LTC3106
300mA Low Voltage
Buck-Boost Converter with
PowerPath and 1.6µA Quiescent Current
Features
Description
Dual Input Buck-Boost with Integrated PowerPath™
Manager
n Ultralow Start-Up Voltages: 850mV Start with No
Backup Source, 300mV with a Backup Source
n Compatible with Primary or Rechargeable Backup
Batteries
n Digitally Selectable V
OUT and VSTORE
n Maximum Power Point Control
n Ultralow Quiescent Current: 1.6μA
n Regulated Output with V or V
IN
STORE Above, Below
or Equal to the Output
n Optional Backup Battery Trickle Charger
n Shelf Mode Disconnect Function to Preserve Battery
Shelf Life
n Burst Mode® Operation
n Accurate RUN Pin Threshold
n Power Good Output Voltage Indicator
n Selectable Peak Current Limit: 90mA/650mA
n Available in Thermally Enhanced 3mm × 4mm 16-Pin
QFN and 20-Pin TSSOP Packages
The LTC®3106 is a highly integrated, ultralow voltage buckboost DC/DC converter with automatic PowerPath management optimized for multisource, low power systems.
At no load, the LTC3106 draws only 1.6µA while creating
an output voltage up to 5V from either input source.
n
If the primary power source is unavailable, the LTC3106
seamlessly switches to the backup power source. The
LTC3106 is compatible with either rechargeable or primary cell batteries and can trickle charge a backup battery
whenever there is an energy surplus available. Optional
maximum power point control ensures power transfer is
optimized between power source and load. The output voltage and backup voltage, VSTORE, are programmed digitally,
reducing the required number of external components.
Zero power Shelf Mode ensures that the backup battery
will remain charged if left connected to the LTC3106 for
an extended time.
Additional features include an accurate turn-on voltage, a
power good indicator for VOUT, a user selectable 100mA
peak current limit setting for lower power applications,
thermal shutdown as well as user selectable backup power
and output voltages.
Applications
n
n
n
n
Wireless Sensor Networks
Home or Office Building Automation
Energy Harvesting
Remote Sensors
L, LT, LTC, LTM, Linear Technology, the Linear logo, Eterna and Burst Mode are registered
trademarks and PowerPath is a trademark of Linear Technology Corporation. All other
trademarks are the property of their respective owners. Protected by U.S. Patents, including
7432695 and 6366066.
Typical Application
Efficiency vs Input Voltage
Solar Cell Input with Primary Battery Backup
100
+
10µF
470µF
SW2
VAUX
VIN
VOUT
2.2µF
LTC3106
1µF
PGOOD
0.01µF
VCC
PRI
47µF
1M
3.3V
50mA
EFFICIENCY (%)
600mV TO 5V
PV CELLS
+
SW1
VSTORE
VCAP
ENVSTR
RUN
PGOOD
VCC
MPP
ILIMSEL
GND
3106 TA01a
110
100
90
90
85
80
80
75
70
VIN EFF.
VIN P.L.
VSTR EFF.
VSTR P.L.
70
65
60
60
50
40
55
30
50
20
45
10
40
0.5
1
1.5
2 2.5 3 3.5 4
INPUT VOLTAGE (V)
4.5
5
POWER LOSS (mW)
3.6V
TL-5955
PRIMARY
BATTERY
IOUT = 50mA
95
10µH
0
5.5
LTC3106 TA01b
3106f
For more information www.linear.com/LTC3106
1
LTC3106
Absolute Maximum Ratings
(Notes 1, 6)
Supply Voltages
VIN, VSTORE, VOUT, VCAP............................ –0.3V to 6V
All Other Pins................................................ –0.3V to 6V
Operating Junction Temperature Range
(Notes 2, 3)............................................. –40°C to 125°C
Storage Temperature Range................... –65°C to 150°C
Lead Temperature (Soldering, 10 sec)
FE Package........................................................ 300°C
Pin Configuration
TOP VIEW
SW2
SW1
VSTORE
VCAP
TOP VIEW
VSTORE
1
20 SW1
VCAP
2
19 SW2
VOUT
3
18 VIN
NC
4
17 GND
VAUX
5
13 RUN
VCC
6
OS1 5
12 ILIMSEL
OS1
7
14 ILIMSEL
OS2 6
11 PRI
OS2
8
13 PRI
PGOOD
9
12 SS1
MPP 10
11 SS2
20 19 18 17
NC 1
16 VIN
VOUT 2
15 GND
VAUX 3
14 ENVSTR
21
GND
MPP
9 10
SS1
8
SS2
7
PGOOD
VCC 4
21
GND
16 ENVSTR
15 RUN
FE PACKAGE
20-LEAD PLASTIC TSSOP
UDC PACKAGE
20-LEAD (3mm × 4mm) PLASTIC QFN
TJMAX = 125°C, θJA = 52°C/W, θJC = 7°C/W (Note 5)
EXPOSED PAD (PIN 21) IS GND, MUST BE SOLDERED TO PCB
TJMAX = 125°C, θJA = 48.6°C/W, θJC = 8.6°C/W (Note 5)
EXPOSED PAD (PIN 21) IS GND, MUST BE SOLDERED TO PCB
Order Information
LEAD FREE FINISH
TAPE AND REEL
PART MARKING*
PACKAGE DESCRIPTION
TEMPERATURE RANGE
LTC3106EUDC#PBF
LTC3106EUDC#TRPBF
LGQH
20-Lead (3mm × 4mm) Plastic QFN
–40°C to 125°C
LTC3106IUDC#PBF
LTC3106IUDC#TRPBF
LGQH
20-Lead (3mm × 4mm) Plastic QFN
–40°C to 125°C
LTC3106EFE#PBF
LTC3106EFE#TRPBF
LTC3106FE
20-Lead Plastic TSSOP
–40°C to 125°C
LTC3106IFE#PBF
LTC3106IFE#TRPBF
LTC3106FE
20-Lead Plastic TSSOP
–40°C to 125°C
Consult LTC Marketing for parts specified with wider operating temperature ranges. *The temperature grade is identified by a label on the shipping container
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.
3106f
2
For more information www.linear.com/LTC3106
LTC3106
Electrical Characteristics
The l denotes the specifications which apply over the specified junction
temperature range, otherwise specifications are at TA = 25°C (Note 2). VIN = 1.5V, VOUT = 3.3V, VSTORE = 3.6V and VAUX in regulation unless
otherwise noted.
PARAMETER
VIN Start-Up Voltage
VIN Maximum Operating Voltage
VIN Minimum Operating Voltage
VIN Minimum No-Load Start-Up Power
VIN Undervoltage Quiescent Current
Shutdown Current – VIN
Quiescent Current – VIN
VSTORE Maximum Operating Voltage
VSTORE Minimum Operating Voltage
VSTORE Under Voltage Lockout
VSTORE Operating Voltage (Note 7)
Output Regulation Voltage
Quiescent Current – VAUX
Quiescent Current – VOUT
Quiescent Current – VSTORE
Shutdown Current – VSTORE
Shelf Mode VSTORE Leakage Current
N-Channel MOSFETs – Leakage Current
P-Channel MOSFETs – Leakage Current
N-Channel MOSFET B and C Switch RDS(ON)
P-Channel MOSFET A1 RDS(ON)
P-Channel MOSFET A2 RDS(ON)
P-Channel MOSFET D1 RDS(ON)
P-Channel MOSFET D2 RDS(ON)
CONDITIONS
Start-Up from VIN, VOUT = VAUX = VSTORE = 0V, RUN = VIN
VSTORE in Operating Voltage Limits, RUN > 0.613V,
ENVSTR Pin > 0.8V (Minimum Voltage Is Load Dependent)
Start-Up from VIN, RUN = VIN, VOUT = VAUX = VSTORE = 0V
Start-Up from VIN, RUN = VIN, VOUT = VAUX = VSTORE = 0V
VSTORE = 0V, RUN = 0
TJ = –40°C to 85°C (Note 4)
MIN
TYP
0.85
0.25
l
l
l
l
Switching Enabled, VOUT in Regulation, Non-Switching
Switching Enabled, VOUT in Regulation, Non-Switching,
TJ = –40°C to 85°C (Note 4)
PRI = VCC, ENVSTR = VSTORE
VOUT in Regulation, VCAP Shorted to VSTORE, PRI = VCC,
ENVSTR = VSTORE
PRI = VCC, ENVSTR = VSTORE
SS1 = 0V, SS2 = 0V
OV
UV
l
l
l
1.730
3.90
2.70
SS1 = 0V, SS2 = VCC
OV
UV
l
l
SS1 = VCC, SS2 = 0V
OV
UV
SS1 = VCC, SS2 = VCC
0.3
MAX
1.2
5.1
0.35
UNITS
V
V
V
12
1
300
300
0.1
0.1
2
750
450
1
0.3
µW
µA
nA
nA
µA
µA
4.3
V
V
1.778
4.00
2.78
1.826
4.10
2.86
2.81
1.85
2.90
1.90
2.99
1.95
l
l
2.91
2.08
3.00
2.15
3.08
2.21
OV
UV
l
l
3.90
2.91
4.00
3.00
4.10
3.08
1.8V VOUT Selected
TJ = –40°C to 85°C (Note 4)
2.2V VOUT Selected
TJ = –40°C to 85°C (Note 4)
3.3V VOUT Selected
TJ = –40°C to 85°C (Note 4)
5V VOUT Selected
TJ = –40°C to 85°C (Note 4)
Enabled, VOUT in Regulation, Non-Switching,
TJ = –40°C to 85°C (Note 4)
Enabled, VOUT in Regulation, Non-Switching,
TJ = –40°C to 85°C (Note 4)
Enabled, VOUT in Regulation, Non-Switching, VCAP Shorted
to VSTORE
TJ = –40°C to 85°C (Note 4)
VIN = 0V, VCAP Shorted to VSTORE, ENVSTR = 0V
TJ = –40°C to 85°C (Note 4)
Isolated VSTORE, ENVSTR = 0V
B and C Switches
A1, A2, D1 and D2 Switches
VIN = 5V
VIN = 5V
VSTORE = VCAP = 4.2V
VOUT = 3.3V
VSTORE = VCAP = 4.2V
l
1.75
1.755
2.14
2.145
3.22
3.23
4.90
4.92
1.8
1.8
2.2
2.2
3.3
3.3
5.0
5.0
1.85
1.845
2.25
2.245
3.40
3.38
5.10
5.08
V
V
V
V
V
V
V
V
V
V
V
V
V
V
V
V
V
1.6
1.6
0.1
0.1
0.1
3
2.5
1
0.3
1
µA
µA
µA
µA
µA
0.1
0.1
0.1
0.1
0.1
0.1
0.5
0.5
1.9
0.9
2.9
0.3
0.7
0.3
25
1
1
µA
µA
µA
nA
µA
µA
Ω
Ω
Ω
Ω
Ω
l
2.1
l
l
l
l
l
l
l
l
3106f
For more information www.linear.com/LTC3106
3
LTC3106
Electrical Characteristics
The l denotes the specifications which apply over the specified junction
temperature range, otherwise specifications are at TA = 25°C (Note 2). VIN = 1.5V, VOUT = 3.3V, VSTORE = 3.6V and VAUX in regulation unless
otherwise noted.
