For the legacy chip, an input capacitor (C_IN) ≥1 μF is required (the amount of capacitance can be increased without limit). Any good-quality tantalum or ceramic capacitor can be used. The capacitor must be located no more than half an inch from the input pin and returned to a clean analog ground.

For the new chip, although an input capacitor is not required for stability, good analog design practice is to connect a capacitor from IN to GND. This capacitor counteracts reactive input sources and improves transient response, input ripple, and PSRR. Use an input capacitor if the source impedance is more than 0.5 Ω. A higher value capacitor can be necessary if large, fast rise-time load or line transients are anticipated or if the device is located several inches from the input power source.