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I'm in the process of designing my first PCB. For the power supply, I have a 4.5V battery pack fed into a voltage regulator that outputs 3.3V. This section of the PCB and governing schematic are shown below:

enter image description here

enter image description here

The battery pack, voltage regulator, and the rest of the components on the PCB are connected to the same ground plane.

Is this OK or should I do something differently in the design such as separating ground for the battery pack and the rest of the circuit?

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  • \$\begingroup\$ What is your layer count and stackup? Your thermal relief connections on caps look WAY too small, there are no stitching vias near the caps to your actual ground plane (if you have one). The GND pin on your voltage regulator is not well connected to GND at all. The clearance between your polygon pour and your tracks isn't big enough. Track widths for some of the 3V3 connections are unnecessarily small, from what I can tell. \$\endgroup\$ – Captainj2001 Oct 4 '19 at 20:45
  • \$\begingroup\$ It's a 2 layer board and I am assigning the top layer to GND in this case. Is there a rule of thumb for how thick the thermal relief connections should be as well as the clearance between the polygon pour and tracks? Also the other tracks connected to the 3.3V (as well as the rest of the tracks on the PCB) are 0.2mm thick. For this board I am drawing at max 200mA of current so I thought it would be a sufficient thickness. \$\endgroup\$ – abjf4t8 Oct 4 '19 at 21:13
  • \$\begingroup\$ 0.2mm is 7.9 mils (roughly) which is close to what most board houses will limit you to for their cheapest manufacturing process. You should make your traces as large as possible for routing power around the board. Your thermal reliefs will need to be at least the minimum dimension your board house is willing to manufacture. They will let you know what that is on their website or they will reject your files when they run them through their DRC. You should also get rid of the useless GND island to the left of the GND pin on your regulator. Clearance is usually 6 mil minimum for cheap processes. \$\endgroup\$ – Captainj2001 Oct 7 '19 at 14:59
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Looks good, keep the ground plane the same. Grounds should be seperated for noise or isolation, otherwise it can cause problems. The ground needs to be the same, otherwise the circuit would not function,as the current would not flow back to the source.

Is this OK or should I do something differently in the design such as separating ground for the battery pack and the rest of the circuit?

You should not do something different, you should have one ground plane, it should be on the bottom layer. If you can't put it on the bottom layer, whatever your design does, ground should be as continuous as possible, if you have large currents (over 1A) then use a PCB trace size calculator to find out if there will be issues. You may want a few stitching traces (to tie ground together). If that truly is the design you end up with.

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    \$\begingroup\$ +1 to counter undeserved down-vote. \$\endgroup\$ – The Photon Oct 4 '19 at 20:49
  • \$\begingroup\$ See my comment on the main question. I feel like we must be looking at different layouts. \$\endgroup\$ – Captainj2001 Oct 4 '19 at 20:57
  • \$\begingroup\$ @Captainj2001 The question states, "should I separate the grounds?" The answer is 'NO'. You can run a ground on the top layer if necessary, it's not advised but if you need to free up some board space, it is definitely possible and the layout is fine above. However, separating the grounds is not fine and will result in a non functioning circuit. Thanks for voting \$\endgroup\$ – Voltage Spike Oct 4 '19 at 21:28
  • \$\begingroup\$ Thanks for the reply. Why is a GND plane on the bottom layer better than one on the top layer? Also to make GND on the bottom layer would I just connect all the SMD components to a via that routes to the bottom layer? \$\endgroup\$ – abjf4t8 Oct 4 '19 at 21:32
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    \$\begingroup\$ @VoltageSpike Downvote removed since this isn't actually a PCB review question, even though it should be because there are multiple things that should be changed that OP doesn't realize are bad. \$\endgroup\$ – Captainj2001 Oct 7 '19 at 15:01

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