Demonstration Circuit 625 is a constant-frequency synchronous Buck-Boost converter using the LTC3441. The input range is from 2.4V to 5.5V, making it ideal for single- cell lithium-ion or three-cell NiCd/NiMH battery applications. This converter provides up to 95% efficiency, much higher than traditional Buck-Boost converters. For 2.5V minimum input voltage, this converter can provide up to 1A load current. The output voltage is set at 3.3V. A different output voltage in the range of 2.4V to 5.25V can be obtained by changing one of the feedback resistors. The switching frequency is set at 1MHz, which is a good trade-off between efficiency and size. Applying twice the desired frequency at the MODE/SYNC pin can also synchronize the switching frequency between 1.15MHz to 1.7MHz. In shutdown, the IC draws less than 1μA. When using long wire connections to the input sources (such as wall adaptors), there can be input over voltage transients during initial plug-in. C8 is installed on DC625 to damp the possible voltage transients. C8 is not needed for any application when input source is close to the regulator. Please refer to Application Note 88 for details.