Design rules for stable propeller operation and overclocking
Sapieha
Posts: 2,964
Hi All
As I stated it is possible to run Propeller with more that 80-96MHz.
But it is not posible on badly constructed PCB boards.
In nature Propeler chip is variable power consumption and that will have consequences with omit (BIG
4.7-10 uF if possibly Tantalum) capacitors Near Propeller chip parallel with one smal ceramic capacitor.
Standart Voltage Regulators can't handle that fast power variations withouth them.
Even with 80MHz it is recomended to add them. As many people have reported it have problem with PLL
without that capacitors.
It is normal behavior on PLL that it will have stable Voltage threshold to function corectly and with
omiting that capacitors it is not posible to have stable Voltage in Propeller chip.
With every COG start else exit from WAIT instructions Propeler chip dramaticaly change power consumption
and that have impact on PLL.
It even consume more power with unstable Voltage (Not all transistors on chip can work stable in ON and
OFF state) and that impact on Propellers function.
Best Regards.
Sapieha - Christoffer J
As I stated it is possible to run Propeller with more that 80-96MHz.
But it is not posible on badly constructed PCB boards.
In nature Propeler chip is variable power consumption and that will have consequences with omit (BIG
4.7-10 uF if possibly Tantalum) capacitors Near Propeller chip parallel with one smal ceramic capacitor.
Standart Voltage Regulators can't handle that fast power variations withouth them.
Even with 80MHz it is recomended to add them. As many people have reported it have problem with PLL
without that capacitors.
It is normal behavior on PLL that it will have stable Voltage threshold to function corectly and with
omiting that capacitors it is not posible to have stable Voltage in Propeller chip.
With every COG start else exit from WAIT instructions Propeler chip dramaticaly change power consumption
and that have impact on PLL.
It even consume more power with unstable Voltage (Not all transistors on chip can work stable in ON and
OFF state) and that impact on Propellers function.
Best Regards.
Sapieha - Christoffer J
Comments
Why "Sapieha", BTW?
Leon
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Amateur radio callsign: G1HSM
Suzuki SV1000S motorcycle
Only 100 nF is to smal to handle fast power variations on Propeller chip.
That can function on 80MHz with programs that not have many active WAIT instructions.
But if You run extensive program that have all COGs on and many WAIT instructions that put temporary Propeller chip in LOW then HIGH power consumption it can have impact on its functionality.
Ps. If You Overclock it that can have very big impact
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Nothing is impossible, there are only different degrees of difficulty.
For every stupid question there is at least one intelligent answer.
Don't guess - ask instead.
If you don't ask you won't know.
If your gonna construct something, make it·as simple as·possible yet as versatile as posible.
Sapieha
It seems that it is preferable to run a crystal at say 12.5MHz and PLLx8 rather than 6.25MHz and PLLx16. From what Sapieha has said, the crystal will always be multiplied up PLLx16 and then if necessary it will be divided back down. Now with a 6.25MHz crystal, no division would take place and the clock would "JITTER" causing more power usage and possible PLL failure. However, with a 12.5MHz crystal, a division by 2 would take place and the clock would be "Jitter" free.
Thanks Sapieha
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Links to other interesting threads:
· Home of the MultiBladeProps: TriBladeProp, SixBladeProp, website (Multiple propeller pcbs)
· Single Board Computer:·3 Propeller ICs·and a·TriBladeProp board (ZiCog Z80 Emulator)
· Prop Tools under Development or Completed (Index)
· Emulators: Micros eg Altair, and Terminals eg VT100 (Index)
· Search the Propeller forums (via Google)
My cruising website is: ·www.bluemagic.biz·· MultiBladeProp is: www.bluemagic.biz/cluso.htm
Leon
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Amateur radio callsign: G1HSM
Suzuki SV1000S motorcycle
Post Edited (Leon) : 6/2/2009 1:20:53 PM GMT
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Links to other interesting threads:
· Home of the MultiBladeProps: TriBladeProp, SixBladeProp, website (Multiple propeller pcbs)
· Single Board Computer:·3 Propeller ICs·and a·TriBladeProp board (ZiCog Z80 Emulator)
· Prop Tools under Development or Completed (Index)
· Emulators: Micros eg Altair, and Terminals eg VT100 (Index)
· Search the Propeller forums (via Google)
My cruising website is: ·www.bluemagic.biz·· MultiBladeProp is: www.bluemagic.biz/cluso.htm
It is not only·Output pins that is problem.
It is momentary power varies in Propeller core with Start of new COG else Exit from WAIT instructions.
Standard chips have constant power consumption that give them more reliable Voltage to its Core.
Propeller chip have Variable Core power consumption that give more requirements on power/Voltage stablity
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Nothing is impossible, there are only different degrees of difficulty.
For every stupid question there is at least one intelligent answer.
Don't guess - ask instead.
If you don't ask you won't know.
If your gonna construct something, make it·as simple as·possible yet as versatile as posible.
Sapieha
Post Edited (Sapieha) : 6/2/2009 2:06:34 PM GMT
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Largos - a nano operating system for the Propeller
www.mikronauts.com - a new blog about microcontrollers
Parallax doesn't seem to bother about it, though. They only have one decoupling capacitor for the Propeller and a bulk capacitor by the regulator, a couple of inches away, on the Proto board.
