FeaTures
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LTC3441
High Current Micropower
Synchronous Buck-Boost
DC/DC Converter
DescripTion
The
LTC
®
3441
is a high efficiency, fixed frequency, buck-
boost DC/DC converter that operates efficiently 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 product ideal for single lithium ion or multicell ap-
plications where the output voltage is within the battery
voltage range.
The device includes two 0.10Ω N-channel MOSFET
switches and two 0.11Ω P-channel switches. External
Schottky diodes are optional, and can be used for a mod-
erate efficiency improvement. The operating frequency
is internally set to 1MHz and can be synchronized up to
1.7MHz. Quiescent current is only 25µA in Burst Mode
operation, maximizing battery life in portable applica-
tions. Burst Mode operation is user controlled and can
be enabled by driving the MODE/SYNC pin high. If the
MODE/SYNC pin is driven low or with a clock, then fixed
frequency switching is enabled.
Other features include a 1µA shutdown, soft-start control,
thermal shutdown and current limit. The LTC3441 is
available in a thermally enhanced 12-lead (4mm
×
3mm)
DFN package.
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Regulated Output with Input Above, Below or Equal
to the Output
Single Inductor, No Schottky Diodes
High Efficiency: Up to 95%
25µA Quiescent Current in Burst Mode
®
Operation
Up to 1.2A Continuous Output Current from a Single
Lithium-Ion
True Output Disconnect in Shutdown
2.4V to 5.5V Input Range
2.4V to 5.25V Output Range
1MHz Fixed Frequency Operation
Synchronizable Oscillator
Selectable Burst Mode or Fixed Frequency Operation
<1µA Quiescent Current in Shutdown
Small, Thermally Enhanced 12-Lead (4mm × 3mm)
DFN package
applicaTions
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Handheld Computers
Handheld Instruments
MP3 Players
Digital Cameras
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.
Typical applicaTion
Li-Ion to 3.3V at 1A Buck-Boost Converter
L1
4.7µH
4
9
2.5V TO 4.2V
10
1
Li-Ion
*
C
IN
10µF
7
3
5
8
12
11
2
6
15k
1.5nF
100
V
OUT
3.3V
1A
EFFICIENCY (%)
340k
C
OUT
22µF
200k
95
90
85
80
75
70
65
60
55
*1 = Burst Mode OPERATION
0 = FIXED FREQUENCY
C
IN
: TAIYO YUDEN JMK212BJ106MG
C
OUT
: TAIYO YUDEN JMK325BJ226MM
L1: TOKO A916CY-4R7M
3441 TA01
Efficiency vs V
IN
V
OUT
= 3.3V
I
OUT
= 200mA
SW1
PV
IN
V
IN
LTC3441
SW2
V
OUT
FB
V
C
PGND
I
OUT
= 1A
SHDN/SS
PGND
MODE/SYNC
GND
50
2.5
3
3.5
4
V
IN
(V)
4.5
5
5.5
3441 TA02
3441fc
For more information
www.linear.com/LTC3441
1
LTC3441
absoluTe MaxiMuM raTings
(Note 1)
pin conFiguraTion
TOP VIEW
SHDN/SS
GND
PGND
SW1
SW2
PGND
1
2
3
4
5
6
13
12 FB
11 V
C
10 V
IN
9
8
7
PV
IN
V
OUT
MODE/SYNC
V
IN
, V
OUT
Voltage ....................................... – 0.3V to 6V
SW1, SW2 Voltage
DC............................................................ –0.3V to 6V
Pulsed < 100ns ....................................... –0.3V to 7V
SHDN/SS,
MODE/SYNC Voltage ................ –0.3V to 6V
Operating Temperature Range (Note 2) .. –40°C to 85°C
Maximum Junction Temperature (Note 4)............. 125°C
Storage Temperature Range.................. –65°C to 125°C
DE12 PACKAGE
12-LEAD (4mm
×
3mm) PLASTIC DFN
T
JMAX
= 125°C
θ
JA
= 53°C/W 1-LAYER BOARD,
θ
JA
= 43°C/W 4-LAYER BOARD
θ
JC
= 4.3°C/W, EXPOSED PAD IS PGND (PIN 13)
MUST BE SOLDERED TO PCB
orDer inForMaTion
LEAD FREE FINISH
LTC3441EDE#PBF
TAPE AND REEL
LTC3441EDE#TRPBF
http://www.linear.com/product/LTC3441#orderinfo
PART MARKING
3441
PACKAGE DESCRIPTION
12-Lead (4mm × 3mm) Plastic DFN
TEMPERATURE RANGE
–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.
elecTrical characTerisTics
PARAMETER
Input Start-Up Voltage
Output Voltage Adjust Range
Feedback Voltage
Feedback Input Current
Quiescent Current—Burst Mode Operation
Quiescent Current—SHDN
Quiescent Current—Active
NMOS Switch Leakage
PMOS Switch Leakage
NMOS Switch On Resistance
PMOS Switch On Resistance
Input Current Limit
Max Duty Cycle
Min Duty Cycle
Frequency Accuracy
MODE/SYNC Threshold
V
FB
= 1.22V
CONDITIONS
The
l
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. V
IN
= V
OUT
= 3.6V,unless otherwise noted.
