LMK04832: Shift phase dynamically by Dynamic Digital Delay

Hello Michiaki,

If using dynamic digital delay, then the minimum delay you can do is by half a VCO cycle (note that you need to use the half step feature for this); therefore, if the VCO frequency is a multiple of the reference frequency, then the phases can be adjusted dynamically. However, to better help you/corroborate this, please tell me more about your system, your goals with your delays/why you need to delay your outputs, and the exact frequencies you're working with. If you have a .tcs file, please also attach it. Thanks!

Best,

Andrea

Hi Andrea,

For example to understand easily, in case of CLKout at 3GHz, customer can select VCO frequency = 3GHz, reference frequency = 250MHz with half step function using Dynamic Digital Delay for the dynamic phase shift at 90° ?

Thank you and best regards,

Michiaki Tanii

Hi Andrea,

We want your clear yes, no answer to clarify if our understanding is correct or not at first.

For the below example, is our understanding correct ?

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For example to understand easily, in case of CLKout at 3GHz, customer can select VCO frequency = 3GHz, reference frequency = 250MHz with half step function using Dynamic Digital Delay for the dynamic phase shift at 90° ?

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For the 6GHz output operation which your point out, customer understand LMK04832 doesn’t support 6GHz but they want to know if the device can work pseudo 6GHz by shifting 90 degree phase because the device has already been used in another project.

Your understanding would be highly appreciated.

Michiaki Tanii

Hello Michiaki,

I want to clarify, are trying to achieve a 180 degree phase shift or 90 degree phase shift? Your diagram shows a 180 degree phase shift (refer to diagram below):

Michiaki Tanii said:

For example to understand easily, in case of CLKout at 3GHz, customer can select VCO frequency = 3GHz, reference frequency = 250MHz with half step function using Dynamic Digital Delay for the dynamic phase shift at 90° ?

This assumption is correct if you meant 180 degrees instead of 90 degrees and the phase shift is done tot he 3-GHz signal. Basically, this is the correct statement: "...in case of CLKout at 3GHz, customer can select VCO frequency = 3GHz, reference frequency = 250MHz, and set another CLKout with half step function using Dynamic Digital Delay for the dynamic phase shift of 180° from the 3-GHZ CLKout"

Michiaki Tanii said:

For the 6GHz output operation which your point out, customer understand LMK04832 doesn’t support 6GHz but they want to know if the device can work pseudo 6GHz by shifting 90 degree phase because the device has already been used in another project.

How is the customer aiming to achieve this, i.e create a clock from two CLKouts of the LMK04832? I am curious to learn more about their system.

Let me know if you have any other questions.

Good Luck,

Andrea

Hi Andrea,

Regarding your point it out, your understanding is correct.

Customer would like to generate pseudo 6GHz with interleaved operation by phase shift at 180 degree. Therefore, they just would like to make sure if LMK04832 can support to adjust phase by half period.

And we got additional inquiry as below.

You mentioned that the device can support to use half cycle of VCO frequency for minimum delay. It means that delay timing would be depend on the accuracy of duty of VCO CLK.

Could you share the data of accuracy for duty of VCO CLK ?

Thank you and best regards,

Michiaki Tanii

Hi Andrea,

Could you share the exact number of torelance for 50% duty ?

Thank you and best regards,

Michiaki Tanii

Hello Michiaki,

Let me reach out to the design team for the specific tolerance and I'll let you know.

Best,

Andrea

Hi Andrea,

Let me summarize my understanding based on your answer.

Regarding the tolerance, accuracy of duty of VCO CLK, there is no tolerance, really accurate of duty of VCO CLK at 50% duty cycle.

Customer will use two 180 degree phase-shifted outputs. In that case, customer need to care of the skew between different CLKouts. It means the skew will cause 60ps delay between outputs.

Is my understanding correct ?

Thank you and best regards,

Michiaki Tanii