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使用CSMC.18工艺，在DC综合前添加IOpad,在顶层对IOpad module进行例化；
这个是工艺库中给出module：module pc18o002 (I, PAD, CS3);其中的CS3应该如何连接？
下面是对CS3的介绍，看不太懂，求大神支招：
CS3 pin in p* cells is a leakage current preventing control pin which prevents the leakage
current. It connects to the ground cell named pv0e_dec. The ground cell pv0e_dec contains logic
to detect power-on sequence. When the IO power supply voltage VD33 has been turned on
whereas the core power supply voltage VDD has not yet, CS3 pin will be high and equals to VD33
so as to prevent large uncertain leakage current. When both VD33 and VDD power are turned on,
then CS3 pin will be low and all the I/O cells will be in normal condition.
In CSMC DUP standard IO, different voltages are supplied to the pre-driver(lower voltage) and
post-driver(higher voltage).
(1) Power up Higher Voltage First
A large bus leakage current may occur due to different power on sequence between core
power and I/O power as power up VD33 first than VDD power. Pv0e_dec cell contains power on
sequence detect signal (namely CS3) to mitigate the leakage current efficiently. CS3 signal is
provided to control I/O cells while detecting power on sequence import in higher voltage power
up first. If any power on sequence problem (VD33 first) is detected, CS3 signal will set output
buffers to high Z state. If there is no power on sequence problem, CS3 signal is set to logic 0 and
it will not affect I/O functions.
CS3 signal should be distributed to all cells for better assembling. As a special ground PAD,
at least one pv0e_dec must be provided in each power domain. pv0e_dec provides VSSPST pad
which should be used to replace the existing pv0e in each power domain. For each power
domain, one pv0e_dec cell is needed to provide CS3 signal for other cells in the same domain.
Note: If chose pv0e_dec cell, the “pcut_dec” IO filler cell will not be chosed, as pcut_dec
filler IO cell make “CS3” directly connect to VSS “logic 0”. If chose pcut_dec IO cell, the pv0e_dec
IO function will gone, power up higher voltage first will not be deceted.
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发表于 2019-9-6 13:30:28
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