FEATURES
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LTC3127
1A Buck-Boost DC/DC
Converter with Programmable
Input Current Limit
DESCRIPTION
The
LTC
®
3127
is a wide V
IN
range, highly efficient, 1.35MHz
fixed frequency buck-boost DC/DC converter that operates
from input voltages above, below or equal to the output
voltage. The LTC3127 features programmable average
input current limit, making it ideal for power-limited input
sources. The input current limit is programmed with a
single resistor and is accurate from 0.2A to 1A of average
input current.
The topology incorporated provides a continuous
transfer function through all operating modes. Other
features include <1μA shutdown current, pin-selectable
Burst Mode operation and thermal overload protection.
The LTC3127 is housed in thermally enhanced 10-lead
(3mm
×
3mm
×
0.75mm) DFN packages and 12-lead
MSOP packages.
L,
LT, LTC, LTM, Linear Technology, Burst Mode and the Linear logo are registered trademarks
and PowerPath and ThinSOT are trademarks of Linear Technology Corporation. All other
trademarks are the property of their respective owners.
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Programmable (0.2A to 1A) ±4% Accurate Average
Input Current Limit
Regulated Output with Input Voltages Above,
Below or Equal to the Output
1.8V to 5.5V (Input) and 1.8V to 5.25V (Output)
Voltage Range
0.6A Continuous Output Current: V
IN
> 1.8V
1A Continuous Output Current: V
IN
> 3V
Single Inductor
Synchronous Rectification: Up to 96% Efficiency
Burst Mode
®
Operation: I
Q
= 35μA (Pin Selectable)
Output Disconnect in Shutdown
<1μA Shutdown Current
Small, Thermally Enhanced 10-Lead (3mm
×
3mm
×
0.75mm) DFN and 12-Lead MSOP Packages
APPLICATIONS
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USB Powered GSM Modems
Supercap Charger
Handheld Test Instruments
PC Card Modems
Wireless Terminals
TYPICAL APPLICATION
USB or Li-Ion (500mA Maximum Input Current) to 3.3V
L1
4.7µH
SW1
V
IN
MODE
SHDN
FB
V
C
PROG
SGND PGND
32.4k
100pF
499k
3127 TA01
Efficiency vs V
IN
100
300mA LOAD
320k
EFFICIENCY (%)
USB OR Li-Ion
2.9V to 5.5V
SW2
V
OUT
V
OUT
3.3V
90
80
OFF ON
10µF
2.2mF
182k
70
60
50
V
OUT
= 3.3V
L = 4.7µH
F = 1.35MHz
3
3.5
4.5
4
V
IN
(V)
5
5.5
3127 TA01a
L1: COILCRAFT XPL4020-472ML
3127fa
For more information
www.linear.com/LTC3127
1
LTC3127
ABSOLUTE MAXIMUM RATINGS
(Note 1)
V
IN
, V
OUT
Voltage .......................................... –0.3 to 6V
SW1, SW2 DC Voltage ................................... –0.3 to 6V
SW1, SW2 Pulsed (<100ns) Voltage .............. –0.3 to 7V
MODE, FB, V
C
Voltage .................................... –0.3 to 6V
SHDN
Voltage ............................................... –0.3 to 6V
PROG Voltage ................................................ –0.3 to 6V
Operating Junction Temperature Range
(Note 2) ....................................................–40°C to 85°C
Maximum Junction Temperature (Note 5) ........... 125°C
Storage Temperature Range .................. –65°C to 125°C
PIN CONFIGURATION
TOP VIEW
SW1
V
IN
SHDN
MODE
PROG
1
2
3
4
5
11
PGND
10 SW2
9 V
OUT
8 V
C
7 FB
6 SGND
PGND
SW1
V
IN
SHDN
MODE
PROG
1
2
3
4
5
6
TOP VIEW
12
11
10
9
8
7
PGND
SW2
V
OUT
V
C
FB
SGND
13
PGND
DD PACKAGE
10-LEAD (3mm
×
3mm) PLASTIC DFN
T
JMAX
= 125°C,
θ
JA
= 43°C/W (NOTE 6)
EXPOSED PAD (PIN 11) IS PGND, MUST BE SOLDERED TO PCB
MSE PACKAGE
12-LEAD PLASTIC MSOP
T
JMAX
= 125°C,
θ
JA
= 40°C/W (NOTE 6)
EXPOSED PAD (PIN 11) IS PGND, MUST BE SOLDERED TO PCB
ORDER INFORMATION
LEAD FREE FINISH
LTC3127EDD#PBF
LTC3127EMSE#PBF
TAPE AND REEL
LTC3127EDD#TRPBF
LTC3127EMSE#TRPBF
http://www.linear.com/product/LTC3127#orderinfo
PART MARKING
LDYD
3127
PACKAGE DESCRIPTION
10-Lead (3mm
×
3mm) Plastic DFN
12-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.
