Datasheet LTC3448 (Analog Devices)

LTC3448 1.5MHz/2.25MHz, 600mA Synchronous Step-Down Regulator with LDO Mode
U FEATURES DESCRIPTIO
■
High Efficiency: Up to 96%
The LTC®3448 is a high efficiency, monolithic, synchronous ■
Very Low Quiescent Supply Current: 32
µ
A During
buck regulator using a constant frequency, current mode
Linear Regulator Operation
architecture. Supply current during operation is only 32µA ■
600mA Output Current (Buck Converter)
(linear regulator mode) and drops to <1µA in shutdown. The ■
Optionally Operates as Linear Regulator Below
2.5V to 5.5V input voltage range makes the LTC3448 ide-
3mA—External or Automatic ON/OFF
ally suited for single Li-Ion battery-powered applications. ■
2.5V to 5.5V Input Voltage Range
100% duty cycle provides low dropout operation, extend- ■
1.5MHz or 2.25MHz Constant Frequency Operation
ing battery life in portable systems. At moderate output load
or External Synchronization
levels, PWM pulse skipping mode operation provides very ■
No Schottky Diode Required
low output ripple voltage for noise sensitive applications. ■
Low Dropout Operation: 100% Duty Cycle
The LTC3448 automatically switches into linear regulator ■ 0.6V Reference Allows Low Output Voltages ■ Shutdown Mode Draws < 1µA Supply Current operation at very low load currents to maintain <5mVP-P ■ Current Mode Operation for Excellent Line and output voltage ripple. Supply current in this mode is Load Transient Response typically 32µA. The switch to linear regulator mode occurs ■ Overtemperature Protected at a threshold of 3mA. Linear regulator operation can be set ■ Low Profile (3mm × 3mm) 8-Lead DFN and 8-Lead to on, off or automatic turn on/off. MSOP Packages Switching frequency is selectable at either 1.5MHz or
U
2.25MHz, allowing the use of small surface mount induc-
APPLICATIO S
tors and capacitors. ■ Cellular Telephones The internal synchronous switch increases efficiency and ■ Personal Information Appliances eliminates the need for an external Schottky diode. Low ■ Wireless and DSL Modems output voltages are easily supported with the 0.6V feed- ■ Digital Still Cameras back reference voltage. The LTC3448 is available in a low ■ MP3 Players profile 3mm × 3mm DFN package or thermally enhanced ■ Portable Instruments 8-lead MSOP. , LTC and LT are registered trademarks of Linear Technology Corporation. All other trademarks are the property of their respective owners. Protected by U.S. Patents including 5481178, 6580258, 6304066, 6127815, 6498466, 6611131. Others pending.
U Efficiency and Power Loss vs Load Current TYPICAL APPLICATIO
100 1 VIN = 3.6V V
1.5V High Efficiency Regulator with Automatic LDO Mode
90 OUT = 1.5V TA = 25°C 80 0.1 POWER LOSS (W) 70 2.2µH EFFICIENCY VIN V V OUT 60 IN 2.5V TO 5.5V SW 1.5V POWER LOSS C C 50 0.01 IN RUN VOUT OUT 4.7µF LTC3448 4.7µF 474k 22pF 40 MODE EFFICIENCY (%) 30 FREQ VFB 0.001 SYNC 316k 20 GND 10 0 0.0001 3448 TA01a 0.0001 0.001 0.01 0.1 1 LOAD CURRENT (A) 23448 TA01b 3448f 1