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AD9959 4 channel DDS does not appear to be behaving as expected...

Question asked by mwfortner on Nov 23, 2012
Latest reply on Jan 3, 2013 by mwfortner

Hello,

 

I have a local customer who is using the AD9959 4 channel/500MSPS DDS within their design and the part does not appear to be behaving as expected.

 

The expectation is as follows:

.When the Profile pin is Low, the output is zero amplitude (register 6)

-When the Profile pin is High, the output is maximum amplitude (register A)

 

Note here that the customer was able to program the DDS as a single-tone output, but not a modulated one.

 

They feel that they may have other issues, but because they are in a time crunch, they would like to verify first that they are programming the AD9959 correctly.

 

To that point, here is what they are currently programming within the part for channel 0 only:

 

#Pulse Sync_IO(SDIO_3) high

#Write to CSR_SETTING (0)    0x00  0x12                                   Channel 0 only

#Write to FR1_SETTING (1)     0x01  0xB0  0x00  0x00               PLL divider = 12

#Write to CFR_SETTING (3)    0x03  0x40  0x03  0x01                Amplitude modulation

#Write to CFTW0 (4)                 0x04  0x05  0x55  0x55  0x55      Frequency

#Write to LSRR (7)                    0x07  0xFF  0xFF                         Necessary for 2-level modulation, no RU/RD?

#Write to RDW (8)                     0x08  0xFF  0xC0  0x00  0x00     Necessary for 2-level modulation, no RU/RD?

#Write to FDW (9)                     0x09  0xFF  0xC0  0x00  0x00     Necessary for 2-level modulation, no RU/RD?

#Write to CW1 (A)                     0x0A  0xFF  0xC0  0x00  0x00     Necessary for 2-level modulation, no RU/RD?

#Pulse I/O_UPDATE High        Transfer to current registers

 

They noted that they are not programming register 6 because it is already zero.  Is this correct?

 

Does the code provided above appear correct as well?

 

Let me know if there is any supporting information on the desired configuration that's needed to help t-shoot the problem.

 

Thanks in advance for your help.

 

Mike

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