Electronic – Daisy chaining switching supplies

It is difficult to answer you precisely because you are in a pre-design phase and don't have a final schematic.

Thinking about signal integrity and EMC/EMI issues is good, but it is maybe too early to consider them as blocking issues. As a beginner it is difficult to make a "perfect" schematic and layout from scratch. That's why, IMHO, you should provide a schematic and a bit of pre-layout, that we will be able to "correct" (in a good way).

Nevertheless, here is some tips and documents that can help you design your board:

• If you have space, don't be afraid of adding spare components/PCB footprints

In your case, you could put some spare capacitor and ferrite bead footprints at the output of your SMPS, for future filtering for EMI. If you don't use a parallel footprint (mostly capacitors), you just don't have to solder the component, and for a series component, you can put a 0 Ohm resistor of the same SMD footprint.

• You are not the first at designing simple SMPS at these frequencies

Having questions is good, but don't be too afraid to make a mistake (if you have the possibility, mostly as student or hobbyist, you are able to do some mistake without "problem"), you will learn more with mistakes than with good (but maybe not so good) design every time. FPGA test board have some 3 to 5 or 6 small SMPS to power the FPGA. Ok they are not on 2-layers PCB but it's not impossible ;)

Finally some documents, guidelines for analog/power design:

• PCB Design Guidelines for Reduced EMI, TI
• AN-1149 Layout Guidelines for Switching Power Supplies, TI
• AN 136 PCB Layout Considerations for Non-Isolated Switching Power Supplies, Linear
• AN1031 Considerations in Designing the Printed Circuit Boards of Embedded Switching Power Supplies, Fairchild

Make R1 a pull-down. Instead of connecting Q1-c to M1 and Q1-e to ground, connect Q1-c to Vin and Q1-e to M1-gate with R1 pull-down to ground. Make R1 ~ 30 \$\Omega\$ (maybe 100mA will be enough to turn off FET fast enough). Connect M1 source to ground and M1 drain to L1 and D1 anode. (Note: This approach of using R1 as a pull-down assumes that Q1 is the Q1 internal to the MC34063. This seemed to be the intent of the OP. If there is an additional or external BJT, the Vbe drop from Vin would be too great and FET would likely not turn on.)

MC34063 normally operates in DCM since it is a hysteretic controller, and these types of controllers are more stable with DCM. (Note that boosts in CCM can have very high Q power modulator response that can ring with hysteretic control.)

Boosts operate kind of like a bucket brigade, switch turns on charging inductor with energy, switch turns off - inductor dumps energy through diode to output. Fill then dump, fill then dump ... repeat. Hence boosts always output pulsed current through D1, and rely on the output capacitance to smooth out the output.

If you are operating at a switching frequency of 33kHz, make L1 ~ 10uH for DCM (needs to be less than 11uH). Of course, peak inductor current will be about 3A. Find a 3A Schottky for D1.