LTC3106
1
3106f
For more information www.linear.com/LTC3106
Typical applicaTion
FeaTures DescripTion
300mA Low Voltage
Buck-Boost Converter with
PowerPath and 1.6µA Quiescent Current
The LT C
®
3106 is a highly integrated, ultralow voltage buck-
boost DC/DC converter with automatic PowerPath man-
agement 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.
If the primary power source is unavailable, the LTC3106
seamlessly switches to the backup power source. The
LTC3106 is compatible with either rechargeable or pri-
mary 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 volt-
age 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 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 VOUT and VSTORE
n Maximum Power Point Control
n Ultralow Quiescent Current: 1.6μA
n Regulated Output with VIN or VSTORE 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
n Wireless Sensor Networks
n Home or Office Building Automation
n Energy Harvesting
n Remote Sensors
L, LT , LT C , LT M , 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.
Efficiency vs Input Voltage
Solar Cell Input with Primary Battery Backup
+
+
10µH
VSTORE
VCAP
ENVSTR
RUN
VCC
PRI
VAUX
TL-5955
PRIMARY
BATTERY
3.6V
600mV TO 5V
PV CELLS
VOUT
PGOOD
MPP
ILIMSEL
GND
LTC3106
VIN
1M
VCC
PGOOD
3106 TA01a
2.2µF
47µF
3.3V
50mA
10µF
1µF
0.01µF
470µF
SW1 SW2
V
IN
EFF.
V
IN
P.L.
V
STR
EFF.
V
STR
P.L.
INPUT VOLTAGE (V)
0.5
1
1.5
2
2.5
3
3.5
4
4.5
5
5.5
40
45
50
55
60
65
70
75
80
85
90
95
100
0
10
20
30
40
50
60
70
80
90
100
110
EFFICIENCY (%)
POWER LOSS (mW)
LTC3106 TA01b
IOUT = 50mA
LTC3106
2
3106f
For more information www.linear.com/LTC3106
pin conFiguraTion
absoluTe MaxiMuM raTings
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
(Notes 1, 6)
20 19 18 17
7 8
TOP VIEW
21
GND
UDC PACKAGE
20-LEAD (3mm × 4mm) PLASTIC QFN
9 10
6
5
4
3
2
1
11
12
13
14
15
16
NC
VOUT
VAUX
VCC
OS1
OS2
VIN
GND
ENVSTR
RUN
ILIMSEL
PRI
VCAP
VSTORE
SW1
SW2
PGOOD
MPP
SS2
SS1
TJMAX = 125°C, θJA = 52°C/W, θJC = 7°C/W (Note 5)
EXPOSED PAD (PIN 21) IS GND, MUST BE SOLDERED TO PCB
FE PACKAGE
20-LEAD PLASTIC TSSOP
1
2
3
4
5
6
7
8
9
10
TOP VIEW
20
19
18
17
16
15
14
13
12
11
VSTORE
VCAP
VOUT
NC
VAUX
VCC
OS1
OS2
PGOOD
MPP
SW1
SW2
VIN
GND
ENVSTR
RUN
ILIMSEL
PRI
SS1
SS2
21
GND
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 LT C 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.
Storage Temperature Range .................. –65°C to 150°C
Lead Temperature (Soldering, 10 sec)
FE Package ....................................................... 300°C
LTC3106
3
3106f
For more information www.linear.com/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 CONDITIONS MIN TYP MAX UNITS
VIN Start-Up Voltage Start-Up from VIN, VOUT = VAUX = VSTORE = 0V, RUN = VIN l0.85 1.2 V
VIN Maximum Operating Voltage 5.1 V
VIN Minimum Operating Voltage VSTORE in Operating Voltage Limits, RUN > 0.613V,
ENVSTR Pin > 0.8V (Minimum Voltage Is Load Dependent)
l0.25 0.3 0.35 V
VIN Minimum No-Load Start-Up Power Start-Up from VIN, RUN = VIN, VOUT = VAUX = VSTORE = 0V 12 µW
VIN Undervoltage Quiescent Current Start-Up from VIN, RUN = VIN, VOUT = VAUX = VSTORE = 0V l1 2 µA
Shutdown Current – VIN VSTORE = 0V, RUN = 0
TJ = –40°C to 85°C (Note 4)
l300
300
750
450
nA
nA
Quiescent Current – VIN Switching Enabled, VOUT in Regulation, Non-Switching l0.1 1 µA
Switching Enabled, VOUT in Regulation, Non-Switching,
TJ = –40°C to 85°C (Note 4)
0.1 0.3 µA
VSTORE Maximum Operating Voltage PRI = VCC, ENVSTR = VSTORE l4.3 V
