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Design >> RF Design >> Generating 25 % Duty cycle (Rail to Rail) LO at 5 GHz in 130nm Tech Node
https://designers-guide.org/forum/YaBB.pl?num=1317619000

Message started by Ricky Chen on Oct 2^nd, 2011, 10:16pm

Title: Generating 25 % Duty cycle (Rail to Rail) LO at 5 GHz in 130nm Tech Node
Post by Ricky Chen on Oct 2^nd, 2011, 10:16pm

Dear Friends,

Is it possible to generate 25 % Duty Cycle Rail-to-Rail LO (running at 5 GHz) from a 5 GHz Reference Clock in 130 nm Technology Node.

The FO4 delay of 130 nm node is approximately 65 pS. The 25% Duty cycle LO is supposed to drive a switch of reasonable size.

Title: Re: Generating 25 % Duty cycle (Rail to Rail) LO at 5 GHz in 130nm Tech Node
Post by raja.cedt on Oct 3^rd, 2011, 3:59am

hello,
i have done some 50% duty cycle correction at this frequency, there i used to compare avg value of the clock by vdd/2 and drive the feedback loop. may be you can try by comparing .25*vdd. Any kind of fedback is welcome. You can find the fig for understanding.

One more thing why you need 25% duty cycle?

Thanks,
Raj.

Title: Re: Generating 25 % Duty cycle (Rail to Rail) LO at 5 GHz in 130nm Tech Node
Post by Ricky Chen on Oct 3^rd, 2011, 7:51am

Hello,

The actual question is whether one can generate a 25 % duty cycle Square wave (Rail-Rail i.e 1.2V-0V) in 130 nm Technology Node with the present available state-of the art techniques without using INDUCTOR .

Please Note this square wave is to drive a SWITCH. So here whether the Technology is the LIMIT.

Title: Re: Generating 25 % Duty cycle (Rail to Rail) LO at 5 GHz in 130nm Tech Node
Post by RFICDUDE on Oct 3^rd, 2011, 5:22pm

Guess this depends on the technology.

Over process the high Vt corners will limit how much current you can slew for the capacitance of the device plus whatever load you are driving.

You may find you must burn a lot of current to meet the rise/fall times for the pulses you want to generate.

Title: Re: Generating 25 % Duty cycle (Rail to Rail) LO at 5 GHz in 130nm Tech Node
Post by rfcooltools.com on Oct 16^th, 2011, 10:38pm

Ricky Chen,

depending on absolute accuracy you could do something like this but the output is a dynamic logic and needs to be reset and powerdown has to be handled.

http://rfcooltools.com

Title: Re: Generating 25 % Duty cycle (Rail to Rail) LO at 5 GHz in 130nm Tech Node
Post by vp1953 on Oct 17^th, 2011, 12:02pm

Hi Ricky,

This should be doable - you can use a divide by 2 circuit with LO as input (standard cell or TSPC) and logically AND it with the LO (after inserting delay to take care of propogation delay through the divide by 2) - along the lines of Rfcooltool's idea.

Title: Re: Generating 25 % Duty cycle (Rail to Rail) LO at 5 GHz in 130nm Tech Node
Post by Ricky Chen on Nov 1^st, 2011, 3:56am

vp1953 wrote on Oct 17^th, 2011, 12:02pm:

Thanks vp1953.

But the FO4 delay in 130 nm Technology is 65 ps. So if you are getting 25 % duty cycle at 5 GHz Rail-to-rail (1.2 V - 0 ) clock means:- Your duty cycle period (ON time) will be only 50 ps. So the clock has to rise and fall within 50 ps to give you 25 % duty cycle).

is it possible without using INDUCTOR ?

Thanks
-ricky

Title: Re: Generating 25 % Duty cycle (Rail to Rail) LO at 5 GHz in 130nm Tech Node
Post by loose-electron on Nov 1^st, 2011, 3:46pm

A different approach:

Use different phases of a clock.

For example - Stay with the 5GHz clock, and set up a 4 phase clock at this rate. You now have an "edge rate" at the 25% duty cycle points. Combine the signals to get the needed control signals.

You may need to use current steering logic in some places to get the higher frequency signals.