LTC3105
400mA Step-Up DC/DC
Converter with Maximum Power
Point Control and 250mV Start-Up
FEATURES
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DESCRIPTION
The LTC
®
3105 is a high efficiency step-up DC/DC converter
that can operate from input voltages as low as 225mV. A
250mV start-up capability and integrated maximum power
point controller (MPPC) enable operation directly from low
voltage, high impedance alternative power sources such as
photovoltaic cells, TEGs (thermoelectric generators) and
fuel cells. A user programmable MPPC set point maximizes
the energy that can be extracted from any power source.
Burst Mode operation, with a proprietary self adjusting
peak current, optimizes converter efficiency and output
voltage ripple over all operating conditions.
The AUX powered 6mA LDO provides a regulated rail for
external microcontrollers and sensors while the main
output is charging. In shutdown, I
Q
is reduced to 10µA
and integrated thermal shutdown offers protection from
overtemperature faults. The LTC3105 is offered in 10-lead
3mm × 3mm × 0.75mm DFN and 12-lead MSOP packages.
L,
LT, LTC, LTM, Linear Technology, the Linear logo 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.
Low Start-Up Voltage: 250mV
Maximum Power Point Control
Wide V
IN
Range: 225mV to 5V
Auxiliary 6mA LDO Regulator
Burst Mode
®
Operation: I
Q
= 24µA
Output Disconnect and Inrush Current Limiting
V
IN
> V
OUT
Operation
Antiringing Control
Soft Start
Automatic Power Adjust
Power Good Indicator
10-Lead 3mm × 3mm × 0.75mm DFN and 12-Lead
MSOP Packages
APPLICATIONS
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Solar Powered Battery/Supercapacitor Chargers
Energy Harvesting
Remote Industrial Sensors
Low Power Wireless Transmitters
Cell Phone, MP3, PMP and GPS Accessory Chargers
TYPICAL APPLICATION
Single Photovoltaic Cell Li-Ion Trickle Charger
10µH
225mV TO 5V
PHOTOVOLTAIC
CELL
80
70
V
OUT
4.1V
1020k
FB
MPPC
OFF ON
40.2k
1µF
SHDN
AUX
GND
PGOOD
LDO
FBLDO
4.7µF
3105 TA01a
Output Current vs Input Voltage
MPPC DISABLED
V
OUT
= 3.3V
–
10µF
LTC3105
V
OUT
OUTPUT CURRENT (mA)
+
V
IN
SW
60
50
40
30
20
10
0
0.2
0.3
V
OUT
= 4.2V
Li-Ion
332k
2.2V
10µF
V
OUT
= 5V
0.4 0.5 0.6 0.7 0.8
INPUT VOLTAGE (V)
0.9
1.0
3105 TA01b
3105fa
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LTC3105
ABSOLUTE MAXIMUM RATINGS
(Note 1)
SW Voltage
DC............................................................ –0.3V to 6V
Pulsed (<100ns) ...........................................–1V to 7V
Voltage, All Other Pins ................................. –0.3V to 6V
Operating Junction Temperature
Range (Note 2).........................................–40°C to 85°C
Maximum Junction Temperature (Note 4) ............ 125°C
Storage Temperature.............................. –65°C to 150°C
Lead Temperature (Soldering, 10 sec.)
MS Package ...................................................... 300°C
PIN CONFIGURATION
TOP VIEW
FB
LDO
FBLDO
SHDN
MPPC
1
2
3
4
5
11
GND
10 AUX
9 V
OUT
8 PGOOD
7 SW
6 V
IN
FB
LDO
FBLDO
SHDN
MPPC
GND
1
2
3
4
5
6
TOP VIEW
12
11
10
9
8
7
AUX
V
OUT
PGOOD
SW
V
IN
GND
DD PACKAGE
10-LEAD (3mm
×
3mm) PLASTIC DFN
T
JMAX
= 125°C,
θ
JA
= 43°C/W,
θ
JC
= 3°C/W
EXPOSED PAD (PIN 11) IS GND, MUST BE SOLDERED TO PCB
MS PACKAGE
12-LEAD PLASTIC MSOP
T
JMAX
= 125°C,
θ
JA
= 130°C/W,
θ
JC
= 21°C/W
ORDER INFORMATION
LEAD FREE FINISH
LTC3105EDD#PBF
LTC3105EMS#PBF
TAPE AND REEL
LTC3105EDD#TRPBF
LTC3105EMS#TRPBF
PART MARKING
LFQC
3105
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.