Leon
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Amateur radio callsign: G1HSM
Suzuki SV1000S motorcycle
Post Edited (Leon) : 6/2/2009 2:25:51 PM GMT
I thought the deal with the smoked PLL's was more related to not having a sufficiently low impedance connection between all the propeller various power pins, not decoupling as such. I've been wrong before however.
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"VOOM"?!? Mate, this bird wouldn't "voom" if you put four million volts through it! 'E's bleedin' demised!
Leon
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Amateur radio callsign: G1HSM
Suzuki SV1000S motorcycle
You are corect on smoked PLL's.
But JITTER on PLL's and bad behavior is direct related to decoupling capacitors (Rather momentary curent/Voltage pumps).
10uF capacitors in that case acts as momentary bateries for Propellers CORE's/PLL's to give them stable Voltage.
Ps. But it has same problem. To bad voltage to ON/OFF of PLL's transistors that can give them unreliable state's. And that can open 2 transistors in opposite state.
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Nothing is impossible, there are only different degrees of difficulty.
For every stupid question there is at least one intelligent answer.
Don't guess - ask instead.
If you don't ask you won't know.
If your gonna construct something, make it·as simple as·possible yet as versatile as posible.
Sapieha
Post Edited (Sapieha) : 6/2/2009 2:37:40 PM GMT
Leon
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Amateur radio callsign: G1HSM
Suzuki SV1000S motorcycle
If You look on USB ProtoBoard them added 2 Tantalum capasitors for stablity on it.
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Nothing is impossible, there are only different degrees of difficulty.
For every stupid question there is at least one intelligent answer.
Don't guess - ask instead.
If you don't ask you won't know.
If your gonna construct something, make it·as simple as·possible yet as versatile as posible.
Sapieha
Sapieha has done a lot of work in overclocking and has discussed with Chip his findings.
So 100nF, 4.7uF Tant, 12.5MHz, PLLx8 and 100MHz here we come...
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Links to other interesting threads:
· Home of the MultiBladeProps: TriBladeProp, SixBladeProp, website (Multiple propeller pcbs)
· Single Board Computer:·3 Propeller ICs·and a·TriBladeProp board (ZiCog Z80 Emulator)
· Prop Tools under Development or Completed (Index)
· Emulators: Micros eg Altair, and Terminals eg VT100 (Index)
· Search the Propeller forums (via Google)
My cruising website is: ·www.bluemagic.biz·· MultiBladeProp is: www.bluemagic.biz/cluso.htm
Leon
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Amateur radio callsign: G1HSM
Suzuki SV1000S motorcycle
-Phil
On my designs in that case I use 33uF Tantalums.
4.7 - 10uF is smallest posible that give Propeller stablity and I never use that smal capacitors to stabilize Regulators Voltage if I have more that only one IC
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Nothing is impossible, there are only different degrees of difficulty.
For every stupid question there is at least one intelligent answer.
Don't guess - ask instead.
If you don't ask you won't know.
If your gonna construct something, make it·as simple as·possible yet as versatile as posible.
Sapieha
I too will take this into consideration for future designs....
Regards,
Coley
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PropGFX - The home of the Hybrid Development System and PropGFX Lite
And I am NOT saying this because I am going to be selling 6.25MHz crystals, but because of the high PLL clock.
I am however taking Saieah's excellent advice, and adding extra capacitors to my layouts as per his advice. 100MHz here I come!
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Largos - a nano operating system for the Propeller
www.mikronauts.com - a new blog about microcontrollers
Not all caps are created equal. Adding a "bunch of caps" is not the same as selecting those that do the job intended. You basically need two kinds: a filter cap, in the tens-of-uF range, that conforms to the requirements of the regulator, and multiple, localized ceramic bypass caps in the 0.1uF to 2.2uF range. The latter are used for transient control to eliminate power dips and ground bounce at a chip's supply pins. They need to have a very low ESR to be effective, which ceramic caps provide.
-Phil
Even then the inductance of any piece of the cct will affect their effectiveness, right down to the internal parts of the substrate itself. You could end up worrying about everything and building nothing. ESR is usually measured around 100KHz which is ok for ccts that don't pulse things at 100MHz. The slew rate of those 100MHz+++ clock edges are the cause of power drag and therefore heat. For stability that power must be available in an impedance suitable for those rates, this also means the chip will have more power to suck into itself, regardles if any of it is routed out again.
This why there is a stated max to all those figures, after that "your on your own ..."
Even my tormented Prop goes at 14.3MHz /8
I'm fairly sure those Tantalums are there for a different reason, however I can't find the thread at the moment.
Going from my rusty memory, the USB proto-board used a slightly different regulator configuration and there was a problem with some of the regulators squealing as they were unstable. This was worked around by adding those Tantalum caps. There was a long thread about it with lots of help and interaction from Paul Baker at the time.
<edit> found it
http://forums.parallax.com/showthread.php?p=735731
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"VOOM"?!? Mate, this bird wouldn't "voom" if you put four million volts through it! 'E's bleedin' demised!
Leon
▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
Amateur radio callsign: G1HSM
Suzuki SV1000S motorcycle
This must discourage the connection being put onto each without extra layout work. Not much I know, but threads seem to tell stories of this happening.