This design example is powered by a rechargeable battery that can be a building block in many portable applications. Noise-sensitive portable electronics require an efficient, small-size solution for their power supply. Traditional LDOs are known for their low efficiency in contrast to low-input, low-output voltage (LILO) LDOs such as the TPS7A14. The use of a bias rail in the TPS7A14 allows the main power path of the LDO to operate at a lower input voltage, thus reducing the voltage drop across the pass transistor and maximizing device efficiency. Because the voltage drop across the pass transistor can be so low, the efficiency of the TPS7A14 can approximate that of a dc-dc converter. Equation 8 calculates the efficiency for this design.

Equation 8 reduces to Equation 9 because the design example load current is much greater than the quiescent current of the bias rail.