THVD1550: Customer Feedback_Waveform Distortion

Dear Teams,

Have a nice day!

Here is Dylan from NWC MM Team FAE. 

Could you help my customer to identify the root cause of waveform distortion of THVD1550 and how to solve it?

RR: 100Ku

Background:

It has waveform distortion occurs when used RS-485 to transmit long distance and multi-node data showing in the picture 1. Normally, the waveform should be a square wave, while the rising sahpe of the waveform is more like a triangular wave. This phenomenon occurs when it has multi-node (>26 node) or long distance

Comparison:

Customer used Maxim’s MAX485 and TI’s SN75LBC184 to test, and it performs normally.

Support Needed:

1. Could you help the customer review his schematic diagram (Figure 2) and waveform (Figure1) to find out the root cause?
2. Could you provide a soltuion to solve it?

                                          Figure 1: Waveform

                                                                                               Figure 2: Schematic Diagram of THVD1550

Thanks!

Dylan