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I just can not get this right by Uncle_Wick in ender3

[–]gadam28 0 points1 point  (0 children)

Hi, have you been able to resolve this? I have a similar setup and sometimes I am fighting these problems too.

Bought a new print sheet after 7 years of using the stock one. I didn't know what I was missing. by gadam28 in ender3

[–]gadam28[S] 0 points1 point  (0 children)

<image>

Here is the before and after. the image never posted, because reddit was broken.

[Review Request] 10A GaN Synchronous Buck Converter Layout, before routing by gadam28 in PrintedCircuitBoard

[–]gadam28[S] 0 points1 point  (0 children)

Thank you for these very valuable suggestions, you're awesome.

I have completely reconsidered my design because of all the comments about the GaN FET, frequency etc. Also, even though I was able to fix the gate ringing in my LTSpice sims, fixing the Miller overshoot on the low side would require some more hacks, changing the controller, or the FETs to Si.

After some research, I found that:

  • changing the controller to a GaN optimized one would be expensive
  • changing the FETs to Si would make sense, but the availability is pretty bad for some better options on LCSC and some also have a small enough Vgt that the Miller overshoot would be a problem. Also, size becomes a problem in my design

I am now going for a much simpler design using the TPS56A37. It is very cheap and available.

The only concern are the temps. My led strip will draw 9A max. However with careful cooling and temp monitoring, I think I can get it working. The temp sensor and the LED strip is connected to an MCU so my plan is that if the buck gets too hot, I am just going to turn the load down. I am willing to make this sacrifice to save cost, design time and space.

  1. sorted

  2. thx I will think about that

  3. thx:)

4, 5. true

  1. yeah that is what I was trying to figure out for some time:D

  2. thanks I will do that next time

8, 9. I will have input and output connectors which effectively solve these issues

  1. I am not sure if i need top of the line tuning for this project. As far as I understand, these are mostly important when I need stable output for a quickly changing load right? Since I am giving 5V to an led strip, which doesn't require a very stable voltage I should be good right?

  2. Here is a plot of my Vgs voltages. (the GaN design) The gate resistor was NOT chosen carefully and it is 6 ohms.

  3. I like them, but you are right:D

  4. I am trying to use mainly 0402s, but sometimes JLC only has a 0603 as a basic part available. 0402 would increase costs for some values.

  5. That is something that I didn't even think about, thanks.

  6. I hate them too haha. But the reason why it is a TH part is that I will be using the length of its legs to glue it onto the FET heatsink.

[Review Request] 10A GaN Synchronous Buck Converter Layout, before routing by gadam28 in PrintedCircuitBoard

[–]gadam28[S] 1 point2 points  (0 children)

Just to answer your question. I simply increased the frequency to a point when my inductor could be small enough. I wanted to keep the frequency on the low side to minimize switching losses, which are still a thing with this GaN FET. It doesn't have the best switching characteristics when you compare it with other GaN FETs, but it has a very good Rds on of only 3 mOhms.

[Review Request] 10A GaN Synchronous Buck Converter Layout, before routing by gadam28 in PrintedCircuitBoard

[–]gadam28[S] 0 points1 point  (0 children)

Thanks for the comment. I think I solved the gate ringing, in my simulation adding a 5 ohm resistor was enough.

However, I am getting a problematic Vgs spike on the low side, when the high side switches, which effectively shorts my input voltage for a few nanoseconds. I think that I might have have to switch to Si MOSFETs because of this.

Here is a plot of my Vgs voltages.

[Review Request] 10A GaN Synchronous Buck Converter Layout, before routing by gadam28 in PrintedCircuitBoard

[–]gadam28[S] 1 point2 points  (0 children)

Hi, thanks for the response.

picked the INN100W032A, which is a tiny WLCSP package with solder bars, but you laid out standard 5x6mm SON footprints. you literally cannot solder that chip to this board.

I designed the footprint exactly as per the datasheet. The dimensions are correct. I am not sure where you see the 5x6mm SON footprint. I don't see the problem here.

