The LP2985 allows for low-noise performance with the use of a bypass capacitor that is connected to the internal band-gap reference with the BYPASS pin. This high-impedance band-gap circuitry is biased in the microampere range and, thus, cannot be loaded significantly, otherwise, the output (and, correspondingly, the output of the regulator) changes. Thus, for best output accuracy, dc leakage current through C_BYPASS must be minimized as much as possible and must never exceed 100 nA. The C_BYPASS capacitor also impacts the start-up behavior of the regulator. Inrush current and start-up time increase with larger bypass capacitor values.

Use a 10-nF capacitor for C_BYPASS. Ceramic and film capacitors are good choices for this purpose.