Doc:
http://www.onsemi.com/pub/Collateral/MC34063A-D.PDF
http://www.onsemi.com/pub/Collateral/AN920-D.PDF
http://www.ti.com/lit/ds/symlink/mc33063a.pdf
http://www.ti.com/lit/an/slva252b/slva252b.pdf

		Vout + VF
ton/toff = ----------------------
	   Vin(min) - Vsat - Vout

(ton + toff) = 1/f  < 10us  (f<100kHz)

	ton + toff
toff = ------------
       ton/toff + 1

ton = (ton+toff) - toff

Ct = ton * 40 uA/V

Ipk(sw) = 2Iout(max)

Rsc = 0.3 / Ipk(sw)

		  Vin(min) - Vsat - Vout
L(min) = ton(max) ----------------------
			Ipk(sw)

| Vout | = 1.25 ( 1 + R2 / R1 )

Vripple(p-p) = Ipk * ( (ton+toff) / (8*Cout) + ESR )

	(ton+toff)     Vripple(p-p)
Cout =	---------- / ( ------------ - ESR )
	    8	           Ipk

| Vout | = 1.25 * ( 1 + Rtop / Rbot )

///

Rsc have, at current limit, 0.3V, so it must have a sufficient
power rating Vsc = 0.3V,  Imax = Vsc / Rsc, Psc = Imax * Vsc.

 Imax   Rsc  Psc
  A     Ohm   W 
 1.36  0.22  0.40   
 0.91  0.33  0.30
 0.64  0.47  0.20
 0.44  0.68  0.13
 0.30  1.00  0.09

Note, that standard chip resistors have theese power limits:
  3216/1206 0.25W
  2012/0805 0.125W
  1608/0603 0.1W
  1005/0402 0.063W

///
Common output voltages.

$ ./Rtop.pl Rbot=10k 3.3 5 9 10 12 15 18 20 24
 Rbot  =   10.000 kOhm
 Vref  =    1.250 V   
    Rtop          Vout
  16.400 kOhm   3.300 V   
  30.000 kOhm   5.000 V   
  62.000 kOhm   9.000 V   
  70.000 kOhm  10.000 V   
  86.000 kOhm  12.000 V   
 110.000 kOhm  15.000 V   
 134.000 kOhm  18.000 V   
 150.000 kOhm  20.000 V   
 182.000 kOhm  24.000 V   

$ ./Rtop.pl Rbot=6.8k 3.3 5 9 10 12 15 18 20 24
 Rbot  =    6.800 kOhm
 Vref  =    1.250 V   
    Rtop          Vout
  11.152 kOhm   3.300 V   
  20.400 kOhm   5.000 V   
  42.160 kOhm   9.000 V   
  47.600 kOhm  10.000 V   
  58.480 kOhm  12.000 V   
  74.800 kOhm  15.000 V   
  91.120 kOhm  18.000 V   
 102.000 kOhm  20.000 V   
 123.760 kOhm  24.000 V