VSTORE Minimum Operating Voltage VOUT in Regulation, VCAP Shorted to VSTORE, PRI = VCC,
ENVSTR = VSTORE
2.1 V
VSTORE Under Voltage Lockout PRI = VCC, ENVSTR = VSTORE l1.730 1.778 1.826 V
VSTORE Operating Voltage (Note 7) SS1 = 0V, SS2 = 0V OV
UV
l
l
3.90
2.70
4.00
2.78
4.10
2.86
V
V
SS1 = 0V, SS2 = VCC OV
UV
l
l
2.81
1.85
2.90
1.90
2.99
1.95
V
V
SS1 = VCC, SS2 = 0V OV
UV
l
l
2.91
2.08
3.00
2.15
3.08
2.21
V
V
SS1 = VCC, SS2 = VCC OV
UV
l
l
3.90
2.91
4.00
3.00
4.10
3.08
V
V
Output Regulation Voltage 1.8V VOUT Selected
TJ = –40°C to 85°C (Note 4)
l1.75 1.8 1.85 V
1.755 1.8 1.845 V
2.2V VOUT Selected
TJ = –40°C to 85°C (Note 4)
l2.14 2.2 2.25 V
2.145 2.2 2.245 V
3.3V VOUT Selected
TJ = –40°C to 85°C (Note 4)
l3.22 3.3 3.40 V
3.23 3.3 3.38 V
5V VOUT Selected
TJ = –40°C to 85°C (Note 4)
l4.90 5.0 5.10 V
4.92 5.0 5.08 V
Quiescent Current – VAUX Enabled, VOUT in Regulation, Non-Switching,
TJ = –40°C to 85°C (Note 4)
l1.6
1.6
3
2.5
µA
µA
Quiescent Current – VOUT Enabled, VOUT in Regulation, Non-Switching,
TJ = –40°C to 85°C (Note 4)
l0.1
0.1
1
0.3
µA
µA
Quiescent Current – VSTORE Enabled, VOUT in Regulation, Non-Switching, VCAP Shorted
to VSTORE
TJ = –40°C to 85°C (Note 4)
l0.1
0.1
1
0.3
µA
µA
Shutdown Current – VSTORE VIN = 0V, VCAP Shorted to VSTORE, ENVSTR = 0V
TJ = –40°C to 85°C (Note 4)
l0.1
0.1
0.7
0.3
µA
µA
Shelf Mode VSTORE Leakage Current Isolated VSTORE, ENVSTR = 0V 0.1 25 nA
N-Channel MOSFETs – Leakage Current B and C Switches 0.1 1 µA
P-Channel MOSFETs – Leakage Current A1, A2, D1 and D2 Switches 0.1 1 µA
N-Channel MOSFET B and C Switch RDS(ON) VIN = 5V 0.5 Ω
P-Channel MOSFET A1 RDS(ON) VIN = 5V 0.5 Ω
P-Channel MOSFET A2 RDS(ON) VSTORE = VCAP = 4.2V 1.9 Ω
P-Channel MOSFET D1 RDS(ON) VOUT = 3.3V 0.9 Ω
P-Channel MOSFET D2 RDS(ON) VSTORE = VCAP = 4.2V 2.9 Ω
LTC3106
4
3106f
For more information www.linear.com/LTC3106
PARAMETER CONDITIONS MIN TYP MAX UNITS
P-Channel MOSFET AUXSW RDS(ON) VAUX = 5.4V 3 Ω
P-Channel VSTORE Isolation MOSFET RDS(ON) VSTORE = 4.2V 2 Ω
Peak Current Limit (VOUT) 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
l
l
l
l
530
60
140
60
725
100
200
100
mA
mA
mA
mA
VALLEY Current Limit 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
l
l
l
l
300
10
30
10
400
44
70
44
mA
mA
mA
mA
Peak Current Limit (VSTORE Charging) VSTORE Powered from VIN l60 100 mA
PGOOD Threshold VOUT Falling, Percentage Below VOUT –11 –9 –7 %
PGOOD Hysteresis Percentage of VOUT 3 %
PGOOD Voltage Low IPGOOD = 100µA 0.2 V
PGOOD Leakage Current VPGOOD = 5V 0.1 10 nA
VIH Digital Input High Logic Level Pins: OS[1:2], SS[1:2], ILIMSEL, ENVSTR, PRI l0.8 V
VIL Digital Input Low Logic Level Pins: OS[1:2], SS[1:2], ILIMSEL, ENVSTR, PRI l0.3 V
Digital Input Leakage Current Pin Voltage = 5.2V,
Pins: OS[1:2], SS[1:2], ILIMSEL, PRI
0.1 10 nA
ENVSTR Input Leakage Current l44 80 nA
Auxiliary Voltage Threshold VAUX Rising 5.2 V
Auxiliary Voltage Hysteresis VAUX Falling, Restart VAUX Charging 50 mV
MPP Pin Output Current VMPP = 0.6V l1.21 1.5 1.72 µA
MPP Pin Shutdown Current VMPP = VCC 0.1 10 nA
MPP Disable Threshold Voltage Below VCC –1 –0.8 V
RUN Threshold - Enable Reference l0.15 0.4 0.55 V
Accurate RUN Threshold - Enable Switching
from VIN
RUN Pin Voltage Increasing
TJ = –40°C to 85°C (Note 4)
l0.585
0.591
0.6
0.6
0.615
0.609
V
V
Accurate RUN Hysteresis 100 mV
RUN Input Current 0.1 10 nA
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
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.
