Datasheet LTC3548-1 (Analog Devices)

LTC3548-1 Dual Synchronous, Fixed Output 2.25MHz Step-Down DC/DC Regulator
FEATURES DESCRIPTION
n
High Effi ciency: Up to 95%
The LTC®3548-1 is a dual, fi xed output, constant-frequency, n
1.8V at 800mA/1.575V at 400mA
synchronous step-down DC/DC converter. Intended for low n
Very Low Quiescent Current: Only 40μA
power applications, it operates from 2.5V to 5.5V input n
2.25MHz Constant-Frequency Operation
voltage range and has a constant 2.25MHz switching n
High Switch Current: 1.2A and 0.7A
frequency, allowing the use of tiny, low cost capacitors n
No Schottky Diodes Required
and inductors with a profi le ≤1mm. The output voltage n
VIN: 2.5V to 5.5V
for channel 1 is fi xed at 1.8V and for channel 2 is fi xed n Current Mode Operation for Excellent Line at 1.575V. Internal synchronous 0.35Ω, 1.2A/0.7A power and Load Transient Response switches provide high effi ciency without the need for ex- n Short-Circuit Protected ternal Schottky diodes. Burst Mode® operation provides n Low Dropout Operation: 100% Duty Cycle high effi ciency at light loads. n Ultralow Shutdown Current: IQ < 1μA To further maximize battery runtime, the P-channel n Small Thermally Enhanced 3mm × 3mm MOSFETs are turned on continuously in dropout (100% DFN Packages duty cycle), and both channels draw a total quiescent cur- rent of only 40μA. In shutdown, the device draws <1μA.
APPLICATIONS
The LTC3548-1 is available in both thin (0.75mm) and n ultrathin (0.55mm) 3mm PDAs/Palmtop PCs × 3mm DFN packages. n Digital Cameras L, LT, LTC, LTM, Linear Technology, the Linear logo and Burst Mode are registered trademarks n Cellular Phones of Linear Technology Corporation. All other trademarks are the property of their respective owners. Protected by U.S. Patents, including 5481178, 6127815, 6304066, 6498466, 6580258 n Portable Media Players 6611131.. n PC Cards n Wireless and DSL Modems
TYPICAL APPLICATION LTC3548-1 Effi ciency Curve/Power Loss
100 1000 VIN 2.7V TO 5.5V CIN 95 10μF V RUN1 RUN2 IN CER 90 100 POWER LOSS (mW) V LTC3548-1 OUT1 = 1.8V 85 V 4.7μH 2.2μH OUT2 VOUT1 1.575V SW2 SW1 1.8V 80 10 400mA 800mA VOUT2 = 1.575V V V C OUT2 OUT1 C OUT2 OUT1 C C 75 EFFICIENCY (%) 10μF FF2 FF1 10μF 330pF 330pF CER V V FB2 FB1 CER 70 1 GND 3548-1 F01 65 CHANNEL 1 CHANNEL 2 60 0.1 1 10 100 1000
Figure 1. 1.8V/1.575V at 800mA/400mA Step-Down Regulators
LOAD CURRENT (mA) 35481 F01b 35481fc 1