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USB Hosts Hubs Transceivers

16huuser
New Contributor

Hello,

I am a designer looking to use CY7C65634-28LTXCT in my design. The crystal is said to have a drive level with a  minimum of 600uW. The crystal recommended by Cypress is ECS-120-20-4 which only has a drive level max of 500uW. I have seen support recommend adding a series resistor on XOUT to keep the drive level underneath the max of the crystal. Are there any recommended values for this or a way to calculate drive level with this added resistor? I am struggling to select this resistor for my design.

Thanks

Eric Huus

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Sananya_14
Moderator
Moderator

Hello Eric,

The recommended crystal ratings are the maximum ratings which means we recommend a 600uW crystal to make sure power dissipation does not exceed the drive level of the crystal. Please check the actual power dissipation of HX2VL on your board using the equation in section 3.2.1 of AN72332 based on your crystal's parameters and if its below 500uW, you could go ahead and use it in your design.

For selecting a resistor to reduce the power dissipation, you could refer to this link from ECS.

Best Regards,

Sananya

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