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.
LTC3106
5
3106f
For more information www.linear.com/LTC3106
Typical perForMance characTerisTics
VIN Power Loss vs Load Current VIN Efficiency vs Load Current VIN Power Loss vs Load Current
VIN Efficiency vs Load Current VIN Power Loss vs Load Current
Light Load Power Loss vs Input
Voltage (VIN)
VIN Efficiency vs Load Current VIN Power Loss vs Load Current VIN Efficiency vs Load Current
TA = 25°C unless otherwise noted.
V
OUT
= 1.8V
VIN = 1V
VIN = 2V
VIN = 3V
VIN = 4V
VIN = 5V
LOAD CURRENT (mA)
0.001
0.01
0.1
1
10
100
500
0
10
20
30
40
50
60
70
80
90
100
EFFICIENCY (%)
3106 G01
V
OUT
= 1.8V
VIN = 1V
VIN = 3V
VIN = 5V
LOAD CURRENT (mA)
0.001
0.01
0.1
1
10
100
500
0.01
0.1
1
10
100
1k
POWER LOSS (mW)
3106 G02
V
OUT
= 2.2V
LOAD CURRENT (mA)
0.001
0.01
0.1
1
10
100
500
0
10
20
30
40
50
60
70
80
90
100
EFFICIENCY (%)
3106 G03
VIN = 1V
VIN = 2V
VIN = 3V
VIN = 4V
VIN = 5V
V
OUT
= 2.2V
LOAD CURRENT (mA)
0.001
0.01
0.1
1
10
100
500
0.01
0.1
1
10
100
1k
POWER LOSS (mW)
3106 G04
VIN = 1V
VIN = 3V
VIN = 5V
V
OUT
= 3.3V
LOAD CURRENT (mA)
0.001
0.01
0.1
1
10
100
500
0
10
20
30
40
50
60
70
80
90
100
EFFICIENCY (%)
3106 G05
VIN = 1V
VIN = 2V
VIN = 3V
VIN = 4V
VIN = 5V
V
OUT
= 3.3V
LOAD CURRENT (mA)
0.001
0.01
0.1
1
10
100
500
0.01
0.1
1
10
100
1k
POWER LOSS (mW)
3106 G06
VIN = 1V
VIN = 3V
VIN = 5V
V
OUT
= 5V
LOAD CURRENT (mA)
0.001
0.01
0.1
1
10
100
500
0
10
20
30
40
50
60
70
80
90
100
EFFICIENCY (%)
vs Load Current
3106 G07
VIN = 1V
VIN = 2V
VIN = 3V
VIN = 4V
VIN = 5V
V
OUT
= 5V
LOAD CURRENT (mA)
0.001
0.01
0.1
1
10
100
500
0.01
0.1
1
10
100
1k
POWER LOSS (mW)
3106 G08
VIN = 1V
VIN = 3V
VIN = 5V
VOUT = 1.8V AT 10µA
VOUT = 5V AT 10µA
VOUT = 1.8V AT 2µA
VOUT = 5V AT 2µA
INPUT VOLTAGE, V
IN
(V)
0
0.5
1
1.5
2
2.5
3
3.5
4
4.5
5
10
100
1k
POWER LOSS (µW)
3106 G09
LTC3106
6
3106f
For more information www.linear.com/LTC3106
Typical perForMance characTerisTics
TA = 25°C unless otherwise noted.
