fsw				= 500 kHz
Nomin Vin		= 48 V
Max Vin			= 48 V
VinRipple		= 0.5V
Vout			= 36.6 V
Rd				= ???
Iled			= 0.45 A
LED I ripple	= 0.05 A
L I ripple		= 0.4 A
UVLO turn on	= 10 V
UVLO VHys		= 1 V
Eff				= 0.95


# Roff

Take Coff = 1 nF

−(1−(36.6÷(0.95×48))
--------------------
1nF+20pF×500kHz×ln(1-(1.24/36.6))

= 11.2kΩ

Closest E96 is 11 kΩ


This makes toff

  -(1nF+20pF)*11kΩ*ln(1-(1.24V/36.6V))
= 387 ns


And fsw
= (1-(36.6V/(0.95*48)))/387ns = 510 kHz


+-------------------
| Coff = 1nF
| Roff = 11 kΩ
+-------------------


# Inductor ripple

L = (36.6V*387ns)/.4 = 35 µH

Closest E12 inductor is 33 µH

So really,

ILRipple = 36.6V * 387 ns / 33 µH = 429 mA


+-------------------
| L= 36 µH
+-------------------


# Average LED current

ILmax = ILED + 1/2*ILripple
      = .45 + 1/2*.429 = 0.665 A

Take Vadj = 1.24 V

Rsense = 1.24/(5*ILmax)
       = 1.24/(5*.665) = 0.373 Ω

Closest E96 is... 0.373 Ω

ILed = 1.24/(5*0.373) - (ILripple/2)
     = 0.45 A

+------------------
| Rsense = 0.373 Ω
+------------------


# Output capacitance

Rd is about 10 Ω for this part

Zc = (10Ω*ILEDRipple)/(ILripple-ILEDRipple)
   = 1.32 Ω

CoMIN = 1/(2π×fsw×Zc)
      = 236 nF

+------------------
| Co = CoMin * 1.75 = 413 nF
|    = 500 nF (let's round)
+------------------


# Input capacitance

ton = 1/fsw - toff
    = 1/510kHz - 387ns
    = 1.6 µs

CinMIN = 0.45A*1.6µs/0.5V = 1.44 µF
Multiply by 2 for safety, 2.8 µF
2.7 µF is the closest in the E12.

+------------------
| Cin = 2.7 µF
+------------------

Check that IinRMS is sane:

IinRMS = Iled*fsw*sqrt(ton*toff)
       = 181 mA


# PFET

Minimum voltage rating 48 V

Minimum current rating = Iled * (Vo/(Vin*η)
= .45 * (36.6/(48*0.95)
= 361 mA

Chosen part:
ZXMP7A17KTC
Rds(on) = 0.16 Ω
Continuous drain I = 5.7 A
Vds = 70 V
Qg = 9.6 nC

ItRMS = ILed*sqrt(36.6V/(48V*0.95) * (1+1/12*(LIripple/Iled)²))
      = 0.45 * sqrt (36.6V/(48V*0.95) * (1+1/12*(.429/.45)²))
      = 434 mA

Pt = ItRMS² * Rds(on)
   = .434² * .16
   = 69 mW

# Diode

Diodes has to be good for 48 V

Id = (1-(36.6/(48*η)))*Iled
   = 124 mA

Chosen diode:
B1100-13-F
Vf = 0.79 V
Vrrm = 100 V
If = 1 A
Ifsm = 30 A


Pd = Vd * Id = 0.124 A * .79
   = 98 mW

So a 2.5 °C rise, well good


# UVLO

Copy UVLO from datasheet.

Ruv2 = 49.9 kΩ
Rub1 = 6.98 kΩ