LTC3539/LTC3539-2
2A, 1MHz/2MHz
Synchronous Step-Up
DC/DC Converters
FEATURES
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DESCRIPTION
The
LTC
®
3539/LTC3539-2
are synchronous, 2A step-up
DC/DC converters with output disconnect. Synchronous
rectification enables high efficiency in the low profile
2mm × 3mm DFN package. Battery life is extended with
a 700mV start-up voltage and operation down to 500mV
once started.
A switching frequency of 1MHz (LTC3539) or 2MHz
(LTC3539-2) minimizes solution footprint by allowing the
use of tiny, low profile inductors and ceramic capacitors.
The current mode PWM design is internally compensated,
reducing external parts count. The LTC3539/LTC3539-2
feature a pin-enabled automatic Burst Mode operation at
light load conditions. Anti-ring circuitry reduces EMI by
damping the inductor in discontinuous mode. Additional
features include a low shutdown current of under 1µA and
thermal overload protection.
The LTC3539/LTC3539-2 are offered in a 2mm × 3mm ×
0.75mm DFN package.
L,
LT, LTC, LTM and Burst Mode are registered trademarks and ThinSOT is a trademark of
Linear Technology Corporation. All other trademarks are the property of their respective owners.
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Delivers 3.3V at 900mA From 2 Alkaline/NiMH Cells
Delivers 5V at 900mA From a Lithium-Polymer
Battery
V
IN
Start-Up Voltage: 700mV
1.5V to 5.25V V
OUT
Range
Up to 94% Efficiency
V
IN
> V
OUT
Operation
±1.5% Feedback Voltage Tolerance
1MHz (LTC3539) or 2MHz (LTC3539-2) Fixed
Frequency Operation
Output Disconnect
Selectable Burst Mode
®
or PWM Operation
10µA Quiescent Current
Logic Controlled Shutdown: <1µA
Requires Only 6 External Components
Low Profile (2mm × 3mm × 0.75mm) DFN Package
APPLICATIONS
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Medical Instruments
Portable Bar Code Scanners
Noise Canceling Headphones
Portable GPS Navigation
Handheld PCs
TYPICAL APPLICATION
Wide V
IN
, High Power 3.3V Regulator
4.7µH
V
IN
1.8V TO 3.6V
2.2µF
EFFICIENCY (%)
V
IN
LTC3539
PWM BURST
MODE
V
OUT
1M
OFF ON
SHDN
GND
FB
PGND
562k
3539 TA01a
Efficiency and Power Loss vs Load Current
100
90
80
EFFICIENCY
100
POWER LOSS (mW)
1000
SW
V
OUT
3.3V
600mA
22µF
×
2
70
60
V = 2.4V
50 V
IN
= 3.3V
OUT
40
30
20
10
0
0.1
1
FREQUENCY = 1MHz
FREQUENCY = 2MHz
10
100
I
LOAD
AVERAGE (mA)
10
POWER LOSS
1
33pF
0.1
1000
3539 TA01b
35392fc
For more information
www.linear.com/3539/3539-2
1
LTC3539/LTC3539-2
ABSOLUTE MAXIMUM RATINGS
(Note 1)
PIN CONFIGURATION
TOP VIEW
SW 1
PGND 2
GND 3
V
IN
4
9
8 V
OUT
7 MODE
6 FB
5
SHDN
V
IN
Voltage ................................................... –0.3V to 6V
SW Voltage
DC............................................................ –0.3V to 6V
Pulsed <100ns ......................................... –0.3V to 7V
SHDN,
FB, MODE Voltage ............................ –0.3V to 6V
V
OUT
............................................................. –0.3V to 6V
Operating Temperature (Notes 2, 5) .........–40°C to 85°C
Storage Temperature Range .................. –65°C to 125°C
DCB PACKAGE
8-LEAD (2mm
×
3mm) PLASTIC DFN
T
JMAX
= 125°C,
θ
JA
= 64°C/W (NOTE 6)
EXPOSED PAD (PIN 9) IS GND, MUST BE SOLDERED TO PCB
ORDER INFORMATION
LEAD FREE FINISH
LTC3539EDCB#PBF
LTC3539EDCB-2#PBF
TAPE AND REEL
LTC3539EDCB#TRPBF
LTC3539EDCB-2#TRPBF
PART MARKING
LDCS
LDPH
PACKAGE DESCRIPTION
8-Lead (2mm × 3mm) Plastic DFN
8-Lead (2mm × 3mm) Plastic DFN
TEMPERATURE RANGE
–40°C to 85°C
–40°C to 85°C
Consult LTC Marketing for parts specified with wider operating temperature ranges.
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/
ELECTRICAL CHARACTERISTICS
PARAMETER
Input Voltage Range
Minimum Start-Up Voltage
Output Voltage Adjust Range
Feedback Voltage
Feedback Input Current
Quiescent Current - Shutdown
Quiescent Current - Active
Quiescent Current - Burst
N-Channel MOSFET Switch Leakage Current
P-Channel MOSFET Switch Leakage Current
N-Channel MOSFET Switch On Resistance
P-Channel MOSFET Switch On Resistance
N-Channel MOSFET Current Limit
V
FB
= 1.2V
CONDITIONS
After Start-Up
The
l
denotes the specifications which apply over the specified
temperature range of –40°C to 85°C, otherwise specifications are at T
A
= 25°C. V
IN
= 1.2V, V
OUT
= 3.3V, unless otherwise noted.
