DAC38J84EVM: 1

Bowei Yang

Part Number: DAC38J84EVM
Other Parts Discussed in Thread: LMK04828

Tool/software:

I don't understand the frequency relation in this setup(TI_JESD204_IP_KCU105_DAC38J84_841.zip ) which is the answer in this question.

https://e2e.ti.com/support/data-converters-group/data-converters/f/data-converters-forum/1062013/dac38j84evm-dac-pll-out-of-lock

Why the J17 is fed by a 409.6MHz signal? I see from vivado that there's a pll ip convert a 80MHz to 20MHz which is the sys_clk. And I think this in reality should be 78.125 to 19.53125MHz and that sys_clk can drive a 2.44MHz sine wave shown in the end. But I don't understand how the clock chip convert a external 409.6MHz to 78.125MHz. In the LMK04828 controls clock output setting, the DCLK divider is 32 which I think means the external 409.6 is down convert to 409.6/32 to 12.8MHz.

over 1 year ago

0 Bowei Yang over 1 year ago

Prodigy 30 points

By the way, in my design I tried this setup but somehow there's no output from the dac. I used 156.25MHz as clock in and the clock from CLKout 12 is just 156.25/(Divider I set) MHz

0 Matthew Kramer over 1 year ago in reply to Bowei Yang

TI__Expert 3950 points

Hello,

The GUI/EVM was designed for an older firmware that used different clocking parameters. You can go into the LMK04828 controls and set the clock dividers up accordingly based off what the new firmware needs.

If you can give me what dac update rate/interpolation you are trying to use with LMFS = 841 I can help with the clock setup.

Regards,

Matt

0 Bowei Yang over 1 year ago in reply to Matthew Kramer

Prodigy 30 points

Hi Matthew,

Thanks for the response. The actual dac update rate I want to have is 156.25MSPS and interpolation is 1(I think this means no interpolation). What external clock should I use and please help me set the clock. The CLKout0 will be my GT reference clock and CLKout1 will be SYSREF. I also use CLKout12 as my sys_clk which is for the lane_data in the tx IP.

0 Chase W over 1 year ago in reply to Bowei Yang

TI__Mastermind 24550 points

Closing for duplicate thread

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DAC38J84EVM: 1