LTC3443
High Current Micropower
600kHz Synchronous Buck-Boost
DC/DC Converter
FEATURES
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DESCRIPTIO
Regulated Output with Input Above, Below or Equal
to the Output
Single Inductor, No Schottky Diodes
High Efficiency: Up to 96%
28µA 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
600kHz Fixed Frequency Operation
Synchronizable Oscillator
Selectable Burst Mode or Fixed Frequency Operation
<1µA Quiescent Current in Shutdown
Small, Thermally Enhanced 12-Lead
(4mm
×
3mm
×
0.8mm) DFN package
The LTC
®
3443 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 part is pin
for pin compatible with its predecessor, the LTC3441, with
a lower operating frequency (600kHz), and a V
C
pin clamp
circuit during Burst Mode operation. The topology incor-
porated in the IC provides a continuous transfer function
through all operating modes, making the product ideal for
single Lithium Ion or multicell applications where the out-
put 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
moderate efficiency improvement. The operating frequency
is internally set to 600kHz and can be synchronized up to
1.2MHz. Quiescent current is only 28µA 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 is driven low or with a clock, then fixed fre-
quency switching is enabled.
Other features include a 1µA shutdown, soft-start control,
thermal shutdown and current limit. The LTC3443 is
available in a thermally enhanced 12-lead (4mm
×
3mm)
DFN Package.
APPLICATIO S
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Handheld Computers
Handheld Instruments
MP3 Players
Digital Cameras
, LTC and LT are registered trademarks of Linear Technology Corporation.
Burst Mode is a registered trademark of Linear Technology Corporation.
U.S. Patent #’s 6404251, 6166527
TYPICAL APPLICATIO
6µH
Li-Ion to 3.3V at 1A Buck-Boost Converter
220pF
SW1
V
IN
2.5V
TO 4.2V
Li-Ion
10µF
PV
IN
SW2
340k
EFFICIENCY (%)
V
OUT
3.3V
1A
100
95
90
85
80
75
70
65
60
55
V
OUT
LTC3443
V
IN
FB
SHDN/SS
V
C
2.2k
15k
560pF
200k
44µF
(2
×
22µF)
MODE/SYNC GND
PGND
PGND
3443 TA01
50
2.7
U
Efficiency vs V
IN
I
OUT
= 200mA
I
OUT
= 1A
V
OUT
= 3.3V
3.2
3.7
4.2
V
IN
(V)
4.7
5.2
3443 TA02
U
U
sn3443 3443fs
1
LTC3443
ABSOLUTE
(Note 1)
AXI U
RATI GS
PACKAGE/ORDER I FOR ATIO
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
ORDER PART
NUMBER
LTC3443EDE
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
DE PART MARKING
3443
Consult LTC Marketing for parts specified with wider operating temperature ranges.
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
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
V
FB
= 1.22V
CONDITIONS
The
●
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
45
1
900
7
10
UNITS
V
V
V
nA
µA
µA
µA
µA
µA
Ω
Ω
A
%
%
2.4
1.19
1.22
1
28
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
510
0.4
3.2
88
0
600
0.01
90
14
300
690
1.4
1
Boost (% Switch C On)
Buck (% Switch A In)
●
●
●
●
●
V
MODE/SYNC
= 5.5V
When IC is Enabled
When EA is at Max Boost Duty Cycle
V
SHDN
= 5.5V
●
0.4
1
2
0.01
1.4
2.4
1
sn3443 3443fs
2
U
%
kHz
V
µA
dB
µA
µA
V
V
µA
W
U
U
W W
W
LTC3443
ELECTRICAL CHARACTERISTICS
Note 1:
Absolute Maximum Ratings are those values beyond which the life
of a device may be impaired.
Note 2:
The LTC3443E 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.
