DAC38RF80: JESD204B supported Formats clarification

LALIT VERMA

Expert 1655 points

Part Number: DAC38RF80
Other Parts Discussed in Thread: DAC38RF89

Hi TI,

We are using three DAC38RF80 in our design.We are planning to use internal PLL.

DAC has two VCOs and their ranges are:

VCO 0: 5.24Ghz - 6.72Ghz

VCO 1: 7.960Ghz - 9Ghz

Now, in Table 9 of datasheet, for L-M-F-S-Hd = 22210 and 8x interpolation , the maximum sampling rate is 5GSPS.

But this frequency is not in range of either VCO of DAC internal PLL.

Then how this is supported?

Our second query is :

Are the JESD204B modes given in table 9, only supported modes or can we use other settings also like using 10x interpolation for L-M-F-S-Hd = 22210 which is not mentioned in Table 9.

If we use PLL bypass mode with external clock , then can we use the DAC in modes which are not specified(like using 10x interpolation which are not supported by some modes in Table 9) in Table 9(max sampling rate will be less than 9GSPS.)

Thanks,

Lalit

over 5 years ago

0 dBrock over 5 years ago

TI__Genius 12780 points

Hi Lalit,

One of our experts is looking into this question, and will be back with you soon.

Best Regards,

Dan

0 jim s over 5 years ago

TI__Guru* 91947 points

Lalit,

For query #1, you can achieve this rate if you use external DAC clock or switch to the DAC38RF89, which has a 5GHz VCO.

For query #2, the only options available are the ones shown in this table. Even though the part can have a serdes rate and sampling rate within specification if using 10x interpolation in this mode, there are other clocks and logic blocks that will not support this mode. This is why this is not an option in the table.

Regards,

Jim

0 LALIT VERMA over 5 years ago in reply to jim s

Expert 1655 points

Hi Jim,

Thanks for the reply.

I have one more query.

In section 8.3.2 of datasheet, it is mentioned that there is a limit on the lowest serdes lane rate supported.

What is the minimum Serdes lane rate supported when using DAC38RF80 internal PLL clock or external clock?

Thanks,

Lalit

0 jim s over 5 years ago in reply to LALIT VERMA

TI__Guru* 91947 points

Lalit,

The minimum serdes rate is 781.25Mbps. This is the lowest rate that can be used by the 8 serdes data lines. This rate can be calculated using the following equation:

Regards,

Jim

0 LALIT VERMA over 5 years ago in reply to jim s

Expert 1655 points

Hi Jim,

I am not able to see the equation which you have posted in your reply.

Can you please post it again or tell me the equation no. and page no. of DAC38RF80 datasheet?

Thanks,

Lalit

0 jim s over 5 years ago in reply to LALIT VERMA

TI__Guru* 91947 points

1643.Jesd clk divider.docxLalit,

See attached document.

Regards,

Jim

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DAC38RF80: JESD204B supported Formats clarification