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Linear Technology Electronic Components Datasheet

LTC3549 Datasheet

250mA Low VIN Buck Regulator

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LTC3549
250mA Low VIN Buck
Regulator in 2mm × 3mm DFN
FEATURES
1.6V to 5.5V Input Voltage Range
Internal Soft-Start
Low Ripple Burst Mode® Operation
Output Ripple: <20mVP-P
IQ: 50µA
2.25MHz Constant-Frequency Operation
www.DaHtiagShheEeffit4cUi.ecnocmy: Up to 93%
250mA Output Current (VIN = 1.8V, VOUT = 1.2V)
450mA Peak Inductor Current
No Schottky Diode Required
Low Dropout Operation: 100% Duty Cycle
0.611V Reference Voltage
Stable with Ceramic Capacitors
Shutdown Mode Draws <1µA Supply Current
Current Mode Operation for Excellent Line and Load
Transient Response
Overtemperature Protection
Available in a Low Profile (0.75mm) 6-Lead
(2mm x 3mm) DFN Package
U
APPLICATIO S
2 AA-Cell Applications
Cellular Phones
Digital Cameras
MP3 Players
DESCRIPTIO
The LTC®3549 is a high efficiency, monolithic synchronous
buck regulator using a constant-frequency, current mode
architecture. The output voltage is adjusted via an external
resistor divider.
A fixed switching frequency of 2.25MHz is supported.
This switching frequency allows the use of small surface
mount inductors and capacitors, including ceramics.
Supply current during Burst Mode operation is only 50µA
dropping to < 1µA in shutdown. The 1.6V to 5.5V input
voltage range makes the LTC3549 ideally suited for single
cell Li-Ion, Li-Metal and 2-cell alkaline, NiCd or NiMH
battery-powered applications. 100% duty cycle capabil-
ity provides low dropout operation, extending battery
life in portable systems. Burst Mode operation can be
user-enabled, increasing efficiency at light loads, further
extending battery life.
The internal synchronous switch increases efficiency and
eliminates the need for an external Schottky diode. Internal
soft-start offers controlled output voltage rise time at start-
up without the need for external components.
, 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.
TYPICAL APPLICATIO
High Efficiency Step-Down Converter
VIN
1.8V TO
5.5V
4.7µF
CER
LTC3549
SW
VIN
RUN
MODE VFB
GND
3.3µH*
22pF
137k 200k
*TDK VLF3012AT-3R3MR87
3549 TA01
VOUT
1.5V
4.7µF
CER
Burst Mode Efficiency, VOUT = 1.5V
100 1
90
80
0.1
70
60
50 0.01
40
30
20
10
0
0.1
VIN = 1.8V
VIN = 2.5V
VIN = 3.1V
POWER LOST
0.001
AT VIN = 2.5V
0.0001
1 10 100 1k
LOAD CURRENT (mA)
3549 TA02
3549f
1


Linear Technology Electronic Components Datasheet

LTC3549 Datasheet

250mA Low VIN Buck Regulator

No Preview Available !

LTC3549
ABSOLUTE AXI U RATI GS
(Note 1)
Input Supply Voltage................................... –0.3V to 6V
RUN, VFB, MODE Voltages .............–0.3V to (VIN + 0.3V)
SW Voltage < 100ns Pulse.............–0.3V to (VIN + 0.3V)
Operating Temperature Range (Note 2) ... –40°C to 85°C
Junction Temperature (Note 3) ........................... 125°C
Storage Temperature Range.................. –65°C to 125°C
UW U
PACKAGE/ORDER I FOR ATIO
TOP VIEW
654
7
www.DataSheet4U.com
123
DCB PACKAGE
6-LEAD (2mm × 3mm) PLASTIC DFN
TJMAX = 125°C, θJA = 64°C/W
EXPOSED PAD (PIN 7) IS GND
MUST BE SOLDERED TO PCB
ORDER PART NUMBER DCB PART MARKING
LTC3549EDCB
LBZR
Order Options Tape and Reel: Add #TR
Lead Free: Add #PBF Lead Free Tape and Reel: Add #TRPBF
Lead Free Part Marking: http://www.linear.com/leadfree/
Consult LTC Marketing for parts specified with wider operating temperature ranges.
ELECTRICAL CHARACTERISTICS The denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C, VIN = 2.2V.
SYMBOL
PARAMETER
CONDITIONS
MIN TYP MAX UNITS
VIN
VRUN
IRUN
VMODE
IMODE
VFB
IVFB
ΔVOVL
ΔVFB
ΔVOUT
IPK
Input Voltage Range
RUN Threshold
RUN Leakage Current
MODE Threshold
MODE Leakage Current
Regulated Feedback Voltage
Feedback Current
ΔVFBOVL Overvoltage Lockout
Reference Voltage Line Regulation
Output Voltage Line Regulation
Peak Inductor Current
1.6
0.3
VRUN = 0 or 2.2V
0.3
VMODE = 0 or 2.2V
TA = 25°C (Note 4)
0°C ≤ TA ≤ 85°C (Note 4)
–40°C ≤ TA ≤ 85°C (Note 4)
0.599
0.597
0.596
ΔVOVL = ΔVFBOVL – VFB (Note 6)
1.6V < VIN < 5.5V (Note 4)
IOUT = 100mA, 1.6V < VIN < 5.5V (Note 7)
VFB = 0.5V or VOUT = 90%
40
0.3
0.7
0.01
0.65
0.01
0.611
0.611
0.611
60
0.04
0.04
0.45
5.5
1.1
1
1.1
1
0.623
0.623
0.626
±30
80
0.4
0.4
0.6
V
V
µA
V
µA
V
V
V
nA
mV
%/V
%/V
A
VLOADREG
Output Voltage Load Regulation
Pulse Skip Mode, VOUT = 1.2V,
50mA < ILOAD < 250mA (Note 7)
0.5 %
3549f
2


Part Number LTC3549
Description 250mA Low VIN Buck Regulator
Maker Linear Technology
Total Page 16 Pages
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