Constraints are displayed in the Constraints window. These are used for device matching. When Animate runs, common circuit topologies, such as diff pairs, current mirrors and cascode stages are automatically identified and constraints set for them. Constraints can be set manually by, for example, selecting them in the schematic and using the ‘Create Constraint’ menu command, or by clicking on the Match icon in the Constraints window.
On the top right of the Constraints window are various icons:
|Deletes selected constraint.|
|Undoes a constraint change.|
|Redoes a constraint change.|
|Resets (clears) constraints.|
|Saves or loads constraints to an XML constraint file.|
Instance constraints are constraints applied to instances. They include match constraints and grouped match constraints. Instances without constraints are shown in the Unconstrained Instances section.
Net constraints are constraints applied to nets. They include Width (only used for routing), Critical Path (the instances forming the net critical path) and Net Pin Side (the access direction for IO pins).
Design constraints are constraints applied to the current design. They include:
- Pattern Routing - Options to enable/disable routing of structures such as diffpairs, current mirrors.
- Routing Options - fine control over routing.
- Source/Drain Contact Sharing - whether devices can share contacts or diffusion, if their respective diffusion areas are on the same net.
- Resizing of resistors and capacitors - if resizing is allowed.
- Maximum Layout Width - the layouts Animate generates will be limited to those less than this limit. Note that Animate cannot generate designs of a fixed size, and specifying a value too low may result in Animate being unable to create any layouts that fall within the limit.
- Maximum Layout Height - as above.
- Recommended Rules - Animate can use recommended foundry rules if present in the technology information.
- Reccomended Rule Excluded Instances - control on an instance basis of recommended rules.
- Maximum Number of Fingers Strapped with Poly - the maximum number of gate poly fingers that can share a common contact.
Style allows the choice of Mirrored Base Analog, Base Analog, Sub Base Analog or Digital. If Mirrored Base Analog is checked, then Animate will generate layout that is mirrored about a central vertical line of symmetry.
Devices that will be assigned to the left hand side are highlighted red in the schematic; devices that will be assigned to the right hand side are highlighted green, devices that are centred on the line of symmetry are highlighted yellow and devices that are asymmetric in blue. For m factor devices that can be split into half left side, half right side, they are shown with both red and green highlighting. Devices that are part of a match group are shown highlighted with a red/green shading transition.
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