MIN
0.5
0.7
l
l
TYP
MAX
5
0.88
5.25
1.218
50
1
500
18
10
20
UNITS
V
V
V
V
nA
µA
µA
µA
µA
µA
Ω
Ω
A
I
LOAD
= 1mA, V
OUT
= 0V
1.5
1.182
1.200
1
0.01
300
10
0.1
0.1
0.09
0.125
V
SHDN
= 0V, Not Including Switch Leakage, V
OUT
= 0V
Measured on V
OUT
, Non-Switching
Measured on V
OUT
, FB > 1.230V
V
SW
= 5V
V
SW
= 5V, V
OUT
= 0V
V
OUT
= 3.3V
V
OUT
= 3.3V
l
2
2.6
35392fc
2
For more information
www.linear.com/3539/3539-2
LTC3539/LTC3539-2
ELECTRICAL CHARACTERISTICS
PARAMETER
Maximum Duty Cycle
Minimum Duty Cycle
Switching Frequency
MODE Input High Voltage
MODE Input Low Voltage
MODE Input Current
SHDN
Input High Voltage
SHDN
Input Low Voltage
SHDN
Input Current
V
SHDN
= 1.2V
V
SHDN
= 3.3V
0.3
1
V
MODE
= 1.2V
0.88
0.3
1
2
0.3
CONDITIONS
V
FB
= 1.15V
V
FB
= 1.3V
LTC3539
LTC3539-2
l
l
l
l
The
l
denotes the specifications which apply over the specified
temperature range of –40°C to 85°C, otherwise specifications are at T
A
= 25°C. V
IN
= 1.2V, V
OUT
= 3.3V, unless otherwise noted.
MIN
87
0.7
1.8
0.88
0.3
1
TYP
90
0
1
2
1.3
2.4
MAX
UNITS
%
%
MHz
MHz
V
V
µA
V
V
µA
µA
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 LTC3539E/LTC3539E-2 is guaranteed to meet performance
specifications from 0°C to 85°C. Specifications over –40°C to 85°C
operating temperature range are assured by design, characterization and
correlation with statistical process controls.
Note 3:
Specification is guaranteed by design and not 100% tested in
production.
Note 4:
Current measurements are made when the output is not switching.
Note 5:
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
temperature may result in device degradation or failure.
Note 6:
Failure to solder the exposed backside of the package to the PC
board ground plane will result in a thermal resistance much higher than
64°C/W.
TYPICAL PERFORMANCE CHARACTERISTICS
Efficiency vs Load Current and
V
IN
, V
OUT
= 1.8V
100
90
80
EFFICIENCY (%)
70
60
50
40
30
20
10
0
0.1
1
V
IN
= 1V
V
IN
= 1.2V
V
IN
= 1.5V
10
100
LOAD CURRENT (mA)
0.1
POWER LOSS
EFFICIENCY
10
100
POWER LOSS (mW)
EFFICIENCY (%)
1000
100
90
80
70
60
50
40
30
20
10
0
0.1
(T
A
= 25°C unless otherwise noted)
Efficiency vs Load Current and
V
IN
, V
OUT
= 3.3V
1000
EFFICIENCY
100
POWER LOSS (mW)
10
POWER LOSS
1
V
IN
= 1.2V
V
IN
= 1.8V
V
IN
= 3V
1
10
100
LOAD CURRENT (mA)
1
0.01
1000
0.1
1000
3539 G01
3539 G02
35392fc
For more information
www.linear.com/3539/3539-2
3
LTC3539/LTC3539-2
TYPICAL PERFORMANCE CHARACTERISTICS
100
90
80
EFFICIENCY (%)
70
60
50
40
30
20
10
0
0.1
1
V
IN
= 2.4V
V
IN
= 3.6V
V
IN
= 4.2V
10
100
LOAD CURRENT (mA)
POWER LOSS
1
10
EFFICIENCY
100
POWER LOSS (mW)
(T
A
= 25°C unless otherwise noted)
Efficiency vs Load Current and
V
IN
, V
OUT
= 5V
1000
200
180
160
INPUT CURRENT (µA)
140
120
100
80
60
40
20
0
No Load Input Current vs V
IN
V
OUT
= 1.8V
V
OUT
= 2.5V
V
OUT
= 3.3V
V
OUT
