For this design example, the 1.0-V, fixed-version TPS7A0210 is selected. A dual AA Alkaline battery was used, thus a 1.0-µF input capacitor is recommended to minimize transient currents drawn from the battery. A 1.0-µF output capacitor is also recommended for excellent load transient response. The dropout voltage (V_DO) is kept within the TPS7A02 dropout voltage specification for the 1.0-V output voltage option to keep the device in regulation under all load and temperature conditions for this design. Use the recommend 1-µF input and output capacitor because the input source has a high equivalent series resistor (ESR) of 600 mΩ (typ). The very small ground current consumed by the regulator maintains a high current efficiency as compared to the load current consumed by the system, as shown in Figure 8-5 which allows for long battery life. Equation 6 can be used to calculate the current efficiency (I_η) of this system.