400mA Buck Regulator with Dual
150mA LDOs in 2mm × 2mm DFN
n Triple Output Supply From a Single 2.9V to 5.5V Input
n Buck DC/DC: Fixed 1.2V Output, Up to 400mA
n LDO1: Fixed 2.8V Output, Up to 150mA
n LDO2: Fixed 1.8V Output, Up to 150mA
n ±2.5% Reference Accuracy
n Constant-Frequency 2.25MHz Operation
n Minimum External Component Count
n Current Mode Operation for Excellent Line and Load
n Internal Soft-Start for Each Output
n Single Enable Pin Turns On/Shuts Down All Three
n Tiny 2mm × 2mm × 0.75mm DFN Package
n DMB and DVB-H Cellphones
n Handheld Products (PDA, PMP, GPS)
n Multivoltage Power for Digital Logic, I/O, FPGAs,
CPLDs, ASICs, CPUs, and RF Chipsets
The LTC®3672B-2 is a triple power supply composed of
a 400mA synchronous buck regulator and two 150mA
low-dropout linear regulators (LDOs). 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-2 regulates 1.2V at the buck output, 2.8V
at the LDO1 output, and 1.8V at the LDO2 output. Exter-
nal 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-2.
The LTC3672B-2 is available in a 2mm × 2mm × 0.75mm
8-Lead DFN package.
, LT, LTC and LTM are registered trademarks of Linear Technology Corporation.
All other trademarks are the property of their respective owners.
2.9V TO 5.5V
VIN VIN1 SW
2.8V, UP TO 150mA
(SUBJECT TO DROPOUT
Buck DC/DC Efﬁciency vs Buck Load
90 VIN = 2.9V
80 VIN = 3.6V
70 VIN = 5.5V
50 100 150 200 250 300 350 400