| ??? 07/05/06 13:57 Modified: 07/05/06 14:05 Read: times |
#119676 - Of course, this is no excuse for fumblin Responding to: ???'s previous message |
Erik said:
I agree that it is advantageous to use slew rate limited transcievers, but I do not agree with the implication in the above that if you do, you can forget the other rules. I did never imply, that you can forget the rules! No, there's often the problem, that customers change the RS485 cable and finally result in a situation, where a cable is connected which does not 100%-ly match the termination impedances. In such a case, especially if the cables are very long, a slew rate controlled driver is extremely helpful! Also, cables are imperfect, always! They should be 100%-ly symmetrical, but they aren't in reality. Here, signals with really fast edges can cause big problems, especially if you want to use a shielded cable, but can only use soft grounding techniques. Here again, a slew rate controlled driver is extremely helpful! No one should use non slew rate controlled RS485 drivers today, unless he needs highest data transmission rates. But then his application needs special care and treatment anyway... Again, imperfections of used components can severely cause data transmission problems, even if all the design rules are fullfiled. Then the use of slew rate controlled drivers can drastically enhance the system performance and reliability. Kai |
