| ??? 07/07/08 14:09 Modified: 07/07/08 14:14 Read: times |
#156476 - ESD Responding to: ???'s previous message |
Per said:
I'll still go forsom Linear or Maxim driver with 15 kV ESD protection... Make no mistake, this nice chip internal ESD protection feature should not make you hilarious. It's no good idea at all to invite ESD to enter your PCB. So, use Ceradiodes between A/B-lines and signal ground right at the connector. Don't forget to also transmit signal ground. Connect signal ground right at the connector to the chassis ground via a 100n-cap, paralleled by a 30...40V bipolar transzorb and 1M resistance. Only SMD-parts on large copper traces in combination with a solid ground plane will do. Avoid all kind of wires for these connections, so avoid "pigtailing"!! It's best to use a shielded RS485 cable and to connect the shield at both ends to chassis ground. But let signal ground float using the above mentioned soft grounding technique. That's exactly what the PROFIBUS people do. This design will make you immune against ESD, Bursts and Surges (CE conform). Even, if you route the A/B-lines internally of chassis away from the connector. All sort of filtering and protectioning must happen right at the connector!!!!!!!! Kai |
| Topic | Author | Date |
| RS485 on straight wires? | 01/01/70 00:00 | |
| terminate with the "characteristic impedance" and | 01/01/70 00:00 | |
| Possible | 01/01/70 00:00 | |
| No so good | 01/01/70 00:00 | |
| The idea of pairing and twisting... | 01/01/70 00:00 | |
| Telephone Cable... | 01/01/70 00:00 | |
| If not straight wires | 01/01/70 00:00 | |
| sorry Per | 01/01/70 00:00 | |
| it's okay | 01/01/70 00:00 | |
| We use Cat-5 cables... | 01/01/70 00:00 | |
| ESD | 01/01/70 00:00 | |
| Which end? | 01/01/70 00:00 | |
| If ... | 01/01/70 00:00 | |
485/422/profibus | 01/01/70 00:00 | |
| 485 cable | 01/01/70 00:00 |