DAC38J84EVM: NCO MODE

Asaf Samira

Prodigy 160 points

Part Number: DAC38J84EVM
Other Parts Discussed in Thread: DAC38J84, DAC37J84

Hi,

I configured DAC 38j84 to NCO mode (attached) with :

Fsample= 1920MHz

Fout= 620MHz

Coarse DAC Gain = 10

I got an extra loss of 2.5dB in IOUTAP SMA (SINX/X and both transformers attenuation were considered).

What is wrong with my configuration?

Thanks,

Asaf

nco_620.cfg

over 4 years ago

0 jim s over 4 years ago

TI__Guru* 91947 points

Asaf,

See attached documents. You should get a tone out at about 0dBm. You can get more gain if you enable the mixer gain. This will add 6dB of gain.

Regards,

Jim

DAC38RF82_NCO_620MHz.cfg DAC38RF82_NCO_620M_ref_821.pptx

0 Asaf Samira over 4 years ago in reply to jim s

Prodigy 160 points

Hi Jim,

I am using DAC3XJ8XEVM REV D (dac38j84),

may you send a configuration file and measurements for this one?

Thanks,

Asaf

0 jim s over 4 years ago in reply to Asaf Samira

TI__Guru* 91947 points

DAC38J84_Fs_1200_NCO_500.cfgAsaf,

The max sampling rate for this part is 1230MHz. The attached config file used a sample rate of 1200Msps and the NCO was at 500MHz. As you get closer to Fs/2, the sinx/x roll off will start to attenuate the tone. I was reading a power level around -7.3dBm with this setup with the mixer gain off.

Regards,

Jim

0 Asaf Samira over 4 years ago in reply to jim s

Prodigy 160 points

Hi,

Can you explain please why the max sampling rate for this part is 1230MHz?

According to the component datasheet the max sampling rate is 2500MHz.

Maximum Sample Rate:

DAC37J84: 1.6 GSPS
DAC38J84: 2.5 GSPS

My set-up is as below (External clock):

0 jim s over 4 years ago in reply to Asaf Samira

TI__Guru* 91947 points

Asaf,

My mistake. I was using 1X interpolation with my setup and this has a max sample rate of 1230. You are correct with the sample rates you mentioned. You should still see similar results whether using 1200MHz or 1920MHz. Your setup looks fine.

Regards,

Jim

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DAC38J84EVM: NCO MODE