PARAMETER
P-Channel MOSFET AUXSW RDS(ON)
P-Channel VSTORE Isolation MOSFET RDS(ON)
Peak Current Limit (VOUT)
VALLEY Current Limit
Peak Current Limit (VSTORE Charging)
PGOOD Threshold
PGOOD Hysteresis
PGOOD Voltage Low
PGOOD Leakage Current
VIH Digital Input High Logic Level
VIL Digital Input Low Logic Level
Digital Input Leakage Current
ENVSTR Input Leakage Current
Auxiliary Voltage Threshold
Auxiliary Voltage Hysteresis
MPP Pin Output Current
MPP Pin Shutdown Current
MPP Disable Threshold
RUN Threshold - Enable Reference
Accurate RUN Threshold - Enable Switching
from VIN
Accurate RUN Hysteresis
RUN Input Current
CONDITIONS
VAUX = 5.4V
VSTORE = 4.2V
VOUT Powered from VIN, ILIMSEL > 0.8V
VOUT Powered from VIN, ILIMSEL = 0V
VOUT Powered from VSTORE, ILIMSEL > 0.8V
VOUT Powered from VSTORE, ILIMSEL = 0V
VOUT Powered from VIN, ILIMSEL > 0.8V
VOUT Powered from VIN, ILIMSEL = 0V
VOUT Powered from VSTORE, ILIMSEL > 0.8V
VOUT Powered from VSTORE, ILIMSEL = 0V
VSTORE Powered from VIN
VOUT Falling, Percentage Below VOUT
Percentage of VOUT
IPGOOD = 100µA
VPGOOD = 5V
Pins: OS[1:2], SS[1:2], ILIMSEL, ENVSTR, PRI
Pins: OS[1:2], SS[1:2], ILIMSEL, ENVSTR, PRI
Pin Voltage = 5.2V,
Pins: OS[1:2], SS[1:2], ILIMSEL, PRI
MIN
l
l
l
l
l
l
l
l
l
l
530
60
140
60
300
10
30
10
60
–11
l
0.1
l
l
RUN Pin Voltage Increasing
TJ = –40°C to 85°C (Note 4)
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 LTC3106 is tested under pulsed load conditions such that
TJ ≈TA. The LTC3106E is guaranteed to meet specifications from 0°C to 85°C
junction temperature. Specifications over the –40°C to 125°C operating
junction temperature range are assured by design, characterization and
correlation with statistical process controls. The LTC3106I is guaranteed over
the full –40°C to 125°C operating junction temperature range. The junction
temperature (TJ) is calculated from the ambient temperature (TA ) and power
dissipation (PD)according to the formula:
TJ = TA + (PD)(θJA°C/W)
where θJA is the package thermal impedance. Note the maximum ambient
temperature consistent with these specifications is determined by specific
operating conditions in conjunction with board layout, the rated package
thermal resistance and other environmental factors.
Note 3: This IC includes overtemperature protection that is intended to
protect the device during momentary overload conditions. The maximum
l
MAX
–7
10
0.8
l
VAUX Rising
VAUX Falling, Restart VAUX Charging
VMPP = 0.6V
VMPP = VCC
Voltage Below VCC
TYP
3
2
725
100
200
100
400
44
70
44
100
–9
3
0.2
0.1
1.21
–1
0.15
0.585
0.591
44
5.2
50
1.5
0.1
–0.8
0.4
0.6
0.6
100
0.1
0.3
10
80
1.72
10
0.55
0.615
0.609
10
UNITS
Ω
Ω
mA
mA
mA
mA
mA
mA
mA
mA
mA
%
%
V
nA
V
V
nA
nA
V
mV
µA
nA
V
V
V
V
mV
nA
rated junction temperature will be exceeded when this protection is active.
Continuous operation above the maximum operating junction temperature
may impair device reliability or permanently damage the device.
Note 4: Specification is guaranteed by design and not 100% tested in
production.
Note 5: Failure to solder exposed backside of the package to the PC board
will result in a higher thermal resistance
Note 6: Voltage transients on the switch pins beyond the DC limits
specified in Absolute Maximum Ratings are non-disruptive to normal
operation when using good layout practices as described elsewhere in the
data sheet and as seen on the demo board.
Note 7: If PRI = GND, then charging is enabled on VSTORE whenever
surplus energy is available from VIN. The OV and UV thresholds are the
maximum charge and discharge levels controlled by the LTC3106.
Note 8: Some of the IC electrical characteristics are measured in an
open-loop test configuration that may differ from the typical operating
conditions. These differences are not critical for the accuracy of the
parameter and will not impact operation.
3106f
4
For more information www.linear.com/LTC3106
LTC3106
Typical Performance Characteristics
1k
VOUT = 1.8V
60
50
40
30
VIN = 1V
VIN = 2V
VIN = 3V
VIN = 4V
VIN = 5V
20
10
0
0.001
0.01
0.1
1
10
LOAD CURRENT (mA)
POWER LOSS (mW)
70
VOUT = 1.8V
10
1
0.01
0.001
0.1
1
10
LOAD CURRENT (mA)
100
VOUT = 2.2V
90
0.1
vs Load
100
90
0.1
1
10
LOAD CURRENT (mA)
Current
VOUT = 3.3V
0.01
40
VIN = 1V
VIN = 2V
VIN = 3V
VIN = 4V
VIN = 5V
30
20
10
0
0.001
100 500
0.01
0.1
1
10
LOAD CURRENT (mA)
3106 G04
1k
VOUT = 3.3V
10
1
0.1
0.01
0.001
100 500
VIN = 1V
VIN = 3V
VIN = 5V
0.01
VIN Power Loss vs Load Current
1k
V OUT = 5V
40
VIN = 1V
VIN = 2V
VIN = 3V
VIN = 4V
VIN = 5V
30
20
10
0.01
0.1
1
10
LOAD CURRENT (mA)
100 500
3106 G07
POWER LOSS (mW)
50
10
1
0.1
0.01
0.001
VIN = 1V
VIN = 3V
VIN = 5V
0.01
0.1
1
10
LOAD CURRENT (mA)
100 500
3106 G08
0.1
1
10
LOAD CURRENT (mA)
100 500
3106 G06
Light Load Power Loss vs Input
Voltage (VIN)
VOUT = 1.8V AT 10µA
VOUT = 5V AT 10µA
VOUT = 1.8V AT 2µA
VOUT = 5V AT 2µA
100
60
100 500
VIN Power Loss vs Load Current
3106 G05
VOUT = 5V
70
0.1
1
10
LOAD CURRENT (mA)
100
50
80
EFFICIENCY (%)
1k
60
VIN Efficiency vs Load Current
0
0.001
VIN = 1V
VIN = 2V
VIN = 3V
VIN = 4V
VIN = 5V
30
3106 G03
VIN Efficiency vs Load Current
70
VIN = 1V
VIN = 3V
VIN = 5V
0.01
40
0
0.001
100 500
POWER LOSS (µW)
0.01
0.001
50
10
80
EFFICIENCY (%)
POWER LOSS (mW)
100
1
60
20
VIN = 1V
VIN = 3V
VIN = 5V
0.01
70
3106 G02
VIN Power Loss vs Load Current
10
VOUT = 2.2V
80
0.1
100 500
VIN Efficiency vs Load Current
90
3106 G01
1k
100
100
80
EFFICIENCY (%)
VIN Power Loss vs Load Current
EFFICIENCY (%)
90
VIN Efficiency vs Load Current
POWER LOSS (mW)
100
TA = 25°C unless otherwise noted.
100
10
0
0.5
1
1.5 2 2.5 3 3.5 4
INPUT VOLTAGE, VIN (V)
4.5
5
3106 G09
3106f
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5
LTC3106
Typical Performance Characteristics
VSTORE/VCAP Efficiency vs
Load Current
90
VSTORE/VCAP Power Loss vs
Load Current
100
VOUT = 1.8V
80
POWER LOSS (mW)
EFFICIENCY (%)
60
50
40
30
20
0
0.001
0.01
0.1
1
10
LOAD CURRENT (mA)
0.01
0.001
100
0.01
60
50
40
30
100
0.01
0.1
1
10
LOAD CURRENT (mA)
30
0.01
0.1
1
10
LOAD CURRENT (mA)
100
3106 G16
100
20
VOUT = 5V
18
16
1
0.01
0.001
0.1
1
10
LOAD CURRENT (mA)
No Load Input Current
vs Input Voltage
0.1
VSTORE/VCAP = 4.2V
VSTORE/VCAP = 3.1V
VSTORE/VCAP = 2V
0.01
3106 G15
INPUT CURRENT (µA)
40
10
0.01
0.001
100
10
POWER LOSS (mW)
EFFICIENCY (%)
80
50
VSTORE/VCAP = 4.2V
VSTORE/VCAP = 3.1V
VSTORE/VCAP = 2V
1
VSTORE/VCAP Power Loss vs
Load Current
VOUT = 5V
100
VOUT = 3.3V
3106 G14
VSTORE/VCAP Efficiency vs
Load Current
0.1
1
10
LOAD CURRENT (mA)
0.1
VSTORE/VCAP = 4.2V
VSTORE/VCAP = 3.1V
VSTORE/VCAP = 2V
3106 G13
0
0.001
100
70
0
0.001
100
60
0.01
VSTORE/VCAP Power Loss vs
Load Current
10
10
70
VSTORE/VCAP = 4.2V
VSTORE/VCAP = 3.1V
VSTORE/VCAP = 2V
3106 G12
VOUT = 3.3V
20
20
30
0
0.001
100
POWER LOSS (mW)
0.1
90
0.1
1
10
LOAD CURRENT (mA)
80
EFFICIENCY (%)
POWER LOSS (mW)
90
1
100
40
VSTORE/VCAP Efficiency vs
Load Current
100
0.1
1
10
LOAD CURRENT (mA)
50
3106 G11
VSTORE/VCAP = 4.2V
VSTORE/VCAP = 3.1V
VSTORE/VCAP = 2V
0.01
60
10
VOUT = 2.2V
0.01
0.001
70
20
3106 G10
10
80
1
VSTORE/VCAP Power Loss vs
Load Current
100
VOUT = 2.2V
90
VSTORE/VCAP = 4.2V
VSTORE/VCAP = 3.1V
VSTORE/VCAP = 2V
0.1
VSTORE/VCAP = 4.2V
VSTORE/VCAP = 3.1V
VSTORE/VCAP = 2V
10
100
VOUT = 1.8V
10
70
VSTORE/VCAP Efficiency vs
Load Current
EFFICIENCY (%)
100
TA = 25°C unless otherwise noted.
VSTORE/VCAP = 4.2V
VSTORE/VCAP = 3.1V
VSTORE/VCAP = 2V
0.01
0.1
1
10
LOAD CURRENT (mA)
100
3106 G17
14
12
10
8
6
4
2
0
1
2
3
4
INPUT VOLTAGE (V)
5
3106 G18
3106f
6
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LTC3106
Typical Performance Characteristics
Normalized VOUT, Accurate RUNTH
vs Temperature
30
10
PERCENT CHANGE (%)
PERCENT CHANGE (%)
20
0
–10
–20
–30
–40
–50 –32 –14 4 22 40 58 76 94 112 130
TEMPERATURE (°C)
3106 G19
1.0
ACCURATE RUN THRESHOLD
0.9
VOUT = 3.3V
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
–0.0
–0.1
–0.2
–0.3
–0.4
–0.5
–50 –30 –10 10 30 50 70 90 110 130 150
TEMPERATURE (°C)
Normalized Input Voltage UVLO
vs Temperature
1.0
0.9
0.8
0.7
PERCENT CHANGE (%)
Normalized RUN Threshold
vs Temperature
TA = 25°C unless otherwise noted.