= 5V
I
OUT
(mA)
2000
1800
1600
1400
1200
1000
800
600
400
200
Maximum Output Current vs V
IN
L = 2.2µH
0.1
1000
0
1
2
V
IN
(V)
3
4
5
3539 G04
3539 G03
0
0.7 1.1 1.5 1.9 2.3 2.7 3.1 3.5 3.9 4.3 4.7 5.1
V
IN
(V)
3539 G05
V
OUT
= 1.8V
V
OUT
= 2.5V
V
OUT
= 3.3V
V
OUT
= 5V
Minimum Load Resistance During
Start-Up vs V
IN
10000
V
OUT
= 3.3V
50
45
40
LOAD CURRENT (mA)
Burst Mode Threshold Current
vs V
IN
; V
OUT
= 1.8V
C
OUT
= 44µF
f
SW
= 1MHz
50
45
40
LOAD CURRENT (mA)
35
30
25
20
15
10
5
Burst Mode Threshold Current
vs V
IN
; V
OUT
= 2.5V
C
OUT
= 44µF
LOAD RESISTANCE ( )
1000
35
30
25
20
15
10
5
0
0.7
f
SW
= 2MHz
ENTER BURST
0.8
0.9
1
1.1 1.2
V
IN
(V)
1.3
1.4
1.5
LEAVE BURST
f
SW
= 1MHz
LEAVE BURST
100
f
SW
= 2MHz
ENTER BURST
10
0.1
0.65
0.75
0.85
0.95
V
IN
(V)
1.05
1.15
3539 G06
0
0.7
0.9
1.1
3539 G07a
1.3 1.5
V
IN
(V)
1.7
1.9
2.1
3539 G07b
Burst Mode Threshold Current
vs V
IN
; V
OUT
= 3.3V
60
50
LOAD CURRENT (mA)
LOAD CURRENT (mA)
40
30
20
ENTER BURST
10
0
0.7 0.9 1.1 1.3 1.5 1.7 1.9 2.1 2.3 2.5 2.7
V
IN
(V)
3539 G07c
C
OUT
= 44µF
100
90
80
70
60
50
40
30
20
10
Burst Mode Threshold Current
vs V
IN
; V
OUT
= 5V
C
OUT
= 44µF
NORMALIZED CURRENT LIMIT (A)
Normalized Current Limit vs V
OUT
1.10
1.05
1.00
0.95
0.90
0.85
0.80
1.0
LEAVE BURST
f
SW
= 1MHz
f
SW
= 2MHz
f
SW
= 1MHz
LEAVE BURST
f
SW
= 2MHz
ENTER BURST
0
0.7 1.1 1.5 1.9 2.3 2.7 3.1 3.5 3.9 4.3
V
IN
(V)
3539 G07d
1.5
2.0
2.5 3.0 3.5
V
OUT
(V)
4.0
4.5
5.0
3539 G08
35392fc
4
For more information
www.linear.com/3539/3539-2
LTC3539/LTC3539-2
TYPICAL PERFORMANCE CHARACTERISTICS
0.30
0.25
NORMALIZED R
DS(ON)
( )
0.20
R
DS(ON)
( )
0.15
0.10
NMOS
0.05
0
1.5
R
DS(ON)
vs V
OUT
1.3
1.2
1.1
1.0
0.9
0.8
R
DS(ON)
Change vs Temperature
0.50
0.25
CHANGE IN V
FB
(%)
0
–0.25
–0.50
–0.75
V
FB
vs Temperature
PMOS
2.0
2.5
3.0 3.5 4.0
V
OUT
(V)
4.5
5.0
5.5
3539 G09
0.7
–50
–30
–10 10
30
50
TEMPERATURE (°C)
70
90
3539 G10
–1.00
–60 –40 –20 0
20 40 60
TEMPERATURE (°C)
80
100
3539 G11
Start-Up Voltage vs Temperature
0.80
0.75
1mA LOAD
0.70
V
IN
(V)
0.65
0.60
0.55
0.50
–50
NO LOAD
SW PIN
2V/DIV
V
OUT
20mV/DIV
AC-COUPLED
INDUCTOR
CURRENT
500mA/DIV
Fixed Frequency SW and I
L(AC)
SW PIN
5V/DIV
V
OUT
20mV/DIV
AC-COUPLED
INDUCTOR
CURRENT
200mA/DIV
Burst Mode SW and I
L(AC)
500ns/DIV
V
IN
= 2.4V
V
OUT
= 3.3V AT 400mA
C
OUT
= 22µF
3539 G13
5µs/DIV
V
IN
= 3.3V
V
OUT
= 5V
C
OUT
= 22µF
3539 G14
–25
0
25
50
TEMPERATURE (°C)
75
100
3539 G12
Load Step, Fixed Frequency
V
OUT
50mV/DIV
AC-COUPLED
LOAD
CURRENT
200mA/DIV
500µs/DIV
V
IN
= 2.4V
V
OUT
= 3.3V
C
OUT
= 22µF
I
LOAD
= 100mA TO 250mA STEP
3539 G15
Load Step, Burst Mode Operation
V
OUT
50mV/DIV
AC-COUPLED
LOAD
CURRENT
200mA/DIV
500µs/DIV
V
IN
= 2.4V
V
OUT
= 3.3V
C
OUT
= 22µF
I
LOAD
= 20mA TO 170mA
3539 G16
35392fc
For more information
www.linear.com/3539/3539-2
5
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