plates and the routing channels in the lower-plates are
interchanged successively. In this placement, it requires at
most five times metal layer pitch in one routing channel.
However, the routing channel space can be reduced if we
change the locations of some unit capacitors in the placement.
Fig. 8 shows another common-centroid placement by
adjusting the original one. The routing channel space of the
new placement only requires at most four times metal layer
pitch. Therefore, the total layout area is reduced. To handle the
consideration of routing channel space in the placement phase,
we add a penalty term to the cost function in our simulated
annealing based algorithm. The objective of this penalty term
is to make each column of the resulting placement have the
least number of different unit capacitors.
V. CONCLUSION
In this paper, we have pointed out some of routing-aware
placement algorithms for modem analog integrated circuits
and showed our ideas for solving them. Since considering
placement and routing in analog designs are very difficult, we
believe there still exists a lot of room for improving these
approaches.
ACKNOWLEDGMENT
This work was supported in part by National Science
Council of Taiwan under Grant No's NSC-99-2220-E-006-
019 and NSC-98-2221-E-006-156-MY3.