# Tag Info

39

I can't understand why we need to use a ground plane at 1/4 wavelength and 1/2 wavelength not needed. A 1/2 $\lambda$ dipole has voltage and current waves like this: - Picture from Wikipedia. Now, if you focus your eye at dead centre of the picture you will see that the voltage is always zero volts. This is because a dipole is optimally driven with a ...

36

You got to think in terms of shared impedance (not resistance, really impedance). Consider the parts of the circuit that use GND as a 0V reference for sensitive analog purposes. Obviously you want each of these "0V references" to be at the same "0V" potential. However current running through the GND plane will introduce an extra error voltage on top of each ...

20

Simply introducing SLITS into the GND plane may suffice to largely keep digital/power/relay/motor trash out of the delicate analog areas. [ EDIT June 9 Showed a narrow region will achieve 12dB/square attenuation. EDIT June 2019 Remember to slit the Power Plane as well (suggested by barleyman)] simulate this circuit – Schematic created using CircuitLab ...

18

The 1meg resistor is needed to safeguard the user from faults from other equipment connected to mains earth. Keep in mind that the wrist strap is a permanent connection to the electric system of the building. If another piece of equipment experiences a fault, there could be a big fault current through the mains earth wiring system. That means that, in ...

12

I suspect it's because it's as if you poured copper and it filled the empty space on the board like a liquid. See the paint bucket tool in many graphics programs.

12

Can a ground plane be used as a current return path? The major benefit for using ground planes is that they are used for this very reason. For instance, any circuit using a "perfect" ground plane guarantees that the local return path of current is directly beneath the forward (non ground) current flow: - The bottom-line is that current takes the path of ...

12

The first one uses a star grounding scheme, which works well in some circumstances: low frequencies, absence of incoming EMI/RFI... which means it is an increasingly less useful scheme in today's world... However, before talking about the loop, I'd like to point out that your design is single-supply, thus chips draw supply current and dumps it into the ...

12

A quarter wave monopole antenna doesn't have to have a ground plane... unless you want it to radiate EM energy with a certain efficiency and pattern. EM radiation requires accelerating electrical charges, which usually implies a voltage differential between two separated areas in space. A conductive ground plane is a particularly good region of voltage ...

11

According to the help system of eagle, you can use the command RIPUP @; to ripup all polygons. You can limit this to polygons of a list of signals by RIPUP @ GND VCC MYSIGNAL; You can define a keyboard shortcut for RIPUP @; and another for RATSNEST; to simply toggle between filled and non-filled polygons. By the way: You can also en-/disable the filling ...

10

As a rule, the ground of the circuit serve as a reference point for all signals. That is why it must have very low voltage difference across the circuit. It is generally not true for the Vcc - as long as no signals are measured relative to the Vcc, some bigger voltage differences are acceptable. The total current in the Vcc line is equal to the current of ...

10

High frequency return currents want to follow the outward currents due to inductance. If you force the return currents to take a different path then a couple of bad things happen. You create a loop that can receive and transmit magnetic interference. You introduce extra inductance in the signal path which can reduce signal integrity. Note that digital ...

9

For a 2-layer board its pretty common to have one dedicated GND layer and use the other layer for all signals and power. In any case, prevent long traces on the GND layer, otherwise you may have unnecessary long GND return paths (due to the split GND plane/islands). For multi-layer designs, its good practice to have at least one 100% dedicated GND layer ...

8

Before you expand the board to 6 planes, at least stop wasting what you have. What exactly do you imagine a dedicated power plane does for you? Think about it instead of blindly following someone else's religion. Yes, I know a lot of designs are like that, but without a solid technical reason it's just mass superstition. Use wide enough traces for the ...

8

It's suggesting that there is a "star-point" that "power ground" and "feedback/control ground" use as their points of reference to 0V. Anything that should/must connect to power ground i.e. input decoupling caps, output decoupling caps and main ground on the chip should be separate from ground on the feedback potential divider (not used on your design). ...

8

The real key is ALWAYS placement, do this intelligently and either setup can work for something like this, get it too badly wrong and not only will the board be very hard to route, but it will be hard to get the precision you want. Solid planes rule when you have fast stuff going on, anytime you have edge rates in the few ns region (Clock rate does not ...

