dihoc
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« on: November 24, 2007, 04:20:58 16:20 » |
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Hi,
I build a project with ad9852 and pic but i need IC that can divide the freq up to 100mhz (74 series is too slow and ECL serie is too complcate) for my DDS project (control frequency).
Thanks,
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zorx
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« Reply #1 on: November 25, 2007, 03:15:44 15:15 » |
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Can you be more specific? Post block diagram and specify the position of divider circuit.
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ipek
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« Reply #2 on: November 25, 2007, 04:38:56 16:38 » |
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search and find AD9852 and AD9854 approx same pin to pin small fonction ratio. ham radio collected source http://rapidshare.com/files/72206347/ham-9854.rar.htmlapprox size 21 mb. dds chip easy find Analog Device first register...than sample only two like it % send.... bye. |
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dihoc
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« Reply #3 on: November 26, 2007, 03:09:23 15:09 » |
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it 's will be a poor man signal general can go up to 100mhz with ability to control frequency and amplitude.The purpose of the divider is divide the output of the AD9852 that will feedback to Pic to control the output frequency.
unable to see link, please post in text mode.
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avralam
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« Reply #4 on: November 26, 2007, 07:28:09 19:28 » |
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Why for DDS feedback? PIC generates only codes for driving DDS and LCD. 74ac161?
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telfo2007
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« Reply #5 on: November 26, 2007, 10:45:00 22:45 » |
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I tried SPxxxx IC series, with some problemas (my hobby prototype was noisy!!!), but more or less it worked. Motorola has also a lot... Check this url: http://www.xs4all.nl/~ganswijk/chipdir/f/divider.htmI hope this helps... |
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dihoc
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« Reply #6 on: November 28, 2007, 04:32:46 04:32 » |
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thank you for all your help,but still don't see the link so don't have any idea.
out put of DDS will go back to internal comparator and output of the comparator should be divide down before enter to the frequency counter of the PIC (low voltage pic 3.3v 4mhz)
Posted on: November 28, 2007, 05:10:44 05:10 - Automerged
the output of the comparator will be -3.3 and should be divide by 8 0r 64 before that enter to the frequency counter ( microchip application 16f84)
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piclover
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« Reply #7 on: November 28, 2007, 10:54:23 10:54 » |
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Instead 74 series of IC try 74AC... . 74AC series is much, much faster.
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dihoc
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« Reply #8 on: November 29, 2007, 03:08:45 03:08 » |
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so i will check the 74ac series. How about mc12080 , it is easier to use?
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piclover
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« Reply #9 on: November 29, 2007, 07:29:19 07:29 » |
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One note for 74AC series: to work properly input level of signal must be TTL or U can do a trick with biasing inputs with VCC/2. From input one resistor (100k) to VCC, another to GND. In that case U must AC couple signal to 74AC... If use MC12080 need only few mV of signal, for 74AC... with bias need few hundred mV of signal. Your turn to decide  |
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dihoc
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« Reply #10 on: December 01, 2007, 01:28:08 01:28 » |
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thank you for your help. Will order mc12080 to see how it work.
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mr_sri
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« Reply #11 on: December 14, 2007, 12:59:21 00:59 » |
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Why you need feed back? I have project with AD9852 and PIC too, but i only calculate the FTW (frequency tuning word) to control the freq.
You can calibrate the output freq with ADD or SUB the FTW number depend on the error
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dihoc
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« Reply #12 on: December 14, 2007, 07:15:31 07:15 » |
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that will give the errors to modify the FTW and make sure that 9852 has been set to the right frequency. i don't need the scope to check.
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