前两天有朋友问怎么检查出有超压风险的器件。他们应用的场景是存在负压的情况。导致在电源与这个负压电源之间的器件有耐压不够的风险。下面是我搭个简单示意图，主要就是找出粉色的器件是否是5v器件，如果不是需要报出来。上面的pmos也是需要做检查如果在正压电源域下，衬底不是接正压电源同样需要报出来。
如果在复杂的电路中快速检查出这些风险点，我推荐他使用perc来检查。以前有写过多篇检查低压器件接到高压信号的perc脚本。稍作修改即可满足这样的检查需求。
很方便的检查出risk的mos，perc支持flatten和hierarchy的cdl，同样可以检查spice和layout 数据。
Perc的参考code在文章最后面。
是否还有其他方式可以检查出来，这里介绍下PrimeSim 的CCK feature也可以提供类似的检查。
CCK 是primeSim 中用于做ERC和ESD 检查的feature。像一些floating gate node analysis，Hi-Z node analysis，DC path analysis，device parameter analysis，misssing level shifter analysis，等等。我们可以使用built-in command 与API 来定制相关的检查。跟perc 有些相似。
这里举个简单的例子：检查mos的width/length的比是否小于8.
对应的网表如下：
下面是cck的tcl script：
# callback function to check the device w/l ratioproc wlratioCheck {inst} {global resultFileglobal wlratioMaxset type [ cckGetInstType $inst ]if { $type==$::CCK_MOS } {set w [cckGetInstProp $inst "w"]set l [cckGetInstProp $inst "l"]if { $w/$l < $wlratioMax } {set instName [ cckGetInstFullName $inst ]puts $resultFile "device $instName W/L ratio is smaller than $wlratioMax"}}return $CCK_FALSE}# checking flow starts from reading in the netlistset wlratioMax 8.0netlist add20.spset fileName "cck.wl"set resultFile [ open $fileName w ]cckSearcInst -proc wlratioCheckclose $resultFile
The cck.wl output file contains the following example result:device m172 W/L ratio is smaller than 8.0device m174 W/L ratio is smaller than 8.0device m175 W/L ratio is smaller than 8.0
PERC的参考代码如下：
LVS POWER NAME "?VDD?"LVS GROUND NAME "?VSS?"VARIABLE HV_POWER "VDD25"VARIABLE HV_NPOWER "VDDN25"LAYOUT CASE YESSOURCE CASE YESPERC NETLIST SOURCEPERC REPORT "perc.rep"MASK SVDB DIRECTORY "svdb" QUERYPERC LOAD perclib INIT init SELECTdeviceInRiskVoltageCheck//========= Include Files ===========TVF FUNCTION perclib [/*package require CalibreLVS_PERCproc deviceInRiskVoltageCheck {} {set rules "Device has risk\n"perc::check_device \-pinPathType { {s d} {HV_Domain} } -condition voltageRisk_cond \-comment "$rules"}proc init {} {array set ::mos {}set ::mos(IO5_mos) [list pch45 nch45]set ::mos(IO_mos) [list pch18 nch18 pch25 nch25]set ::mos(All) [concat $::mos(IO5_mos) $::mos(IO_mos)]perc::define_net_type "Power" lvsPowerperc::define_net_type "Ground" lvsGroundperc::define_net_type "AllPad" lvsTopPortsif {[perc::expand_list [tvf::svrf_var HV_POWER] -type net] != ""} {puts ">>[perc::expand_list [tvf::svrf_var HV_POWER] -type net]"perc::define_net_type "HV_Domain" [perc::expand_list [tvf::svrf_var HV_POWER] -type net]}if {[perc::expand_list [tvf::svrf_var HV_NPOWER] -type net] != ""} {puts ">>[perc::expand_list [tvf::svrf_var HV_NPOWER] -type net]"perc::define_net_type "NHV_Domain" [perc::expand_list [tvf::svrf_var HV_NPOWER] -type net]}perc::create_net_path -subtype $::mos(All) -pin {s d} -break {Power || Ground} -exclude {Power Ground}perc::create_net_path -type $::mos(All) -pin {s d}}proc voltageRisk_cond {instance} {set select 0set mosType [perc::type $instance]set mosName [perc::subtype $instance]if {[lsearch $::mos(IO_mos) $mosType] || [lsearch $::mos(IO_mos) $mosName]} {if {[perc::is_pin_of_path_type $instance {S D} {HV_Domain}] == 1 && \[perc::is_pin_of_path_type $instance {S D} {NHV_Domain}] == 1 } {if {[perc::is_pin_of_path_type $instance {B} {HV_Domain}] ==1} {set select 0} else {set select 1}}} else {set select 0}return $select}*/]
