32. what are the measures or precautions to be taken in the Design when the chip has both analog and digital portions

Designing for Optimal integration of Analog and Digital

• As today's IC has analog components also inbuilt , some design practices are required for optimal integration.
• Ensure in the floorplanning stage that the analog block and the digital block are not siting close-by, to reduce the noise.
• Ensure that there exists seperate ground for digital and analog ground to reduce the noise.
• Place appropriate guard-rings around the analog-macro's.
• Incorporating in-built DAC-ADC converters, allows us to test the analog portion using digital testers in an analog loop-back fashion.
• Perform techniques like clock-dithering for the digital portion.

33. what are the steps incorporated for Engineering Change Order[ECO]

As more and more complex the IC design is , and with lot of first time application , is more prone to

last minute changes, there should be provision in the design-flow to accomodate the functional and timing bugs. The step to perform this called as Engineering change order(ECO).

• Ensure that the design has spare functional gates well distributed across the layout.
• Ensure that the selection the spare gates, has many flavours of gates and universal gates, so that any functionality could be achieved.