VCO design and measurement

[STOIKOV]

hello! I designed a ring vco, simulated and did its layout. Then I simulate the extracted circuit (LEdit) and simulated again to obtain a frequency against control voltage curve. So the chip was fabricated and the experimental results show that the oscillation frequency is about 15 or 20% above the simulation frequency.

I hoped to obtain in lab a frequency below the simulated, maybe due to other parasitics not considered, but the frequency measured is larger.

Is this a normal behavior ? How can I justificate this percent of error. I was thinking on process variations, what do you think ?

 

[jfyan]

hello! I designed a ring vco, simulated and did its layout. Then I simulate the extracted circuit (LEdit) and simulated again to obtain a frequency against control voltage curve. So the chip was fabricated and the experimental results show that the oscillation frequency is about 15 or 20% above the simulation frequency.

I hoped to obtain in lab a frequency below the simulated, maybe due to other parasitics not considered, but the frequency measured is larger.

Is this a normal behavior ? How can I justificate this percent of error. I was thinking on process variations, what do you think ?

hi,
maybe it is a fast process. and you can check the ckt by simulating the ring osc ckt in fast corner.

good luck
jeff

 

[STOIKOV]

what means simulate in "fast corner" ?

 

[isaacnewton]

what means simulate in "fast corner" ?

CMOS corner models. Fast NMOS/Fast PMOS.

 

[STOIKOV]

I'm using a Mosis process, the fast model is a simulator option or a complete model like level=49 that currently am using ?

 

[isaacnewton]

It's a complete model.

I'm using a Mosis process, the fast model is a simulator option or a complete model like level=49 that currently am using ?

 

[henryhd]

I want design a ring oscillator,can you provide me some tutorial by ADS. and i want to know how can i builde the MOS component i need,and my operated frequency is about 5GHz!thank you!

 

[ahmad_abdulghany]

I want design a ring oscillator,can you provide me some tutorial by ADS. and i want to know how can i builde the MOS component i need,and my operated frequency is about 5GHz!thank you!

I think that there're built-in samples for ring osc in ADS.. look for them..

 

[henryhd]

thank you and i'll try it !

 

[qslazio]

hello! I designed a ring vco, simulated and did its layout. Then I simulate the extracted circuit (LEdit) and simulated again to obtain a frequency against control voltage curve. So the chip was fabricated and the experimental results show that the oscillation frequency is about 15 or 20% above the simulation frequency.

I hoped to obtain in lab a frequency below the simulated, maybe due to other parasitics not considered, but the frequency measured is larger.

Is this a normal behavior ? How can I justificate this percent of error. I was thinking on process variations, what do you think ?

take a look at the temperature difference between simulation and silicon.
vco frequency is sensitive to temperature.

 

[evilguy]

that your layout is well match?