DC BUCK
DC BUCK should be follow RTK recommended components as below plot, and PN.
Recommended DC BUCK
MT8102NSBR
MP1605(non P2P)
TPS62822(non P2P)

DC BUCK is highly correlated with system stability, RF performance, and power consumption. It requires extensive testing and verification. Replacing components is not recommended. Customers who insist on modifying must meet the following conditions and conduct their own testing and assume the consequences.
3.3V DC-DC Power Specification
Must meet:
When Vin≧3.6V ; Iout=0A, then Vout=3.3V±3% and Vout ripple peak to peak < 100mV
When Vin≧3.6V ; Iout=1A , then Vout=3.3V±3% and Vout ripple peak to peak < 100mV
When Iout=0A→1A ; Electrical load switch frequency = 500Hz, Electrical load slew rate setting=2.5A/us, then Vout ripple peak to peak < 100mV
When Iout=1A→0A ; Electrical load switch frequency = 500Hz, Electrical load slew rate setting=2.5A/us, then Vout ripple peak to peak < 100mV
For battery application, when Vin=3.4V ~ 4.2V then Vout should be stable.
Have Auto-Discharge function.
Have Enable pin function to reset AmebaPro.
Soft start time < 1.2ms
Recommend:
Constant-on-time or DCS topology
For battery application, Low IQ and good power efficiency.
Duty ratio could be 100%
Iout Max. rating > 1.5A