Block Planning

Question 1

What’s block planning step #1?

Answer 1

Read and understand the design rules.

Question 2

What’s block planning step #2?

Answer 2

Understand the schematics.

Question 3

What’s block planning step #3?

Answer 3

Find out if there are area constraints or imposed aspect ratios.

Question 4

What’s block planning step #4?

Answer 4

Use recommended widths for power and ground. Handles the current density, reduces IR drop and avoids electro-migration.

Question 5

What’s block planning step #5?

Answer 5

Get to know the interfaces between this block and others: where the external signals are coming from or going to, and correct metals for pins.

Question 6

What’s block planning step #6?

Answer 6

Find out about any high-speed or critical nets in the block. They deserve shorter routings, and possibly wider metal widths and wire shielding.

Question 7

What’s block planning step #7?

Answer 7

Check for special design rules and requirements, such as clearance among blocks, guard-rings, device matching, special shielding, adding/subtracting layers due to manufacturing or lithographic reasons.

Question 8

What’s block planning step #8?

Answer 8

Install feed-throughs (spare lines) within the block if needed.

Question 9

What’s block planning step #9?

Answer 9

Think of a simple and efficient way to create and organize the layout cell hierarchy.

Question 10

What are the most important signals, in order?

Answer 10

1. vss
2. vdd
3. clock-nets
4. other high-frequency lines
5. critical nets (analog signals)