LTC3544B_15 Datasheet, PDF (1/18 Pages) Linear Technology – Quad Synchronous Step-Down Regulator

LTC3544B
Quad Synchronous
Step-Down Regulator: 2.25MHz,
300mA, 200mA, 200mA, 100mA
Features
■ _{High Efficiency: Up to 95%}
■ _{Four Independent Regulators Provide Up to 300mA,}
200mA, 200mA and 100mA Output Current
■ _{2.25V to 5.5V Input Voltage Range}
■ _{2.25MHz Constant Frequency Operation}
■ _{No Schottky Diodes Required}
■ _{Low Dropout Operation: 100% Duty Cycle}
■ _{Pulse Skipping at Low Load for Minimum Ripple}
■ _{0.8V Reference Allows Low Output Voltages}
■ _{Shutdown Mode Draws <1µA Supply Current}
■ _{Current Mode Operation for Excellent Line and Load}
Transient Response
■ _{Overtemperature Protected}
■ _{Low Profile (3mm × 3mm) 16-Lead QFN Package}
Applications
■ _{Cellular Telephones}
■ _{Personal Information Appliances}
■ _{Wireless and DSL Modems}
■ _{Digital Still Cameras}
■ _{Media Players}
■ _{Portable Instruments}
Description
The LTC^®3544B is a quad, high efficiency, monolithic
synchronous buck regulator using a constant frequency,
current mode architecture. The four regulators operate in-
dependently with separate run pins. The 2.25V to 5.5V input
voltage range makes the LTC3544B well suited for single
Li-Ion/polymer battery-powered applications. 100% duty
cycle provides low dropout operation, extending battery
runtime in portable systems. At moderate and low output
load levels PWM pulse skip mode operation provides very
low output ripple voltage for noise sensitive applications.
Switching frequency is internally set to 2.25MHz, al-
lowing the use of small surface mount inductors and
capacitors.
The internal synchronous switches increase efficiency
and eliminate the need for external Schottky diodes. Low
output voltages are easily supported with the 0.8V feedback
reference voltage.
The LTC3544B is available in a low profile (0.75mm)
(3mm × 3mm) QFN package.
L, LT, LTC, LTM, Linear Technology and the Linear logo 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, 5994885.
Typical Application
High Efficiency Quad Step-Down Converter
V_IN
2.25V TO 5.5V
V_OUT2
1.5V
4.7µF
CER
4.7µF
CER
4.7µH
93.1k
107k
V_CC
RUN200B
SW200B
V_FB200B
PV_IN
RUN200A
SW200A
V_FB200A
LTC3544B
V_OUT4
1.8V
4.7µF
CER
3.3µH
133k
107k
RUN300
SW300
V_FB300
GNDA
RUN100
SW100
V_FB100
PGND
3.3µH
100k
V_OUT3
0.8V
4.7µF
CER
10µH
59k
118k
V_OUT1
1.2V
4.7µF
CER
3544B TA01a
Efficiency vs Load Current, 300mA
Channel, All Other Channels Off
100
1
V_OUT = 1.5V
90 T_A = 25°C
80
70
EFFICIENCY
0.1
60
50
POWER LOSS
40
30
0.01
20
10
0
0.0001
0.001
0.01
V_IN = 2.5V
V_IN = 3.6V
V_IN = 4.3V _0.001
0.1
1
LOAD CURRENT (A)
3544B TA01b
3544bfb