Post by thread:Network for intelligent home, MAX487

On Fri 28 Nov, W.E. van Bemmel[SMTP:spam_OUTbemspanTakeThisOuTXS4ALL.NL] wrote: > > If wheater allows I will use my lawnmower to chop the goat and ignite > the barbecue by GPS controlled LASER. > > More seriously however, to stay [on topic], > > What is the virtue of slew rate limited RS485 devices like Maxim's 487 > compared > to non-limited ones like MAX485, of which I have some samples? > I can think of RFI, spikes, reflections... > > Who knows? Slew-rate limited devices like the MAX487 have their edge rate decreased to approx. 1us (5V/us). This means that the highest radiated frequencies are on the order of 1MHz instead of 40MHz, which greatly reduces EMI. Additionally, the maximum unterminated cable length is approx L_max = 9 * t_r due to reflections where t_r is the rise time in ns, and L_max is the length in cm (90m for 1us). This means that you can have long stubs on your network -- and that makes it a lot easier to route cable. Frank ------------------------------------------------------------------------ Frank A. Vorstenbosch Phone: +44-181-636 3391 Electronics & Software Engineer or: +44-181-636 3000 Eidos Technologies Ltd., Wimbledon, London Mobile: +44-976-430 569