Datasheet LTC3407A-2 (Analog Devices)

LTC3407A-2 Dual Synchronous 800mA, 2.25MHz Step-Down DC/DC Regulator
U FEATURES DESCRIPTIO
■
High Efficiency: Up to 95%
The LTC®3407A-2 is a dual, constant frequency, synchro- ■
Low Ripple (<35mVPK-PK) Burst Mode Operation;
nous step-down DC/DC converter. Intended for low power
IQ = 40
μ
A
applications, it operates from a 2.5V to 5.5V input voltage ■
2.25MHz Constant Frequency Operation
range and has a constant 2.25MHz switching frequency, ■
No Schottky Diodes Required
enabling the use of tiny, low cost capacitors and inductors ■
Low RDS(ON) Internal Switches: 0.35
Ω 1mm or less in height. Each output voltage is adjustable ■ Current Mode Operation for Excellent Line from 0.6V to 5V. Internal synchronous 0.35Ω, 1A power and Load Transient Response switches provide high efficiency without the need for ■ Short-Circuit Protected external Schottky diodes. ■ Low Dropout Operation: 100% Duty Cycle A user selectable mode input is provided to allow the user ■ Ultralow Shutdown Current: IQ <1μA to trade-off ripple noise for low power efficiency. Burst ■ Output Voltages from 5V down to 0.6V Mode® operation provides the highest efficiency at light ■ Power-On Reset Output loads, while Pulse Skip Mode provides the lowest ripple ■ Externally Synchronizable Oscillator noise at light loads. ■ Optional External Soft-Start ■ Small Thermally Enhanced MSOP and 3mm × 3mm To further maximize battery life, the P-channel MOSFETs DFN Packages are turned on continuously in dropout (100% duty cycle),
U
and both channels draw a total quiescent current of only
APPLICATIO S
40μA. In shutdown, the device draws <1μA. ■ PDAs/Palmtop PCs , LT, LTC, LTM and Burst Mode are registered trademarks of Linear Technology Corporation. All other trademarks are the property of their respective owners. Protected by ■ Digital Cameras U.S. Patents including 5481178, 6580258, 6304066, 6127815, 6498466, 6611131. ■ Cellular Phones ■ Wireless and DSL Modems
U TYPICAL APPLICATIO 1mm High 2.5V/1.8V at 800mA Step-Down Regulators Efficiency/Power Loss Curve
100 1 VIN = 2.5V 2.5V TO 5.5V 90 1.8V 10μF 100k 80 RUN/SS2 V 0.1 IN RUN/SS1 POWER LOSS (W) 70 MODE/SYNC POR RESET 60 LTC3407A-2 50 0.01 2.2μH 2.2μH VOUT2 = 2.5V VOUT1 = 1.8V 40 SW2 SW1 AT 800mA AT 800mA EFFICIENCY (%) 22pF 22pF 30 0.001 20 VIN = 3.3V Burst Mode OPERATION V V FB2 FB1 10 887k 887k NO LOAD ON OTHER CHANNEL GND 280k 442k 0 0.0001 10μF 10μF 1 10 100 1000 LOAD CURRENT (mA) 3407A2 TA02 3407A2 TA01 3407a2f 1