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a problem about gndd!/vddd! in cadence

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wookey

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global vdd mixed cadence

hi all, I meet a problem about gndd! as blow:

When I run a simulation with spectre in cadence, the DC voltage of global signal (gndd! ) is not ground (0V), but -1.235V for example. So, how can I appropriately set a envirnment option about gndd! so as to set it's voltage to ground?

p.s. the cadence system seems set gnd! to ground as default.
 

cadence gndd gnda gnd

use GND that has 0 under it.
 

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    wookey

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inherited connection, cadence

m.salehi said:
use GND that has 0 under it.
Click to expand...

It do work. the circuit is mixed signal and it has 2 power supply: vdda and vddd. so I hope I could use both gnda and gndd to design the circuit, but not GND both for analog or digital side.
 

cadence gnda gndd

I give u advise.
Use gndd! and vddd!, gnda! and gndd! as u planed, but connect them to the gnd and vdd though parasitics elements (they isn't passed to layout)
1) though presistors, if analog and digital rails is connected to same pin.
2) after pin though series connected presistor and pinductor (package lumped elements), if it's used different pins.
Alway take into account package parasitics.
Note: It's better to use inhereded connections neither global definition like gndd!. Look for "inherited connection flow" in cadence help.
 

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    wookey

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cadence gnd! 0

you also can interpolate a vdc which is 0 volts between gndd! and 0 ,ot vddd! and vdd! in spectre netlist
 

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    wookey

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inherited connection flow cadence

Use .connect command,
.connect gndd! gnd
.connect vdd! vdd

And run simulation
 

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    wookey

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global pin define voltage cadence

there is a disadvantage about the method of tie vddd! to vdd!, gndd! to gnd!. I can not apply different voltage levels to vddd! and vdd!. However, I will take this method if there is no other ways.

Thanks all!
thank you for you special advise, DenisMark!
 

cadence inherited connections flow

gndd! is only a global node, not default for 0V
 

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