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12

A schematic is not meant to be a drawing of a circuit, and shouldn't be used that way. The "pins" in a schematic just show connections. Put them wherever they need to go to make the drawing understandable, and don't worry about what they convey physically.


11

I'll start by answering your second question. Generally you should place pins in your schematic symbol so that it produces the neatest schematic possible. Usually this means power on the top, ground on the bottom, inputs on the left, and outputs on the right. I generally place the pin for the bottom pad logically based on its function. 9 times out of 10 ...


9

Your calculations check out for the given values, but keep in mind that the dielectric constant of FR-4 is not tightly controlled, and may vary between 4.35 and 4.7 between manufacturers [1]. Since your trace length is very short, this variation will not have a big effect (you can try the values in the calculator). For more demanding applications, special ...


6

I would add caution to @B. Kraemer's answer. While it may work if implemented properly, I have personally seen EMC problems with power plane-layers that were solved with moving decoupling capacitors more locally to reduce loop area. I am fixing another person's design currently where partial planes were used and some decoupling was not local (about 15mm) to ...


6

I am sorry to be the bearer of bad news! There are a few things that stand out. In addition, even after these problems are corrected, there's still going to be a lot of learning and analysis to do. Please don't take my suggestions as criticism; RF is tricky :) Also, there have been hundreds of books written on RF. I can tell you some things to look for, but ...


6

In these situations for prototyping I do something like this: You cut the traces on the PCB if you need to install the choke. That way you don't impedance problems from soldering wires. The problem with this setup is once you cut the PCB traces, you can't go back. Another way to do this would be to put 0 ohm resistors in series with the choke. Or you could ...


6

for this short of a distance (under 1/8th of a wavelength) impedance requirements get a lot looser, so on that premise its more than suitable, and lines up with my own calculator. As to the layout, I cannot particularly fault it, you're keeping good separation between it and other nearby signals, you have vias right next to the signal ground so the return ...


4

Normally trace width and separation is adjusted so that the traces will have the necessary characteristic impedance, so it looks like another transmission line just like the cable does. If the PCB traces are not very long then the mismatch is minimal even if impedance is not matched. Some connectors have controlled impedanve but not all, in this case the ...


4

It is literally on page 3 of the datasheet, which you linked in the question. Where exactly is the confusion? It states very clearly that Adj/GND in the SOT-223 is pin 1. Vin pin 3, and Vout is pins 2 and 4. There should be no need to double check if you read this table. Remember the input and output capacitors.


4

To what others have said, I'll add, You probably don't want to let the ground fill in between the pads of your DC-blocking capacitor. This will probably lead to excess capacitance to ground, and degrade the return loss of your RF input. You may want to move the RF connector a bit further away, so that the blocking capacitor doesn't have to be directly ...


4

That's not a very manufacturable design. Here's a more sensible design when you want to avoid getting solder paste into the thermal vias: As the source of the above photos mentions, having solder paste over the vias can cause production defects.


3

You can keep the tracks wide up as close as you can get, then taper down. If the connector is a single row and there's access i.e. the connector isn't at the edge, you can approach from both directions. and you can also use both sides and via them together further away. If it's more than 2 layers, you can also parallel up the inner layers too, but typically ...


3

Unless you're etching this yourself, a clearance of 0.2 mm probably won't be a problem for the manufacturer. 0.127 mm (5 mil) is not uncommon, and 0.152 mm (6 mil) is even more common. I would check your board house's requirements and modify the DRC rules to match what they are expecting. Then if there are any specific issues based on your manufacturer's ...


3

The official PCIe spec from PCI-SIG has this information. It’s downloadable from the PCI-SIG site for a fee, it’s free download for PCI-SIG members. Link: https://pcisig.com/specifications By the way, Supermicro lists that kind of adapter (half-high to 2x NVMe.) Here it is on Amazon: https://www.amazon.com/Supermicro-AOC-SLG3-2M2-PCIe-Add-Card/dp/B071S3ZY8P ...


3

The "blob" in the picture is a depiction of an ASIC physical layout created by a place-and-route algorithm. These algorithms often use randomized simulating annealing methods to place logic within a grid. These methods don't inherently favor a rectilinear layout; they often create layouts with an organic, cloud-like appearance. Similar algorithms are used ...


