Author Topic: PSU & PCB Placement  (Read 225 times)

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Offline jnestor481Topic starter

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PSU & PCB Placement
« on: January 20, 2025, 07:03:28 pm »
Hello All,

So I'm doing a personal project PCB and am considering placing a small Traco power supply (PN: TMR 3-2423WI) on the board. The max current draw I expect to see is around 50mA on either rail.  But I also have sensitive millivolt level signals coming from a sensor and going into an instrumentation amplifier on the board. I'm not certain if this is a wise idea or not.

I was planning on having the board be about 2.25" (57.15cm) square, and have 4 layers with 2 power planes for positive and negative 15V, and the top and bottom would be signal layers with a ground pour stitched together with vias. But yea just not sure if placing a power supply about 3/4" (1.9 cm) away from sensitive millivolt level signals would be a dumb idea or not. Any advice would be much appreciated. Thanks.
 

Offline thm_w

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Re: PSU & PCB Placement
« Reply #1 on: January 20, 2025, 10:45:26 pm »
Switching frequency says 100kHz minimum. So you may get some noise in that area. Though its a 3W converter, and 50mA is very little draw so if you shield the traces I can't see it being much.

You can also consider what rail is powering the converter, and having a spot for filtering ahead of the converter. Which can be shorted out if not needed.

Is your sensitive signal DC or relatively low frequency? If so most of the noise can be filtered out.
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Offline ahsrabrifat

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Re: PSU & PCB Placement
« Reply #2 on: January 22, 2025, 12:43:16 pm »
Place the power supply as far away as possible from the sensitive analog section. A distance of 3/4" may work. Isolate the power planes for the ±15V supply from the ground plane.These planes should not directly overlap sensitive analog traces on adjacent layers.
 


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