AD9911 DDS frequency synthesizer

Feb 12, 2009 6 Replies
P

Hi All,



I have been struggling with the Analog Devices chip AD9911 for over a week and still no luck. The SPI Clk and Data are perfect, all the analog and digital voltages are set as specified in the data sheet. Here are some of my register values



CSR - 0x"22" FR1 - 0x"1800" FR2 - 0x"0000" CFR - 0x"000382" CTW0 - 0x"9810624D" CPOW0 - 0x"0000"



My target is to generate an ouput frequency of 74.25Mhz with a 25 Mhz system clock. Am I overlooking something obvious, have you faced similar issues with this chip. Any help in resolving the problem are welcome.



Regards PC


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S

Have not used that particular chip, but I suspect something to do with the SPI-- data/clock phase-- there are 4 possibilities, number of bits, total number of clocks, or format (MSB first is default, right?)

Best regards, Spehro Pefhany

"it\'s the network..." "The Journey is the reward" speff@interlog.com Info for manufacturers: http://www.trexon.com Embedded software/hardware/analog Info for designers: http://www.speff.com
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A

What problem? You didn't mention any details. Wrong frequency? Amplitude? Shape? No output at all? Chip overheating? What?

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P

I Don't get any output at all, although I get a sync_clk output ( 25 /

4) . The chip is configured in the single bit 3 wire mode, the SPI read is also unsucessful. The data sheet doesn't say much about SPI programming though.
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A

It's a current-mode DAC. You do have a current to voltage converter at the output?

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L

re

if spi reads don't work, there's a very good chance spi writes don't work either so chase that first

-Lasse

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R

Any test outputs ? How about testpattern. Incremental approaches ?

Rene

PC wrote:

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