On Sat, 22 Apr 2006 23:53:43 +1200, you wrote:

>> According to Jan Axelson's book a 36 ohm resistor is required
>> in series at each drivers output, to act as source terminations
>
>Hmmm, thanks Colin. I guess then that those who don't put them
>in aren't in spec. I did think maybe there was a termination or
>impedance reason (like RS485 etc)

Not necessarily - the USB chip may have internal resistors (e.g. FT232R)
You should use whatever the chip manufacturer reccommends.

 

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