MIN
●
●
●
TYP
2.3
MAX
2.4
5.25
1.25
50
40
1
900
7
10
UNITS
V
V
V
nA
µA
µA
µA
µA
µA
Ω
Ω
A
%
%
2.4
1.19
1.22
1
25
0.1
520
0.1
0.1
0.10
0.11
V
C
= 0V, MODE/SYNC = 3V (Note 3)
V
OUT
=
SHDN
= 0V, Not Including Switch Leakage
MODE/SYNC = 0V (Note 3)
Switches B and C
Switches A and D
Switches B and C
Switches A and D
●
2
70
100
0.85
0.4
3.2
88
0
1
1.15
1.4
Boost (% Switch C On)
Buck (% Switch A In)
●
●
●
●
●
%
MHz
V
3441fc
2
For more information
www.linear.com/LTC3441
LTC3441
elecTrical characTerisTics
PARAMETER
MODE/SYNC Input Current
Error Amp AV
OL
Error Amp Source Current
Error Amp Sink Current
SHDN/SS
Threshold
SHDN/SS
Threshold
SHDN/SS
Input Current
When IC is Enabled
When EA is at Max Boost Duty Cycle
V
SHDN
= 5.5V
●
The
l
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. V
IN
= V
OUT
= 3.6V,unless otherwise noted.
CONDITIONS
V
MODE/SYNC
= 5.5V
MIN
TYP
0.01
90
14
300
0.4
1
2
0.01
1.4
2.4
1
MAX
1
UNITS
µA
dB
µA
µA
V
V
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 LTC3441E 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 preformed when the outputs are not
switching.
Note 4:
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.
Typical perForMance characTerisTics
Efficiency
100
90
80
EFFICIENCY (%)
70
60
50
40
30
20
10
V
OUT
= 3.3V
0
0.1
1
L = 4.7µH
C
OUT
= 47µF
I
OUT
= 1A
V
OUT
= 3.3V
1µs/DIV
3441 G02
V
OUT
Ripple at 1A Load
BUCK
V
IN
= 4.2V
V
OUT
10mV/DIV
AC-COUPLED
BUCK-BOOST
V
IN
= 3.3V
BOOST
V
IN
= 2.7V
Burst Mode
OPERATION
V
IN
= 4.2V
V
IN
= 2.7V
V
IN
= 3.6V
10
I
OUT
(mA)
100
1000
3441 G17
Load Transient Response,
100mA to 1A
SW1
2V/DIV
Switch Pins in Buck-Boost Mode
SW1
2V/DIV
Switch Pins Entering
Buck-Boost Mode
V
OUT
100mV/DIV
1A
100mA
SW2
2V/DIV
SW2
2V/DIV
100µs/DIV
3441 G01
V
IN
= 3.3V
V
OUT
= 3.3V
I
OUT
= 500mA
50ns/DIV
3441 G03
V
IN
= 4.2V
V
OUT
= 3.3V
I
OUT
= 500mA
50ns/DIV
3441 G04
3441fc
For more information
www.linear.com/LTC3441
3
LTC3441
Typical perForMance characTerisTics
Switch Pins Before Entering
Boost Mode
630
SW1
2V/DIV
620
610
V
IN
+ V
OUT
CURRENT (µA)
600
590
580
570
560
550
540
530
520
–55
–25
5
35
65
TEMPERATURE (°C)
95
125
3441 G06
Active Quiescent Current
V
IN
= V
OUT
= 3.6V
1.241
1.236
FEEDBACK VOLTAGE (V)
1.231
1.226
1.221
1.216
1.211
1.206
1.201
Feedback Voltage
V
IN
= V
OUT
= 3.6V
SW2
2V/DIV
V
IN
= 3V
V
OUT
= 3.3V
I
OUT
= 500mA
50ns/DIV
3441 G05
1.196
–55
–25
5
35
65
TEMPERATURE (°C)
95
125
3441 G07
Burst Mode Quiescent Current
50
V
IN
= V
OUT
= 3.6V
90
Feedback Voltage Line Regulation
V
IN
= V
OUT
= 2.4V TO 5.5V
EA SOURCE CURRENT (µA)
20
Error Amp Source Current
V
IN
= V
OUT
= 3.6V
V
IN
+ V
OUT
CURRENT (µA)
LINE REGULATION (dB)
40
80
15
30
70
10
20
10
–55
–25
5
35
65
TEMPERATURE (°C)
95
125
3441 G08
60
–55
–25
5
35
65
TEMPERATURE (°C)
95
125
3441 G09
5
–55
–25
5
35
65
TEMPERATURE (°C)
95
125
3441 G10
Error Amp Sink Current
400
V
IN
= V
OUT
= 3.6V
1.2
Output Frequency
V
IN
= V
OUT
= 3.6V
3.4
Current Limit
V
IN
= V
OUT
= 3.6V
