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How to use the layout of 0.25 process in 0.18 design?

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Process 0.25 to 0.18

I get a design of bandgap in 0.25um process, including schematic and layout. I want to use it in my design. But it is using 0.18 process.

I have simulated the schematic in .18 process model. The performance is good. Can I ues the layout of .25 process to a .18 process design? I have finished the other parts of blocks in .18 process. Of course, I can clean the DRC and LVS.

Will it introduce any problem to the performance of layout?

Thanks.
 

Re: Process 0.25 to 0.18

I dont think you can do that as the characteristics of the transistor iteslf quite changes dramtically from the "idealized" one when you get down to .18 um tech from 0.25 tech.
srivatsan
 

Re: Process 0.25 to 0.18

If you use NPN, you'd better follow the design rule guidelines to achieve reliable/better performance.

If not, I don't see any problem if you simulate the old design in new model and DRC/LVS clean in new technology. The only possible demerit is the area penalty.

regards,
jordan76
 

Re: Process 0.25 to 0.18

jordan76 said:
If you use NPN, you'd better follow the design rule guidelines to achieve reliable/better performance.

If not, I don't see any problem if you simulate the old design in new model and DRC/LVS clean in new technology. The only possible demerit is the area penalty.

regards,
jordan76
Click to expand...

I use CMOS process. But in a bandgap circuit, there are some PNP transistors created by CMOS. I can not understand what is the design rule you told.

Thanks.
 

Re: Process 0.25 to 0.18

If you have done all the corner simulations in the new process, and your circuit works well, then you have no reason to fear. As for the lateral PNP's, the process design kit provides unit cells, which might be different from the cells used in the previous process. So you might have to substitute the old cell with the new one. But since in a bandgap circuit, its only the ratio which is important, even this isnt really necessary.
 

Re: Process 0.25 to 0.18

I think you need to do a new design. That's safer. I assume that for now you have just simulated the (extracted) circuit using the 0.18um models. If you have had a working circuit, that should not take long, though.
 

Re: Process 0.25 to 0.18

If you understand the existing 0.25u topology, you should probably start with that, unless it needs a power supply greater than what you are using on the 0.18u process, and assuming that equivalent devices (PNP, resistors) are available.

You may be able to scale some of the devices for the new topology, but my guess is that there could be matching issues if you scale too small.

(Of course, all of this assumes that you are looking for the same reference voltage from both processes...)
 

Process 0.25 to 0.18

how you deal with the power? 1.8v or 3.3v?
 

Re: Process 0.25 to 0.18

if you design .25um bandgap Vcc=3.3
and 0.18um still vcc=3.3v ..

don't need re-design ..

but if you use vcc=2.5 or 1.8v --> re-design
and if Vcc=1.8 bandgap=1.2xx it is diffcult design
you can not cascode MOS (poor PSRR) ..
 

Re: Process 0.25 to 0.18

for analog you must redesign it
for digital it maybe ok from 0.25 to 0.18
but not from 0.18 to 0.25
 

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