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.
2
3127fa
For more information
www.linear.com/LTC3127
LTC3127
ELECTRICAL CHARACTERISTICS
PARAMETER
Input Operating Range
Output Voltage Range
Feedback Voltage
Feedback Input Current
Input Quiescent Current – Burst Mode Operation
Input Quiescent Current – Shutdown
Output Quiescent Current – Shutdown
Input Quiescent Current – Active
Input Current Limit
V
FB
= 1.25V
V
FB
> 1.225, V
MODE
= V
IN
(Note 4)
V
SHDN
= 0V, Including SW Leakage
V
IN
= 0V, V
SHDN
= 0V, Including SW Leakage
V
FB
> 1.225V, V
MODE
= 0V (Note 4)
R
PROG
= 32.4k (Note 3)
0°C to 85°C (Note 3)
–40°C to 85°C (Note 3)
R
PROG
= 48.1k (Note 3)
R
PROG
= 48.1k , –40°C to 85°C (Note 3)
Peak Current Limit
Reverse-Current Limit
P-Channel MOSFET Leakage
N-Channel MOSFET On-Resistance
P-Channel MOSFET On-Resistance
Maximum Duty Cycle
Minimum Duty Cycle
Frequency Accuracy
SHDN
Input High Voltage
SHDN
Input Low Voltage
SHDN
Input Current
MODE Input High Voltage
MODE Input Low Voltage
MODE Input Current
V
MODE
= 5.5V
V
SHDN
= 5.5V
l
l
l
l
l
l
The
l
denotes the specifications which apply over the specified operating
junction temperature range, otherwise specifications are at T
J
= 25°C. V
IN
= 3.6V, V
OUT
= 3.3V, unless otherwise noted.
CONDITIONS
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l
MIN
1.8
1.8
1.165
TYP
MAX
5.5
5.25
UNITS
V
V
V
nA
µA
µA
µA
µA
mA
mA
mA
mA
mA
A
A
µA
mΩ
mΩ
mΩ
mΩ
%
%
1.195
1
35
0.1
0.1
400
1.225
50
4
4
520
540
540
884
914
0.45
4
480
465
430
745
728
2
0.15
500
500
500
796
796
2.5
0.3
0.1
140
170
160
190
Switches A and D
Switch B
Switch C
Switch A
Switch D
Boost( % Switch C On)
Buck (% Switch A On)
l
l
l
l
l
l
80
100
1
1.2
90
0
1.35
1.7
0.3
0.01
1
0.3
0.01
1
%
MHz
V
V
µA
V
V
µA
1.2
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 LTC3127 is guaranteed to meet performance specifications
from 0°C to 85°C. Specifications over the –40°C to 85°C operating
junction temperature range are assured by design, characterization and
correlation with statistical process controls. Note that the maximum
ambient temperature is determined by specific operating conditions in
conjunction with board layout, the rated package thermal resistance and
other environmental factors.
Note 3:
Specification is guaranteed when the inductor current is in
continuous conduction.
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
43°C/W.
