Hi Team,
(1) Customer is asking if we have 485 theoretical slew rate or drive current vs. distance graph? If we don't include any extra EQ feature device, only compare to regular type 485, thanks for help.
(2) Also, is output swing at no load has anything to do with max distance it can go? Assume same device SN65HVD485 but different date code, I just want to know if this is directly related or partially or not so much, thanks.
Regards,
Andrew
Hi Andrew,
1. Here is a theorectical plot of data rate vs distance for RS-485:
We do offer an RS-485 transceiver with receive EQ so if an extended distance is needed please have a look at the SN65HVD23.
2. Vod with no load will be larger than the typical 2V that we see an RS-485 driver put out. This is because there is no voltage drop across the termination resistors in the network. Theoretically this could lead to a longer transmission distance but with out any termination resistors signal integrity can become an issue due to reflections and standing waves on the bus. The max data rate will also be limited in an application that does not use termination resistors. The data rate is not the issue though the rise and fall time is the issue as transceivers that support faster data rates have faster edge rates and they can cause a lot of over shoot and ringing on an unterminated bus. The termination resistor help in dampening this out. Here is a blog on the topic if you are interested: https://e2e.ti.com/blogs_/b/analogwire/archive/2016/05/19/get-connected-how-to-operate-your-rs-485-links-without-termination
Please let me know what other questions you have?
![[FAE] Andrew Wang](https://e2e.ti.com:443/cfs-filesystemfile/__key/communityserver-components-imagefileviewer/communityserver-components-avatars-00-00-07-45-83/4TN3ECJKFL7N.jpg_2D00_32x32x2.jpg?_=638280017690204870)