0.6
0.5
0.4
0.3
0.2
0.1
–0.0
–0.1
–0.2
–50 –30 –10 10 30 50 70 90 110 130 150
TEMPERATURE (°C)
3106 G21
3106 G20
Start-Up Into Resistive Load
L = 10µH
600
1k
Maximum Output Current vs
Input Voltage (VIN)
Maximum Output Current vs
Input Voltage (VSTORE/VCAP)
1k
ILIMSEL = HI
ILIMSEL = HI
RMIN (Ω)
400
300
200
100
10
VOUT = 1.8V
VOUT = 2.2V
VOUT = 3.3V
VOUT = 5V
100
0
0.5
1
1.5
2 2.5 3 3.5 4
INPUT VOLTAGE (V)
4.5
5
1
5.5
0
0.5
1
3106 G22
Normalized VIN Start-Up Voltage
vs Temperature
8
OUTPUT CURRENT (mA)
OUTPUT CURRENT (mA)
500
100
1.5 2 2.5 3 3.5 4
INPUT VOLTAGE, VIN (V)
4.5
100
10
1
1.5
5
3106 G23
Maximum Output Current vs
Input Voltage (VIN)
VOUT = 1.8V
VOUT = 2.2V
VOUT = 3.3V
VOUT = 5V
2
2.5
3
3.5
4
INPUT VOLTAGE, VSTORE/VCAP (V)
4.5
3106 G24
Maximum Output Current vs
Input Voltage (VSTORE/VCAP)
100
6
2
0
–2
–4
–6
10
ILIMSEL = LO
VOUT = 1.8V
VOUT = 2.2V
VOUT = 3.3V
VOUT = 5V
–8
–10
–12
–50 –30 –10 10 30 50 70 90 110 130 150
TEMPERATURE (°C)
3106 G25
OUTPUT CURRENT (mA)
OUTPUT CURRENT (mA)
PERCENT CHANGE (%)
4
1
0
0.5
1
1.5 2 2.5 3 3.5 4
INPUT VOLTAGE, VIN (V)
4.5
5
3106 G26
10
1.5
ILIMSEL = LO
VOUT = 1.8V
VOUT = 2.2V
VOUT = 3.3V
VOUT = 5V
2
2.5
3
3.5
4
INPUT VOLTAGE, VSTORE/VCAP (V)
4.5
3106 G27
3106f
For more information www.linear.com/LTC3106
7
LTC3106
Typical Performance Characteristics
Normalized Output Voltage
Regulation vs Load Current
L = 10µH
LOAD REGULATION (%)
1
COUT = 47µF
ILIMSEL = HI
COUT = 100µF
COUT = 47µF
0.5
0
IL
200mA/DIV
–0.5
–1.0
–1.5
ILOAD
100mA/DIV
–2.0
100µs/DIV
–2.5
–3.0
0.001
0.01
0.1
1
10
LOAD CURRENT (mA)
Normalized MPP Output vs
Temperature
Inductor Current vs Load Current
3106 G29
PERCENT CHANGE FROM 25°C (%)
1.0
TA = 25°C unless otherwise noted.
0
–1
–2
–3
–4
–50 –30 –10 10 30 50 70 90 110 130 150
TEMPERATURE (°C)
100 500
3106 G30
3106 G28
No Load Input Current vs Input
Voltage, MPP Enabled
5VIN to 3.3VOUT Load Step 10mA
to 300mA
700
5VIN to 3.3VOUT Load Step 100µA
to 40mA
COUT = 47µF
COUT = 47µF, ILIMSEL = LO
INPUT CURRENT (µA)
600
500
VOUT
200mV/DIV
400
VOUT
200mA/DIV
VOUT
100mV/DIV
COUT = 100µF
40mA
300mA
300
ILOAD
200mA/DIV
200
100
ILIMSEL = HI
0
0.4
1.3
2.2
3.2
INPUT VOLTAGE (V)
4.1
ILOAD
20mA/DIV
10mA
1ms/DIV
100µA
3106 G32
100µA
5ms/DIV
3106 G33
5
3106 G31
Boost Mode at VIN = 1.5V
VOUT = 3.3V, 100mA
Buck-Boost Mode at VIN = 3.5V
VOUT = 3.3V 100mA
VAUX
50mV/DIV
VAUX
20mV/DIV
VOUT
50mV/DIV
VOUT
100mV/DIV
VAUX
50mV/DIV
VOUT
100mV/DIV
IL
200mA/DIV
IL
400mA/DIV
IL
200mA/DIV
50µs/DIV
L = 10µH
COUT = 47µF
ILIMSEL = HI
Buck Mode at VIN = 4.3V
VOUT = 3.3V, 100mA
50µs/DIV
3106 G34
50µs/DIV
3106 G35
L = 10µH
COUT = 47µF
ILIMSEL = HI
3106 G36
L = 10µH
COUT = 47µF
ILIMSEL = HI
3106f
8
For more information www.linear.com/LTC3106
LTC3106
Typical Performance Characteristics
No-Load Start-Up from Low
Power Source VSTORE = 0V,
VIN = RUN
Buck Mode at VIN = 5V
VOUT = 3.3V, 300mA
VAUX
100mV/DIV
VIN
1V/DIV
IL
200mA/DIV
50µs/DIV
3106 G37
RUN
2V/DIV
5s/DIV
150
VIN = 2V, COUT = 47µF
VIN = 5V, COUT = 47µF
VIN = 2V, COUT = 100µF
VIN = 5V, COUT = 100µF
125
120
100
80
60
40
100
L = 10µH
100
200
VIN = 2V, COUT = 47µF
VIN = 5V, COUT = 47µF
VIN = 2V, COUT = 100µF
VIN = 5V, COUT = 100µF
180
L = 10µH
75
50
3106 G40
200
175
75
0
0.0001 0.001
L = 10µH
VIN = 2V, COUT = 47µF
VIN = 5V, COUT = 47µF
VIN = 2V, COUT = 100µF
VIN = 5V, COUT = 100µF
0.01
0.1
1
LOAD CURRENT (mA)
10
100
3106 G43
RIPPLE VOTLAGE (mVP-P)
125
100
L = 10µH
120
100
80
60
40
0.01
0.1
1
LOAD CURRENT (mA)
10
0
0.0001 0.001 0.01 0.1
1
10
LOAD CURRENT (mA)
100
100
150
125
1k
3106 G42
1.8V Output Voltage Ripple
vs Load Current (ILIMSEL High)
150
25
140
3106 G41
5V Output Voltage Ripple
vs Load Current (ILIMSEL Low)
50
160
VIN = 2V, COUT = 47µF
VIN = 5V, COUT = 47µF
VIN = 2V, COUT = 100µF
VIN = 5V, COUT = 100µF
20
0
0.0001 0.001
1k
3106 G39
5V Output Voltage Ripple
vs Load Current (ILIMSEL High)
1.8V Output Voltage Ripple
vs Load Current (ILIMSEL Low)
100
VIN = 2V, COUT = 47µF
VIN = 5V, COUT = 47µF
VIN = 2V, COUT = 100µF
VIN = 5V, COUT = 100µF
RIPPLE VOTLAGE (mVP-P)
0
0.0001 0.001 0.01 0.1
1
10
LOAD CURRENT (mA)
RIPPLE VOTLAGE (mVP-P)
500µs/DIV
25
20
ILOAD = 30mA
COUT = 47µF
3106 G38
3.3V Output Voltage Ripple
vs Load Current (ILIMSEL Low)
RIPPLE VOTLAGE (mVP-P )
RIPPLE VOTLAGE (mVP-P)
140
VOUT, 3.3V
200mV/DIV
VOUT CHARGING
PGOOD
2V/DIV
3.3V Output Voltage Ripple
vs Load Current (ILIMSEL High)
VIN, 2V
100mV/DIV
RIPPLE VOTLAGE (mVpp)
L = 10µH
COUT = 47µF
ILIMSEL = HI
160
VSTORE, 3V
100mV/DIV
VAUX CHARGING
VOUT, 3.3V
2V/DIV
180
VSTORE to VIN Switchover
PIN = 100µW
VIN_OC = 1.8V
VOUT
50mV/DIV
200
TA = 25°C unless otherwise noted.
L = 10µH
100
75
50
75
VIN = 2V, COUT = 47µF
VIN = 5V, COUT = 47µF
VIN = 2V, COUT = 100µF
VIN = 5V, COUT = 100µF
L = 10µH
50
25
25
0
0.0001 0.001 0.01 0.1
1
10
LOAD CURRENT (mA)
100
1k
3106 G44
0
0.0001 0.001
0.01
0.1
1
LOAD CURRENT (mA)
10
100
3106 G45
3106f
For more information www.linear.com/LTC3106
9
LTC3106
Typical Performance Characteristics
TA = 25°C unless otherwise noted.
5V VIN to 1.8V VOUT Load Step
10µA to 50mA
Output Voltage Ripple
5V VIN, 3.3V VOUT 200mA
5V VIN to 1.8V VOUT Load Step
10µA to 200mA
VAUX CHARGING
VAUX
100mV/DIV
ILOAD
50mA/DIV
VOUT
100mV/DIV
10µA
ILOAD
200mA/DIV
10µA
50mA
COUT = 47µF
3106 G46
ILIMSEL = LOW
500µs/DIV
3106 G47
ILIMSEL = HIGH
Maximum Slew Rate vs Input
Voltage
1k
1.1
1.0
OUTPUT CURRENT (mA)
INPUT VOLTAGE SLEW RATE (V/µs)
1.2
0.8
0.7
0.6
0.5
0.4
0.2
3
3.5
4
4.5
INPUT VOLTAGE VIN (V)
3106 G48
ILIMSEL = HI
100
10
1
VOUT = 1.8V
VOUT = 2.2V
VOUT = 3.3V
VOUT = 5V
0.1
1.5
5
500µs/DIV
Maximum Output Current vs
Input Voltage (VSTORE Shelf Mode)
0.1
0
2.5
COUT = 100µF
VOUT (AC)
100mV/DIV
VOUT (AC)
50mV/DIV
100µs/DIV
10µA
VOUT (AC)
100mV/DIV
COUT = 100µF
ILIMSEL = HIGH
COUT = 100µF
200mA
COUT = 47µF
VOUT (AC)
50mV/DIV
IL
500mA/DIV
10µA
2
3106 G49
Maximum Output Current vs
Input Voltage (VSTORE Shelf Mode)
2.5
3
3.5
4
INPUT VOLTAGE, VSTORE (V)
4.5
3106 G50
Normalized Average Minimum
Operating VSTORE vs Temperature
15.0
100
PRI = HI
10
ILIMSEL = LO
2
VOUT = 1.8V
VOUT = 2.2V
VOUT = 3.3V
VOUT = 5V
2.5
3
3.5
4
INPUT VOLTAGE, VSTORE (V)
4.5
CHANGE IN VSTORE (%)
OUTPUT CURRENT (mA)
12.5
10.0
7.5
5.0
2.5
0
–2.5
–5.0
–50 –30 –10 10 30 50 70 90 110 130 150
TEMPERATURE (°C)
3106 G51
3106 G52
3106f
10
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LTC3106
Pin Functions
(QFN/TSSOP)
NC (Pin 1/Pin 4): No Connect. Not electrically connected
internally. May be connected to PCB ground or left floating.
VOUT (Pin 2/Pin 3): Programmable Output Voltage. Connect
at least a 22μF low ESR capacitor to GND as close to the
part as possible. Capacitor size may increase depending
on output voltage ripple and load current requirements.
VAUX (Pin 3/Pin 5): Auxiliary Voltage. This pin is a generated
voltage rail used to power internal circuitry only. Connect
a 2.2μF minimum ceramic capacitor to GND as close to
the part as possible. Larger capacitors may also be used
depending on the application start-up requirements. If
larger capacitors are used maintain a minimum 10:1 VOUT
to VAUX capacitor value ratio.
VCC (Pin 4/Pin 6): Internal Supply Rail. Do not load. Used
for powering internal circuitry and biasing the programming inputs only. Decouple with a 0.1μF ceramic capacitor
placed as close to the part as possible.