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/
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LTC3105
ELECTRICAL CHARACTERISTICS
PARAMETER
Step-Up Converter
Input Operating Voltage
Input Start-Up Voltage
Output Voltage Adjust Range
Feedback Voltage (FB Pin)
V
OUT
I
Q
in Operation
V
OUT
I
Q
in Shutdown
MPPC Pin Output Current
SHDN
Input Logic High Voltage
SHDN
Input Logic Low Voltage
N-Channel SW Pin Leakage Current
P-Channel SW Pin Leakage Current
N-Channel On-Resistance: SW to GND
P-Channel On-Resistance: SW to V
OUT
Peak Current Limit
Valley Current Limit
PGOOD Threshold (% of Feedback Voltage)
LDO Regulator
LDO Output Adjust Range
LDO Output Voltage
Feedback Voltage (FBLDO Pin)
Load Regulation
Line Regulation
Dropout Voltage
LDO Current Limit
LDO Reverse-Blocking Leakage Current
External Feedback Network, V
AUX
> V
LDO
V
FBLDO
= 0V
External Feedback Network
I
LDO
= 1mA to 6mA
V
AUX
= 2.5V to 5V
I
LDO
= 6mA, V
OUT
= V
AUX
= 2.2V
V
LDO
0.5V Below Regulation Voltage
V
IN
= V
AUX
= V
OUT
= 0V, V
SHDN
= 0V
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l
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The
l
denotes the specifications which apply over the full operating
junction temperature range, otherwise specifications are at T
A
= 25°C (Note 2). V
AUX
= V
OUT
= 3.3V, V
LDO
= 2.2V, V
IN
= 0.6V, unless
otherwise noted.
CONDITIONS
MIN
0.225
0.25
1.5
0.984
1.004
24
10
9.72
l
l
TYP
MAX
5
0.4
0.36
5.25
1.024
UNITS
V
V
V
V
V
µA
µA
(Note 5)
T
J
= 0°C to 85°C (Note 5)
l
l
l
V
FB
= 1.10V
SHDN
= 0V
V
MPPC
= 0.6V
1.1
10
10.28
0.3
µA
V
V
µA
µA
Ω
Ω
A
A
V
IN
= V
SW
= 5V, V
SHDN
= 0V
V
IN
= V
SW
= 0V, V
OUT
= V
AUX
= 5.25V
1
1
0.5
0.5
10
10
V
FB
= 0.90V, V
MPPC
= 0.4V (Note 3)
V
FB
= 0.90V, V
MPPC
= 0.4V (Note 3)
V
OUT
Falling
0.4
0.275
85
1.4
2.148
0.984
0.5
0.35
90
95
5
2.2
1.004
0.40
0.15
105
2.236
1.024
%
V
V
V
%
%
mV
mA
µA
6
12
1
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 LTC3105 is tested under pulsed load conditions such that
T
J
≈
T
A
. The LTC3105E is guaranteed to meet specifications from
0°C to 85°C junction temperature. Specifications over the –40°C to 85°C
operating junction temperature range are assured by design, character-
ization and correlation with statistical process controls. Note that the
maximum ambient temperature consistent with these specifications is
determined by specific operating conditions in conjunction with board
layout, the rated package thermal impedance and other environmental
factors.
Note 3:
Current measurements are performed when the LTC3105 is not
switching. The current limit values measured in operation will be somewhat
higher due to the propagation delay of the comparators.
Note 4:
This IC includes over temperature 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 impair device reliability.
Note 5:
The LTC3105 has been optimized for use with high impedance
power sources such as photovoltaic cells and thermoelectric generators.
The input start-up voltage is measured using an input voltage source with
a series resistance of approximately 200mΩ and MPPC enabled. Use of the
LTC3105 with lower resistance voltage sources or with MPPC disabled may
result in a higher input start-up voltage.
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LTC3105
TYPICAL PERFORMANCE CHARACTERISTICS
V
IN
= 0.6V, unless otherwise noted.
