Analog Devices LTC3106 | Demoboard DC2255A

Description

Demonstration circuit DC2255A features the LTC®3106,an ultralow input voltage buck-boost DC/DC converterwith automatic PowerPath™ management optimized formultisource, low power systems. Burst Mode® operationarchitecture allows the LTC3106 to run very efficiently withas little as 1.6μA of input current at no load.Programmable accurate RUN threshold as well as maximumpower point control (MPPC) allow for simple optimizationof power transfer between the power source andthe input supply to the DC2255A. Selectable peak currentlimit (100mA or 725mA) also allows the LTC3106 to adaptto a wide variety of input supplies.An accurate RUN threshold voltage of VIN = 1.2V is setby positioning the shunt on JP12 in the middle position.This threshold is set by the values of R4 and R5. Formaximum power point control setpoint above 0.6V, it isusually better to use the accurate RUN functionality. Seethe data sheet for more details. Maximum power pointcontrol is enabled by setting JP5 to VCC. The value of R3sets the MPPC threshold.The DC2255A has four user selectable output voltages:1.8V, 2.2V, 3.3V and 5V. When the LTC3106 is enabled,the PGOOD pin asserts low if VOUT is below the regulationvoltage. If JP3 is set to VOUT the red PGOOD indicator LEDon the board lights up when the output is in regulation.L, LT, LTC, LTM, Linear Technology, the Linear logo, Dust and Burst Mode are registeredtrademarks and PowerPath is a trademark of Linear Technology Corporation. All othertrademarks are the property of their respective owners.PERFORMANCE SUMMARYThis is a visual indication of VOUT being in regulation andis not needed for normal operation. To minimize currentconsumed, set JP3 to NC.The LTC3106 can operate with either a primary or secondarybattery on its VSTORE supply. In secondary mode(JP7 set to GND), the part will use excess power to tricklecharge the battery on VSTORE. There are four pin selectableOV/UV thresholds for the battery voltage in this mode toallow operation with a variety of secondary batteries. Ifthe DC2255A is operated in secondary mode, a Schottkydiode must be placed between the SW2 and VAUX pins.The LTC3106 requires no external compensation andprovides good line and load transient response acrossthe entire VIN range for each output voltage setting. Thissimplifies the design process while reducing the externalcomponent count.The LTC3106 data sheet has detailed information aboutthe operation, specifications, and applications of the part.The data sheet should be read in conjunction with thisquick start guide.

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