The original output voltage of the MAX668EVKIT is 12V@1A, if you want to change it to 5V@4V, you can change the following parameters:
a. The input capacitor
C1: 150uF 20%, 6.3V, X5R ceramic capacitor (1206)
Murata GRM31CR60J157ME11#
b. Inductor
Coilcraft SER1052-152ML-152L
c. The frequency setting resistor
R4: 110K ohm
d. Current-sense resistor
R1: Use three 0.02 ohm resistors in parallel
e. The output voltage divider resistor
R2: 75 k ohm
f. The capacitor in the compensator circuit
C7: 6.8 pF
f. MOSFET
N1: NCH; PG-TDSON8; PD-(28W); I-(58A); V-(25V)
INFINEON BSC050NE2LS
g. Diode
D1: RECT; SMT; PIV=200V; IF=6.0A; -65 DEGC TO +175 DEGC
Didoes Inc. PDU620-13
h. Output capacitor
C5, C6 : 150uF 20%, 6.3V, X5R ceramic capacitor (1206)
Murata GRM31CR60J157ME11#
Use three 150uF capacitors in parallel
i. To eliminate output voltage ripple, a RC circuit can be connected in parallel with R3. We recommend using a 3.9k ohm resistor and 22nF capacitor.