OS1, OS2 (Pins 5, 6/Pins 7, 8): VOUT Select Programming
Inputs. Connect the pins to ground or VCC to program the
output voltage according to Table 1.
PGOOD (Pin 7/Pin 9): Power Good Indicator. Open-drain
output that is pulled to ground if VOUT falls 8% below
its programmed voltage. The PGOOD pin is not actively
pulled to ground in shutdown. If pulled high the PGOOD
pin will float high and will not be valid until 3.5ms after
the part is enabled.
MPP (Pin 8/Pin 10): Set Point Input for Maximum Power
Point Control. Connect a resistor from MPP to GND to
program the activation point for the MPP comparator. To
disable the MPP circuit, connect MPP directly to the VCC pin.
SS1, SS2 (Pins 10, 9/Pins 12, 11): VSTORE Select Programming Inputs. Connect the pins to ground or VCC to
program the VSTORE voltage range according to Table 2.
Only valid if PRI is low. Tie both to ground if PRI is high.
PRI (Pin 11/Pin 13): Primary Battery Enable Input. Tie to
VCC to enable the use of a non-rechargeable primary battery and to disable VSTORE pin charge capability. SS[1:2]
are ignored if PRI = VCC. Tie to GND to use a secondary
battery and enable charging.
ILIMSEL (Pin 12/Pin 14): Current Limit Input Select. Tie
to GND to disable the automatic power adjust feature and
operate at the lowest peak current or tie to VCC to enable
the power adjust feature for operation at higher peak
inductor currents.
RUN (Pin 13/Pin 15): Input to enable the IC and to set
custom VIN undervoltage thresholds. There are two
thresholds on the RUN pin. A voltage greater than 400mV
(typ) will enable certain internal IC functions. The accurate
RUN threshold is set at 600mV and enables VIN as an
input. Tie this pin to VIN or connect to an external divider
from VIN to provide an accurate undervoltage threshold.
Tie to >600mV to allow sub-600mV operation from VIN.
The accurate RUN pin threshold has 50mV of hysteresis
provided internally.
ENVSTR (Pin 14/Pin 16): Enable VSTORE Input. Tie to
VSTORE to enable VSTORE as a backup input. Grounding this
pin disables the use of VSTORE as a backup input source.
GND (Pin 15/Pin 17 and Pin 21 Exposed Pad): Connect
to PCB ground for internal electrical ground connection
and for rated thermal performance.
VIN (Pin 16/Pin 18): Main Supply Input. Decouple with
minimum 10µF capacitor. Input capacitor value may be
significantly larger (>100µF) depending on source impedance and load requirements. If larger capacitors are used a
1µF min ceramic capacitor should be also placed as close
to the VIN pin as possible.
SW1, SW2 (Pins 18, 17/Pins 20, 19): Buck-Boost Converter Switch Pins. Connect inductor between SW1 and
SW2 pins.
VSTORE (Pin 19/Pin 1): Secondary Supply Input. A primary
or secondary rechargeable battery may be connected from
this pin to GND to power the system in the event the input
voltage is lost. When PRI pin is low, current will be sourced
from this pin to trickle charge the storage element up to
the maximum selected storage voltage. When PRI is high
no charging will occur. Tie this pin to VCAP for primary
3106f
For more information www.linear.com/LTC3106
11
LTC3106
Pin Functions
(QFN/TSSOP)
or high capacity secondary battery applications. For low
capacity sources only tie VSTORE directly to the battery.
Tie to GND if unused.
batteries. Tie to VSTORE for primary or high capacity
secondary battery applications. Decouple to GND with a
capacitor large enough to handle the peak load current
from VSTORE. Tie to GND if unused.
VCAP (Pin 20/Pin 2): VSTORE Isolation Pin. Isolates VSTORE
from the decoupling capacitor for low capacity backup
Block Diagram
SW1
VCAP
SW2
SWD2
VBEST
VAUX
VSTORE
AUXSW
SWA2
VIN VCAP
VBEST
VOUT
VBEST
SWA1
VSTR_EN
DRIVERS
SWB
IVAL/IZERO
DETECT
ADJ
VBEST
CNTRL
VCAP
SS2
600mV
RUN
600mV
400mV
VIN
600mV
–
+
VSTORE
COMP
VIN
VOUT
VSTORE
VAUX
SLEEP
COMP
START LOGIC,
CONTROL LOGIC
AND STATE MACHINE
–
+
–
+
UVLO
COMP
THERMAL
SHUTDOWN
MPP
COMP
ENVSTR
VREF
ILIMSEL
VOUT
VOLTAGE
REFERENCE
OS1
FB
OS2
600mV
ADJ
PWR ADJ
PRI
GND
VCC
ACCURATE RUN
COMP
RUN
COMP
ADJ
+
–
VBEST
–
+
– +
IPEAK
DETECT
SWC
SS1
VOUT
SWD1
VCC
+
–
VSTR_EN
+
–
VIN
VIN
+
–
PGOOD
COMP
1.5µA
MPP
OUTPUT
CURRENT
MPP
PGOOD
600mV
3106 BD
3106f
12
For more information www.linear.com/LTC3106
LTC3106
Operation
Simplified Operational Flow Chart Using Accurate RUN with Primary Battery Backup
ENVSTR = VSTORE = VCAP
RUN = VIN OR EXTERNAL DIVIDER TAP
PRI = HI
SHUTDOWN
ENVSTR > 0.8V AND/OR
RUN > ENABLE THRESHOLD (0.4V TYP)
1
VBEST* > 1.5V (MAX)
YES
VIN > ACC. RUN THRESHOLD
OR VIN > VIN(TURNON)**
NO
NO
YES
NO
NO
VIN > VIN START-UP VOLTAGE
(0.85V TYP)
VSTORE > VSTORE(MIN)
1
YES
ASYNCHRONOUS
START-UP
NO
YES
VAUX > VAUX THRESHOLD
VOUT > 1.2V (TYP)
YES
SYNCHRONOUS
SWITCHING
NO
VAUX > 5.2V (TYP)
VOUT IN REGULATION
YES
START
COMPLETE/SLEEP
* VBEST IS THE GREATER OF VAUX,
VIN, VSTORE, VOUT
** VIN(TURNON) = 0.6V • (1 +R1/R2)
3106 SD01
3106f
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13
LTC3106
Operation
Simplified Operational Flow Chart Using VIN UVLO with Primary Battery Backup
ENVSTR = VSTORE = VCAP
RUN > 0.6V (TYPICALLY TIED TO VSTORE)
PRI = HI
SHUTDOWN
ENVSTR > 0.8V AND/OR
RUN > ENABLE THRESHOLD (0.4V TYP)
1
VBEST* > 1.5V (MAX)
YES
VIN > VIN(UVLO)
0.3V (TYP)
NO
NO
NO
NO
VIN > VIN START-UP VOLTAGE
(0.85V TYP)
VSTORE > VSTORE(MIN)
1
YES
ASYNCHRONOUS
START-UP
NO
YES
VAUX = VAUX THRESHOLD
VOUT > 1.2V (TYP)
YES
SYNCHRONOUS
SWITCHING
NO
VAUX > 5.2V (TYP)
VOUT IN REGULATION
YES
START
COMPLETE/SLEEP
* VBEST IS THE GREATER OF VAUX,
VIN, VSTORE, VOUT
3106 SD02
3106f
14
For more information www.linear.com/LTC3106
LTC3106
Operation
Simplified Operational Flow Chart Using Accurate RUN with Rechargeable Battery Backup
ENVSTR = VSTORE = VCAP
RUN = VIN OR EXTERNAL DIVIDER TAP
PRI = GND
SHUTDOWN
ENVSTR > 0.8V AND/OR
RUN > ENABLE THRESHOLD (0.4V TYP)
1
VBEST* > 1.5V (MAX)
YES
VIN > ACC. RUN THRESHOLD
OR VIN > VIN(TURNON)**
NO
NO
YES
NO
NO
VIN > VIN START-UP VOLTAGE
(0.85V TYP)
VSTORE(UV) < VSTORE < VSTORE(OV)
OR NO IF VSTORE LOCKED OUT***
1
YES
ASYNCHRONOUS
START-UP
NO
YES
VAUX = VAUX THRESHOLD
VOUT > 1.2V (TYP)
YES
SYNCHRONOUS
SWITCHING
NO
VAUX > 5.2V (TYP)
VOUT IN REGULATION
YES
VSTORE > VSTORE(OV)
* VBEST IS THE GREATER OF VAUX,
VIN, VSTORE, VOUT
NO
CHARGE VSTORE
YES
** VIN(TURNON) = 0.6V • (1 + R1/R2)
*** VSTORE IS LOCKED OUT AS AN INPUT UNTIL
VAUX = VAUX TH, IF VSTORE IS LESS THAN
VSTORE(UV) WHEN LTC3106 IS FIRST ENABLED
START
COMPLETE/SLEEP
3106 SD03
3106f
For more information www.linear.com/LTC3106
15
LTC3106
Operation
Simplified Operational Flow Chart Using VIN UVLO with Rechargeable Battery Backup
ENVSTR = VSTORE = VCAP
RUN > 0.6V (TYPICALLY TIED TO VSTORE)
PRI = HI
SHUTDOWN
ENVSTR > 0.8V AND/OR
RUN > ENABLE THRESHOLD (0.4V TYP)
1
VBEST* > 1.5V (MAX)
YES
VIN > VIN(UVLO)
0.3V (TYP)
NO
NO
NO
YES
NO
VIN > VIN START-UP VOLTAGE
(0.85V TYP)
VSTORE(UV) < VSTORE < VSTORE(OV)
OR NO IF VSTORE LOCKED OUT***
1
YES
ASYNCHRONOUS
START-UP
NO
YES
VAUX = VAUX THRESHOLD
VOUT > 1.2V (TYP)
YES
SYNCHRONOUS
SWITCHING
NO
VAUX > 5.2V (TYP)
VOUT IN REGULATION
YES
VSTORE > VSTORE(OV)
* VBEST IS THE GREATER OF VAUX,
VIN, VSTORE, VOUT
NO
CHARGE VSTORE
YES
*** VSTORE IS LOCKED OUT AS AN INPUT UNTIL
VAUX = VAUX TH, IF VSTORE IS LESS THAN
VSTORE(UV) WHEN LTC3106 IS FIRST ENABLED
START
COMPLETE/SLEEP
3106 SD04
3106f
16
For more information www.linear.com/LTC3106
LTC3106
Operation
Introduction
The LTC3106 is a high performance two input, synchronous buck-boost converter with low quiescent current
over a wide input voltage range (refer to graph G18). The
PowerPath control architecture allows the use of a single
inductor to generate a user selectable fixed regulated
output voltage through seamless transition between either
of the two power inputs. If input power is available (VIN)
or the backup battery is present (VSTORE), the buck-boost
regulator will operate from VIN providing up to 300mA to
the load. Should the VIN source become unavailable the
regulator will select VSTORE/VCAP as its input delivering up
to 90mA to the load. If a rechargeable battery is used as
the backup source, a low current recharge power path is
also provided allowing use of excess input energy to charge
the backup source if the output voltage is in regulation.
User selectable upper and lower thresholds are available
to handle multiple battery chemistries and to protect the
battery from overcharge/deep discharge. Charging can be
externally disabled using the PRI pin for use of a primary
battery as the backup source.
Both configurations are shown in Figure 1. In either configuration, VCAP is always enabled at start-up if ENVSTR
is high to determine if VCAP is within the programmed
voltage range. If VCAP is below the lower threshold it is
latched off during start-up to minimize quiescent current
draw from VCAP. Since the voltage on VCAP is continually
monitored a very small 100nA typical quiescent current
will persist with VCAP in shutdown (ENVSTR tied to GND).
