o   Periphery Placement: Generally place macros around the edges of the core area, leaving the central area for standard cells. This simplifies power delivery to macros and avoids blocking standard cell placement/routing in the core center.

o   Pin Accessibility: Orient macros so their pins face towards the core logic they connect to, minimizing wire length and routing complexity.

o   Channel Spacing: Leave adequate space (channels) between macros and between macros and the core boundary. This space is needed for:

o    Routing nets connecting to macro pins.

o    Placing buffers/inverters near macro pins for timing optimization.

o    Power strap routing.

o    The required channel width depends on pin density, number of connections, and available routing layers. A rough estimate: Channel Width ≈ (Number of Pins * Pin Pitch) / (Number of Available Routing Layers). Add margin (5-10%).

o   Avoid Notches

o   Alignment: Align macros neatly to facilitate power grid construction and routing.

o   Keep-out Margins (Halos): Define halos around macros (especially hard macros) to prevent standard cells from being placed too close to macro pins, which can cause congestion. The size depends on pin density and expected buffering needs.

o   Power Considerations: Place power-hungry macros close to power pads/bumps if possible. Ensure adequate power strap access between macros.

Noise Sensitivity: Separate noise-sensitive analog macros from noisy digital macros.