On Fri, 30 Nov 2001 11:13:45 -0800, you wrote:

>
>    I assume that you're referring to the Cypress EZ-USB Development
>    Kit schematic.  We include the ESD protection chip on that board
>    because it's likely to be used in an environment that'll expose
>    it to lots of ESD.  In products that don't have that exposure, it
>    can be omitted and you can rely on the 2-3KV ESD protection
>    provided by the EZ-USB chip itself.  I would expect the PIC
>    inputs to have about the same level of protection as the EZ-USB
>    chips.
>

Actually, I'm using the docs for another USB development board as a
guide. Sorry, I've forgotten the link right off-hand but *it* is
probably based on Cypress's design. I'm primarily a bit-twiddler with
a pretty good hardware background (more at the tech level than the
design level). I try to provide a heads-up to the hardware guy I'm
working with whenever I can.

>    The 22-ohm resistors are for impedance matching.  Cypress's
>    oldest EZ-USB chips require those external resistors, but all
>    the newer ones incorporate them into the chip.  The PIC16C745
>    requires external resistors.

The 16C745/765 datasheet (DS41124C) shows D+ and D- connected directly
to the micro.=20

I finally got the PICDEM-USB User's Guide (DS41174A). Microchip's site
has a bad link on the 'download' button for it but the 'view' button
works. There are no external resistors shown in their schematic.

Did I perhaps miss an errata sheet somewhere?

>
>    I'm glad to see that our documentation is helping you design your
>    product, even if you ARE using Microchip microcontrollers
>    instead of our (cheaper, faster, better) parts.
>

At this point, I'm pretty much locked in to the Microchip parts but
I've certainly got my eyes open for any opportunity to use the Cypress
EZ-USB in the future. It certainly looks like one sweet piece of
silicon. :=3D)

Regards, Bob

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