LTC3672B-1_15 Datasheet, PDF (1/12 Pages) Linear Technology – Monolithic Fixed-Output 400mA Buck Regulator with Dual

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 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. 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-1.
The LTC3672B-1 is available in a 2mm × 2mm × 0.75mm
8-Lead DFN package.
L, LT, LTC and LTM are registered trademarks of Linear Technology Corporation. All other
trademarks are the property of their respective owners.
TYPICAL APPLICATION
V_IN
2.9V TO 5.5V
2.2MF
ENABLE
INPUT
4.7MH
V_IN
SW
GND BUCKOUT
ENALL
V_IN1
LDO1
LTC3672B-1
LDO2
3672b1 TA01
10MF
1MF
1MF
V_OUT1
1.8V
400mA
(250mA IF LDO1
FULLY-LOADED)
V_OUT2
1.2V
150mA
V_OUT3
2.8V
UP TO 150mA
(SUBJECT TO DROPOUT
LIMITATIONS)
Buck DC/DC Efficiency vs Load
100
95 _{VIN = 2.9V}
90
85
80
V_IN = 5.5V
V_IN = 3.6V
75
70
65
60
0
50 100 150 200 250 300 350 400
I_LOAD (mA)
3672b1 TA01b
3672B1f
1