Designing 4.3 V voltage regulator
Maybe a Si diode (forward voltage ca. 0.6-0.7V) is a good enough regulator.
You can use it to reduce 5V to ca. 4.3V.







simulate this circuit &ndash; Schematic created using CircuitLab

You can not use an ordinary voltage regulator (e.q. LM317) to regulate from 5V to 4.3V because the voltage difference between input and output voltage is to low. If you want to use an voltage regulator IC it must be a Low Drop one.