3127fa
For more information
www.linear.com/LTC3127
3
LTC3127
TYPICAL PERFORMANCE CHARACTERISTICS
Efficiency vs Load Current
100
90
V
OUT
= 1.8V
PWM
100
90
80
EFFICIENCY (%)
70
60
50
40
30
20
10
0
0.1
1
V
IN
= 2.9V
V
IN
= 3.6V
V
IN
= 4.3V
10
100
LOAD CURRENT (mA)
1000
3127 G02
(T
J
= 25°C, unless otherwise noted )
Efficiency vs Load Current
V
OUT
= 3.3V
BURST
EFFICIENCY (%)
100
90
Efficiency vs Load Current
V
OUT
= 5V
80 BURST
EFFICIENCY (%)
70
60
50
40
30
20
10
0
0.1
1
V
IN
= 1.8V
V
IN
= 3.6V
V
IN
= 5V
10
100
LOAD CURRENT (mA)
1000
3127 G01
80 BURST
70
60
50
40
30
20
10
0
0.1
1
V
IN
= 4.5V
V
IN
= 5V
V
IN
= 5.5V
10
100
1000
LOAD CURRENT (mA)
10000
3127 G03
PWM
PWM
Average Input Current Limit
vs V
IN
(Normalized)
2
1
INPUT CURRENT LIMIT (%)
0
–1
–2
–3
–4
–5
1.8 2.2 2.6
3.4 3.8 4.2 4.6
V
IN
(V)
5.4
3127 G04
Average Input Current Limit
vs Temperature (Normalized)
2
1
INPUT CURRENT LIMIT (%)
0
–1
–2
–3
–4
–5
–45 –30 –15
0 15 30 45 60
TEMPERATURE (°C)
90
V
OUT
= 3.3V
R
PROG
= 32.4k
INPUT CURRENT LIMIT (A)
1.1
1.0
0.9
0.8
0.7
0.6
0.5
0.4
Maximum Programmable Input
Current vs V
IN
V
OUT
= 3.3V
R
PROG
= 32.4k
3
5
75
1.8 2.2 2.6
3
3127 G05
3.4 3.8 4.2 4.6
V
IN
(V)
5
5.4
3127 G21
Quiescent Current vs V
IN
(Fixed
Frequency Mode–Not Switching)
430
410
INPUT CURRENT (µA)
INPUT CURRENT (µA)
390
370
350
330
310
290
270
1.8 2.2 2.6
3
3.4 3.8 4.2 4.6
V
IN
(V)
5
5.4
3127 G06
38
37
36
35
34
33
Burst Mode Quiescent Current
vs V
IN
No Load Input Current vs V
IN
in
Burst Mode Operation
52.5
52.0
INPUT CURRENT (µA)
51.5
51.0
50.5
50.0
49.5
49.0
V
OUT
= 3.3V
32
1.8 2.2 2.6
3
3.4 3.8 4.2 4.6
V
IN
(V)
5
5.4
3127 G07
48.5
1.8 2.2 2.6
3
3.4 3.8 4.2 4.6
V
IN
(V)
5
5.4
3127 G08
4
3127fa
For more information
www.linear.com/LTC3127
LTC3127
TYPICAL PERFORMANCE CHARACTERISTICS
Feedback Voltage vs Temperature
(Normalized)
0.20
L = 4.7µH
V
OUT
= 3.3V
V
IN
= 3.6V
V
OUT
REGULATION (%)
0.40
0.30
0.20
0.10
0
–0.10
–0.20
–0.30
–0.40
–0.50
–0.80
–50
–30
50
–10 10
30
TEMPERATURE (°C)
70
90
–0.60
0
200
600
800
400
LOAD CURRENT (mA)
1000
3127 G10
(T
J
= 25°C, unless otherwise noted )
V
OUT
Regulation vs Load Current
(Normalized)
V
OUT
= 3.3V
300
NMOS R
DS(ON)
vs V
IN
0.00
CHANGE (%)
250
R
DS(ON)
(m )
–0.20
200
SWC
150
SWB
–0.40
–0.60
100
1.8
2.4
3
3127 G09
3.6
V
IN
(V)
4.2
4.8
5.4
3127 G11
PMOS R
DS(ON)
vs V
IN
325
Maximum Load Current vs V
IN
2250
2000
LOAD CURRENT (mA)
R
PROG
= 90k
I
LOAD
1A/DIV
V
OUT
= 3.3V
I
IN
1A/DIV
V
OUT
50mV/DIV
Load Transient Response in Fixed
Frequency Mode, No Load to 1A,
Not in Input Current Limit
275
R
DS(ON)
(m )
1750
1500
1250
1000
750
500
SWA
250
4.2
4.8
5.4
V
OUT
= 2.4V
225
SWD
175
V
OUT
= 5V
I
L
1A/DIV
200µs/DIV
3127 G14
125
1.8
2.4
3
3.6
V
IN
(V)
0
1.8 2.2 2.6
3
3.4 3.8 4.2 4.6
V
IN
(V)
5
5.4
3127 G13
V
IN
= 3.6V
V
OUT
= 3.3V
R
PROG
= 90k C
OUT
= 4.4mF
R3 = 499k
C1 = 100pF
3127 G12
Load Transient Response in Fixed
Frequency Mode, No Load to 1A,
in Input Current Limit
MODE = 0V
I
LOAD
1A/DIV
I
IN
500mA/DIV
V
OUT
100mV/DIV
Burst Mode Operation
I
L
500mA/DIV
V
OUT
20mV/DIV
200µs/DIV
V
OUT
= 3.3V
V
IN
= 3.6V
R
PROG
= 32.4k C
OUT
= 4.4mF
R3 = 499k
C1 = 100pF
3127 G15
5µs/DIV
V
OUT
= 3.3V
V
IN
= 3.6V
R
PROG
= 32.4k C
OUT
= 4.4mF
R3 = 499k
C1 = 100pF
3127 G16
3127fa
For more information
www.linear.com/LTC3127
5
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