out operation, extending battery life in portable systems.
Low output voltages are supported with the 0.6V feed-
back reference voltage. Each regulator can supply 300mA
continuous output current.
The input voltage range is 2.5V to 5.5V, making it ideal
for Li-Ion polymer and USB powered applications. Supply
current is only 1μA in shutdown.
An internally set 2.25MHz switching frequency allows the
use of tiny surface mount inductors and capacitors. Inter-
nal soft-start reduces inrush current during start-up. All
outputs are internally compensated to work with ceramic
capacitors. The LTC3547B is available in a low profile
(0.75mm) 3mm × 2mm DFN package. The LTC3547B
is also available in a fixed output voltage configuration
selected via internal resistor dividers (see Table 2).
, 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 6580258, 5481178, 6304066, 6127815, 6498466, 6611131.
APPLICATIO S
■
■
■
■
■
Cellular Telephones
Digital Still Cameras
Wireless and DSL Modems
Portable Media Players
PDAs/Palmtop PCs
TYPICAL APPLICATIO
V
IN
2.5V TO 5.5V
Dual Monolithic Buck Regulator in 8-Lead 3mm × 2mm DFN
100
90
80
RUN2 V
IN
RUN1
V
OUT2
1.8V AT
300mA
4.7μH
10pF
LTC3547B
SW2
SW1
10pF
4.7μH
V
OUT1
2.5V AT
300mA
EFFICIENCY (%)
4.7μF
70
60
50
40
30
20
V
IN
= 2.7V
V
IN
= 3.6V
V
IN
= 4.2V
1
10
100
OUTPUT CURRENT (mA)
V
FB2
4.7μF
475k
237k
GND
V
FB1
150k
475k
4.7μF
3547b TA01
10
0
U
Efficiency vs Output Current
for V
OUT
= 2.5V
1
POWER LOSS (W)
0.1
0.01
0.001
1000
3547bfb
3547b TA01b
U
U
1
LTC3547B
ABSOLUTE
(Note 1)
AXI U RATI GS
V
IN
LTC3547BE .............................................. –0.3V to 6V
LTC3547BI ............................................... –0.3V to 7V
V
FB1
, V
FB2
......................................... –0.3V to V
IN
+0.3V
RUN1, RUN2 ..................................... –0.3V to V
IN
+0.3V
SW1, SW2 (DC) ................................ –0.3V to V
IN
+0.3V
P-Channel Switch Source Current (DC)................500mA
N-Channel Switch Sink Current (DC) ...................500mA
Peak SW Sink and Source Current (Note 5) .........700mA
Ambient Operating Temperature Range (Note 2)
LTC3547BE .......................................... –40°C to 85°C
LTC3547BI ......................................... –40°C to 125°C
Maximum Junction Temperature........................... 125°C
Storage Temperature Range................... –65°C to 125°C
ORDER INFORMATION
LEAD FREE FINISH
LTC3547BEDDB#PBF
LTC3547BEDDB-1#PBF
LTC3547BIDDB #PBF
TAPE AND REEL
LTC3547BEDDB#TRPBF
LTC3547BIDDB #TRPBF
PART MARKING*
LCPD
LCPD
PACKAGE DESCRIPTION
8-Lead (3mm × 2mm) Plastic DFN
8-Lead (3mm × 2mm) Plastic DFN
8-Lead (3mm × 2mm) Plastic DFN
TEMPERATURE RANGE
–40°C to 85°C
–40°C to 85°C
–40°C to 125°C
LTC3547BEDDB-1#TRPBF LCPF
Consult LTC Marketing for parts specified with wider operating temperature ranges. *Temperature grades are identified by a label on the shipping container.
Consult LTC Marketing for information on non-standard lead based finish parts.
For more information on lead free part marking, go to:
http://www.linear.com/leadfree/
For more information on tape and reel specifications, go to:
http://www.linear.com/tapeandreel/
The
●
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. V
IN
= 3.6V, unless otherwise noted.
