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AD9958 (Eval Board) Phase Offset (From 0 to 1Mhz)

Question asked by SamVimaire on Jun 1, 2015
Latest reply on Jun 1, 2015 by LouijieC

Hi.

There is something that I do not understand with the AD9958.

I want to generate 1ms pulse at 1MHz frequency (Starting from 0)

 

the initial conditions are :

- Auto Clear Phase Accumulator option is enabled.

- Output Waveform is Cosine.

- Match Pipe Delays option is enabled

- SYS_CLOCK is 240 MHz.

- FTW0 = 0

- Phase Offset is 0°

 

I send (with AD9958/59 Evaluation Software) FTW0 = 0x01111111 (17895697) for 0,999999996 MHz.

cos (2.Pi*17895697/2^32) = 0,99965732497811026209

and trigger IO_Update

 

Why does the signal starts from 0  And not from +/- 1 ?

 

tek00003.png

 

When I set 90° Phase Offset, what is the cause of the 30ns peak I observe  before the sine signal ?

 

tek00005.png

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