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USB Superspeed Peripherals

Anonymous
Not applicable

Hello

   

 

   

Couple Questions.

   

1) Clarification question on the Vramp spec.  The Voltage Ramp on my supplies which are 3.3V and 1.2V need to be monotonic.  That means the just need to have a smooth and consistent rise rate.  They do not have to have the same ramp rate?  Basically my 3.3V and 1.2V will reach these levels at the same time and therefore their rise rate will be different.

   

2) What is the current draw on the VBUS and VBATT pins?  The Vbus pin states it has an internal regulator to power the USB I/O pins?  Since I'm only using the USB 2.0 function I don't know what the current draw is on these 2 pins? 

   

 

   

Thanks

   

Gary

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3 Replies
Anonymous
Not applicable

Hi gary,

   

1) Please make sure that the power domain decoupling caps follow the recommendations in An70707 application note.

   

2) For current numbers, please refer : 

   

http://www.cypress.com/knowledge-base-article/ez-usb-fx3-power-consumption-kba85505

   

http://www.cypress.com/knowledge-base-article/ez-usb-fx3-vbus-power-consumption-kba90951

   

Regards,

   

- Madhu Sudhan

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Anonymous
Not applicable

Hi Madhu

   

Thanks again for all your answers.

   

But going back to question 1.  I was not too concerned about my caps as I will follow the AN70707 note.  But the datasheet states the a specification called Vramp.  "Voltage ramp rate on core and I/O supplies" in the notes section "Voltage ramp must be monotonic."  So what do you exactly mean by that?  Both the 3.3V and 1.2V for the core voltage and in my case the VIO need to ramp up smoothly?  Do they both have to rise at the same rate?  Or something else?

   

Thank you again.

   

Gary

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AjayB_76
Moderator
Moderator

There is no requirement on the power up sequence for the FX3 device

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