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 PERFOR A CE CHARACTERISTICS
Li-Ion to 3.3V Efficiency
100
90
80
EFFICIENCY (%)
70
60
50
40
30
20
10
0
0.1
1.0
10
100
OUTPUT CURRENT (mA)
1000
3443 G01
Burst Mode
OPERATION
V
IN
= 4.2V
V
IN
= 3.3V
V
OUT
200mV/DIV
AC-COUPLED
MODE
5V/DIV
V
OUT
= 3.3V
V
IN
= 3.3V
I
OUT
= 30mA
500µs/DIV
3443 G03
V
IN
= 2.7V
V
OUT
Ripple at 1A Load
BUCK
V
IN
= 4.2V
V
OUT
20mV/DIV
AC-COUPLED
BUCK-BOOST
V
IN
= 3.3V
BOOST
V
IN
= 2.7V
1A
I
OUT
= 1A
V
OUT
= 3.3V
2µs/DIV
3443 G02
U W
(T
A
= 25°C unless otherwise specified)
MODE Transient Response:
Fixed Frequency to Burst Mode
Operation
MODE Transient Response:
Burst Mode Operation to Fixed
Frequency
V
OUT
100mV/DIV
AC-COUPLED
MODE
5V/DIV
V
OUT
= 3.3V
V
IN
= 3.3V
I
OUT
= 30mA
500µs/DIV
3443 G03
Load Transient Response,
100mA to 1A
V
OUT
100mV/DIV
100mA
100µs/DIV
3443 G03
sn3443 3443fs
3
LTC3443
TYPICAL PERFOR A CE CHARACTERISTICS
Switch Pins in Buck-Boost Mode
SW1
2V/DIV
SW2
2V/DIV
V
IN
= 3.3V
V
OUT
= 3.3V
I
OUT
= 500mA
Switch Pins Before Entering
Boost Mode
630
620
V
IN
+ V
OUT
CURRENT (µA)
600
590
580
570
560
550
540
530
520
–55
–25
5
35
65
TEMPERATURE (°C)
95
125
3443 G07
SW2
2V/DIV
V
IN
= 3V
V
OUT
= 3.3V
I
OUT
= 500mA
50ns/DIV
3443 G06
FEEDBACK VOLTAGE (V)
SW1
2V/DIV
Burst Mode Quiescent Current
50
V
IN
= V
OUT
= 3.6V
LINE REGULATION (dB)
40
80
EA SOURCE CURRENT (µA)
V
IN
+ V
OUT
CURRENT (µA)
30
20
10
–55
–25
5
35
65
TEMPERATURE (°C)
4
U W
95
3443 G09
(T
A
= 25°C unless otherwise specified)
Switch Pins Entering
Buck-Boost Mode
SW1
2V/DIV
SW2
2V/DIV
50ns/DIV
3443 G04
V
IN
= 4.2V
V
OUT
= 3.3V
I
OUT
= 500mA
50ns/DIV
3443 G05
Active Quiescent Current
V
IN
= V
OUT
= 3.6V
1.241
1.236
1.231
1.226
1.221
1.216
1.211
1.206
1.201
Feedback Voltage
V
IN
= V
OUT
= 3.6V
610
1.196
–55
–25
5
35
65
TEMPERATURE (°C)
95
125
3443 G08
Feedback Voltage Line Regulation
90
V
IN
= V
OUT
= 2.4V TO 5.5V
20
Error Amp Source Current
V
IN
= V
OUT
= 3.6V
15
70
10
125
60
–55
–25
5
35
65
TEMPERATURE (°C)
95
125
3443 G10
5
–55
–25
5
35
65
TEMPERATURE (°C)
95
125
3443 G11
sn3443 3443fs
LTC3443
TYPICAL PERFOR A CE CHARACTERISTICS
Error Amp Sink Current
400
V
IN
= V
OUT
= 3.6V
0.70
EA SINK CURRENT (µA)
350
FREQUENCY (MHz)
CURRENT LIMIT (A)
300
250
200
–55
–25
5
35
65
TEMPERATURE (°C)
NMOS R
DS(ON)
0.15
V
IN
= V
OUT
= 3.6V
SWITCHES B AND C
0.13
0.15
0.13
PMOS R
DS(ON)
(Ω)
MINIMUM START VOLTAGE (V)
NMOS R
DS(ON)
(Ω)
0.11
0.09
0.07
0.05
–55
–25
5
35
65
TEMPERATURE (°C)
PI FU CTIO S
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. The exposed pad must be
soldered to PCB ground for optimal thermal performance.
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.
sn3443 3443fs
U W
95
3443 G12
(T
A
= 25°C unless otherwise specified)
Current Limit
3.4
V
IN
= V
OUT
= 3.6V
Output Frequency
V
IN
= V
OUT
= 3.6V
0.65
3.2
0.60
3.0
0.55
125
0.50
–55
–25
5
35
65
TEMPERATURE (°C)
95
125
3443 G13
2.8
–55
–25
5
35
65
TEMPERATURE (°C)
95
125
3443 G14
PMOS R
DS(ON)
V
IN
= V
OUT
= 3.6V
SWITCHES A AND D
2.30
Minimum Start Voltage
2.25
0.11
2.20
0.09
2.15
0.07
95
125
3443 G15
0.05
–50
–25
35
65
5
TEMPERATURE (°C)
95
125
3443 G16
2.10
–55
–25
5
35
65
TEMPERATURE (°C)
95
125
3443 G17
U
U
U
5
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