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firsttimedesigning
Joined: 04 Jul 2007
Posts: 97
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 16 Jan 2008 9:58 Ring Oscillator with Delay |
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i am designing a ring oscillator that will function as a clock generator. However, I would like it to have some delay at the begining. What I mean is that it will delay for 2 seconds, (during that time it will only produce a low voltage signal) and then, it goes to function as a normal clock generator.
the problem is, i dont know how to create such a delay...
any idea?
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renwl
Joined: 26 Apr 2004
Posts: 455
Helped: 23
Location: shanghai,china
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| 16 Jan 2008 10:37 Ring Oscillator with Delay |
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I think that maybe make the gain lower can get it.
however, maybe the ring oscillator will never oscillate again when the gain is not enough.
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catur_3414
Joined: 04 Jan 2008
Posts: 39
Helped: 1
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| 17 Jan 2008 13:59 Re: Ring Oscillator with Delay |
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try this circuit.
adjust the delay with replace the R (50k) and C
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dhasmana
Joined: 19 Jan 2005
Posts: 78
Helped: 8
Location: Bangalore , India.
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| 22 Jan 2008 8:46 Ring Oscillator with Delay |
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Can use a RC circuit (high R less C) and sense the output voltage and generate a bypass signal which will bypass the RC once the level is reached.This will happen only during the startup.
Regards,
Jitendra Dhasmana.
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manish12
Joined: 21 Nov 2006
Posts: 936
Helped: 27
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| 22 Jan 2008 15:25 Re: Ring Oscillator with Delay |
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it is simple one .
this is the best , what you can get !
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Sadegh.j
Joined: 29 Nov 2006
Posts: 677
Helped: 32
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| 24 Jan 2008 9:37 Re: Ring Oscillator with Delay |
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| use an a-stable, easy
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s_babayan
Joined: 06 Dec 2006
Posts: 72
Helped: 2
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| 26 Jan 2008 17:02 Re: Ring Oscillator with Delay |
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dear friend you can use some inverters which can have a determined delay time. so you can use their delay time for the time you require. Hope it will be useful for you.
Samaneh
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lijianheng
Joined: 29 Sep 2006
Posts: 130
Helped: 10
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| 29 Jan 2008 3:55 Re: Ring Oscillator with Delay |
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| DLL? I'm not sure.
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mathuranathan
Joined: 11 Sep 2006
Posts: 195
Helped: 22
Location: Chennai
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| 29 Jan 2008 7:13 Re: Ring Oscillator with Delay |
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You can use a one shot generator which produces a negative pulse for a short duration. This pulse acts as device deactivation pulse during which your ring oscillator stays quiet. The inverter in the design is actually a chain of inverters designed using logical effort method. Many standard CMOS text books and the article by "Sutherland" deals with the design of inverter chains for desired propagation delay using the "Logical Effort" technique.
Advantage of this design is that it does not involve bulkier lumped devices like lumped resistors and capacitors for achieving the delay.
See the attached image for the block design.
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northeast1
Joined: 21 Jun 2007
Posts: 150
Helped: 4
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| 01 Feb 2008 5:38 Re: Ring Oscillator with Delay |
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| firsttimedesigning wrote: |
i am designing a ring oscillator that will function as a clock generator. However, I would like it to have some delay at the begining. What I mean is that it will delay for 2 seconds, (during that time it will only produce a low voltage signal) and then, it goes to function as a normal clock generator.
the problem is, i dont know how to create such a delay...
any idea? |
you can add a power down circuit in the circuit to control the delay
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kumarghz
Joined: 25 Nov 2006
Posts: 15
Helped: 1
Location: Penang, malaysia
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| 03 Feb 2008 18:36 Re: Ring Oscillator with Delay |
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Dear designer,
you may try this circuit as I attached.
you see, the Cap will start to charge upon the circuit activated, however the cap takes time to charge from 0v to 5v (vcc) . At beginning the output of the schmitt trigger is '0' so the AND gate. as the cap charge from 0v and reached the Vth of the schmitt trigger the output of the schmitt trigger goes high and the output of AND gate copy the ring osc.
The delay established here is when the cap charge from 0v to Vth. you may vary the value of Cap & R to achieve desired delay.
Thanks. good luck.
