Jan 27, 2006 #1 M mince Member level 5 Joined Feb 19, 2005 Messages 82 Helped 10 Reputation 20 Reaction score 4 Trophy points 1,288 Location Texas Activity points 1,894 Sometimes ground shields are used to shield from noise. Why do we use ground? Why not Vdd?
Jan 27, 2006 #2 N neoflash Advanced Member level 1 Joined Jul 2, 2005 Messages 492 Helped 10 Reputation 20 Reaction score 2 Trophy points 1,298 Activity points 4,759 Shielding question You can use both. Sometimes, different chips use different power supply, but they share the same ground. That make ground shielding more common.
Shielding question You can use both. Sometimes, different chips use different power supply, but they share the same ground. That make ground shielding more common.
Jan 27, 2006 #3 B bjeservice Member level 2 Joined Jun 8, 2005 Messages 45 Helped 3 Reputation 6 Reaction score 1 Trophy points 1,288 Activity points 1,657 Shielding question also i think that if you use Vdd it may has internal resistance to supply the noise to sink.
Shielding question also i think that if you use Vdd it may has internal resistance to supply the noise to sink.
Jan 29, 2006 #4 T Teddy Advanced Member level 1 Joined Sep 15, 2004 Messages 459 Helped 103 Reputation 206 Reaction score 62 Trophy points 1,308 Activity points 3,861 Re: Shielding question cause ground is considered "ideal" unlike VDD. On VDD is usualy more noise due to the switching.
Re: Shielding question cause ground is considered "ideal" unlike VDD. On VDD is usualy more noise due to the switching.
Jan 29, 2006 #5 VSMVDD Banned Joined Jun 12, 2005 Messages 643 Helped 92 Reputation 184 Reaction score 34 Trophy points 1,308 Location scotland uk Activity points 0 Re: Shielding question to get rid of noise you decouple it to ground becouse all energy take's the shortest return path in an effort to balance its self somewhere else so the noise goes with it hopefully.... i like your use of 'sometimes ' if you decouple to vdd your adding noise to the rest of the circuit again instead of taking it away some where else more negative then vdd + noise 180 deg out of phase with the same negative noise = 0 noise
Re: Shielding question to get rid of noise you decouple it to ground becouse all energy take's the shortest return path in an effort to balance its self somewhere else so the noise goes with it hopefully.... i like your use of 'sometimes ' if you decouple to vdd your adding noise to the rest of the circuit again instead of taking it away some where else more negative then vdd + noise 180 deg out of phase with the same negative noise = 0 noise
Jan 30, 2006 #6 N neoflash Advanced Member level 1 Joined Jul 2, 2005 Messages 492 Helped 10 Reputation 20 Reaction score 2 Trophy points 1,298 Activity points 4,759 Re: Shielding question Teddy said: cause ground is considered "ideal" unlike VDD. On VDD is usualy more noise due to the switching. Click to expand... There should be no difference between GND/PWR on noise wise. They are one loop. Your decoupling strategy should depend on your receiver is referenced to GND or PWR.
Re: Shielding question Teddy said: cause ground is considered "ideal" unlike VDD. On VDD is usualy more noise due to the switching. Click to expand... There should be no difference between GND/PWR on noise wise. They are one loop. Your decoupling strategy should depend on your receiver is referenced to GND or PWR.