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I'm designing a schematic for a system that will utilize plug-in daughter boards. I'd like to provide the daughter boards with high quality 12V, 5V, 3.3V, and 1.2V, with up to 5A, available via pins on the daughter board connector.

The main board will utilize a 12V power supply.

I'm trying to find a good approach to using one or more voltage regulator chips to accomplish this.

I've noticed the LMZ22005 which appears to fit the bill, but I would need to use several in order to offer the desired voltages.

I'd like to request suggestions for how to best accomplish this. The device will be for RF use, so EMI is highly undesirable. Recommendations for other chips or general caveats will be much appreciated.

I would prefer to use SMT parts and cost is not the major consideration.

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Consider LTC3633A. I used it for several designs, it works very good, predictable and according to the datasheet. I suggest using MLCC X7R or X5R for input and output filters (no aluminum or tantalum capacitors!) and running it about 2.5-3.2 MHz.

Two or three "layers" of LC or LRC filters are enough to meet RF requirements for interference. Make sure that the filters have no high Q resonances at any frequency. The PCB design is of major importance: pay a great attention to locate switching currents of each power stage inside a very small area near the chip and its capacitors. Use large current ferrite beads to isolate 12 power supplies to each switching regulator.

However: 1.2 V precision will be greatly compromised by PCB traces / connector resistance. It is better to use local (point-of-load) power supplies for such a low voltage.

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  • \$\begingroup\$ thank you! Is a linear regulator out of the question for SMT at the current levels I require? \$\endgroup\$ – Newton Rogers May 23 '16 at 20:08
  • \$\begingroup\$ 5A at voltage difference 15 V - 5 V = 10 V is 50 W. It is out of question, absolutely. To me, linear regulators are good for currents below 100 mA, and even then it is better to keep the voltage drop very low. \$\endgroup\$ – Master May 23 '16 at 20:14
  • \$\begingroup\$ Looks a good device +1 \$\endgroup\$ – Andy aka May 23 '16 at 20:17

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