Monolithic Fixed-Output 400mA Buck Regulator with Dual 150mA LDOs in 2mm x 2mm DFN

The LTC3672B-1 is a triple power supply composed of a 400mA synchronous buck regulator and two 150mA low dropout 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 loop compensation is internal to the LTC3672B-1.

The LTC3672B-1 is available in a 2mm x 2mm x 0.75mm 8-Lead DFN package.

Buck Vout

LDO 1

LDO 2

LTC3672B-1

1.8V

1.2V

2.8V

LTC3672B-2

1.2V

2.8V

1.8V

Applications

* DMB Cellphones

* Handheld Products (PDA, PMP, GPS)

* Multivoltage Power for Digital Logic, I/O, FPGAs, CPLDs, ASICs, CPUs, and RF Chipsets

* 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