LTC3440
Micropower Synchronous
Buck-Boost DC/DC Converter
Features
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Description
The
LTC
®
3440
is a high efficiency, fixed frequency, Buck-
Boost DC/DC converter that operates from input voltages
above, below or equal to the output voltage. The topology
incorporated in the IC provides a continuous transfer
function through all operating modes, making the prod-
uct ideal for single lithium-ion, multicell alkaline or NiMH
applications where the output voltage is within the battery
voltage range.
The device includes two 0.19Ω N-channel MOSFET
switches and two 0.22Ω P-channel switches. Switch-
ing frequencies up to 2MHz are programmed with an
external resistor and the oscillator can be synchronized
to an external clock. Quiescent current is only 25µA in
Burst Mode operation, maximizing battery life in portable
applications. Burst Mode operation is user controlled and
can be enabled by driving the MODE/SYNC pin high. If the
MODE/SYNC pin has either a clock or is driven low, then
fixed frequency switching is enabled.
Other features include a 1µA shutdown, soft-start con-
trol, thermal shutdown and current limit. The LTC3440
is available in the 10-pin thermally enhanced MSOP and
(3mm
×
3mm) DFN packages.
L,
LT, LTC, LTM, Linear Technology, Burst Mode and the Linear logo 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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Single Inductor
Fixed Frequency Operation with Battery Voltages
Above, Below or Equal to the Output
Synchronous Rectification: Up to 96% Efficiency
25µA Quiescent Current in Burst Mode
®
Operation
Up to 600mA Continuous Output Current
No Schottky Diodes Required (V
OUT
< 4.3V)
V
OUT
Disconnected from V
IN
During Shutdown
2.5V to 5.5V Input and Output Range
Programmable Oscillator Frequency
from 300kHz to 2MHz
Synchronizable Oscillator
Burst Mode Enable Control
<1µA Shutdown Current
Small Thermally Enhanced 10-Pin MSOP and
(3mm
×
3mm) DFN Packages
applications
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Palmtop Computers
Handheld Instruments
MP3 Players
Digital Cameras
typical application
Li-Ion to 3.3V at 600mA Buck-Boost Converter
L1
10µH
4
SW1
SW2
LTC3440
6
7
V
IN
V
OUT
3
V
IN
= 2.7V TO 4.2V
8
SHDN/SS
MODE/SYNC
R
T
FB
V
C
GND
9
C5 1.5nF
10
5
R3
15k
R2
200k
Efficiency vs V
IN
100
V
OUT
3.3V
600mA
V
OUT
= 3.3V
98 I
OUT
= 100mA
96 f
OSC
= 1MHz
94
92
90
88
86
84
82
80
2.5
3.0
3.5
4.0
V
IN
(V)
4.5
5.0
5.5
R1
340k
C2
22µF
Li-Ion
+
C1 *
10µF
2
1
R
T
60.4k
*1 = Burst Mode OPERATION
0 = FIXED FREQUENCY
C1: TAIYO YUDEN JMK212BJ106MG
C2: TAIYO YUDEN JMK325BJ226MM
L1: SUMIDA CDRH6D38-100
3440 TA01
EFFICIENCY (%)
3440 TA02
3440fd
For more information
www.linear.com/LTC3440
1
LTC3440
absolute MaxiMuM ratings
(Note 1)
V
IN
, V
OUT
Voltage ....................................... – 0.3V to 6V
SW1, SW2 Voltage ...................................... –0.3V to 6V
V
C
, R
T
, FB,
SHDN/SS,
MODE/SYNC Voltage .................................. –0.3V to 6V
Operating Temperature Range (Note 2)....–40°C to 85°C
Storage Temperature Range .................. –65°C to 125°C
Lead Temperature (Soldering, 10 sec)................... 300°C
pin conFiguration
TOP VIEW
R
T
MODE/SYNC
SW1
SW2
GND
1
2
3
4
5
11
10 V
C
9 FB
8
SHDN/SS
7 V
IN
6 V
OUT
TOP VIEW
R
T
MODE/SYNC
SW1
SW2
GND
1
2
3
4
5
10
9
8
7
6
V
C
FB
SHDN/SS
V
IN
V
OUT
MS PACKAGE
10-LEAD PLASTIC MSOP
DD PACKAGE
10-LEAD (3mm
×
3mm) PLASTIC DFN
EXPOSED PAD (PIN 11) IS GND
MUST BE SOLDERED TO PCB
T
JMAX
= 125°C,
θ
JA
= 43°C/W,
θ
JC
= 3°C/W
T
JMAX
= 125°C,
θ
JA
= 130°C/W 1 LAYER BOARD
θ
JA
= 100°C/W 4 LAYER BOARD
θ
JC
= 45°C/W
orDer inForMation
LEAD FREE FINISH
LTC3440EDD#PBF
LTC3440EMS#PBF
TAPE AND REEL
LTC3440EDD#TRPBF
LTC3440EMS#TRPBF
http://www.linear.com/product/LTC3440#orderinfo
PART MARKING
LBKT
LTNP
PACKAGE DESCRIPTION
10-Lead (3mm × 3mm) Plastic DFN
10-Lead Plastic MSOP
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 nonstandard 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/.
