Datasheet LTC3446 (Analog Devices)

LTC3446 Monolithic Buck Regulator with Dual VLDO Regulators
FeaTures DescripTion
n
High Efficiency Triple Step-Down Outputs from a
The LTC®3446 combines a synchronous buck DC/DC con-
Single Input Supply
verter with two very low dropout (VLDO) linear regulators n
1A Synchronous Buck Regulator Provides Main
to provide up to three stepped-down output voltages from
Step-Down Output and Powers Two 300mA VLDO™
a single input voltage. The input voltage range is ideally
Linear Regulators
suited for Li-Ion battery-powered applications, as well n
Output Voltages as Low as 400mV (VLDO Outputs)
as powering low voltage logic from 5V or 3.3V rails. The n Power Good Output output voltage range extends down to 0.4V for the VLDO n Input Voltage Range: 2.7V to 5.5V regulators and 0.8V for the buck. n Independent Enable Pin for Each Supply The 1A synchronous buck converter provides the main n Low (140µA Typ) No-Load Quiescent Current with output with high efficiency, typically 85%. The two 300mA All Outputs Enabled VLDO regulators can run off the main output to provide n Constant Frequency Current Mode Operation two additional lower voltage outputs. A built-in supply n 2.25MHz Switching Frequency Uses Small Inductors monitor provides a power good indication. n Defeatable Automatic Burst Mode® Operation for High Efficiency at Light Loads The buck converter switches at 2.25MHz, allowing the use n ±1.5% Reference Accuracy of small surface mount inductors and capacitors. Constant n Overtemperature Protection frequency current mode operation produces controlled n Thermally Enhanced 4mm × 3mm 14-Pin DFN output spectrum and fast transient response. A mode- Package select pin allows automatic Burst Mode operation to be enabled for higher efficiency at light load, or disabled for
applicaTions
lower noise operation down to very light loads. The two VLDO regulators are stable with ceramic output capacitors n Low Power Handheld Devices as small as 1µF. n Low Voltage and Multivoltage Power for Digital L, LT, LTC, LTM and Burst Mode are registered trademarks and VLDO, Hot Swap, PowerPath Logic, I/O, FPGAs, CPLDs, ASICs and CPUs and Bat-Track are trademarks of Linear Technology Corporation. All other trademarks are the property of their respective owners. Protected by U.S. Patents including 5481178, 6611131, 6304066, 6498466, 6580258.
Typical applicaTion
L1 1.8µH VOUT VIN V SW 1.8V
Buck Efficiency vs Buck Load Current
IN 2.9V TO 5.5V 22µF 22µF 59k 400mA MAX X7R X7R 100 BUCKFB PWM Burst Mode MODE 47.5k 90 OPERATION LTC3446 LVIN VOUT 80 PGOOD LVOUT1 1.5V DIGITAL MODESEL 2.2µF 110k 300mA MAX 70 CONTROL ENBUCK X7R ENLDO1 LVFB1 ENLDO2 40.2k EFFICIENCY (%) 60 3.3k VOUT 50 VIN = 2.7V ITH LVOUT2 1.2V VIN = 3.6V 1000pF 2.2µF 80.6k 300mA MAX V X7R IN = 4.2V 40 LVFB2 1 10 100 1000 GND 40.2k LOAD CURRENT (mA) 3446 TA01 L1: TOKO A960AW-1R8M 3446 TA01b 3446ff 1 Document Outline Features Applications Description Typical Application Absolute Maximum Ratings Pin Configuration Order Information Electrical Characteristics Typical Performance Characteristics Pin Functions Block Diagram Operation Applications Information Package Description Revision History Typical Application Related Parts