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DS90UB954-Q1: Precautions when using crystals

Part Number: DS90UB954-Q1

Hi team,

In DS90UB954, crystals are used.
The crystal will be NX3225SA.
The matching of the crystal has been checked and the capacitance of the capacitor has been adjusted.
However, in the noise test, the immunity is weak, so please tell me a little about it.

Question 1
Are there any details that we should pay attention to when connecting the 954 and the crystal?
For example, restrictions on the distance between the components of the 954 and the crystal, or precautions for pattern routing.

Question 2
Looking at the EVM, I see that the 954 and crystal are mounted on different layers.
I think it would be ideal to mount them on the same layer, but is there a reason why you mounted them on different layers?
Please let me know which you would recommend.

Question 3.
In EVM, a shield case can be mounted as part reference H1.
What is the purpose of the shield case?
Is a shield case required when using crystals? Or is it recommended?

Best regards,

Masanori

  • Hello,

    Thank you for your question. I will look into the specifications of your crystal and any precautions or guidelines related to its application with the 954. I will provide an update by the end of tomorrow.

    Regards,

    Darrah

  • Hello,

    Thank you for your patience. To answer your questions, we do not have any specific limitations or restrictions regarding distance between the crystal and device. However we do recommend that you keep the routings as short as possible and surround the crystal with ground areas. If the crystal can not be placed close to the 954 then the traces can be embedded between two ground layers. In this solution the crystal and the 954 will be mounted to the same layer and only the traces connecting them would be embedded. Using a shield case is optional, and should not be necessary if you embed the traces between the ground layers. An EMI shield case is used to protect the signal from any interference. Overall, try to keep the traces as short as possible an keep the crystal and traces surrounded by ground areas and if necessary embed the traces between two ground layers.

  • Hi Darrah,

    Thank you for your response.
    I understand and will close it.

    Best regards,