EA SINK CURRENT (µA)
350
FREQUENCY (MHz)
1.1
CURRENT LIMIT (A)
–25
5
35
65
TEMPERATURE (°C)
95
125
3441 G12
3.2
300
1.0
3.0
250
0.9
200
–55
–25
5
35
65
TEMPERATURE (°C)
95
125
3441 G11
0.8
–55
2.8
–55
–25
5
35
65
TEMPERATURE (°C)
95
125
3441 G13
4
3441fc
For more information
www.linear.com/LTC3441
LTC3441
Typical perForMance characTerisTics
0.15
NMOS R
DS(ON)
V
IN
= V
OUT
= 3.6V
SWITCHES B AND C
0.15
0.14
0.13
PMOS R
DS(ON)
(Ω)
0.12
0.11
0.10
0.09
0.08
0.07
0.06
PMOS R
DS(ON)
V
IN
= V
OUT
= 3.6V
SWITCHES A AND D
MINIMUM START VOLTAGE (V)
2.30
Minimum Start Voltage
0.13
NMOS R
DS(ON)
(Ω)
2.25
0.11
2.20
0.09
2.15
0.07
0.05
–55
–25
5
35
65
TEMPERATURE (°C)
95
125
3441 G14
0.05
–50
–25
35
65
5
TEMPERATURE (°C)
95
125
3441 G15
2.10
–55
–25
5
35
65
TEMPERATURE (°C)
95
125
3441 G16
pin FuncTions
SHDN/SS
(Pin 1):
Combined Soft-Start and Shutdown.
Applied voltage < 0.4V shuts down the IC. Tie to >1.4V to
enable the IC and >2.4V to ensure the error amp is not
clamped from soft-start. An RC from the shutdown com-
mand signal to this pin will provide a soft-start function
by limiting the rise time of the V
C
pin.
GND (Pin 2):
Signal Ground for the IC.
PGND (Pins 3, 6, 13 Exposed Pad):
Power Ground for
the Internal NMOS Power Switches
SW1 (Pin 4):
Switch pin where the internal switches A
and B are connected. Connect inductor from SW1 to SW2.
An optional Schottky diode can be connected from this
SW1 to ground. Minimize trace length to keep EMI down.
SW2 (Pin 5):
Switch pin where the internal switches C
and D are connected. An optional Schottky diode can
be connected from SW2 to V
OUT
(it is required where
V
OUT
> 4.3V). Minimize trace length to keep EMI down.
MODE/SYNC (Pin 7):
Burst Mode Select and Oscillator
Synchronization.
MODE/SYNC = High: Enable Burst Mode Operation.
During the period where the IC is supplying energy to
the output, the inductor peak inductor current will reach
0.8A and return to zero current on each cycle. In Burst
Mode operation the operation is variable frequency,
which provides a significant efficiency improvement at
light loads. The Burst Mode operation will continue until
the pin is driven low.
MODE/SYNC = Low: Disable Burst Mode operation
and maintain low noise, constant frequency operation .
MODE/SYNC = External CLK : Synchronization of the
internal oscillator and Burst Mode operation disable. A
clock pulse width between 100ns and 2µs and a clock
frequency between 2.3MHz and 3.4MHz (twice the
desired frequency) is required to synchronize the IC.
f
OSC
= f
SYNC
/2
V
OUT
(Pin 8):
Output of the Synchronous Rectifier. A filter
capacitor is placed from V
OUT
to GND. A ceramic bypass
capacitor is recommended as close to the V
OUT
and GND
pins as possible.
PV
IN
(Pin 9):
Power V
IN
Supply Pin. A 10µF ceramic ca-
pacitor is recommended as close to the PV
IN
and PGND
pins as possible
3441fc
For more information
www.linear.com/LTC3441
5
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