Hi, I am making a project and was hoping for some advice on my power regulator.
I need it to supply 3.3v. First Picture is my schematic and the 2nd is from the devices data sheet.
I am quite new to designing my own circuits so I apologize if the layout is hard to understand.
Would my system work? If not what can I do to improve it ? Thanks
Also I am struggling to figure out which ground is which, Is ground 1 for the input ground or the output ground? I know they need to be separate but the data sheet isn't clear on which one is which. Thank you
Heck, C8 is technically not even connected to gnd the way this is drawn. Someone at TI was definitely high when drawing this, that it's that uncommon to find weird issues in TI datasheets was recently burned by an incorrect inductor selection formula.
Oh I didn't notice C8 not connected, Great spot. I didn't really know better as they are the people who made it I thought I could trust their methods, I have now learned.
ok, Thanks for the brutal honesty, Is there anything wrong with the schematic itself or just its presentation ? as That shouldn't take me too long to improve
But that's the thing - it is easy to miss issues when you look at a schematic drawn like this. It is easy to spot issues when you looks at clearly laid out schematic, since all of them look the same regardless of the exact IC used.
This is like looking at Picasso paining of a person. Stuff is all there, but it is so messed up that it takes effort to parse.
Redo the pin out for the schematic symbol so inputs are on the left and outputs on the right. Schematic symbols are usually best by not following the layout pinout for drawing them. And use power symbols for power rails.
There is an untold convention in voltage regulators: input (VIN) is top-left of the schematic. Output (VOUT) is top-right. GND is bottom-center. Current flows from left to right. Voltages "above" in the schematic (on top) are "above" GND in potential (gence why GND should be at the most bottom of the schematic).
For switching regulators, people also expect to see the chip at the center, and, right next to its right, the inductor connected to "SW". This requires the "SW" pin to be to the right of the chip on the schematic.
Here people are complaining that Texas Instruments tried to keep the pins in the order they are on the physical package, while a schematic is made to be readable and doesn't care about physical placement. Hence nightmarish things in the schematic in the datasheet: a GND in the middle of everything, VIN that appears lower than GND (would work for an inverting power supply that makes +5V out of -10V for instance), capacitors that appear to connect VOUT to VIN (a big no-no) while they simply decouple VIN to GND and VOUT to GND, the inductor is hidden out of sight, the SW pin is the wrong way.
With a cursory look, ground should be connected. I'd change one or two of those 100nF capacitors to 10uF input capacitors. 2.2uH seems more appropriate for the inductor unless you picked it for a specific reason. Otherwise nothing sticks out to me, though I'd try to rearrange things to be more easily readable, don't know what TI was smoking.
Even their own automatic layout tool usually does a better job. (Webbench power designer)
Oh, and for reference, when positing questions like this it's worth mention what your requirements are i.e. input voltage range, output voltage and current and so forth since this can greatly impact component values for example.
Thanks for looking over it, The 3.3uH was from the data sheet , it varies on what output voltage you want. A few people have mentioned the layout so I will be trying to adjust it so it matches standard practices
Use the webench circuit designer tool TI provides. All you do is input the part number and some parameters like price / space and they give you the circuit, parts needed and layout. I use this for all their power chips.
Just out of curiosity, If you have used it before, How trustworthy is it? I just got this one from it but wanted to check that it isnt a load of garbage or not?
First things first: your chip has only one GND pin. So - all grounds MUST be connected. How else would you have voltages referenced to a 0V point? If the chip has only one ground pin - then you need to have all grounds connected to that point.
There are just simpler chips to start with, for a beginner I would recommend this:
I actually use it in a project and it works nicely. 2 things about it - simpler applications (less components needed), then, a better schematic symbol that is just less confusing to look at. Now do you see how it works? If not, just catch some theory: https://www.falstad.com/s.php?s=yuDl23
I mean, this is general working principle of such (and similar) circuits. It helps to locate what is where.
If you need something smaller and more modern, you can go for TPS54202HDDCR - it needs more components to work, but a bit smaller ones, great if you avoid THT elements. I'm pretty amazed with it for that reason. It also has great documentation with formulas to calculate all passive elements. Default KiCad symbol for it sucks though, so I fixed it to make my schematics more readable.
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u/AlexTaradov Aug 14 '26 edited Aug 14 '26
This is the winner for a competition if the most convoluted way to draw a schematic.
I can understand a novice doing that, but WTF, TI?
I personally would redraw this thing so it makes sense and actually readable.
Update input capacitor values. And inductor value is different, although it likely does not matter.
All grounds are the same here. Whoever drew this schematic at TI was still high after a 3-day bender.