| ??? 04/16/08 02:09 Read: times |
#153419 - Hhm... Responding to: ???'s previous message |
Andy said:
There's no need to have separate analog and digital ground planes, in spite of what most ADC and DAC data sheets tell you. You must be smarter than these developement engineers. Have you tested this with the AD7730? Do you think that high frequency currents run on a straight line from point A to B on a ground plane or do they spread and cover more an area than a straight line? If so, do you still think that having only one ground plane is advantageous? Andy said:
Consider a system with more than one ADC. Where do you connect the ground planes together? A system with more than one ADC usually gives poorer results. Why using a technique suited for more than one ADC if he has only one? Also, even systems containing more than one ADC can benefit from the concept of local ground points. Andy said:
Simply pour one plane, and pay attention to your signal routing. Keep digital and analog signal traces as far away from each other as possible, and avoid allowing them to cross. That's true, though, even when using splitted ground planes. Andy said:
A shield is an extension of the chassis, and as such should be connected to the enclosure. Then make sure your enclosure connects to the circuit common. No! The shield of a cable can be part of the chassis, but need not. Think only about what currents might flow along the cable shield when being improperly connected to the chassis: Ground return currents of power supply, ESD currents from chassis to protective earth, secondary ESD, etc. Very sensitive circuits can contain several different shields, connected to several different local analog grounds, none of them necessarily being connected to the chassis. Kai |
| Topic | Author | Date |
| Load cell shield | 01/01/70 00:00 | |
| Earth ground | 01/01/70 00:00 | |
| where is Earth ground ... | 01/01/70 00:00 | |
| yes but.. | 01/01/70 00:00 | |
| Why Ain- is grounded... | 01/01/70 00:00 | |
| read datasheet of AD7730 | 01/01/70 00:00 | |
| it's correct | 01/01/70 00:00 | |
| try Yourself and tell us result | 01/01/70 00:00 | |
| Connect the shield to analog ground! | 01/01/70 00:00 | |
| I tend to forget | 01/01/70 00:00 | |
| Good idea! | 01/01/70 00:00 | |
| Analog gnd | 01/01/70 00:00 | |
| Exactly! | 01/01/70 00:00 | |
| Ferrite beads trick! | 01/01/70 00:00 | |
| Loadcell Shield | 01/01/70 00:00 | |
| ground planes | 01/01/70 00:00 | |
| Hhm... | 01/01/70 00:00 | |
| re: hmm | 01/01/70 00:00 | |
| interesting | 01/01/70 00:00 | |
| RF | 01/01/70 00:00 | |
| RF GSM | 01/01/70 00:00 | |
| I use use this | 01/01/70 00:00 | |
Walkie talkies | 01/01/70 00:00 | |
| Load Cell Screens | 01/01/70 00:00 | |
| JUST FOR RECORD | 01/01/70 00:00 | |
| Two enclosures, on safety class I requirements | 01/01/70 00:00 | |
| No proof, of course... | 01/01/70 00:00 | |
| Load cell cable problem | 01/01/70 00:00 | |
| fix it | 01/01/70 00:00 | |
| Problem is | 01/01/70 00:00 | |
| so make Digital Load Cell | 01/01/70 00:00 | |
| good idea | 01/01/70 00:00 | |
| give picture | 01/01/70 00:00 | |
| Screens and cables. | 01/01/70 00:00 | |
| "Fixed Structure" | 01/01/70 00:00 | |
| Fixed? | 01/01/70 00:00 |