DS90UB948-Q1: CML register setting and sequence

Roy Chou1

Genius 16055 points

Part Number: DS90UB948-Q1
Other Parts Discussed in Thread: ALP

Hi Team,

I would like to measure eye diagram by CML output. (Video soure from 947, not internal pattern gen)

0x52 ; 0x56 ; 0x57 ; 0x63 is related register.

1. 0x56 should be 0x04, is it right?

2. What is difference between 0x52 and 0x57? how could I set the adress?

3. what is meaning of 0x63? how could I set?

what is the CML register setting sequence?

Thank you for your help.

Regards,

Roy

over 5 years ago

0 Bryan Kahler over 5 years ago

TI__Mastermind 25955 points

Hi Roy,

0x56[3] is the enable. Assuming the reserved registers are all 0b0, the hex value for the register would be 0x08 to power up the CML driver, and 0x00 to power down the CML driver

0x63[0] is used to power down the CML TX. It must be powered down prior to using the pattern generator on the device.

As for setting the address and the sequence, the following post describes how to write to the registers using ALP with respect to he 948 and CMLOUT:

https://e2e.ti.com/support/interface/f/138/t/595666?DS90UB948-Q1-CMLOUT-configuration

Please let me know if any further clarification would be of help!

Sincerely,
Bryan Kahler

0 Roy Chou1 over 5 years ago in reply to Bryan Kahler

TI__Genius 16055 points

Hi Bryan,

Thank you for your reply.

I almost the register setting but I didn't see the setting sequence in the link. Does it mean we don't need to care the setting sequence?

Regards,

Roy

0 Bryan Kahler over 5 years ago in reply to Roy Chou1

TI__Mastermind 25955 points

Hi Roy,

The enable register must be set to enable the functionality.

If you're experiencing an issue with CMLOUT, please share the scope image and script being used so we may analyze.

Sincerely,
Bryan Kahler

0 Roy Chou1 over 5 years ago in reply to Bryan Kahler

TI__Genius 16055 points

Hi Bryan,

Below is CML measurement, I think this is not a good eye diagram.(also couldn't meet datasheet spec) And I have used MAP and pass the MAP process. Do you have any idea why CML test result is like this?