CYUSB Power

[Anonymous]

Hello Again.

   

For current numbers, please refer : 

   

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

   

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

   

I was pointed to these two knowledge base articles.  Thank you very much.  But this leads to another question or probably two.  How is it that the numbers say the VBUS current draw when the board is Bus powered is over 100mA.  USB at least 2.0 states a bus powered device needs to come up with 100mA or less and then enumerate and ask for higher current, 500mA.  So can the FX3 be bus powered off of a USB 2.0 bus since it draws more than 100mA according to the knowledge base articles above?  

   

I know that may computers now just give out more than 100mA so most of the time it won't be an issue but there are some that this is a problem with.

   

By the way will the current numbers be lower if I am running the CYUSB2014 device and how much lower?

   

Thank you

   

Gary

[Anonymous]

HI Gary,

   

We agree that with boot loader the current drawn is more than 100mA and violating the spec. But we believe it will not be a problem because no one will go to certification with bootloader. Also in the end products we will use SPI or I2C for booting.

   

In the final product , you will have the option in firmware to enable or disable the blocks to bring the current down to less than 100mA.

   

Thanks,

   

Krishna.