2.3 Input Capacitance Requirements

Low input-source impedance is necessary for the LDO output to operate properly. When operating using battery power, or in applications with long lead length (> 10 inches) between the input source and the LDO, adding input capacitance is recommended. A minimum of 3.3 µF to 10 µF of capacitance is sufficient for most applications. Given the high input voltage capability of the MCP1781, of up to 55V DC, it is recommended to use an appropriate voltage rating capacitor, and the derating of the capacitance as a function of voltage and temperature needs to be considered. The ceramic capacitor type should be X7R or X8R\L because their dielectrics are rated for use with temperatures between –40°C to +125°C or -55°C to +150°C, respectively.