LTC3544_15 Datasheet, PDF (1/16 Pages) Linear Technology – Quad Synchronous Step-Down Regulator

LTC3544
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}
■ _{Extremely Low Channel-to-Channel Transient}
Crosstalk
■ _{Low Ripple (20mVP-P) Burst Mode Operation:}
I_Q = 70μA (All Channels On)
■ _{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^®3544 is a quad, high efficiency, monolithic
synchronous buck regulator using a constant-frequency,
current mode architecture. The four regulators operate
independently with separate run pins. The 2.25V to 5.5V
input voltage range makes the LTC3544 well suited for
single Li-Ion/polymer battery-powered applications.
100% duty cycle provides low dropout operation, ex-
tending battery runtime in portable systems. Low ripple
Burst Mode^® operation increases efficiency at light loads,
further extending battery runtime with typically only 20mV
of ripple.
Switching frequency is internally set to 2.25MHz, allowing
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 LTC3544 is available in a low profile (0.75mm) (3mm
× 3mm) QFN package.
, LT, LTC and LTM are registered trademarks of Linear Technology Corporation.
Burst Mode is a registered trademark 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
200mA
4.7μF
CER
4.7μF
CER
4.7μH
93.1k
107k
V_OUT4
1.8V
300mA
4.7μF
CER
3.3μH
133k
107k
V_CC
RUN200B
SW200B
V_FB200B
PV_IN
RUN200A
SW200A
V_FB200A
LTC3544
RUN300
SW300
V_FB300
GNDA
RUN100
SW100
V_FB100
PGND
3.3μH
100k
V_OUT3
0.8V
200mA
4.7μF
CER
10μH
59k
118k
V_OUT1
1.2V
100mA
4.7μF
CER
3544B TA01a
Efficiency vs Load Current, 300mA
Channel, All Other Channels Off
100
1
90
80
EFFICIENCY
0.1
70
60
LOSS
50 VOUT = 2.5V
0.01
40 ^{TA = 25°C}
30
20
10
0
0.0001
0.001
0.001
0.01
V_IN = 2.7V
V_IN = 3.6V
V_IN = 4.2V _0.0001
0.1
1
LOAD CURRENT (A)
3544 TA01b
3544fa
1