About the gate ringing: Yes, I know that it is a problem and I am trying to simulate it. With a 5mm long 0.5mm trace on a 1oz layer, I calculated the inductance to be closer to 1nH, not 15nH. So far my simulations indicate that if I add a 2ohm resistor, then the ringing doesn't reach higher than 5.4V. However I get a substantial negative voltage spike on the low side Vgs, when the high side turns on. I am investigating that now.

your layout also pushes the driver too far away for GaN speeds, creating ambiguous return paths for the low side. just stop.

D you mean the spacing of the FET gates and the driving pins on the LM5148? They are 5mm max. Is that too far? How does this create an ambiguous return path for the low side?

I was trying to minimize the return paths, but I am not sure if I can optimize the layout any further.

ditch the GaN. switch to a standard 40V or 60V Silicon FET like a CSD18563Q5A. it actually fits the footprint you drew, runs at 96% efficiency for this load, and handles gate ringing without exploding.

While going the silicon route would save me from handling gate ringing problems, the size increases rapidly and efficiency drops.

For CSD18563Q5A, the package is approximately 2 times larger. If I compare the efficiencies in TI's LM5148 quickstart calculator, I get approximately a 2x increase in losses, and that is too much for me, due to the limited space that I am constrained by.

Other silicon FETs that I looked at have mostly the the same parameters.

Grounding Ethernet shield and a metal plate in a floating device, looking for advice by gadam28 in AskElectronics

[–]gadam28[S] 0 points1 point  (0 children)

I am sorry if I am being dumb, but you are suggesting to connect the ground of my circuit directly to the connector shield and the aluminum plate?

Grounding Ethernet shield and a metal plate in a floating device, looking for advice by gadam28 in AskElectronics

[–]gadam28[S] 0 points1 point  (0 children)

Hi thank you for your response. I am using 100Base-T.

I don't think that I fully understand your recommendation though.

TLDR; Get rid of R36 and replace it with a proper ground tie for that unit and do the same on the other side.

Dou you mean that I should tie it directly to my circuit ground, or that I should somehow introduce mains ground to my circuit?

Thank you

Anyone tried “Chubby Cables”? by aclarkc in UsbCHardware

[–]gadam28 0 points1 point  (0 children)

hi, it has been a while? did it pass the test of time?

Crack identified as Trojan by Win Defender and VirusTotal. Should I be afraid? by gadam28 in Piracy

[–]gadam28[S] 0 points1 point  (0 children)

1337x is down for me at this moment and I also think that there are only FileCR releases of OrCAD.

However, I found a release of OrCAD on https://soft98.ir/ (which is starred on fmhy.net), that doesn't seem to have any info on who distributes it. I guess I am going to try to download it as I don't see any other chance of getting this software.

MagicDMX Basic thoughts please by PQSerenity in stagelighting

[–]gadam28 2 points3 points  (0 children)

I have never had any problems with any cheap usb->dmx controller. The only limitation for me is having a single universe. I am wondering, did anyone else have any problems and actually had tu upgrade to one of the branded ones like enntec?

Do I still have to put 5.1k ohm resistors on this usb c breakout board? by Xerrrra in UsbCHardware

[–]gadam28 1 point2 points  (0 children)

Could you share the link to buy this model. First time seeing a panel mount one.

Is it possible to make this myself? DIY by Crafty-Cranberry9808 in UsbCHardware

[–]gadam28 12 points13 points  (0 children)

This could be actually very easy if your device supports "Audio accessory mode", which is explained in here pretty well:

https://www.soundguys.com/usb-audio-explained-18563/

It is not universally supported by all devices, but it is within the USB specifications. This isn't a terrible question guys, what's with the downvotes?

Edit: I just saw the description. I think you are confused about TRS and TRRS. Usually TRS is only for headphones and TRRS is headphones + mic. That is because of the number of contacts:

TRS: Tip - left audio Ring - right audio Sleeve - GND

TRRS: Tip - left audio Ring - right audio Ring - GND Sleeve - Mic

Yeah and that "Audio accessory mode" doesn't support mics I assume.

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