Some packages are available in 500 unit reels through
designated sales channels with #TRMPBF suffix.
The
●
denotes specifications that apply over the full operating temperature
range, otherwise specifications are at T
A
= 25°C. V
IN
= V
OUT
= 3.6V, R
T
= 60k, unless otherwise noted.
PARAMETER
Input Start-Up Voltage
Input Operating Range
Output Voltage Adjust Range
Feedback Voltage
Feedback Input Current
Quiescent Current, Burst Mode Operation
Quiescent Current, Shutdown
Quiescent Current, Active
NMOS Switch Leakage
V
FB
= 1.22V
V
C
= 0V, MODE/SYNC = 3V (Note 3)
SHDN
= 0V, Not Including Switch Leakage
V
C
= 0V, MODE/SYNC = 0V (Note 3)
Switches B and C
CONDITIONS
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electrical characteristics
MIN
2.5
2.5
1.196
TYP
2.4
MAX
2.5
5.5
5.5
UNITS
V
V
V
V
nA
µA
µA
µA
µA
3440fd
1.22
1
25
0.1
600
0.1
1.244
50
40
1
1000
5
2
For more information
www.linear.com/LTC3440
LTC3440
electrical characteristics
PARAMETER
PMOS Switch Leakage
NMOS Switch On Resistance
PMOS Switch On Resistance
Input Current Limit
Maximum Duty Cycle
Minimum Duty Cycle
Frequency Accuracy
MODE/SYNC Threshold
MODE/SYNC Input Current
Error Amp AVOL
Error Amp Source Current
Error Amp Sink Current
SHDN/SS
Threshold
SHDN/SS
Input Current
When IC is Enabled
When EA is at Maximum Boost Duty Cycle
V
SHDN
= 5.5V
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The
●
denotes specifications that apply over the full operating temperature
range, otherwise specifications are at T
A
= 25°C. V
IN
= V
OUT
= 3.6V, R
T
= 60k, unless otherwise noted.
CONDITIONS
Switches A and D
Switches B and C
Switches A and D
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MIN
TYP
0.1
0.19
0.22
MAX
10
UNITS
µA
Ω
Ω
A
%
%
1
55
100
0.8
0.4
75
0
1
0.01
90
15
380
0.4
1
2.2
0.01
1.5
1
1.2
2
1
Boost (% Switch C On)
Buck (% Switch A On)
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%
MHz
V
µA
dB
µA
µA
V
V
µA
V
MODE/SYNC
= 5.5V
Note 1:
Absolute Maximum Ratings are those values beyond which the
life of the device may be impaired.
Note 2:
The LTC3440E is guaranteed to meet performance specifications
from 0°C to 70°C. Specifications over the – 40°C to 85°C operating
temperature range are assured by design, characterization and
correlation with statistical process controls.
Note 3:
Current measurements are performed when the outputs are not
switching.