Minimum Input Start-Up Voltage
vs Temperature
340
320
THRESHOLD VOLTAGE (mV)
INPUT VOLTAGE (mV)
300
280
260
240
220
200
–45 –30 –15
1000
900
800
700
600
500
400
300
200
100
0 15 30 45 60
TEMPERATURE (°C)
75 90
3105 G01
T
A
= 25°C, V
AUX
= V
OUT
= 3.3V, V
LDO
= 2.2V,
Shutdown Thresholds
vs Input Voltage
IC ENABLE
120
IC Enable Delay vs Input Voltage
100
IC DISABLE
DELAY TIME (µs)
80
60
0
1.25
2.25
4.25
3.25
SUPPLY VOLTAGE, V
IN
OR V
AUX
(V)
5.25
3105 G02
40
1.25
2.25
4.25
3.25
SUPPLY VOLTAGE, V
IN
OR V
AUX
(V)
5.25
3105 G03
MPPC Current Variation
vs Temperature
2.5
2.0
CHANGE FROM 25°C (%)
SOFT-START TIME (ms)
0 15 30 45 60
TEMPERATURE (°C)
75 90
3105 G05
LDO Soft-Start Duration
vs LDO Load
1.25
1.20
1.15
1.10
1.05
1.00
0.95
1.5
1.0
0.5
0
–0.5
–1.0
–1.5
–45 –30 –15
1
3
4
5
2
LDO LOAD CURRENT (mA)
6
3105 G06
V
OUT
I
Q
vs Temperature
During Shutdown
22
20
18
16
I
Q
(µA)
14
12
10
8
6
4
–45 –30 –15
0 15 30 45 60
TEMPERATURE (°C)
75 90
3105 G07
V
IN
for Synchronous Operation
5.0
4.5
MAXIMUM INPUT VOLTAGE (V)
4.0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0
1.5
2.0
2.5 3.0 3.5 4.0 4.5
OUTPUT VOLTAGE (V)
5.0
5.5
3105 G09
SHDN
= 0V
NONSYNCHRONOUS
OPERATION
SYNCHRONOUS
OPERATION
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LTC3105
TYPICAL PERFORMANCE CHARACTERISTICS
V
IN
= 0.6V, unless otherwise noted.
Exiting MPPC Control on
Input Voltage Step
V
IN
VOLTAGE
200mV/DIV
V
MPPC
= 400mV
1.0
0.5
CHANGE FROM 25°C (%)
0
–0.5
–1.0
–1.5
–2.0
15µs/DIV
–2.5
–45 –30 –15
I
VALLEY
EFFICIENCY (%)
I
PEAK
90
80
70
60
50
40
0.25
T
A
= 25°C, V
AUX
= V
OUT
= 3.3V, V
LDO
= 2.2V,
I
PEAK
and I
VALLEY
Current Limit
Change vs Temperature
100
Efficiency vs V
IN
V
OUT
= 3V
I
LOAD
= 10mA
LDO = 2.2V
INDUCTOR
CURRENT
100mA/DIV
MPPC VOLTAGE
200mV/DIV
3105 G10
0 15 30 45 60
TEMPERATURE (°C)
75 90
3105 G11
1.25
2.25
3.25
4.25
INPUT VOLTAGE (V)
5.25
3105 G12
Input and Output Burst Ripple
V
IN
= 0.6V
C
IN
= 470µF
OUTPUT
VOLTAGE
50mV/DIV
SW CURRENT
200mA/DIV
V
OUT
= 3.3V
I
OUT
= 15mA
C
OUT
= 10µF
EFFICIENCY (%)
90
80
70
60
50
40
30
20
10
50µs/DIV
Efficiency vs Output Current and
Power Loss, V
OUT
= 3.3V
V
IN
= 0.6V
V
IN
= 0.8V
V
IN
= 1V
EFFICIENCY
1000
100
POWER LOSS (mW)
10
POWER LOSS
1
INPUT
VOLTAGE
5mV/DIV
3105 G13
0
0.01
0.1
1
10
0.1
100
3105 G14
OUTPUT CURRENT (mA)
Efficiency vs Output Current and
Power Loss, V
OUT
= 5V
100
90
80
EFFICIENCY (%)
70
60
50
40
30
20
0.01
1
10
0.1
OUTPUT CURRENT (mA)
0.1
100
3105 G15
No-Load Input Current
vs Input Voltage
1000
800
700
INPUT CURRENT (µA)
100
600
500
400
300
200
100
0
0.2
0.4
0.6
0.8
INPUT VOLTAGE (V)
1.0
1.2
3105 G16
V
IN
= 3V
V
IN
= 2V
V
IN
= 1.5V
EFFICIENCY
V
OUT
= 3.3V
POWER LOSS (mW)
10
POWER LOSS
1
3105fa
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