8

Choosing ground cutouts on the basis of the signal's speed is only part of the story. The oscillator, and the 'high speed signals' your link talks about, are different situations. The oscillator is recommended to use a specific circuit layout. This is a very small circuit. Follow the data sheet. An adjacent ground plane would introduce much C to ground. It'...

7

You can route across a cut up plane with no issues as long as each cut up plane is paired with a tightly coupled solid (gnd) plane -and- you engineer the PDN (bypass network) to have sufficiently low impedance between all power plane islands and ground (use something like my PDNtool.com for this). If you make the cuts wider than about 1/3 the electrical ...

7

We're only talking about high frequencies here. If there is a DC connection, then there would be no need to split a plane. If you split the plane there is a loop created that has some area. That means there is inductance in the return path and a voltage can appear if the current changes suddenly (as when a signal switches). That's undesirable- it upsets the ...

7

No. There are very few instances in which separate grounds are necessary or good. In this case, you don't even have a mixed-signal system. There's no reason to have split ground planes, and separate grounds will only make things worse. Take care to manage your return currents and keep the buck/boost regulator layout compact. Everything else appears to be ...

7

You have two questions which you think are related since they both concern ground connections. However the questions are not related ! Q1) The actual ground connection, where the return current from the supply flows, are the black wires on the ATX power connector. Indeed the chassis is also connected to the motherboard via the screws but this connection is ...

7

The reasoning is very similar to the trend away from split grounds for digital & analogue. Its all about return current There has actually been a trend away from split ground planes and instead concentrating on placement separation AND consideration for the return current path. Do not split the ground plane, use one solid plane under both analog and ...

7

Let's get one thing absolutely clear: split/partitioned ground planes are never necessary, but they can be a useful technique to mitigate human error. But you can always achieve equal or slightly better performance using a single, unpartitioned or slotted ground plane and careful routing of your board. However, most mixed signal routing is also fairly ...

6

The tiny extra capacitance you will get on the power net will be pretty much irrelevant. It will be low ESR, but it won't be right where you need that, so it won't help much. In your situation, I would not do the power plane. There is little drawback electrically, but it adds just a little more chance you will mess up something. It will also make the ...

6

In the context of an RF antenna, 'ground plane' refers to any plane-like conductive thing near the antenna, which for, say, FM Radio transmission towers, is actually the ground. Like the kind with dirt that you walk on. This is because conductive things generally reflect electromagnetic waves. That also means they block them from passing through to the ...

6

Definitely do not extend the ground plane into the mains area. The relays are providing your safety isolation here. Draw a line (real or imaginary) across the middle of all the relays. Keep all low voltage tracking and components 'this' side of the line, keep all mains stuff 'that' side of the line. That will automatically ensure you maintain adequate ...

6

I disagree with Trevor's advice. In his proposal the secondary high-current loop is crippled by introducing two vias in the switching pass, adding unwanted inductance. It also will introduce current spikes into ground plane, which also has negative effect on overall signal integrity. Follow the recommended layout, even if the feedback loop is somewhat ...

6

Replying as one nonEE who did his share of circuits to another nonEE... First of all you have a clean schematic and a clean layout, so chances are things will just work as they are already. This is the benefit of overthinking the design in the right way. Now, for the questions per-se: Are you overthinking it? That depends what is your definition of "...

6

The short answer is no it won’t make a significant difference. The long answer is that conduction will be slightly worse with solder mask but radiation will be better, assuming that the bare metal is in good condition - the emissivity of a shiny metal surface is generally low, around 0.1 while that of a coated surface is 0.9 or more. Thus bare metal may ...

5

The main rule for such antennas is not to have any metal part near them, be it the board copper or not. Or, if this is impossible, to have them as far as possible. If you look at the area of the module around the antenna, you'll probably see that there is no copper in any of its layers. Given that, and provided that you made a keepout area on all layers of ...

5

A ground plane: provides a low-impedance ground connection, This is important since "ground" is how different components relate to each other. When ground lifts because of impedance noise margin is reduced and errors can result. acts as a EMI shield, If your product needs to undergo any sort of official certification then you can know that half ...

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