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A very URGENT question about AD9915

Question asked by Sercan on Jul 18, 2014
Latest reply on Jul 20, 2014 by Sercan

Hi,

At the datasheet of the AD9915 it is writen that SFDR is less then -57 dBc.
Can it be dBFS?

It is very critical for us to know if the information at the datasheet has a
typing (or any) error or if our measurements have a mistake or if our Ev.Board has a problem.

Can you please urgently let us know your opinion about this subject?

---

Here are our measurements with AD9915 Eval.Board:

   * At the Ev.Board: PLL disabled, Sys-Clk = 2,5 GHz, OSK enabled.
   * Output Freq = 550 MHz  /  Amp (ASF) = FFF. With spectrum analyzer the
carrier signal measured as 550 MHz / -0,715 dBm and the spurious measured as
850 MHz / -59,0 dBm.
   * When we change the Amp (ASF) to 7FF. Spectrum analyzer measurements are:

550 MHz / -6,730 dBm and 850 MHz / -68,0 dBm.

   * When we change the Amp (ASF) to 3FF. Spectrum analyzer measurements are:

550 MHz / -12,755 dBm and 850 MHz / -67,0 dBm.
   * So on.
   * There occurred lots of conditions like this which can be followed by the
attached table.

So, when we decrease the amp. of the carrier, the SFDR feature (being
less than -57dBc) of the AD9915 cannot be achieved / doesnot supporrted by the
DDS.
Can our Ev.Board has a problem or can our measurements have a mistake?

Waitng for your kind reply ASAP.
Best Regards,
Sercan

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