NONISOLATED
VSTORE/VCAP
BACKUP
POWER
ISHDN = 100nA
LTC3106
VSTORE ILIMSEL
VCAP
VCC FOR IPEAK = 170mA
GND FOR IPEAK = 100mA
ISOLATED
VSTORE/VCAP
BACKUP
POWER
ISHDN = 0.1nA
LTC3106
IPEAK = 100mA
VSTORE ILIMSEL
VCAP
3106 F01
Figure 1. VSTORE/VCAP Configurations
Shutdown
VIN
The main input voltage, VIN, can be configured to operate
over an extended voltage range to accommodate multiple
power source types including but not limited to high impedance sources. An accurate RUN pin allows predictable
regulator turn-on at a specified input voltage. Optional
maximum power point control (MPPC) capability is also
integrated into the LTC3106. Either can be used to ensure
maximum power extraction from non-ideal power sources.
VSTORE/VCAP
A backup source can be tied to VSTORE. As shown in the
Block Diagram, VSTORE can be isolated from VCAP by the
isolation switch for near zero current draw requirements
and lower output current levels. When using the isolation
feature the ILIMSEL pin should be tied to ground due to
the increased series resistance the isolation switch adds.
For typical secondary and primary battery backup applications isolation is not needed, VSTORE and VCAP should
be shorted together. In this configuration the ILIMSEL
feature can be used to increase output current to higher.
Either input source can be enabled independently or together. Bring ENVSTR below the worst-case logic threshold of 0.3V to disable VSTORE/VCAP as input or output if
charging is enabled (PRI low). Bringing ENVSTR below
0.3V will also turn off the isolation switch if the LTC3106
is configured to isolate VSTORE from VCAP.
A low voltage logic input on the RUN pin enables some
circuit functions at 400mV typical while an accurate comparator enables VIN as an input. To disable VIN as an input,
RUN must be below the accurate RUN threshold of 600mV
(typ). To put the LTC3106 in shutdown mode the ENVSTR
pin must be below 0.3V and the RUN pin must be brought
below the worst-case low level logic threshold of 150mV.
Accurate RUN Pin
If RUN is brought below the 500mV accurate comparator
falling threshold, the buck-boost converter will inhibit
switching from VIN. Certain control circuits will remain
powered unless RUN is brought below its low level logic
threshold of 400mV. A small amount of current draw on
VIN will still remain in this mode.
3106f
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17
LTC3106
Operation
With the addition of an optional resistor divider as shown
in Figure 2, the RUN pin can be used to establish a user
programmable turn-on and turn-off threshold. This feature
can be utilized to set an application specific VIN undervoltage threshold or to operate the converter from VIN in a
hiccup mode from very low power sources. If VSTORE/VCAP
is available as a backup power source, VIN input power
priority over VSTORE/VCAP is only given if the RUN pin is
above the accurate threshold.
VIN
R1
0.6V
RUN
R2
0.4V
–
+
VOUT
The main output voltage on VOUT can be powered from
either input power source and is user programmed to one
of four regulated voltages using the voltage select pins
OS1 and OS2, according to Table 1. It is recommended
that OS1 and OS2 be tied to either ground or VCC.
Table 1. Output Voltage Selection
ACCURATE RUN COMP
ENABLE VIN
OS1
OS2
0
0
1.8V
0
VCC
2.2V
VCC
0
3.3V
VCC
VCC
5V
LTC3106
+
–
ENABLE VREF,
CLEAR SHUTDOWN
LOW VOLTAGE LOGIC THRESH
3106 F02
Figure 2. Accurate RUN Pin Comparator
The VIN input is enabled when the voltage on RUN exceeds
0.6V (nominal). Therefore, the turn-on voltage threshold
on VIN can be set externally and is given by:
VOUT. When the VAUX voltage drops to 5.1V typical, input
power is briefly diverted to recharge VAUX.
R1
VIN(TURNON) = 0.6V • 1+
R2
The RUN comparator includes a built-in hysteresis of approximately 100mV, so that the typical turn-off threshold
will be;
R1
VIN(TURNOFF) = 0.5V • 1+
R2
VAUX
VAUX is charged up during start-up and is also refreshed
as necessary from VIN or VSTORE/VCAP during normal
operation. Once VAUX is fully charged or greater than
either input voltage source it will power the LTC3106
active circuitry. The VAUX pin should be bypassed with a
minimum 2.2μF capacitor. Once VAUX reaches 5.2V (typ),
VOUT is allowed to start charging. Although minimized
by design techniques the single inductor architecture
allows some parasitic asynchronous charging of VAUX.
An internal shunt regulator limits the maximum voltage
on VAUX to 5.5V typical and shunts any excess current to
OUTPUT VOLTAGE
VCC
An internal decision circuit determines the voltage on the
VCC pin. VCC is the highest voltage of either VIN, VCAP,
VOUT or VAUX. Although the VCC decision circuit is always
active, when start-up is complete during normal operation
VAUX will equal VCC. VCC should be decoupled with a 0.1µF
capacitor placed as close as possible to the VCC pin. VCC
is not designed to source or sink current externally. VCC
may be used to terminate the LTC3106 logic inputs but
should not otherwise be externally loaded.
High Capacity Secondary Battery Backup
Short VSTORE to VCAP for high capacity (>5mAh) backup
power sources such as rechargeable lithium coin cell
batteries, or primary batteries as shown in Figure 3.
To accommodate a variety of battery chemistries and
maximum voltages the VSTORE/VCAP over and undervoltage
thresholds are user programmed to one of four voltage
ranges using the VSTORE/VCAP select pins SS1 and SS2,
according to Table 2.
Table 2. VSTORE Voltage Selection
PRI
SS1
SS2
VSTORE/
VCAP OV
VSTORE/
VCAP UV
0
0
0
0
0
4V
2.78V
Li Carbon
VCC
2.9V
1.9V
2x Rechargeable NiMH
0
VCC
0
VCC
0
3V
2.15V
Rechargeable Li Coin Cell
VCC
4V
3V
Li Polymer/Graphite
VCC
0
0
4.2V
2.1V
Primary, Non-Rechargeable
BATTERY TYPE
3106f
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LTC3106
Operation
L1
SW1
RECHARGEABLE
BACKUP
SOURCE
+
SW2
VSTORE
LTC3106
VAUX
ENVSTR
C1
+
C2
3106 F03
Figures 3 and 4 show an additional Schottky diode (D1)
from SW2 to VAUX. When charging is enabled (PRI =
GND) the addition of a Schottky diode from SW2 to VAUX
is necessary to prevent a VOUT regulation error caused
by the small parasitic output current resulting from the
LTC3106 charging the secondary battery on VSTORE/VCAP.
The additional diode allows for some inrush current to the
VAUX capacitor C3 from either input source that would have
otherwise been blocked by the AUXSW. Figure 5 shows an
alternate Schottky diode configuration with two additional
external components, Q1 and C4, that will still eliminate
the VOUT regulation error but will also significantly reduce
the inrush current.
L1
SW1
SW2
LTC3106
+
INPUT
SOURCE
ENVSTR
DIS
C1
+
D1
VSTORE
VAUX
C3
VCAP
PRI
VIN
C2
+
INPUT
SOURCE
If secondary battery charging is enabled (PRI = GND)
with both the output and VAUX voltages in regulation,
available input power will be diverted to VSTORE/VCAP
to trickle charge the backup power source with a 30mA
typical current limit. Overcharging of the input source is
prevented by the upper limit threshold setting.
RECHARGEABLE
LOW CAPACITY
SOURCE
VSTORE
ENVSTR
C1
VCAP
Figure 3. High Capacity Battery Configuration
(Shown with VSTORE Enabled)
EN
SW1
SW2
LTC3106
BACKUP
SOURCE
PRI
VIN
3106 F04
Figure 4. Low Capacity Battery Configuration
(Shown with VSTORE Disabled, ENVSTR Tied to Ground)
0.1µF
Q1
D1
C3
VCAP
INPUT
SOURCE
D1
L1
+
VAUX
4.7µF
PRI
VIN
C2
3106 F05
Figure 5. Rechargeable Battery Configuration with
Inrush Current Limiting
Low Capacity Secondary Battery and True Isolation
For very low capacity batteries an isolation switch between
VSTORE and VCAP provides for true input source isolation
and near zero current draw (0.4V typ)
the LTC3106 has a typical start-up voltage of 0.85V with
input currents as low as 15µA or ~12µW of input power.
If the source impedance is high enough to cause VIN to
drop below the VIN comparator threshold, start-up is
terminated until the input capacitance is again charged to
approximately 0.85V. Operation continues in this manner
until start-up is complete. Input source impedance due
to the source itself or due to the input source’s expected
environmental conditions determine the required size
of the input capacitance on VIN to facilitate a successful
start-up. Recommendations are presented in the Input
Capacitor Selection and Typical Applications sections of
this document.
3106f
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LTC3106
Operation
Normal Operation
Boost Mode
When VAUX is in regulation (~5.2V) and VOUT is greater
than 1.2V typical, the converter will enter normal operation.
When VIN < VOUT – 300mV, the LTC3106 operates in
boost or step-up mode. Referring to Figure 6 when VOUT
falls below the programmed regulation voltage, switches
A and C are turned on (VIN is applied across the inductor) and current is ramped until IPEAK is detected. When
this occurs, C is turned off, D is turned on and current is
delivered to the output capacitor (VIN – VOUT is applied
across the inductor). Inductor current falls when D is on,
until an IVALLEY is detected. Terminating at IVALLEY results
in an increased load current capability for a given peak
current. This AC then AD switch sequence is repeated until
the output is pumped above the programmed regulation
voltage, a final IVALLEY is detected, and the part returns
to sleep mode.
Always prioritizing VIN over VCAP, the integrated PowerPath
control circuitry provides seamless transition between input
sources as needed to maintain regulation of the output
voltage and to periodically recharge VAUX.
An accurate comparator is used to monitor the output voltage as it continues to charge to one of the user selected
fixed output voltage values. If VOUT is above this voltage
value no switching occurs and only quiescent current is
drawn from the power source (sleep mode). When VOUT
drops below the fixed output voltage the LTC3106 “wakes
up”, switching commences, and the output capacitor is
again charged. The value of the output capacitor, the load
current, input source and the output voltage comparator
hysteresis (~1%) all determine the number of current pulses
required to pump up the output capacitor before the part
returns to sleep. Normalized input and output voltages
in the various modes as well as typical inductor current
waveforms are shown in Figure 6. Only VIN is shown but
the VSTORE/VCAP power path have the same architecture.
Regions of the current waveforms where switches A and
D are on provide the highest efficiency since energy is
transferred directly from the input source to the output.
VIN
Buck Mode
When VIN > VOUT + 700mV, the LTC3106 operates in buck
or step-down mode. At the beginning of a buck mode cycle
(Figure 6 right side) switches A and D are turned on (VIN
– VOUT is applied across the inductor), current is delivered
to the output and ramped up until IPEAK is detected. When
this occurs, A is turned off, B is turned on and inductor
current falls (–VOUT across the inductor) until an IVALLEY
is detected. This AD then BD switch sequence is repeated
VOUT
VIN
VOUT
A
D1
VIN
L
SW1
B
SW2
C
IMAX
IPEAK
tOFF
tOFF
tOFF
BD AC AD BD AC
BUCK-BOOST MODE
AD
IVALLEY
IZERO
AC AD AC AD
BOOST MODE
AC
AD
BD
AD
BD AD BD
BUCK MODE
3106 F06
Figure 6. Operating Voltage and Current Waveforms
3106f
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21
LTC3106
Operation
until the output is pumped above its regulation voltage, a
final IVALLEY is detected, and the part returns to sleep mode.
