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Using the Pad Frame
A 24-pin Pad Frame has been created for your project layout. The pad frame and its cells are available in the pads_tsmc02d library on the linux server. Add the following lines to your cds.lib file.
DEFINE pads_tsmc02d /usa/vsaxena/analog_course/pads_tsmc02d
The pad frame appears as below:
These basic pads designs are without ESD diodes. There are several cells in a I/O pad library. Here, we have PadNC (no connect), PadVdd (supply pad), PadGnd (ground pad), and PadAnalog (Pad for analog signals) as shown below. The PadFC is the frame corner cell. A designer can create custom padframe as needed for their designs using these cells. Commercial I/O pad cells include complex ESD, I/O circuits and guard rings.
You will notice two pad rings. The out ring is connect to the supply (vdd!) and the inner ring is connected to (gnd!). These rings provide low resistance access to the supply rails for making connection. In a commercial I/O Pad ring, you will see separate digital and analog rings as shown below:
You design goes in the empty area in the middle. Connect vdd! and gnd! to the I/O rings and the input and output signals to the PadAnalog pins.
