LTC3548-1 Datasheet, PDF (1/16 Pages) Linear Technology – Dual Synchronous, Fixed Output 2.25MHz Step-Down DC/DC Regulator

FEATURES
n _{High Efficiency: Up to 95%}
n _{1.8V at 800mA/1.575V at 400mA}
n _{Very Low Quiescent Current: Only 40μA}
n _{2.25MHz Constant Frequency Operation}
n _{High Switch Current: 1.2A and 0.7A}
n _{No Schottky Diodes Required}
n _{VIN: 2.5V to 5.5V}
n _{Current Mode Operation for Excellent Line}
and Load Transient Response
n _{Short-Circuit Protected}
n _{Low Dropout Operation: 100% Duty Cycle}
n _{Ultralow Shutdown Current: IQ < 1μA}
n _{Small Thermally Enhanced 3mm × 3mm}
DFN Packages
APPLICATIONS
n _{PDAs/Palmtop PCs}
n _{Digital Cameras}
n _{Cellular Phones}
n _{Portable Media Players}
n _{PC Cards}
n _{Wireless and DSL Modems}
LTC3548-1
Dual Synchronous, Fixed
Output 2.25MHz Step-Down
DC/DC Regulator
DESCRIPTION
The LTC^®3548-1 is a dual, fixed output, constant frequency,
synchronous step-down DC/DC converter. Intended for low
power applications, it operates from 2.5V to 5.5V input
voltage range and has a constant 2.25MHz switching
frequency, allowing the use of tiny, low cost capacitors
and inductors with a profile ≤1mm. The output voltage
for channel 1 is fixed at 1.8V and for channel 2 is fixed
at 1.575V. Internal synchronous 0.35Ω, 1.2A/0.7A power
switches provide high efficiency without the need for ex-
ternal Schottky diodes. Burst Mode^® operation provides
high efficiency at light loads.
To further maximize battery runtime, the P-channel
MOSFETs are turned on continuously in dropout (100%
duty cycle), and both channels draw a total quiescent cur-
rent of only 40μA. In shutdown, the device draws <1μA.
The LTC3548-1 is available in both thin (0.75mm) and
ultra-thin (0.55mm) 3mm × 3mm DFN packages.
L, 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 U.S. Patents
including 5481178, 6580258, 6304066, 6127815, 6498466, 6611131.
TYPICAL APPLICATION
V_IN
2.7V TO 5.5V
V_OUT2
1.575V
400mA
C_OUT2
10μF
CER
C_IN
10μF
CER
4.7μH
C_FF2
330pF
V_IN RUN1 RUN2
LTC3548-1
SW2
SW1
V_OUT2
V_OUT1
V_FB2
GND
V_FB1
2.2μH
C_FF1
330pF
V_OUT1
1.8V
800mA
C_OUT1
10μF
CER
3548-1 F01
Figure 1. 1.8V/1.575V at 800mA/400mA Step-Down Regulators
LTC3548-1 Efficiency Curve/Power Loss
100
1000
95
90
100
V_OUT1 = 1.8V
85
80 _{VOUT2 = 1.575V}
10
75
70
1
65
CHANNEL 1
CHANNEL 2
60
0.1
1
10
100
1000
LOAD CURRENT (mA)
35481 F01b
35481fb
1