Buck-Boost Mode
If (VOUT – 700mV) < VIN < (VOUT + 300mV), the LTC3106
operates in 4-switch step-up/step-down mode. Returning
to Figure 6 (center) when VOUT falls below its regulation
voltage, switches A and C are turned on and current is
ramped until IPEAK is detected. As with boost mode operation, C is then turned off, D is turned on and current is
delivered to the output. When A and D are on, the inductor
current slope is dependent on the relationship between
VIN, VOUT, and the RDS(ON) of the switches. In 4-switch
mode, a tOFF timer is used to terminate the AD pulse.
Once the tOFF timer expires, switch A is turned off, B is
turned on, inductor current is ramped down and VOUT is
applied across the inductor until IVALLEY is detected. This
sequence is repeated until the output is regulated, BD
switches are turned on, and a final IVALLEY is detected.
Anti-cross conduction circuitry in all modes ensures the
P-channel MOSFET and N-channel MOSFET switch pairs
(A and B or D and C) are never turned on simultaneously.
Note all three operational modes function the same if powering from VSTORE/VCAP when VIN is not available. Simply
consider VIN in the preceding paragraphs as VSTORE/VCAP.
Undervoltage Lockout (UVLO)
and Very Low VIN Operation
Maximum Power Point Operation
As an alternative to using an external divider on the RUN
pin (or for maximum power point thresholds below the
600mV RUN pin threshold) the maximum power point control circuit allows the user to set the optimal input voltage
operating point for a given power source. The MPP circuit
hysteretically regulates the average VIN voltage to the MPP
threshold. When VIN is greater than the MPP voltage, input
power is taken from VIN to supply the load. If the VIN power
source does not have enough power for the load it will
decrease. When VIN is less than the MPP threshold voltage
the input transitions to VSTORE/VCAP if available. VIN power
may then recharge the input capacitor voltage and as it rises
above the MPP threshold the process repeats. VIN MPP
regulation is then maintained using this “burst” technique.
If VSTORE is disabled or in undervoltage, no switching
occurs until VIN again rises above the MPP threshold and
only quiescent current is drawn from the power source
(same as sleep mode).
To set the MPP threshold a 1.5µA (typical) source current
is provided at the MPP pin. An external resistor to ground
allows an arbitrary MPP threshold voltage setting. See
Figure 7.
MPP FUNCION
ENABLED
MPP FUNCION
DISABLED
LTC3106
IQ = 10.5µA
LTC3106
IQ = 1.5µA
MPP
R3
There is an undervoltage lockout (UVLO) circuit within
the LTC3106 to allow very low voltage VIN operation.
If the LTC3106 is configured so that the RUN pin is
externally driven to a voltage greater than the 600mV accurate RUN threshold, the VIN UVLO function allows the
input voltage to remain viable as an input source down
to ~250mV. Below this threshold VIN is disabled and the
input source will transition to VSTORE/VCAP, assuming
VSTORE/VCAP is within its programmed range, until VIN rises
above ~300mV, where input power again transitions to
VIN. The VIN input is always given priority over the VSTORE/
VCAP input if VIN is viable.
VCC
MPP
1.2µA
3106 F07
Figure 7. MPP Configurations
Note that when the MPP function is used the nominal
quiescent current increases from 1.5µA (typical) to 10.5µA
(typical). To disable the MPP feature and eliminate the
additional IQ, simply tie MPP to VCC.
PGOOD Comparator
The LTC3106 provides an open-drain PGOOD output that
pulls low if VOUT falls more than 10% (typical) below its
programmed value. When VOUT rises to within 8% (typical)
of its programmed value, the internal PGOOD pull-down
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LTC3106
Operation
will turn off and PGOOD will go high if an external pullup resistor has been provided. An internal deglitch filter
prevents nuisance trips of PGOOD due to short transients
(1mF). A list of high value
storage capacitor manufacture’s is listed in Table 4. For
larger bulk output capacitors an additional low effective
series resistance (ESR) output capacitor of 10μF should
be added and connected as close to the IC pin as possible.
Regardless of its value, the selected output capacitor must
be rated higher than the voltage selected for VOUT by OS1
and OS2. Likewise the selected input capacitor must be
rated higher than the open-circuit voltage of the VIN source.
Table 4. Recommended Bulk Storage Capacitor Vendors
VENDOR
PART
AVX
BestCap Series
TAJ, TPS Series Tantalum
Vishay
595D Series (Tantalum)
153 CRV (Aluminum, Low Leakage)
150 CRZ (Aluminum, Low Leakage)
196 DLC (Double Layer Aluminum)
Illinois Capacitor
RKR Series (Aluminum, Low Leakage)
DCN Series
Cooper Bussman
KR Series
KW Series
PA, PB, PM, PH Series
Cap-XX
G Series (Dual Cell)
H Series (Dual Cell)
VCC Capacitor Selection
The VCC output of the LTC3106 is generated from the greatest of VIN, VCAP, VAUX or VOUT. A low ESR 0.1μF capacitor
should be used. The capacitor should be located close to the
VCC pin and through the shortest ground traces possible.
VAUX Capacitor Selection
A minimum 2.2µF low ESR capacitor must be used to
decouple VAUX although 4.7μF is more typical for many
applications. Smaller capacitor sizes help reduce VOUT
ripple especially at high load currents while larger capacitor
sizes improve start-up at low output voltages. The capacitor should be located as close to the VAUX pin as possible.
As mentioned in the operations section the AUX D switch
and the VOUT D switch are in parallel. Asynchronous diode
conduction will occur when either VAUX or VOUT is being
serviced by the buck/boost circuitry. For this reason it
is recommended to keep a 10:1 ratio of VOUT to VAUX
capacitor to ensure a proper start-up with low voltage,
high impedance sources. Under most load conditions the
output voltage will be maintained normally although under
true zero load conditions ( 0.8V), smaller inductors may be used to provide a
smaller overall footprint. In all cases, the inductor must
have a low DCR and a saturation current rating greater than
the highest typical peak current limit setting as listed in
the Electrical Characteristics table. If the DC resistance of
the inductor is too high, efficiency will be reduced and the
minimum operating voltage will increase. Note the inductor
value will have a direct effect on the switching frequency.
Table 5. Inductor Vendor Information
VENDOR
PART
Coilcraft
www.coilcraft.com
EPL2014, EPL3012, EPL3015,
LPS3015, LPS3314, XFL3012
Coiltronics
www.cooperindustries.com
SDH3812, SD3814, SD3114, SD3118
Murata
www.murata.com
LQH3NP, LQH32P, LQH44P
Sumida
www.sumida.com
CDRH2D16, CDRH2D18, CDRH3D14,
CDRH3D16
Taiyo-Yuden
www.t-yuden.com
NR3012T, NR3015T, NRS4012T,
BRC2518
TDK
www.tdk.com
VLS3012, VLS3015, VLF302510MT,
VLF302512MT
Toko
www.tokoam.com
DP3015C, DB3018C, DB3020C,
DP418C, DP420C, DEM2815C,
DFE322512C, DFE252012C
Würth
www.we-online.com
WE-TPC 2813, WE-TPC 3816,
WE-TPC 2828
Maximum Power Point Threshold Configuration
There are two methods for maintaining the maximum
power point of an input source on VIN. Already discussed
in this data sheet is a resistive divider on the RUN pin
monitoring VIN. This is useful for >600mV MPP set points.
The LTC3106 also has a dedicated MPP function that can
be used over the full input voltage range as well as input
voltages between the UVLO and RUN pin thresholds. Note
that the LTC3106 IQ increases from 1.6µA (typ) to 10.6µA
(typ) if the MPPC pin functionality is enabled.
The MPP circuit hysteretically controls VIN by setting
a lower voltage threshold on the MPP pin. If VIN drops
below the MPP threshold the converter will stop drawing power from VIN and force a sleep signal. If VSTORE is
within the proper operating range, the output power will
then be taken from VSTORE. If however there is not a valid
3106f
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LTC3106
Applications Information
backup source or if the ENVSTR is low the LTC3106 will
go to sleep and no power will be available to VOUT until
VIN charges the input capacitor voltage above the MPP
threshold. If more power is available at VIN than is needed
to supply VOUT, VIN could rise above the MPP threshold to
the open-circuit voltage of source. This is normal as long
as the open-circuit voltage is below the maximum allowed
input voltage. The MPP pin voltage is set by connecting
a resistor between the MPP pin and GND, as shown in
Figure 4. The MPP voltage is determined by the equation:
The application circuit in Figure 9 shows the LTC3106
interfaced with the AM-1816 solar cell supplemented with
a CR2032 primary battery configured to deliver power
to a pulsed load output. Though an energy harvesting
system can eliminate the need for batteries, it also serves
to supplement and increase battery life. When enough
ambient energy is available the battery is unloaded and
is only used when the ambient source is inadequate, not
only extending battery life but improving reliability. Even
when battery use is necessary, the PRI pin configures the
VSTORE input for use of a primary battery, here the CR2032,
extending the input voltage range, thereby increasing use
of the available capacity than would be possible with a
direct battery-MCU connection.
VMPP = 1.5μA • RMPP (MΩ)
Disable the MPP function by tying the MPP pin to VCC.
Design Example 1: Photovoltaic or Solar Energy
Harvesting with Primary Battery Backup
The main input voltage, VIN, of the LTC3106 is designed
to accommodate high impedance solar cells over a wide
voltage range. Solar cells are classified according to their
output power level, material employed (crystal silicon,
amorphous silicon, compound semiconductor) and application space (indoor or outdoor lighting). Sanyo Electric’s
Amorton product line (a subsidiary of Panasonic) offers a
variety of solar cells for various light conditions (For typical
light conditions see Table 6) and power levels as well the
ability to customize cells for specific application size and
shapes. An additional list of companies that manufacture
small solar cells (also referred to as modules or solar
panels) suitable for use with the LTC3106 is provided in
Table 7.
In traditional battery hyp. only wireless nodes the main
control unit (MCU) is connected directly to the battery.
Several factors contribute to reduced battery capacity in
these applications. Typically these wireless systems poll
the node at a very low frequency with long low power
inactive periods and occasional high current bursts when
communicating with the node. The peak current during the
pulsed load is much greater than the nominal drain current given by the battery manufacturer reducing capacity
beyond that specified at the typical static drain current.
Further, the usable input voltages for most MCUs (2V min
typ) limit the usable capacity.
10µH
3V
CR2032 +
LITHIUM
COIN CELL
47µF
SW1
VSTORE
VCAP
ENVSTR
SW2
VAUX
2.2µF
LTC3106
VIN THRESHOLD = 3.8V MIN
+
VOC = 4.9V SANYO
ISC = 82µA AM1816
100µF
6.3V
×3
10M
10µF
47µF
PGOOD
VIN
2M
365k
3.3V, ~200µW
VOUT
VIN
0.01µF
RUN
VCC
PRI
ILIMSEL
GND
MPP
OS1
OS2
SS1
SS2
VDD Tx
EN
GND
VCC
3106 F09
Figure 9. Solar Harvester with Primary Battery Backup
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LTC3106
Applications Information
1.0
Table 6. Typical Light Conditions
0.9
Meeting Room
200
0.8
Corridor
200
0.6
Office Desk
400 to 700
Lab
500 to 1000
Outdoors (Overcast)
1000 to 2000
Outdoors (Clear)
>2000
IPANEL (mA)
ILLUM. (Lux)
http://panasonic.net/energy/amorton/en/
PowerFilm
http://www.powerfilmsolar.com/
G24 Power
http://www.gcell.com/
SolarPrint
http://www.solarprint.ie/
Alta Devices
http://www.altadevices.com
1000 LUX
0.5
500
LUX
0.4
0.3
200 LUX
0.1
Table 7. Small Photovoltaic Panel Manufacturers
Sanyo
Sanyo 1816
1800 LUX
PPANEL (mW)
LOCATION
0
0
0.7
1.5
2.2 3.0 3.7
VPANEL (V)
4.4
5.2
5.9
3106 F10
Figure 10. Measured I-V and P-V Curves
Under Variable Light Conditions
The I-V and P-V curve for the AM-1816 panel is shown
in Figure 10. The maximum power from the cell (PMAX)
changes with light level but the voltage at PMAX changes
only slightly. The VIN threshold voltage in this application
example is set to equal the voltage at PMAX using the
resistive divider on the RUN pin. 4.2V is chosen for the
VIN(OV) set point so that it is slightly below. With internal
hysteresis the VINUV is then 3.8V so the average VIN
voltage of ~4V is at the maximum power point from the
manufacturer I-V and P-V data on the AM-1816 solar cell.