typical perForMance characteristics
Li-Ion to 3.3V Efficiency
(f
OSC
= 300kHz)
100
90
80
Burst Mode
OPERATION
Li-Ion to 3.3V Efficiency,
Power Loss (f
OSC
= 1MHz)
100
90
80
Burst Mode
OPERATION
V
IN
= 4.2V
V
IN
= 2.5V
V
IN
= 3.3V
10
1000
Li-Ion to 3.3V Efficiency
(f
OSC
= 2MHz)
100
90
Burst Mode
OPERATION
100
80
POWER LOSS (mW)
EFFICIENCY (%)
EFFICIENCY (%)
70
60
50
40
30
20
0.1
f
OSC
= 300kHz
V
IN
= 2.5V
EFFICIENCY (%)
V
IN
= 4.2V
V
IN
= 3.3V
70
60
50
40
30
70
60
50
40
30
20
0.1
f
OSC
= 2MHz
1
10
100
OUTPUT CURRENT (mA)
1000
3440 G03
V
IN
= 2.5V
V
IN
= 4.2V
V
IN
= 3.3V
V
IN
= 3.3V
1
10
100
1
OUTPUT CURRENT (mA)
1000
3440 G01
20
0.1
f
OSC
= 1MHz
10
100
1
OUTPUT CURRENT (mA)
0.1
1000
3440 G02
3440fd
For more information
www.linear.com/LTC3440
3
LTC3440
typical perForMance characteristics
Switch Pins During Buck/Boost
Switch Pins on the Edge of
Buck/Boost and Approaching Boost
Switch Pins on the Edge of
Buck/Boost and Approaching Buck
SW1
2V/DIV
SW1
2V/DIV
SW1
2V/DIV
SW2
2V/DIV
SW2
2V/DIV
SW2
2V/DIV
V
IN
= 3.78V
V
OUT
= 3.3V
I
OUT
= 250mA
50ns/DIV
3440 G04
V
IN
= 3.42V
V
OUT
= 3.3V
I
OUT
= 250mA
50ns/DIV
3440 G05
V
IN
= 4.15V
V
OUT
= 3.3V
I
OUT
= 250mA
50ns/DIV
3440 G06
Switch Pins in Buck Mode
Switch Pins in Boost Mode
V
OUT
Ripple During Buck,
Buck/Boost and Boost Modes
Buck
V
IN
= 5V
V
OUT
10mV/DIV
AC Coupled
Buck/Boost
V
IN
= 3.78V
Boost
V
IN
= 2.5V
SW1
2V/DIV
SW1
2V/DIV
SW2
2V/DIV
SW2
2V/DIV
V
IN
= 5V
V
OUT
= 3.3V
I
OUT
= 250mA
250ns/DIV
3440 G07
V
IN
= 2.5V
V
OUT
= 3.3V
I
OUT
= 250mA
250ns/DIV
3440 G08
L = 10µH
C
OUT
= 22µF
I
OUT
= 250mA
f
OSC
= 1MHz
1µs/DIV
3440 G09
Active Quiescent Current
550
V
IN
= V
OUT
= 3.6V
V
IN
+ V
OUT
CURRENT (µA)
40
Burst Mode Quiescent Current
V
IN
= V
OUT
= 3.6V
E/A SOURCE CURRENT (µA)
20
Error Amp Source Current
V
IN
= V
OUT
= 3.6V
V
IN
+ V
OUT
CURRENT (µA)
500
30
15
450
20
10
400
–55
–25
5
35
65
TEMPERATURE (°C)
95
125
3440 G10
10
–55
–25
5
35
65
TEMPERATURE (°C)
95
125
3440 G11
5
–55
–25
5
35
65
TEMPERATURE (°C)
95
125
3440 G12
4
3440fd
For more information
www.linear.com/LTC3440
LTC3440
typical perForMance characteristics
Output Frequency
1.10
V
IN
= V
OUT
= 3.6V
0.30
NMOS R
DS(ON)
V
IN
= V
OUT
= 3.6V
SWITCHES B AND C
FEEDBACK VOLTAGE (V)
Feedback Voltage
1.236
V
IN
= V
OUT
= 3V
1.05
FREQUENCY (MHz)
0.25
NMOS R
DS(ON)
( )
1.00
0.20
1.216
0.95
0.15
0.90
–55
–25
5
35
65
TEMPERATURE (°C)
95
125
3440 G13
0.10
–55
–25
5
35
65
TEMPERATURE (°C)
95
125
3440 G14
1.196
–55
–25
5
35
65
TEMPERATURE (°C)
95
125
3440 G15
Feedback Voltage Line Regulation
90
V
IN
= V
OUT
= 2.5V TO 5.5V
Error Amp Sink Current
430
V
IN
= V
OUT
= 3.6V
0.30
PMOS R
DS(ON)
V
IN
= V
OUT
= 3.6V
SWITCHES A AND D
390
PMOS R
DS(ON)
( )
80
E/A SINK CURRENT (µA)
LINE REGULATION (dB)
410
0.25
0.20
70
370
0.15
60
–55
–25
5
35
65
TEMPERATURE (°C)
95
125
3440 G16
350
–55
–25
5
35
65
TEMPERATURE (°C)
95
125
3440 G17
0.10
–55
–25
5
35
65
TEMPERATURE (°C)
95
125
3440 G18
Boost Max Duty Cycle
90
V
IN
= V
OUT
= 3.6V
R
T
= 60k
MINIMUM START VOLTAGE (V)
Minimum Start Voltage
2.40
Current Limit
3000
PEAK SWITCH
2500
V
IN
= V
OUT
= 3.6V
85
DUTY CYCLE (%)
2.35
CURRENT LIMIT (A)
80
2000
AVERAGE INPUT
1500
2.30
75
70
–55
–25
5
35
65
TEMPERATURE (°C)
95
125
3440 G19
2.25
–55
–25
5
35
65
TEMPERATURE (°C)
95
125
3440 G20
1000
–55
–25
5
35
65
TEMPERATURE (°C)
95
125
3440 G21
3440fd
For more information
www.linear.com/LTC3440
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