-kumar
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sp
Joined: 01 Jan 2004
Posts: 418
Helped: 27
Location: Floating Garden
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| 12 Feb 2008 17:02 Ring Oscillator with Delay |
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haha so most people here is analog type (cap, gain, astable)... I'm a digital one so I would suggest that we use control logic to do the initial delay...
normally your ring oscillator will have a "enable" to start the ring loop, so perhaps you can use a counter to count till two second before you assert the "enable". this need to be done whenever you want to assert the "enable" for your ring oscillator...
hope this is useful 
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hock
Joined: 28 May 2001
Posts: 1040
Helped: 11
Location: India
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| 12 Feb 2008 18:56 Re: Ring Oscillator with Delay |
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if you post it in analog forum you will get analog replys only. please post your request in digital forum.
hock
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Asif2008
Joined: 07 Mar 2008
Posts: 24
Helped: 1
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| 07 Mar 2008 21:29 Re: Ring Oscillator with Delay |
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| dear u should study the david and pozar
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chip2000
Joined: 01 Mar 2008
Posts: 6
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| 07 Mar 2008 21:45 Re: Ring Oscillator with Delay |
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you could use a powe supply voltage supervisor ic like the tl7705 that will produce a programmable pulse when you connect the power. (it was design to give the reset signal) you will AND gate this signal with your clock
Alternatively you can use o CD4541 ic that will drive the AND gate that blocks the clock. the CD4541 has reset on power circuit and gives programmable delay...
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armixic
Joined: 09 Mar 2006
Posts: 30
Helped: 2
Location: U.S.A
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| 15 Mar 2008 2:39 Re: Ring Oscillator with Delay |
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| 2 second is too long for a on-chip delay. try to use some logic control sequence to power-up the ring.
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sudhakarj.tech
Joined: 27 Feb 2008
Posts: 16
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| 17 Mar 2008 9:41 Ring Oscillator with Delay |
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Hi Asif2008,
Can you have the soft copy of DAVID & POZAR for analog ckt design, or can u send me the link corresponding to........or can u plz send it to me on
>>>>>>>>sudhakarj.tech(at)gmail.com<<<<<<<<<
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jecyhale
Joined: 19 Feb 2008
Posts: 431
Helped: 46
Location: China
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| 01 Apr 2008 7:52 Re: Ring Oscillator with Delay |
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| Use an counter to count the dealy.
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butterfish
Joined: 26 Oct 2005
Posts: 123
Helped: 6
Location: china
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| 23 Apr 2008 8:04 Re: Ring Oscillator with Delay |
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| You can use a RC delay, and divide it to 2S sqware wave.
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heng155
Joined: 19 Nov 2005
Posts: 20
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| 24 Apr 2008 14:01 Ring Oscillator with Delay |
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| You can use a much small & slower Ring Oscillator to set the timng.
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mady79
Joined: 30 Mar 2004
Posts: 88
Helped: 6
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| 26 Apr 2008 0:00 Re: Ring Oscillator with Delay |
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| If u got a clock in a system ,set counter and add a synchronous wait signal after the count is reached .hope this helps
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yezeg
Joined: 12 Jan 2006
Posts: 15
Helped: 1
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| 26 Apr 2008 14:30 Ring Oscillator with Delay |
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2 second's delay is too long for a on chip delay.The R and C is so big!
if the accuracy is hight ,you can choose digital control.
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deba_fire
Joined: 03 Jul 2007
Posts: 4
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| 26 Apr 2008 16:12 Re: Ring Oscillator with Delay |
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Hi,
Use a latch in front of your oscillator with delay of 2s.When you power it on it will give a delay of 2s then after this disable the latch.
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northeast1
Joined: 21 Jun 2007
Posts: 150
Helped: 4
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| 28 Apr 2008 5:06 Re: Ring Oscillator with Delay |
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| firsttimedesigning wrote: |
i am designing a ring oscillator that will function as a clock generator. However, I would like it to have some delay at the begining. What I mean is that it will delay for 2 seconds, (during that time it will only produce a low voltage signal) and then, it goes to function as a normal clock generator.
the problem is, i dont know how to create such a delay...
any idea? |
Please add a counter before the OSC, and after 2 second to start the osc.
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rillyxue
Joined: 03 Jan 2007
Posts: 27
Helped: 1
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| 14 May 2008 4:13 Re: Ring Oscillator with Delay |
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| using a pd start control circuit before your pd. i have designed such a circuit.
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rficdesigner
Joined: 17 Jun 2008
Posts: 19
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| 17 Jun 2008 17:51 Ring Oscillator with Delay |
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Thanks you guys.
Have nice day.
I need some points!
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