Analog Pad frame(ring) wiring

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edabrduser

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I am using 0.35um process and the library has some analog pads (The chip is an op-amp). Each of the pads has four terminals.

Vddo, Vddr
gndo, vsub

The op-amp needs only Vdd and gnd.

Should I short Vddo and Vddr for Vdd.
And gndo and vsub(substrate is grounded anyway) to get gnd?

The ESD circuit has two parts. The first one has some diodes to power(Vddo) and ground pins(gndo). This part is connected to the second through a diffusion resistor. The second part has some more diodes to power(Vddr) and ground(vsub).

Any suggestions on how to wire them?

I don't think I am allowed to post the schematic of the analog pads!
 

Yes，you can have this short if all circuits quiet like opamp. I think these more PADs are used to separated noisy circuit from quiet circuit. For ESD, two parts are the first-stage ESD and the secondary-stage ESD. The big size one is the first-stage ESD while small size one is the secondary-stage ESD. The resistor between them is used to limit current of the secondary-stage ESD.
 

Thanks. I've read somewhere that Vddo and Vddr should be shorted at the Vdd pad and the gndo and gndr pads should be shorted at Gnd pad. Is this the normal way to do it?
 

Yes. It is called Kelvin Connection or Star Connection.
 
For such case i think it's OK to connect different rings. But it's a good practice if u have an ability to place extra pads to supply vddo/vsso and connect appropriate rings to it. It's allows to reduce noise etc. Moreover if u utilize "multigate" technology vdd and vddo voltages could be different.
 
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