The output capacitor (C OUT ) is necessary forachieving a smooth output voltage. The ESR ofthe capacitor should be sufficiently largecompared to the capacitance; otherwise, thesystem may behave in an unexpected way, andthe current ripple may be very high. V FB changesfrom 185mV to 215mV when the powerMOSFET switches on. To charge the capacitorand generate 215mV at FB, the system needsESR and some inductor current. For example,for a 5V V OUT , if the forward capacitor is 0.1µF,the suggested ESR range of the output capacitoris 100mΩ to 250mΩ. Tantalum or aluminumelectrolytic capacitors with a small ceramiccapacitor are recommended