DAC39J84: Test Tone

Des Coghlan

Part Number: DAC39J84

Can the DAC3XJ8X family output a test tone, independent of a functioning JESD interface? Assume it is given a reference clock, and the it 's internal PLL is programmed as needed. Can I output a tone using coarse N*Fs/8 or the NCO ?

over 4 years ago

0 jim s over 4 years ago

TI__Guru* 91947 points

Des,

Yes you can. See attached example which uses the TI DAC38JxxEVM and GUI.

Regards,

Jim

6825.DAC38J84 100MHz NCO Test.pptx

0 Des Coghlan over 4 years ago

Prodigy 100 points

Please identify the control registers needed make this happen. Also, the copy of the register config file from the test set up you used.

0 jim s over 4 years ago in reply to Des Coghlan

TI__Guru* 91947 points

Registers involved are 0x02, 0x0d, 0x14, 0x15, 0x16, 0x1F and 0x2F. The config file used to test this is attached. This creates a 100MHz NCO with a 983.04MHz input clock.

Regards,

Jim

100M_NCO_983.04_Fs_no_LMK.cfg

0 Des Coghlan over 4 years ago in reply to jim s

Prodigy 100 points

Please clarify. Is register 0x30 = sifdc, the constant value sent to the DAC core when sifdac_ena is asserted - reg0x2F, bit 0? You set it to '0000'; how do I interpret the value; are sifdc = '0000' and '1111' equivalent to peak max RF output power, whereas, whereas '1000' and '0111' are minimum RF level?

0 jim s over 4 years ago in reply to Des Coghlan

TI__Guru* 91947 points

When using the DAC in NCO only mode, we set the DAC to minimum output from the digital input. This can be done in two ways. Set the constant input to 0x0000 and set the DAC to Offset Binary mode (0x2 bit 1) or set the constant input to 0x8000 with the DAC set to 2's comp. The coarse gain is then used to adjust the output gain if needed (0x03 bits 15:12).

Data converters

Data converters forum

DAC39J84: Test Tone