Note the RUN pin resistive divider will add a VIN dependent load on the input source. The divider current would
be equal to:
IINDIV(STATIC)
4V
= 1.6µA
(2.21M+ 432k)
In this application the load is a low power proprietary RF
profile (Figure 11). The regions of operation are described,
output and power losses are tabulated and the peak levels
for each are given in Table 8. The total average output power
needed in this application can be calculated to be 191µW.
Table 8. Application Load Profile Power Budget for Figure 11
REGION
INTERVAL Tn CHARGE InTn DUTY CYCLE
(ms)
(µC)
(%)
INTERVAL
MCU
FUNCTION
PEAK
CURRENT In
(mA)
Region 1
Wake
0.3
1
0.3
0.1
INTERVAL
OUTPUT
POWER
(mW)
1.0
LTC3106
POWER
AVERAGE
LOSS (FROM
OUTPUT
CURVES)
POWER (µW)
(mW)
1
0.2
LTC3106
AVERAGE
POWER
LOSS (µW)
0.2
Region 2
Pre-Processing
8
0.6
4.8
0.1
26.4
16
3
1.8
Region 3
Rx/Tx
20
1
20
0.1
66.0
66
5
5.0
Region 4
Processing
8
0.5
4
0.0
26.4
13
3
1.5
Region 5
Rx/Tx
20
1
20
0.1
66.0
66
5
5.0
Region 6
Sleep/Idle
0.001
1000
1
99.5
0.003
3
0.02
19.9
Total Period: 1004ms
Total Avg Power: 165µW
Total Avg. Power Loss: 37µW
3106f
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LTC3106
Applications Information
CURRENT
ACTIVE
ACTIVE
ACTIVE
INACTIVE/
SLEEPING
INACTIVE/
SLEEPING
ACTIVE
INACTIVE/
SLEEPING
TA
TB
TIME
CURRENT
IPK2
IPK1
IBACK
REGION 1
T1
REGION
2
REGION 3
T2
REGION
4
T3
REGION 5
T4
REGION 6
T5
T6
TIME
3106 F11
Figure 11. Application Load Profile for Schematic in Figure 8
The total average LTC3106 power loss over the same
regions of operation for the load profile is 37µW. The divider load adds an additional 5µW of input power loss for
a total input power requirement of 207µW. The calculated
average efficiency, including the resistive divider is then
η = 165µW/207µW which is 80%. The available power from
the AM-1816 at 200lux is about 400µW. With a converter
efficiency of about 80% the 400µW will power the total
207µW average load with some margin. If the light conditions become less favorable the available input power may
drop below that needed to maintain the output voltage.
The LTC3106 configuration in Figure 9 will operate with
VIN in “hiccup” mode turning on as VIN increases above
4.2V and turning off if VIN droops below 3.8V. With VIN
off, power is then taken from VSTORE until VIN recovers
and increases above the 4.2V threshold.
If the light conditions become more favorable VIN will
rise to the open-circuit voltage of the harvested source.
Note if the open-circuit voltage of the harvested source
will exceed the maximum voltage rating, an appropriate
clamp should be added to prevent damage to the LTC3106.
Figure 10 shows the open-circuit voltage of the AM-1816
can be greater than 5V. If full light is expected, a low
reverse leakage current Zener diode is recommended to
clamp VIN. The DZ23, AZ23 and GDZ series with a Zener
voltage of 4.7V or 5.1V are a good choice.
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29
LTC3106
Applications Information
To optimize use of the harvested source and increase the
battery life of the backup source it is important to size the
input capacitor to handle the average power load for the
load profile at the lowest light level. Referring again to
Table 8 to sum the required charge for the load and using
the input capacitor sizing equation:
C VIN =
(2/η• VOUT • ΣlnTn ) (µF )
(V
IN(OV)
2
– VIN(UV)2
)
Peltier cells are available in a wide range of sizes and power
capabilities, from less than 10mm square to over 50mm
square. They are typically 2mm to 5mm in height. A list
of Peltier cell manufacturers is given in Table 9.
Table 9. Peltier Cell Manufacturers
Micropelt
www.micropelt.com
CUI, Inc
www.cui.com (Distributor)
The average efficiency (η) with VIN = 4.2V and VOUT =
3.3V is 0.8. The VIN(OV) and VIN(UV) thresholds are already
determined and ∑InTn can be found in the load profile table.
CVIN is found to be 184µF. A single 220µF low leakage
Tantalum chip capacitor could be used. For the lowest
leakage solution and to add design margin 2× 100µF,
6.3V, ±10% ceramic capacitors are selected.
If the VIN source is unavailable the primary battery on
VSTORE will continue to supply the load. To offload the peak
current load from the battery and minimize the effect of
high peak currents degrading the rated battery capacity the
lowest peak current setting on the LTC3106 is chosen. In
addition, the VSTORE capacitor design should follow that of
the VIN capacitor. Using the same method but replacing the
OV and UV thresholds with the max and min VSTORE input
voltages the value of the VSTORE capacitor is calculated to
be 38µF. For design margin a low ESR 10V, 47µF ceramic
capacitor is used.
Design Example 2: Thermoelectric Harvesting from
Peltier cell (TEG) with Rechargeable Battery Backup
A Peltier cell (also known as a thermoelectric cooler) is made
up of a large number of series-connected P-N junctions,
sandwiched between two parallel ceramic plates. Although
Peltier cells are often used as coolers by applying a DC
voltage to their inputs, they will also generate a DC output
voltage, using the Seebeck effect, when the two plates are
at different temperatures. The polarity of the output voltage
will depend on the polarity of the temperature differential
between the plates. The magnitude of the output voltage
is proportional to the magnitude of the temperature differential between the plates. In this manner, a Peltier cell
is referred to as a thermoelectric generator (TEG).
Fujitaka
www.fujitaka.com/pub/peltier/english/thermoelectric_power.html
Ferrotec
www.ferrotec.com/products/thermal/modules
Kryotherm
www.kryothermusa.com
Laird Technologies
www.lairdtech.com
Marlow Industries
www.marlow.com
Nextreme
www.nextreme.com
TE Technology
www.tetech.com/Peltier-Thermoelectirc-Cooler-Modules.html
Tellurex
www.tellurex.com
The low voltage capability of the LTC3106 design allows
it to operate from a TEG with temperature differentials as
low as 20°C, making it ideal for harvesting energy in many
industrial applications in which a temperature difference
exists between two surfaces or between a surface and the
ambient environment.
The application circuit in Figure 12 shows the LTC3106
interfaced with a TEG supplemented with a Li-ion rechargeable (secondary) battery, both configured to deliver power
to a low power pulsed load output. With the RUN pin connected to VSTORE, the application circuit is configured to
take advantage of the 300mV input voltage UVLO. In this
configuration VIN will operate in “hiccup” mode turning on
as VIN increases above 0.3V and turning off if VIN droops
50mV below 0.3V to maintain an average power to the
output without allowing the input to fall to zero. Assuming
a good battery voltage the output power will be supplied by
the battery when the input voltage drops below the UVLO
threshold and transition back to the input when the input
charges up above the UVLO threshold.
3106f
30
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LTC3106
Applications Information
In addition to providing power to the output when the
harvested power is not adequate, the secondary battery
also provides a reservoir for excess harvested energy.
If the output is in regulation harvested power is diverted
to charge the secondary battery. The maximum charge
voltage and low battery threshold are programmed by
the SS1 and SS2 pins. In Figure 12 SS1 and SS2 are
configured to provide a worst-case upper threshold of
4.16V and a worst-case low battery threshold of 2.88V
(refer to Table 2). Charging of the secondary battery
will terminate at the upper threshold to prevent excessive battery voltage. Since the ENVSTR pin is held high
in this application, a prolonged absence of harvested
power results in the output being maintained solely by
the battery.
With VCAP and VSTORE connected together, the battery
will be disconnected from the internal power path at the
low battery threshold to protect Li-Ion batteries from
permanent damage due to deep discharge. A low ESR
10µF capacitor is used to decouple the VSTORE/VCAP pin.
Similar to the previous design example the load profile
is another low power proprietary RF profile (Figure 13).
The RxTx rate of this load pulse is 2 seconds. The regions
of operation are described, output and power losses are
tabulated and the peak levels for each are given in Table 10.
The total average output power needed in this application
can be calculated to be 42µW.
The total average LTC3106 power loss over the same
regions of operation for the load profile is 31µW. The
total input power requirement is 73µW. The calculated
average efficiency, including the resistive divider is then
η = 42µW/73µW which is 0.58. Although this may seem
low it is important to realize the load current is quite low
(2µA) a majority of the time (sleep/idle region) where the
average power loss from the LTC3106 is only 20µW.
To minimize use of the secondary battery and prolonging
its long term lifetime, it is important to optimize the use
of the harvested source by dimensioning the input capacitor to handle the average power load for the load profile
at the lowest temperature differential. Referring again to
10µH
PANASONIC NCR18650B
LITHIUM ION
CELL
+
47µF
SW1
VSTORE
VCAP
ENVSTR
RUN
SW2
VAUX
ZLLS400
SCHOTTKY
2.2µF
LTC3106
MARLOW TEG
RC12-2.5-01LS
WITH 40MM × 40MM × 35MM
FINNED HEATSINK
+
0.3V TO 3.5V
+
470µF
6.3V
×2
3.3V, ~50µW
VOUT
VIN
10M
10µF
47µF
PGOOD
0.01µF
VCC
PRI
ILIMSEL
GND
MPP
OS2
OS1
SS2
SS1
VDD Tx
EN
GND
VCC
VCC
3106 F12
Figure 12. TEG Harvester with Secondary Battery Backup
3106f
For more information www.linear.com/LTC3106
31
LTC3106
Applications Information
Table 11 to sum the required charge for the load and using
the input capacitor sizing equation:
C VIN =
(2/η• VOUT • ΣlnTn )
(V
INOV
2
– VINUV 2
)
The chosen capacitor should be rated for a voltage greater
than the maximum open-circuit voltage of the harvested
source and/or clamped to an appropriate voltage. If the
open circuit TEG voltage is expected to be greater than the
maximum rating of the input pin, it is recommended that
a low reverse leakage current 4.7V or 5.1V Zener diode
be used to clamp VIN.
Table 11. Low Capacity Li-Ion and Thin Film Battery
Manufacturers
VENDOR
PART
CYMBET
EnerChip CBC Series
Infinite Power Solutions
THINERGY MEC2000 and MEC100 Series
GM Battery
GMB and LiPo Series
Large value storage capacitor manufactures are listed
in Table 4. The application in Figure 12 uses 2× 470µF
Tantalum chip capacitors.
The average efficiency (η) with VIN(OV) = 0.3V and VIN(UV)
= 0.25V, the input UVLO upper and lower thresholds respectively, and a VOUT of 3.3V is the already calculated η
= 0.58. The ∑InTn can be found in the load profile table.
CVIN is then found to be 973µF. At such low harvested
power levels, the input capacitor values can be quite large.
