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Your favourite PHI2 source
Crystal Oscillator can 82%  82%  [ 9 ]
Crystal + Inverter circuit 0%  0%  [ 0 ]
Microcontroller 18%  18%  [ 2 ]
6502/65C02 (i.e. the CPU) 0%  0%  [ 0 ]
555 Timer(!) 0%  0%  [ 0 ]
Push button(!!) 0%  0%  [ 0 ]
Total votes : 11
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 Post subject: Re: PHI2 source
PostPosted: Sun Aug 30, 2015 3:25 pm 
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BitWise wrote:
Rob Finch wrote:
Anybody ever use a ceramic resonator ? I've tried them a couple of time but found them to be too unstable.

Only with PICs. They seemed to work ok with them.

Same here. No problem at all with them, with PICs.

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 Post subject: Re: PHI2 source
PostPosted: Sun Aug 30, 2015 5:39 pm 
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There's no particular brand of oscillator I prefer, but the package style is important when space is at a premium. Recently I cobbled together an adapter that lets me use an oscillator intended for surface-mount (see datasheet attached). The resulting assembly is much smaller than a can -- about the width of a DIP IC, and considerably shorter.

I found it easier to flip the oscillator upside down to expose the soldering surface. Viewed in this way, the pads are numbered clockwise. Upside down also allowed me to avoid shorts between the bypass cap and the oscillator's metal lid, which is grounded.

Attachment:
Oscillator SMD.pdf [210.58 KiB]
Downloaded 51 times
Attachment:
adapter for SMD oscillator.jpg
adapter for SMD oscillator.jpg [ 85.88 KiB | Viewed 602 times ]
Attachment:
SMD oscillator orientation .JPG
SMD oscillator orientation .JPG [ 43.28 KiB | Viewed 598 times ]

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 Post subject: Re: PHI2 source
PostPosted: Sun Aug 30, 2015 8:06 pm 
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Dr Jefyll wrote:
There's no particular brand of oscillator I prefer, but the package style is important when space is at a premium. Recently I cobbled together an adapter that lets me use an oscillator intended for surface-mount (see datasheet attached). The resulting assembly is much smaller than a can -- about the width of a DIP IC, and considerably shorter.

I found it easier to flip the oscillator upside down to expose the soldering surface. Viewed in this way, the pads are numbered clockwise. Upside down also allowed me to avoid shorts between the bypass cap and the oscillator's metal lid, which is grounded.

Attachment:
Oscillator SMD.pdf
Attachment:
adapter for SMD oscillator.jpg
Attachment:
SMD oscillator orientation .JPG

What is the pin spacing on that assembly? It looks tiny.

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 Post subject: Re: PHI2 source
PostPosted: Sun Aug 30, 2015 10:09 pm 
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It's pretty small, alright. The pin spacing is .1". Here's a photo using some .1" protoboard as a backdrop, and shaded to show the mounting footprint. Except for not being upside down, the oscillator is positioned as in my previous post -- ie; the overall footprint is in "landscape" orientation, and the oscillator is rotated portrait-wise.

Although my adapter is implemented as a removable daughterboard, the same wiring technique could mount the oscillator directly to the main board.
Attachment:
oscillator scale.JPG
oscillator scale.JPG [ 223.92 KiB | Viewed 587 times ]


The shot below shows the oscillator in its natural (SMD) habitat. :) If you're doing a custom PCB (not protoboard) then this is the way to go. On this board the plate-through holes are on a .1" grid, and the SOIC IC location is .050" lead pitch. For scale I put a rectangular can-type oscillator on the left, with its narrow dimension visible.
Attachment:
oscillator comparison.JPG
oscillator comparison.JPG [ 328.19 KiB | Viewed 587 times ]


It's worth mentioning that suppliers have less and less incentive to stock through-hole parts nowadays. So, as time goes by, you're more and more likely to find your favorite frequency only available in SMD.

-- Jeff

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 Post subject: Re: PHI2 source
PostPosted: Mon Aug 31, 2015 5:57 am 
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I've used a similar oscillator here, soldered directly on 100 mil grid that was intended for expansion connector:

viewtopic.php?f=4&t=2453&start=15#p24803


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 Post subject: Re: PHI2 source
PostPosted: Mon Aug 31, 2015 11:46 am 
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Dr Jefyll wrote:
There's no particular brand of oscillator I prefer, but the package style is important when space is at a premium. Recently I cobbled together an adapter that lets me use an oscillator intended for surface-mount (see datasheet attached). The resulting assembly is much smaller than a can -- about the width of a DIP IC, and considerably shorter.

I found it easier to flip the oscillator upside down to expose the soldering surface. Viewed in this way, the pads are numbered clockwise. Upside down also allowed me to avoid shorts between the bypass cap and the oscillator's metal lid, which is grounded.

Attachment:
Oscillator SMD.pdf
Attachment:
adapter for SMD oscillator.jpg
Attachment:
SMD oscillator orientation .JPG

This is a an excellent idea. I've got a few SMD ones lying around which I thought about throwing away as most of the stuff I do is thru-hole. I can now try this and see what happens :).


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 Post subject: Re: PHI2 source
PostPosted: Mon Aug 31, 2015 12:05 pm 
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BigDumbDinosaur wrote:
banedon wrote:
I'll pre-empt the poll and suggest crystal oscillator can wins...

Actually, I use an oscillator feeding into a flip-flop for a strong signal with a near-exact 50 percent duty cycle.

Quote:
...but if so what particular brand do people prefer and are there any gotchas to look out for?

I use the ECS 2100AX series, but haven't really found any one brand to be superior to another.

One possible gotcha is the temperature coefficient rating. That could be important if you are dependent on the frequency being very stable with changes in ambient conditions. In practice, few of our creations are likely to be that fussy.

Here's a screen shot of my 65C02v2 project using a 25MHz crystal oscillator being divided down to 12.5MHz using a 74AC74 D-type flip flop. The measurement was taken from the PHI2 (pin 37) of the W65C02S. Lookin' good :). BDD do you use a flip flop with SMD cans?

Attachment:
usingflipflop.png
usingflipflop.png [ 7.71 KiB | Viewed 555 times ]


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 Post subject: Re: PHI2 source
PostPosted: Mon Aug 31, 2015 4:23 pm 
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Arlet wrote:
I've used a similar oscillator here, soldered directly on 100 mil grid that was intended for expansion connector:

viewtopic.php?f=4&t=2453&start=15#p24803
Quote:
As the FPGA is configured, it writes a "0" to the GND pin, and a "1" to the VCC pin of the oscillator, so I didn't have to add any patch wires :)


You're using IO pins of the FPGA to supply power to the oscillator? I love it!! :D

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 Post subject: Re: PHI2 source
PostPosted: Mon Aug 31, 2015 5:18 pm 
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banedon wrote:
BDD do you use a flip flop with SMD cans?

I have not used an SMD can in any of my builds.

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