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Message
From: Rick Collins<opencores.usb@a...>
Date: Fri Mar 5 17:04:17 CET 2004
Subject: [usb] Suspend mode and FPGA:s
At 10:39 AM 3/5/2004, you wrote:
>If you want to put the FPGA in a very low power mode, you will have to
>pick your FPGA for that. I have been doing a lot of searching for
>semi-low power, but mainly 5 volt tolerant FPGAs. Turns out there is a
>lot of overlap between the two. As they shrink the process geometries,
>the 5 volt tolerance goes away and the quiescent current goes up.
>
>I found an ACEX (EP1Kxx) family from Altera that has 5 volt tolerance with
>a quiescent current in the 5 - 10 mA range. This is not within your spec,
>but it may do the job. Altera also makes the Cyclone family (EP1Cxx)
>which is not 5 volt tolerant and has a quiescent current in the 4 - 12 mA
>range (typ) depending on part.
>
>Xilinx lost 5 volt tolerance with the introduction of the Virtex IIE
>family. The quiescent current of the Virtex IIE is in the 100's of
>mA. The Virtex II family has 5 volt tolerance and has a quiescent current
>around 10 - 100 mA depending on the part. The older Spartan XL family is
>both 5 volt tolerant and has a very low quiescent current of about 100 uA.
>
>Certainly it will be easier to work with the newer parts since they also
>tend to be cheaper and larger. But the older parts fit your needs better
>it seems.
>
>What exactly is the wake up criteria in the USB spec? It would be an
>unusual circuit that could do significant processing and still have very
>low power like this (500 uA). But then I guess it is not
>impossible. Does the circuit wake up on the first signal transition on
>the USB bus?
Sorry, all of my references to Virtex above should be changed to
Spartan. Xilinx introduced the Spartan family as a low cost version of the
XC4000 family. Then the low cost version of the Virtex/Virtex E family was
the Spartan II/IIE and now the low cost version of the Virtex II family is
the Spartan 3. I was looking at the Spartan II/IIE data sheets and wrote
Virtex II/IIE. I don't even think there *is* a Virtex IIE family.
:)
Arius - A Signal Processing Solutions Company
Specializing in DSP and FPGA design URL http://www.arius.com
4 King Ave 301-682-7772 Voice
Frederick, MD 21701-3110 301-682-7666 FAX
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