PAD FRAME
At the final stage of an IC design, the layout of the system must be routed to a pad frame. Essentially, this pad frame connects the design to pins -- the pins that are the inputs/outputs of the IC.In this class, you will be using the following pad frame that can be configured to meet your system's particular needs. You should download each of the .mag files and put them in the appropriate directory. You should only edit padframe.mag -- do not edit any other cell. A description of the files follows.
- padframe.mag -- Top level
layout that includes instances of all
the other cells included in the pad-frame layout. To use
this layout, first open up this layout and change the pad types to the
appropriate type to meet your needs. Directions on this procedure
are included below.
- padSM_inor.mag -- INOR
pad type. This pad contains
electrostatic discharge (ESD) protection circuitry in the form of
diodes. Use this pad type for all voltage inputs and any current
inputs/outputs. Do not use this for voltage outputs.
- padSM_wide.mag -- WIDE
pad type. This pad contains a
wide-range OTA in the pad structure for buffering a voltage
output.
Use this pad type only for
voltage outputs.
- padSM_corner_Bias.mag
-- Corner pad that contains two INOR pads
and one
pad for Bias! (which is pin 5). This Bias! is the bias voltage
that will be used to set the tail current in the OTAs that are included
in the WIDE pads. You may use the two INOR pads as you would any
other INOR pads. Do not modify this layout.
- padSM_corner_Gnd.mag
-- Corner pad that contains two INOR pads
and one pad for GND! (which is pin 15). This GND! is the ground
you will use for your entire system. You may use the two INOR
pads as you would any other INOR pads. Do not modify this
layout.
- padSM_corner_Vdd.mag -- Corner pad that contains two INOR pads and one pad for Vdd! (which is pin 25). This Vdd! is the power supply you will use for your entire system. You may use the two INOR pads as you would any other INOR pads. Do not modify this layout.
- padSM_corner_Pvdd.mag
-- Corner pad that contains two INOR pads
and one
pad for GND! (which is pin 35). This Pvdd! is the power supply
that you will use to power the pad frame (diode circuitry for ESD
protection and WIDE pad power supplies). You may use the two INOR
pads as you would any
other INOR pads. Do not modify this layout.
In your top-most level of your system, call an instance of the pad frame and connect to the appropriate locations (as are indicated by the labels). Also, remember to connect all GND! and Vdd! connections in your design to GND! and Vdd! terminals on the pad frame.
Changing Pad Types
The pad frame that you may download comes only with INOR pads. However, your design may have voltage outputs which should be buffered with the WIDE pads. To change the type of pad, you may use the following procedure.
- Open padframe.mag and leave the instances unexpanded (they will
look like boxes with nothing inside).
- Select the desired pad that you would like to change from INOR to
WIDE or WIDE to INOR. Use the s
macro to select that pad.
- Delete that pad with the d
macro.
- Before you do anything
else, use the long command "getcell" to create an instance of whatever
pad type you want (for example, type :getcell
padSM_inor or :getcell
padSM_wide). This will automatically put a pad in the same
location.
- Depending on which part of the padframe this pad is in (top,
bottom, left, or right), you may need to rotate the pad so that it has
the same orientiation as those on either side of it. You can use
the :clockwise long command
with the . command (which
repeats the last long command) to orient it in the correct
direction. Therefore, while this particular pad is still
selected, use a combination of :clockwise
and . to get it in the correct
orientation.
- Expand the pads to verify that you have the correct orientation
(using the x macro).
There should not be any DRC errors, but verify this to make sure.
- Repeat for any other pads that you need to change.