Timeline for Is it alright to connect NC (no internal connection) to the ground?
Current License: CC BY-SA 3.0
20 events
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| Mar 24, 2017 at 1:54 | comment | added | tangrs | @Misunderstood That's a fair enough point. | |
| Mar 24, 2017 at 1:47 | comment | added | Misunderstood | @tangrs I did not say parasitic capacitance is not real, I'm saying it is not applicable in this circumstance. Yes there is capacitance between conductors. But when there is zero current flowing in the conductors, the capacitance does not matter. This pin does not have any current flowing through it. And there is only one conductor not two. And enough already about high frequency, there is none of that here either. | |
| Mar 24, 2017 at 1:42 | comment | added | tangrs | Let us continue this discussion in chat. | |
| Mar 24, 2017 at 1:39 | comment | added | tangrs | @Misunderstood I'm also perfectly happy to admit that it's plausible to get NC and DNC mixed up. It's all part of the learning process and I don't see anything wrong with it. I tend to find that learning is much easier when you don't have an ego to stroke. | |
| Mar 24, 2017 at 1:35 | comment | added | tangrs | @Misunderstood To substantiate my points, I can say that parasitic capacitance is a well-known real phenomenon. The linked page mentions: "[There] is always non-zero capacitance between any two conductors; this can be significant at higher frequencies with closely spaced conductors, such as wires or printed circuit board traces." 'Any two conductors' can and does include a NC pin on a chip. | |
| Mar 24, 2017 at 1:34 | comment | added | tangrs | @Misunderstood sigh please tone down the ad hominem. I agree this is going off topic and I'm perfectly happy to admit I might be wrong here but please substantiate your arguments with actual sources and evidence. Your last three comments were pure rubbish containing more personal attacks than actual points of discussion. | |
| Mar 23, 2017 at 23:36 | comment | added | Misunderstood | @tangrs RE: " perfectly plausible to get confused between NC (not connected) vs DNC (do not connect)". You are confused about a lot of things. But being confused about NC vs. DNC is nothing to be proud of and you might want to consider keeping that to yourself. It is not plausible to me as is you other ramblings about irrelevant phenomena. Electrons do not flow in a capacitor??? E God. High frequency??? Irrelevant. Stay on topic, this is about the pin, not what is floating around in your head. | |
| Mar 23, 2017 at 23:30 | comment | added | Misunderstood | @tangrs I almost banged my head against the wall reading your drivel. You capacitor analogy is as stupid as stupid gets. A capacitor has two leads with emf energy on both ends. THIS pin has none. Touch capacitance has nothing this do with this pin because this pin has no parasitic anything. A touch sensor has parasitic capacitance which is altered by touch. Not applicable. This is not only not a high frequency app, it is not even electrical , it a pin attached to an SMD pad with no meaningful electrical characteristics. Why can you not understand without electron flow there is nothing. | |
| Mar 23, 2017 at 23:17 | comment | added | Misunderstood | @catraeus I think parasitics was what someone pulled out of their ass here in an attempt to cover their ass when making unsubstantiated statements. Blame the parasitics, they can't fight back. What you say is true... when it's a pin that has electrons flowing through it. That is not the case here. Did you have a point? "would shut down DDR4" where that came from is beyond comprehension. The pin cannot be used to pass through to anywhere. If there were a via in its pad the pin could in no way effect any current flowing through the pad or via. You are grasping at straws and failing poorly | |
| Mar 23, 2017 at 22:32 | comment | added | catraeus | @tangrs Electric current flow comes from two means. One is actual electrons (or protons) that physically move through space. The other, much more subtle concept, is that electric current flow is due to changing electric fields. Look up Displacement Current | |
| Mar 23, 2017 at 22:29 | comment | added | catraeus | @Misunderstood on parasitic cap. It is from the metal surface of the pin ( it can go for a few mm inside the device on bigger chips) to all of the other circuit conductors that pass nearby. The electric field makes an air capacitor between the pin and other conductors. It is specific to the special cases I indicated. For example, that pin on this device we've been discussing would shut down DDR4 if it was used as a pass-through route. It doesn't do diddly to the 2A current that comes from the ground or power connections of this device. | |
| Mar 23, 2017 at 22:26 | comment | added | catraeus | I have seen some cases where NC actually was intended to say DNC. Reading the datasheet (RTFM as they say) you find whether it has no internal connection or is meant to say that it is a must-not-connect. I double check most everything. I have designed pacemakers, there is no room for "oh well I'm sure that it actually means ... " | |
| Mar 22, 2017 at 7:01 | comment | added | tangrs | @Misunderstood FYI, you're right in saying that electrons don't actually flow through but neither do the electrons in a capacitor. Yet, we say that current can flow through a capacitor. It's the same deal here with the NC pin and anything else with a different potential. You can think of the pins as the plates in a capacitor. Although separated, charges can build up on the pins and makes them act like a capacitor. Although the capacitance is small, in high-frequency applications, can be significant. | |
| Mar 22, 2017 at 6:53 | comment | added | tangrs | @Misunderstood If you're wondering where the capacitance comes from, have a look at how capacitive touch sensors work. The whole principle behind capacitive touch sensors relies on the effect of parasitic capacitance. | |
| Mar 22, 2017 at 6:51 | comment | added | tangrs | @Misunderstood once you start doing high-frequency things, you will find the stray capacitance will become a non-negligible problem. That's what catraeus is talking about. I think it's perfectly plausible to get confused between NC (not connected) vs DNC (do not connect). | |
| Mar 22, 2017 at 4:48 | comment | added | Misunderstood | So for 30-40 years of reading datasheets, you are saying every time you saw a pin marked NC you thought it may be connected to something? Really? Or was that sarcasm. | |
| Mar 22, 2017 at 4:39 | comment | added | Misunderstood | This little parasitic cap, where is it physically? Within the pin between the component body and the SMD pad? If that is the case then there would be no electrons flowing from the pad up the pin. It is an open, near infinite resistance/impedance. Not a single electron is going flowing through the pad is going to travel up the pin because there is no energy potential on that pin, zero. So this pin is sitting on top of a PCB pad, not interfering, not bothering anyone, yet the electrons are going to be upset? Why? | |
| Mar 22, 2017 at 4:04 | comment | added | catraeus | Well ... No internal connection means that there are no silicon connections to that pin, thus it is great for not hurting the device to connect as you please. As for parasitics, there are electrons flowing onto the tiny capacitor that the pin creates to the rest of the world. That parasitic won't upset this application, but if this were high speed or super low current, then it would upset the electrons on the board trace. | |
| Mar 22, 2017 at 3:50 | comment | added | Misunderstood | The datasheet is very clear. "No internal connection. The pins marked NC are true “No Connect” pins". How is that NOT clear???? "it will add parasitics" How will it do that? No electrons will flow through it. It's going to add parasitics to Ground? How? Remember, there is NO INTERNAL CONNECTION, it is not connected to anything. Nowhere for electrons to go. | |
| Mar 22, 2017 at 2:11 | history | answered | catraeus | CC BY-SA 3.0 |