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TSW1400 and DAC3482EVM testing

Dimitar Penev
Intellectual 600 points
Other Parts Discussed in Thread: DAC3482, CDCE62005

Hello,

I had a hard time following the  .

I have followed "3 Basic Test Procedure with TSW1400"  procedure from the DAC348x EVM user's guide exactly
but I get distorted signal definitely having spectrum not as I see in HSDC Pro.

The only subjective factor I can see is 1228.8 MHz at 1.5Vrms signal.
So I decided to use the internal 19.2 MHz oscillator.
I have loaded DAC3482_FDAC_1228p8MHz_4xint_NCO_30MHz_QMCon.txt and
then I have modified the registers  of  CDCE62005  into what I believe is equivalent (but for internal clock)

reg value
00   0x80400000
01   0x813C0321
02   0x81400302
03   0xC10C0303
04   0x00040304
05   0x28001A85
06   0x44AF0776
07   0x145294A7
08   0x20001C08

With this settings I seems to be closer but not exactly I get two energy bumps similar as I see in HSDC Pro
One at around 60MHz and another around 92MHz

Any help rectifying this?  

In addition I wont to use the Multi tone Generator (initially for only one tone ).  
Can someone point me to the settings I should use.
If I just try to create 1 tone at around 50MHz using the same DAC settings I get distorted signal.  

 Thanks
Dimitar 

  • 0
    TI__Guru* 78744 points
    Hi Dimitar,
    The default setting had the DAC3482 enabled with NCO and full-mixer. This circuit requires an initialization signal from software sync (SIF_SYNC). Could you toggle the radio button on the DAC3482 software GUI (under digital) to see if the spectrum improves?
    The HSDC PRO GUI should have a simple multi-tone generator on the lower left hand corner of the GUI. Please set the tone to 20MHz. By default, with NCO set at 30MHz, the 20MHz baseband will be upconverted to 50MHz.
    -Kang
  • 0 in reply to Kang Hsia
    Intellectual 600 points
    Hi Kang,

    Thanks for the pointer.
    After switching on the system today I got sine wave.
    It seems to me the system is not very stable.
    If in doubt I will power cycle until I get some more confidence in it.

    So I have disabled the full-mixer as I don't need for my sine wave experiment and I got a sine wave.

    I have noticed that the measured frequency is not as per the target. (I have set target 11MHz but measured 8.7MHz)
    I hook a a scope at Yb = OSTR_CLK (at R66) and I expected 19.2MHz but I got 15.6MHz.
    So my CDCE62005 PLL seems to osculate at wrong frequency.
    (The settings are as per the register file I have posted in my previous message.)
    This seems to explain why my DAC doesn't generate exact frequency.
    Any reason this can happen?

    I have tried to play with some of the PLL settings:
    EECLK (Enable/Diable )and VCO SEL (High /Low range) seems to change my measured Yb = OSTR_CLK with about 1MHz
    but I have never seen expected 19.2MHz.
    (I have reset the board few times to make sure the results are consistent)

    Thank you.
    Dimitar
  • 0 in reply to Dimitar Penev
    Intellectual 600 points
    Hmm after few power cycles the CDCE62005 PLL set at the correct frequency.
    Probably I am at some marginal stability region or probably I should follow ordered sequence of its settings adjustment?

    Thanks
    Dimitar
  • 0 in reply to Dimitar Penev
    TI__Guru* 78744 points
    Dimitar,
    Most likely the CDCE62005 VCO core was not calibrated and hence the wrong frequency. On the CDCE62005 tap, there is a yellow "Wake-up" button that calibrates the CDCE62005 VCO. Press that to see if the pll-lock LED lights up for the CDCE62005.
    You may also try to adjust the VCO_SEL like you did and press "wake-up" again to see if it helps. My knowledge on this part is limited, and the clocking support forum may be able to help you if you need to change the frequency that you need.
    -Kang