The available power from the TEG at the lowest temperature
differential (dt = 20°C) is about 200µW, enough to power
the total 42µW average load with some margin.
If the conditions become less favorable the available input
power may drop below that is needed at the output, VIN
will drop below the UVLO threshold turning off VIN. With
VIN off, power is then taken from VSTORE until VIN recovers
and increases above the UVLO threshold.
CURRENT
IPK3
IPK2
IPK1
IBACK
REGION 1
REGION 2
T1
REGION
4
REGION 3
T2
T3
REGION 5
T4
T5
TIME
3106 F13
Figure 13. Application Load Profile
3106f
32
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LTC3106
Applications Information
If conditions become more favorable the input capacitor
will charge to a higher voltage terminating at the opencircuit voltage of the harvested source. When the output
is idle under these conditions, excess energy is used to
maintain the charge on the VSTORE battery. Any remaining
excess energy will be stored on the input capacitor and
VIN will rise to the open-circuit voltage of the harvested
source. As already mentioned, if the open-circuit voltage
of the harvested source will exceed the maximum voltage
rating of the pin an appropriate clamp should be added to
prevent damage to the LTC3106.
Most MCUs, even low power wireless specific MCUs,
still load the LTC3106 output with a small current. If,
however, the load current will be less than 400nA the
output regulation error can increase to 5% of the nominal
output voltage depending on sleep period and the size of
the output capacitor.
Table 10. Application Load Profile Power Budget for Figure 11
INTERVAL
PEAK
REGION
CURRENT In INTERVAL Tn CHARGE InTn DUTY CYCLE
MCU FUNCTION
(mA)
(ms)
(µC)
(%)
INTERVAL
OUTPUT
POWER
(mW)
0.007
AVERAGE
OUTPUT
POWER (µW)
LTC3106
POWER
LOSS (FROM
CURVES)
(mW)
LTC3106
AVERAGE
POWER LOSS
(µW)
7
0.2
20.0
Region 1
Sleep/Idle
0.002
2000
4
99.85
Region 2
Pre-Processing
1.7
0.6
1.02
0.03
56
2
3
0.9
Region 3
Tx
17
1
17
0.05
53.1
28
5
7.5
Region 4
Rx
4
0.5
2
0.02
13.2
3
3
1.2
Region 5
Post-Processing
1.7
1
1.7
0.05
5.6
3
5
1.5
Total Period: 2003ms
Total Avg Power: 42.37µW
Total Avg. Power Loss: 31µW
3106f
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33
LTC3106
Typical Applications
The circuit in Figure 14 is a practical example of simple
energy harvesting. The LTC3106 is powered from the
USB bus power when the USB interface is connected for
data transfer to a host. When the USB power is available
VSTORE is disabled as an input, output power will come
from VIN and charging of the battery will occur when
VOUT and VAUX are in regulation. The battery may also
be charged from ambient light on the Sanyo AM-1454
solar cell when the device used to collect data remotely,
extending battery life and the time required between USB
connections. Note that the D01 output from the monitor
goes high and dials the LTC3106 peak current limit higher
when USB power is available.
harvester node and stored with a full charge for some time.
When enabled the battery will supplement the harvested
source and will be recharged with any surplus harvested
energy. A list of thin-film battery manufacturers is listed
in Table 11.
The circuit in Figure 17 shows the LTC3106 configured to
harvest solar energy when possible to prolong the time
before battery service is necessary. The resistive divider
on RUN sets the optimal minimum operating point for the
solar cell on VIN. When available, harvested power on VIN
supplements the power available from the primary battery
extending the life of the battery.
D1
10µH
Figure 15 shows the LTC3106 as a simple dual input, 2.2V
buck-boost converter. One input is from a 5V wall adaptor
and the other from a 3V rechargeable lithium coin cell.
Figure 15 also shows an example of the optional external
inrush current limiting circuit to VAUX.
Li RECHARGEABLE
BATTERY
47µF
VIN
0.1µF
Q1
SW2
VAUX
2.2µF
LTC3106
(3.7V TURN ON)
5V
To take advantage of the very low discharge rate and long
shelf life of low capacity thin film batteries the application
in Figure 16 shows use of the Shelf mode functionality. An
external switch allows the VSTORE pin to be disconnected
from the external bypass capacitor on VCAP as well the
internal power path and threshold detection circuitry
thereby reducing battery discharge to VSTORE pin leakage
plus the self-discharge of the battery itself. A factory
“pre-charged” battery could then be assembled into the
+
SW1
VSTORE
VCAP
ENVSTR
2.2V (300mA)
VOUT
22µF
10M
47µF
PGOOD
2.21M
RUN
VCC
432k
ILIMSEL
MPP
VCC
OS2
SS1
PRI
OS1
GND SS2
0.01µF
3106 F15
D1: DIODES INC ZLLS400
Q1: ZETEX ZMX61P03F
Figure 15. 5V to 2.2V Converter with Rechargeable Battery
Backup and Inrush Current Limiting
10µH
+
NiMH
×2
4.7µF
SW1
VSTORE
VCAP
ENVSTR
SW2
VAUX
ZLLS400
SCHOTTKY
2.2µF
MONITOR PROCESSING
LTC3106
USB BUS
POWER
VOC = 2.4V
ISC = 35µA
VOUT
VIN
SANYO
AM1454
+
4700µF
6.3V
2.21M
1.33M
10M
10µF
VIN
0.1µF
3.3V (90mA/300mA)
47µF
GND
MPP
OS1
SS2
OS2
SS1
MCU
DISPLAY
SENSOR(S)
DATA
EN
DO1
PGOOD
ILMSEL
RUN
VCC
PRI
VDD
GND
VCC
USB
POWER
USB I/O
3106 F14
Figure 14. Portable Medical Device with Ambient Light Harvester or USB Powered Charging
3106f
34
For more information www.linear.com/LTC3106
LTC3106
Typical Applications
10µH
THINERGY
MEC201-10STR
SW1
VSTORE
+
SHELF
MODE
47µF
ZLLS400
SCHOTTKY
SW2
VAUX
4.7µF
ENVSTR
VCAP
WIRELESS SENSOR NODE
LTC3106
VIN THRESHOLD = 3.6V
+
POWERFILM
MPT3.6-75
100µF
6.3V
×2
47µF
1M
1µF
VDD
EN
2.21M
0.01µF
RUN
VCC
MPP
OS2
OS1
PRI
ILIMSEL
SS2
SS1
GND
MCU
SENSOR(S)
PGOOD
VIN
432k
3.3V, (180µW)
VOUT
VIN
GND
VCC
3106 F16
Figure 16. Remote Outdoor Solar Powered Harvester with Thin Film Battery Backup
10µH
3.6V
LITHIUM THIONYL +
CHLORIDE AA CELL
VCELL
SANYO
AM-1815
1µF
47µF
SW1
VSTORE
VCAP
ENVSTR
SW2
VAUX
4.7µF
LTC3106
+
100µF
6.3V
×2
VIN
3V
VOUT
1µF
47µF
1M
PGOOD
2.21M
402k
0.1µF
RUN
VCC
MPP
OS2
OS1
PRI
ILIMSEL
SS2
SS1
VSUPPLY ANTENNA
LNA_EN
LTC5800
GND
VCC
3106 F17
GND
Figure 17. Extended Life Battery Powered Mote for Wireless Mesh Network
3106f
For more information www.linear.com/LTC3106
35
LTC3106
Package Description
Please refer to http://www.linear.com/product/LTC3106#packaging for the most recent package drawings.
UDC Package
20-Lead Plastic QFN (3mm × 4mm)
(Reference LTC DWG # 05-08-1742 Rev Ø)
0.70 ±0.05
3.50 ±0.05
2.10 ±0.05
1.50 REF
2.65 ±0.05
1.65 ±0.05
PACKAGE OUTLINE
0.25 ±0.05
0.50 BSC
2.50 REF
3.10 ±0.05
4.50 ±0.05
RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS
APPLY SOLDER MASK TO AREAS THAT ARE NOT SOLDERED
3.00 ±0.10
0.75 ±0.05
1.50 REF
19
R = 0.05 TYP
PIN 1 NOTCH
R = 0.20 OR 0.25
× 45° CHAMFER
20
0.40 ±0.10
1
PIN 1
TOP MARK
(NOTE 6)
4.00 ±0.10
2
2.65 ±0.10
2.50 REF
1.65 ±0.10
(UDC20) QFN 1106 REV Ø
0.200 REF
0.00 – 0.05
R = 0.115
TYP
0.25 ±0.05
0.50 BSC
BOTTOM VIEW—EXPOSED PAD
NOTE:
1. DRAWING IS NOT A JEDEC PACKAGE OUTLINE
2. DRAWING NOT TO SCALE
3. ALL DIMENSIONS ARE IN MILLIMETERS
4. DIMENSIONS OF EXPOSED PAD ON BOTTOM OF PACKAGE DO NOT INCLUDE
MOLD FLASH. MOLD FLASH, IF PRESENT, SHALL NOT EXCEED 0.15mm ON ANY SIDE
5. EXPOSED PAD SHALL BE SOLDER PLATED
6. SHADED AREA IS ONLY A REFERENCE FOR PIN 1 LOCATION
ON THE TOP AND BOTTOM OF PACKAGE
3106f
36
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LTC3106
Package Description
Please refer to http://www.linear.com/product/LTC3106#packaging for the most recent package drawings.
FE Package
20-Lead Plastic TSSOP (4.4mm)
(Reference LTC DWG # 05-08-1950 Rev Ø)
Exposed Pad Variation CC
6.40 – 6.60*
(.252 – .260)
2.74
(.108)
2.74
(.108)
20 1918 17 16 15 14 13 12 11
6.60 ±0.10
2.74
4.50 ±0.10 (.108)
6.40
2.74 (.252)
(.108) BSC
SEE NOTE 4
0.45 ±0.05
1.05 ±0.10
0.65 BSC
1 2 3 4 5 6 7 8 9 10
RECOMMENDED SOLDER PAD LAYOUT
4.30 – 4.50*
(.169 – .177)
0.09 – 0.20
(.0035 – .0079)
0.25
REF
0.50 – 0.75
(.020 – .030)
NOTE:
1. CONTROLLING DIMENSION: MILLIMETERS
MILLIMETERS
2. DIMENSIONS ARE IN
(INCHES)
3. DRAWING NOT TO SCALE
1.20
(.047)
MAX
0° – 8°
0.65
(.0256)
BSC
0.195 – 0.30
(.0077 – .0118)
TYP
0.05 – 0.15
(.002 – .006)
FE20(CC) TSSOP REV Ø 0413
4. RECOMMENDED MINIMUM PCB METAL SIZE
FOR EXPOSED PAD ATTACHMENT
*DIMENSIONS DO NOT INCLUDE MOLD FLASH. MOLD FLASH
SHALL NOT EXCEED 0.150mm (.006") PER SIDE
3106f
Information furnished by Linear Technology Corporation is believed to be accurate and reliable.
However, no responsibility is assumed for its use. Linear Technology Corporation makes no representaFor more
information
www.linear.com/LTC3106
tion that the interconnection
of its circuits
as described
herein will not infringe on existing patent rights.
37
LTC3106
Typical Application
Simple Wide Input Voltage Buck-Boost Converter
10µH
SW1
VSTORE
VCAP
ENVSTR
VIN
0.6V TO 5V
(0.85V TO START)
SW2
VAUX
2.2µF
LTC3106
VOUT
22µF
10M
47µF
1.8V
300mA
PGOOD
RUN
0.01µF
VCC
PRI
ILIMSEL
GND
MPP
OS2
OS1
SS2
SS1
VCC
3106 TAo2
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PART NUMBER
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COMMENTS
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