| ??? 08/11/11 14:03 Read: times |
#183297 - transils... Responding to: ???'s previous message |
Thank you very much that you had a look at my schema.
Kai Klaas said:
1. There's no cap at the DC-DC-converter between pin2 and pin4 (GND and AGND)! This will inject enormous switching interference directly on the RS485 bus.
Solder a cap of about 10nF directly between pin2 and pin4 with very shortest connections (every millimeter counts!). Sometimes two or more caps in parallel at this place can decrease the switching noise even further. I will put the cap as you suggest. Do you know where I can find this kind of information (about the cap)? I didn't find any reference in the datasheet. Kai Klaas said:
A better approach is to use slew rate limited and ESD tolerant RS485 transceivers, like the LTC1487 e.g., and omit these ferrite beads and transzorbs with their huge capacitances. The LTC1487 is also fail-safe and doesn't need these R8 and R9 voltage divider resistors. So you suggest me to replace ADM485 by LTC1487 and remove the transils, FBs and pull-down and pull-up resistors... It looks like interesting but if no driver is connected on the line, is it not necessary to define voltage levels by the R8 and R9? In the case of lightning, is the internal ESD protection sufficient? The transil can suppress up to 600 W of power... Thank you very much for your answer in advance... |
| Topic | Author | Date |
| Problem with RS232/RS485 converter... | 01/01/70 00:00 | |
| More info please | 01/01/70 00:00 | |
| probably | 01/01/70 00:00 | |
| more info... | 01/01/70 00:00 | |
| yes,i think | 01/01/70 00:00 | |
| input impedance | 01/01/70 00:00 | |
| i'm wrong | 01/01/70 00:00 | |
| what is the right value? | 01/01/70 00:00 | |
| did You tryed capacitor? | 01/01/70 00:00 | |
| thanks... | 01/01/70 00:00 | |
| it works...! | 01/01/70 00:00 | |
| congrats | 01/01/70 00:00 | |
| shape | 01/01/70 00:00 | |
| dont | 01/01/70 00:00 | |
| It is OK. | 01/01/70 00:00 | |
| Hints... | 01/01/70 00:00 | |
| schema | 01/01/70 00:00 | |
| Repair... | 01/01/70 00:00 | |
| transils... | 01/01/70 00:00 | |
| RS485 | 01/01/70 00:00 | |
| Sample Schematic | 01/01/70 00:00 | |
| Thank you very much for the schema... | 01/01/70 00:00 | |
| AVX varistors... | 01/01/70 00:00 | |
| capacitor | 01/01/70 00:00 | |
| capacitors... | 01/01/70 00:00 | |
| GNDs | 01/01/70 00:00 | |
| 1992 | 01/01/70 00:00 | |
| Thanks... | 01/01/70 00:00 | |
Links... | 01/01/70 00:00 |