Bob Barr wrote: > I'm about to do my first USB interfacing with a 16C745 > .... > Cypress's schematic shows a USB6B1 chip between the USB connector > and their EZ-USB micro. There are also two 22 ohm series resistors > (one each in the D+ line and the D- line) between the USB6B1 chip > and the EZ-USB chip. > > Is any of this necessary when connecting USB to the 16C745? I > haven't yet found a schematic for the Microchip USB demo board > (Does one exist?) so I can't tell if I'm looking for trouble or > not. Bob: 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. 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. 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. -Andy === Andrew Warren -- aiw@cypress.com === Principal Design Engineer === Cypress Semiconductor Corporation === === Opinions expressed above do not === necessarily represent those of === Cypress Semiconductor Corporation -- http://www.piclist.com hint: The PICList is archived three different ways. See http://www.piclist.com/#archives for details.