8.2.2.1 Input and Output Capacitor Requirements

Although an input capacitor is not required for stability, if input impedance is very low, it is good analog design practice to connect a 0.1-µF to 1-µF low equivalent series resistance (ESR) capacitor across the input supply near the regulator. This capacitor counteracts reactive input sources and improves transient response, noise rejection, and ripple rejection. A higher-value capacitor may be necessary if large, fast rise-time load transients are anticipated or the device is located several inches from the power source.

The TPS737xx-Q1 requires a 1-µF output capacitor for stability. It is designed to be stable for all available types and values of capacitors. In applications where multiple low ESR capacitors are in parallel, ringing may occur when the product of C_OUT and total ESR drops below 50 nΩF. Total ESR includes all parasitic resistances, including capacitor ESR and board, socket, and solder joint resistance. In most applications, the sum of capacitor ESR and trace resistance meets this requirement.