---
+ Post New Thread
Page 1 of 2 12 LastLast
Results 1 to 20 of 23
  1. #1
    Newbie level 2
    Points: 1,333, Level: 8

    Join Date
    Aug 2005
    Posts
    2
    Helped
    0 / 0
    Points
    1,333
    Level
    8

    high speed low noise divider

    I want to know how to design a high speed(up to 800MHz) D flip-flop in frequency divider. And I also want to know if this D flip-flop need a reset port. Can some one help me? Thank you in advance.

  2. #2
    Full Member level 2
    Points: 2,157, Level: 10
    Achievements:
    7 years registered

    Join Date
    May 2006
    Location
    shanghai,china
    Posts
    148
    Helped
    27 / 27
    Points
    2,157
    Level
    10

    frequency divider d flip-flop

    Quote Originally Posted by spicer
    I want to know how to design a high speed(up to 800MHz) D flip-flop in frequency divider. And I also want to know if this D flip-flop need a reset port. Can some one help me? Thank you in advance.
    hi
    the simplest way is to use the standard cells your foundry provides.
    whether reset or set ports are needed depends your programmable divider.
    jeff



    •   Alt26th June 2007, 10:10

      advertising

        
       

  3. #3
    DZC
    DZC is offline
    Full Member level 3
    Points: 2,872, Level: 12
    DZC's Avatar
    Join Date
    Sep 2006
    Posts
    150
    Helped
    14 / 14
    Points
    2,872
    Level
    12

    cml high speed d-flipflop

    In the case of high speed,you can consider using the Currert Mode Logic.

    Here are some paper that might help you.

    http://www.edaboard.com/viewtopic.php?p=806597#806597



  4. #4
    Full Member level 2
    Points: 2,312, Level: 11
    Achievements:
    7 years registered

    Join Date
    Mar 2007
    Posts
    132
    Helped
    40 / 40
    Points
    2,312
    Level
    11

    how a d flip flop works as a divider

    Quote Originally Posted by jfyan
    Quote Originally Posted by spicer
    I want to know how to design a high speed(up to 800MHz) D flip-flop in frequency divider. And I also want to know if this D flip-flop need a reset port. Can some one help me? Thank you in advance.
    hi
    the simplest way is to use the standard cells your foundry provides.
    whether reset or set ports are needed depends your programmable divider.
    jeff
    Flip-flops used from standard cells may not be able to work at this frequency , you must check it well before using it.
    The need for a reset port depends on the type of counter you are using and the stand-by power consumption you are targetting.



  5. #5
    Junior Member level 1
    Points: 1,488, Level: 8

    Join Date
    Mar 2005
    Posts
    17
    Helped
    1 / 1
    Points
    1,488
    Level
    8

    frequency divider d flip flops

    You can use CML DFFs or TSPC DFFs to gain high speed. All of this are describled in RF Microelectronics of Razavi.



  6. #6
    Full Member level 2
    Points: 2,701, Level: 12
    Achievements:
    7 years registered

    Join Date
    Dec 2006
    Location
    India
    Posts
    147
    Helped
    20 / 20
    Points
    2,701
    Level
    12

    d flip flop frequency divider

    800MHz is not such a high frequency. U need not go to CML for that... Of course it depends on technology. But my gut feeling is that CML is not needed.

    By the look of it, u r trying to design a custom flop. A simple Master-Slave model (containing transmission gates as controlled switches) should be fine for the frequency u r aiming at.. Size the transmission gates properly to get good setup/hold times.

    Requirement for a reset/preset depends on the usage of the flop. If you are using it for clocking out data or used in a register, then its a good idea to have reset. If you are just using it to latch some info then reset may not be needed.

    Hope this helps..



    •   Alt26th June 2007, 17:01

      advertising

        
       

  7. #7
    Full Member level 5
    Points: 2,177, Level: 10

    Join Date
    Feb 2006
    Posts
    265
    Helped
    24 / 24
    Points
    2,177
    Level
    10

    d flip-flop frequency divider

    you should use CML structure.



  8. #8
    Full Member level 2
    Points: 2,701, Level: 12
    Achievements:
    7 years registered

    Join Date
    Dec 2006
    Location
    India
    Posts
    147
    Helped
    20 / 20
    Points
    2,701
    Level
    12

    digital frequency divider dff

    Quote Originally Posted by laglead
    you should use CML structure.
    Why "should"???
    I have designed a custom flop which works till 2GHz in 130nm technology with normal logic only. That is the reason I said it depends on technology..

    It is NOT compulsory to use CML here..



    •   Alt27th June 2007, 16:25

      advertising

        
       

  9. #9
    Member level 4
    Points: 1,727, Level: 9
    rowokii's Avatar
    Join Date
    May 2007
    Posts
    74
    Helped
    14 / 14
    Points
    1,727
    Level
    9

    cml tspc

    I second not using CML if you can. CML back to CMOS at high speed take up lots of power and is another complication.



