DEMO MANUAL DC2255A LTC3106EUDC 300mA, Low Voltage Buck-Boost Converter with PowerPath and 1.6A Quiescent Current DESCRIPTION Demonstration circuit DC2255A features the LTC 3106, This is a visual indication of V being in regulation and OUT an ultralow input voltage buck-boost DC/DC converter is not needed for normal operation. To minimize current with automatic PowerPath management optimized for consumed, set JP3 to NC. multisource, low power systems. Burst Mode operation The LTC3106 can operate with either a primary or sec- architecture allows the LTC3106 to run very efficiently with ondary battery on its V supply. In secondary mode STORE as little as 1.6A of input current at no load. (JP7 set to GND), the part will use excess power to trickle Programmable accurate RUN threshold as well as maxi- charge the battery on V . There are four pin selectable STORE mum power point control (MPPC) allow for simple opti- OV/UV thresholds for the battery voltage in this mode to mization of power transfer between the power source and allow operation with a variety of secondary batteries. If the input supply to the DC2255A. Selectable peak current the DC2255A is operated in secondary mode, a Schottky limit (100mA or 725mA) also allows the LTC3106 to adapt diode must be placed between the SW2 and V pins. AUX to a wide variety of input supplies. The LTC3106 requires no external compensation and An accurate RUN threshold voltage of V = 1.2V is set provides good line and load transient response across IN by positioning the shunt on JP12 in the middle position. the entire V range for each output voltage setting. This IN This threshold is set by the values of R4 and R5. For simplifies the design process while reducing the external maximum power point control setpoint above 0.6V, it is component count. usually better to use the accurate RUN functionality. See The LTC3106 data sheet has detailed information about the data sheet for more details. Maximum power point the operation, specifications, and applications of the part. control is enabled by setting JP5 to V . The value of R3 CC The data sheet should be read in conjunction with this sets the MPPC threshold. quick start guide. The DC2255A has four user selectable output voltages: Design files for this circuit board are available at 1.8V, 2.2V, 3.3V and 5V. When the LTC3106 is enabled, DEMO MANUAL DC2255A PERFORMANCE SUMMARY 100 100 90 90 80 80 70 70 V = 1.2V IN 60 60 V = 1.8V IN V = 2.5V IN V = 3.3V 50 IN 50 V = 4V V = 3V IN STORE V = 5V V = 4V IN STORE 40 40 0.1 1 10 100 1000 0.01 0.1 1 10 100 1000 LOAD (mA) LOAD (mA) dc2255a F01 dc2255a F02 Figure 1. DC2255A Efficiency vs Load with Part Running Figure 2. DC2255A Efficiency vs Load with Part from V . V = 3.3V Running from V Input. V = 3.3V IN OUT STORE OUT V AUX V AUX V OUT V OUT I L I L dc2255a F03 dc2255a F04 Figure 3. DC2255A Normal V , V and Inductor Current Figure 4. DC2255A Load Step Response. V = 3V, V = 3.3V, AUX OUT IN OUT Behavior. The Middle V Charging Period Terminates Early Load Step is from 40mA to 200mA OUT to Charge Up V Because V Takes Priority Over V AUX AUX OUT dc2255af 2 EFFICIENCY (%) EFFICIENCY (%)