The LTC4558 provides the power conversion and signal level translation needed for advanced cellular telephones to interface with 1.8V or 3V subscriber identity modules (SIMs). The device meets all requirements for 1.8V and 3V SIMs and contains LDO regulators to power 1.8V or 3V SIM cards from a 2.7V to 5.5V input. The output voltages can be set using the two voltage selection pins and up to 50mA of load current can be supplied. A channel select pin determines which channel is open for communication. Separate enable pins for each channel allow both cards to be powered at once and allow for faster transition from one channel to the other.