3

I am not so certain that there is a generic "best way" to choose between component selections. There may be a best way for your specific application and only you can determine what works for you. That said, there a multitude of ways that this can be done. Here are a few examples: rotary switch Picture Source dip switch Picture Source header with jumpers ...


3

The style used for creating documentation depends upon the goal of the drawing. When I create a "Schematic", I try to make the drawing useful for Troubleshooting and understanding the function; Visual likeness to reality is intentionally not part of my thinking. When drawing a "Wiring diagram", more thought goes into making the physical reality clear, ...


2

The drawing in the datasheet is the actual package itself, not the pad layout you have on the board. The PCB pads will be slightly larger than the package pads to allow for slightly imprecise placement. This will be corrected by surface tension when the solder is in the molten phase. The PCB shape generated by the IPC wizard will be fine (as long as it meets ...


2

I use Altium for layout and I try to avoid the polygons wherever I can. First, they are cumbersome to create, second you have to take care of the pour order and third, they obscure view of the other layers. I don't know if other layout tools have the same problems though. I use internal planes for boards with 4+ layer count that I want to have GND and/or ...


2

What is an NWELL? Silicon wafers are generally P-type silicon so suitable for making NMOS transistors. PMOS transistors need to be placed in N-type silicon. To provide this, an NWELL area is made and in it the PMOS are placed. Normally the NWELL is connected to the positive supply, VDD. That is needed to keep the NWELL area isolated (by a PN junction ...


2

The DRC rule you are referring to is the separation of two wells at different potentials. DRC has no way of knowing what is the potential of the well (no connectivity information at this level), so if you have two separate NWELLS it will enforce this rule. If you have two NWELLS at the same potential then you have two choices: Directly abut them, so that ...


2

At 1MHz you have nothing to worry about. I've committed atrocities such as passing 8MHz SPI over 30cm ribbon cables with impunity (maybe I got lucky!) When you go higher, say, 30MHz, you have to start worrying about controlled-impedance traces, matching lengths, not taking sharp turns or having vias, and so on, but you are nowhere near that operating regime....


2

I created custom pad shapes (one cut on the right, one on the left), and then replaced the eight corner pins on the package. I started with an IPC-7351B-compliant package created by Library Expert. For the new pads, I started with the dimensions of the IPC-7351b-recommended oval pad, and then manually modified them to create the chamfered corners. I calc'd ...


2

To answer why erase only happens in blocks on a physical level, the actual NAND cells are implemented in a P-well within a deep N-well. Because erase involves setting the substrate to a high voltage so that electrons can tunnel out through F-N tunneling, all the cells within a P-well are set to the same substrate voltage. Based on this image1: the P-well ...


2

I was looking for an answer to remove a junction and found http://www-3.unipv.it/ele1/pspice/pspice91/capqrc.pdf where shift key is used in various operations.So I gave it a shot:) Click on a junction icon in toolbar (two lines normal to each other). Hold shift and click on a junction. Junction is gone/deleted.


2

In short: no, each supply pin in this BGA doesn't need its own capacitor. I suspect you're over-optimizing this. STM32 microcontrollers are fairly forgiving in terms of decoupling needed; in practice 2-3 capacitors placed at opposite corners of the IC, anywhere within 3-5 mm of the supply pins (which also tend to be at corners), works fine. Consider ...


2

With the trace offset, there's an acute angle left between the pad and trace. There's been a lot of discussion over the years about the effect of 'acid traps' on the over-etching of the copper, and difficulty of washing out of the corner after etching. It doesn't seem to be such an issue with photoactivated etching systems, so may be a carryover that's no ...


2

If you do not have temperature sensitive components nearby, conductor temp may be allowed to reach 60'C safely. But if you do want 10'C rise max, then use thermal pads, 3.3mm tracks on 3.5mm spacing 0.2mm gap (8mil) with 1oz base +2 oz plating on outer, with a ground plane to reduce temp rise 50%. Or spread out the traces as Phil has done. Beware that ...


2

Often, pin 2 is not brought out to a pin you can solder to the board. Thus pin 4 is used. The datasheet covers both options. See the TO-252 or DPAK. I use those when higher current is involved to increase the cooling area available. There pin 2 is still connected to the tab, but does not go down to the board for soldering.


2

It would be a dual pad layout joined for either SMD CM choke or any SMD 0R parts or fixed R parts depending on design. The design would be controlled impedance for USB2 (100MHz) or USB 3.


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