LTC3672B-1

LTC3672B-1 Monolithic Fixed-Output 400mA Buck Regulator with Dual 150mA LDOs in 2mm × 2mm DFN FEATURES ■ Triple Output Supply From a Single 2.9V to 5.5V Input ■ Buck DC/DC: Fixed 1.8V Output, Up to 400mA ■ LDO1: Fixed 1.2V Output, Up to 150mA ■ LDO2: Fixed 2.8V Output, Up to 150mA ■ ±2.5% Reference Accuracy ■ Constant Frequency 2.25MHz Operation ■ Minimum External Component Count ■ Current Mode Operation for Excellent Line and Load Transient Response ■ Internal Soft-Start for Each Output ■ Single Enable Pin Turns On/Shuts Down All Three Outputs ■ Tiny 2mm × 2mm × 0.75mm DFN Package APPLICATIONS ■ DMB Cellphones ■ Handheld Products (PDA, PMP, GPS) ■ Multivoltage Power for Digital Logic, I/O, FPGAs, CPLDs, ASICs, CPUs, and RF Chipsets DESCRIPTION The LTC®3672B-1 is a triple power supply composed of a 400mA synchronous buck regulator and two 150mA lowdropout linear regulators (LDOs), where one of the LDOs can be powered from the buck output to improve efficiency. Constant-frequency 2.25MHz operation is maintained down to very light loads. The input supply range of 2.9V to 5.5V is especially well-suited for single-cell Lithium-Ion and Lithium-Polymer applications, and for powering low voltage ASICs from 3.3V or 5V rails. The LTC3672B-1 regulates 1.8V at the buck output, 1.2V at the LDO1 output, and 2.8V at the LDO2 output. External component count is minimal—all that is needed is a single inductor, an input capacitor, and output capacitors for each of the three outputs. Control ...