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My PCB is powered from USB port and includes Recom RKZ0505D for powering dual-supply OPAMPs. Recom gives +5V and -5V outputs. So I have:

  1. Top signal & components
  2. Bottom signal & components
  3. GND
  4. 3.3V
  5. +5V
  6. -5V

What should be the stackup of layers in a 4-layer PCB? There are about 30 ICs on the PCB. Some of them powered from 3.3V and some of them +5/-5V. If the layers used are:

  1. Signal
  2. 3.3V
  3. GND
  4. Signal

Then the power lines +5/-5V will be long. How can I optimize layers and right order?

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I would suggest something more like this:

  1. Signal
  2. GND
  3. +3.3V/+5V/-5V plane shapes
  4. Signal

There's no reason why you can't have your power supply layer have a bunch of smaller plane shapes where they're needed.

As with any four-layer PCB, you'll need to follow some high speed guidelines if you have signals with content >100MHz or so (many square waves even at low frequencies contain frequency content this high). This is especially important for signals on layer 4 since you'll have plane breaks on Layer 3:

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