  10. #10
    Newbie level 6
    Points: 1,190, Level: 7

    Join Date
    Dec 2006
    Location
    Egypt
    Posts
    14
    Helped
    1 / 1
    Points
    1,190
    Level
    7

    cml divider tspc divider

    I used TSPC in my design and it worked well in frequencies larger than 8oo MHz, it is simple unlike CML, so I advise to use TSPC.
    but I have another problem that my design requires DFF that works in 2.4 GHz and TSPC didn't work well in this frequencies and all designs tried (including CML) don't although it is stated in the papers that they can work for this frequency.
    I know I'm missing some thing in providing siutable values for W & L but some one experience to tell me what to do??



  11. #11
    Full Member level 2
    Points: 2,701, Level: 12
    Achievements:
    7 years registered

    Join Date
    Dec 2006
    Location
    India
    Posts
    147
    Helped
    20 / 20
    Points
    2,701
    Level
    12

    flip flop divider

    What is the technology that you are using?



  12. #12
    Newbie level 6
    Points: 1,190, Level: 7

    Join Date
    Dec 2006
    Location
    Egypt
    Posts
    14
    Helped
    1 / 1
    Points
    1,190
    Level
    7

    devider dflipflop

    I'm using TSMC(0.13 u)
    can I reach such high frequency using this technology??



  13. #13
    Member level 4
    Points: 1,727, Level: 9
    rowokii's Avatar
    Join Date
    May 2007
    Posts
    74
    Helped
    14 / 14
    Points
    1,727
    Level
    9

    divider flipflop

    Yes it's possible to go above 2.4G in TSMC .13. I've done TSPC divider that went up to around 4.5G (before layout-extraction low-vt option.) Of course, if you are trying to use it as a generic D-FF with logic between the D-FFs, that's another story....



  14. #14
    Full Member level 2
    Points: 2,701, Level: 12
    Achievements:
    7 years registered

    Join Date
    Dec 2006
    Location
    India
    Posts
    147
    Helped
    20 / 20
    Points
    2,701
    Level
    12

    d flip flop divider

    Quote Originally Posted by ahmed tolba
    I'm using TSMC(0.13 u)
    can I reach such high frequency using this technology??
    If you are using a low vt process, it should definitely be possible...



  15. #15
    Full Member level 1
    Points: 1,790, Level: 9

    Join Date
    Oct 2005
    Posts
    106
    Helped
    5 / 5
    Points
    1,790
    Level
    9

    frequency divider flip

    TSPC is a good choice



  16. #16
    Newbie level 4
    Points: 1,041, Level: 7

    Join Date
    Apr 2007
    Posts
    5
    Helped
    0 / 0
    Points
    1,041
    Level
    7

    Re: D flip-flop in frequency divider

    is it possibe in 0.18um technology to give a clock of 6GHz. I am trying to design a frequency synthesizer which operates at 6Ghz.



  17. #17
    Advanced Member level 5
    Points: 15,234, Level: 29
    khouly's Avatar
    Join Date
    Oct 2003
    Location
    EGYPT
    Posts
    2,371
    Helped
    446 / 446
    Points
    15,234
    Level
    29

    D flip-flop in frequency divider

    yeah 0.18 ring oscillaotr can give u this speed 6 GHz , even u can get more with LC

    and u can use the CML logic to do a dividers , but it will be good experince

    khouly



  18. #18
    Full Member level 3
    Points: 2,404, Level: 11

    Join Date
    Mar 2003
    Location
    eternity
    Posts
    156
    Helped
    24 / 24
    Points
    2,404
    Level
    11

    D flip-flop in frequency divider

    CML is certainly not neccessary, reasonable (<say sub 1024 division ration) freq. dividers can easily be built out of plain vanilla CMOS logic and standard master slave flops and work at 800MHz even in 0.18, not to mention 0.13.

    CML might have advantages in the dividers if you are after extremely low jitter and your loop BW is is very low since it is a very low noise topology (almost no switching noise since it always sinks the same current, even during value changes, this makes it very high power though).
    eternal_nan.
    vlsi design engineer



  19. #19
    Newbie level 4
    Points: 1,041, Level: 7

    Join Date
    Apr 2007
    Posts
    5
    Helped
    0 / 0
    Points
    1,041
    Level
    7

    Re: D flip-flop in frequency divider

    Quote Originally Posted by khouly
    yeah 0.18 ring oscillaotr can give u this speed 6 GHz , even u can get more with LC

    and u can use the CML logic to do a dividers , but it will be good experince

    khouly
    thanks for ur suggestion. ok to be precise i am designing a Direct digital frequency synthesizer. I need a clock of 6Ghz for its operation. Would i Still be able to do it with a ring oscillator?? i was trying to design a flip flop and then subsequently a regsiter to operate at 6GHz. but the maximum i cud get is 1.25-2Ghz..



  20. #20
    Advanced Member level 5
    Points: 15,234, Level: 29
    khouly's Avatar
    Join Date
    Oct 2003
    Location
    EGYPT
    Posts
    2,371
    Helped
    446 / 446
    Points
    15,234
    Level
    29

    D flip-flop in frequency divider

    u need to generate the clock , or just want to design the filpflop

    khouly



+ Post New Thread
Please login
Page 1 of 2 12 LastLast