SYMBOL
V
IN
V
UV
I
FB
V
FBREG1
PARAMETER
V
IN
Operating Voltage
V
IN
Undervoltage Lockout
Feedback Pin Input Current
Regulated Feedback Voltage (V
FB1
)
CONDITIONS
LTC3547BE, LTC3547BE-1,
LTC3547BI
V
IN
Low to High
LTC3547BE, V
FB
= V
FBREG
LTC3547BE-1, V
FB
= V
FBREG
LTC3547BE, 0°C ≤ T
A
≤ 85°C
LTC3547BE, –40°C ≤ T
A
≤ 85°C
LTC3547BI, –40°C ≤ T
A
≤ 125°C
LTC3547BE-1, 0°C ≤ T
A
≤ 85°C
LTC3547BE-1, –40°C ≤ T
A
≤ 85°C
LTC3547BE, 0°C ≤ T
A
≤ 85°C
LTC3547BE, –40°C ≤ T
A
≤ 85°C
LTC3547BI, –40°C ≤ T
A
≤ 125°C
LTC3547BE-1, 0°C ≤ T
A
≤ 85°C
LTC3547BE-1, –40°C ≤ T
A
≤ 85°C
●
●
●
●
●
●
●
●
●
●
●
ELECTRICAL CHARACTERISTICS
V
FBREG2
Regulated Feedback Voltage (V
FB2
)
2
U
W W
W
PIN CONFIGURATION
TOP VIEW
V
FB1
1
RUN1 2
V
IN
3
SW1 4
9
8 V
FB2
7 RUN2
6 SW2
5 GND
DDB PACKAGE
8-LEAD (3mm × 2mm) PLASTIC DFN
T
JMAX
= 125°C,
θ
JA
= 76°C/W
EXPOSED PAD (PIN 9) IS GND
MUST BE SOLDERED TO PCB
MIN
2.5
2.5
TYP
MAX
5.5
6.5
UNITS
V
V
V
nA
μA
V
V
V
V
V
V
V
V
V
V
3547bfb
2.2
3
0.590
0.588
0.588
1.770
1.764
0.590
0.588
0.588
1.180
1.176
0.600
0.600
0.600
1.800
1.800
0.600
0.600
0.600
1.200
1.200
2.5
±30
6
0.610
0.612
0.612
1.830
1.836
0.610
0.612
0.612
1.220
1.224
LTC3547B
ELECTRICAL CHARACTERISTICS
SYMBOL
PARAMETER
Reference Voltage Line Regulation
Output Voltage Load Regulation
Input DC Supply Current
Active Mode (Note 4)
Shutdown
Oscillator Frequency
Peak Switch Current Limit
Channel 1 (300mA)
Channel 2 (300mA)
Channel 1 (Note 3)
Top Switch On-Resistance
Bottom Switch On-Resistance
Channel 2 (Note 3)
Top Switch On-Resistance
Bottom Switch On-Resistance
Switch Leakage Current
Soft-Start Time
RUN Threshold High
RUN Leakage Current
The
●
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. V
CC
= 3.6V, unless otherwise noted.
CONDITIONS
V
IN
= 2.5V to 5.5V
I
LOAD
= 50mA to 300mA
V
FB1
= V
FB2
= 0.95 × V
FBREG
RUN1 = RUN2 = 0V, V
IN
= 5.5V
V
FB
= 0.6V
V
IN
= 2.5V, V
FB
< V
FBREG
, Duty Cycle < 35%
●
MIN
TYP
0.3
0.5
450
0.1
MAX
0.5
UNITS
%/V
%
Δ
V
LINEREG
Δ
V
LOADREG
I
S
700
1
2.7
μA
μA
MHz
mA
mA
f
OSC
I
LIM
1.8
400
400
2.25
550
550
0.8
0.75
0.8
0.75
0.01
R
DS(ON)
V
IN
= 3.6V, I
SW
= 100mA
V
IN
= 3.6V, I
SW
= 100mA
V
IN
= 3.6V, I
SW
= 100mA
V
IN
= 3.6V, I
SW
= 100mA
V
IN
= 5V, V
RUN
= 0V
V
FB
From 10% to 90% Full-Scale
●
●
1.05
1.05
1.05
1.05
1
0.850
1.2
1
Ω
Ω
Ω
Ω
μA
ms
V
μA
I
SW(LKG)
t
SOFTSTART
V
RUN
I
RUN
0.450
0.4
0.650
1
0.01
Note 1:
Stresses beyond those listed under Absolute Maximum Ratings
may cause permanent damage to the device. Exposure to any Absolute
Maximum Rating condition for extended periods may affect device
reliability and lifetime.
Note 2:
The LTC3547BE is guaranteed to meet specified performance
from 0°C to 85°C. Specifications over the –40°C and 85°C operating
temperature range are assured by design, characterization and correlation
with statistical process controls. The LTC3547BI is guaranteed over the
–40°C to 125°C operating temperature range.
Note 3:
The DFN switch on-resistance is guaranteed by correlation to
wafer level measurements.
Note 4:
Dynamic supply current is higher due to the internal gate charge
being delivered at the switching frequency.
Note 5:
Guaranteed by long-term current density limitations.
Note 6:
This IC includes overtemperature protection that is intended
to protect the device during momentary overload conditions. Junction
temperature will exceed 125°C when overtemperature protection is active.
Continuous operation above the specified maximum operating junction
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