VSTORE/VCAP Power Loss vs
Load Current
VSTORE/VCAP Efficiency vs
Load Current
VSTORE/VCAP Power Loss vs
Load Current
VSTORE/VCAP Efficiency vs
Load Current
VSTORE/VCAP Power Loss vs
Load Current
No Load Input Current
vs Input Voltage
VSTORE/VCAP Efficiency vs
Load Current
VSTORE/VCAP Power Loss vs
Load Current
VSTORE/VCAP Efficiency vs
Load Current
V
OUT
= 1.8V
VSTORE/VCAP = 4.2V
VSTORE/VCAP = 3.1V
VSTORE/VCAP = 2V
LOAD CURRENT (mA)
0.001
0.01
0.1
1
10
100
0
10
20
30
40
50
60
70
80
90
100
EFFICIENCY (%)
3106 G10
V
OUT
= 1.8V
LOAD CURRENT (mA)
0.001
0.01
0.1
1
10
100
0.01
0.1
1
10
100
POWER LOSS (mW)
3106 G11
VSTORE/VCAP = 4.2V
VSTORE/VCAP = 3.1V
VSTORE/VCAP = 2V
V
OUT
= 2.2V
LOAD CURRENT (mA)
0.001
0.01
0.1
1
10
100
0
10
20
30
40
50
60
70
80
90
100
EFFICIENCY (%)
3106 G12
VSTORE/VCAP = 4.2V
VSTORE/VCAP = 3.1V
VSTORE/VCAP = 2V
V
OUT
= 2.2V
LOAD CURRENT (mA)
0.001
0.01
0.1
1
10
100
0.01
0.1
1
10
100
POWER LOSS (mW)
3106 G13
VSTORE/VCAP = 4.2V
VSTORE/VCAP = 3.1V
VSTORE/VCAP = 2V
V
OUT
= 3.3V
V
STORE
/V
CAP
= 4.2V
V
STORE
/V
CAP
= 3.1V
V
STORE
/V
CAP
= 2V
LOAD CURRENT (mA)
0.001
0.01
0.1
1
10
100
0
10
20
30
40
50
60
70
80
90
100
EFFICIENCY (%)
3106 G14
V
OUT
= 3.3V
V
STORE
/V
CAP
= 4.2V
V
STORE
/V
CAP
= 3.1V
V
STORE
/V
CAP
= 2V
LOAD CURRENT (mA)
0.001
0.01
0.1
1
10
100
0.01
0.1
1
10
100
POWER LOSS (mW)
3106 G15
V
OUT
= 5V
LOAD CURRENT (mA)
0.001
0.01
0.1
1
10
100
0
10
20
30
40
50
60
70
80
90
100
EFFICIENCY (%)
3106 G16
VSTORE/VCAP = 4.2V
VSTORE/VCAP = 3.1V
VSTORE/VCAP = 2V
V
OUT
= 5V
/V
V
STORE
CAP
= 4.2V
V
STORE
/V
CAP
= 3.1V
V
STORE
/V
CAP
= 2V
LOAD CURRENT (mA)
0.001
0.01
0.1
1
10
100
0.01
0.1
1
10
100
POWER LOSS (mW)
3106 G17
INPUT VOLTAGE (V)
1
2
3
4
5
0
2
4
6
8
10
12
14
16
18
20
INPUT CURRENT (µA)
3106 G18
LTC3106
7
3106f
For more information www.linear.com/LTC3106
Maximum Output Current vs
Input Voltage (VIN)
Maximum Output Current vs
Input Voltage (VSTORE/VCAP)
Normalized VIN Start-Up Voltage
vs Temperature
Maximum Output Current vs
Input Voltage (VIN)
Maximum Output Current
vs
Input Voltage (VSTORE/VCAP)
Normalized VOUT, Accurate RUNTH
vs Temperature
Normalized Input Voltage UVLO
vs Temperature
Typical perForMance characTerisTics
TA = 25°C unless otherwise noted.
TEMPERATURE (°C)
–50
–32
–14
4
22
40
58
76
94
112
130
–40
–30
–20
–10
0
10
20
30
PERCENT CHANGE (%)
3106 G19
ACCURATE RUN THRESHOLD
VOUT = 3.3V
TEMPERATURE (°C)
–50
–30
–10
10
30
50
70
90
110
130
150
–0.5
–0.4
–0.3
–0.2
–0.1
–0.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1.0
PERCENT CHANGE (%)
3106 G20
TEMPERATURE (°C)
–50
–30
–10
10
30
50
70
90
110
130
150
–0.2
–0.1
–0.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1.0
PERCENT CHANGE (%)
3106 G21
INPUT VOLTAGE (V)
0.5
1
1.5
2
2.5
3
3.5
4
4.5
5
5.5
0
100
200
300
400
500
600
R
MIN
(Ω)
3106 G22
ILIMSEL = HI
VOUT = 1.8V
VOUT = 2.2V
VOUT = 3.3V
VOUT = 5V
INPUT VOLTAGE, V
IN
(V)
0
0.5
1
1.5
2
2.5
3
3.5
4
4.5
5
1
10
100
1k
OUTPUT CURRENT (mA)
3106 G23
ILIMSEL = HI
INPUT VOLTAGE, V
STORE
/V
CAP
(V)
1.5
2
2.5
3
3.5
4
4.5
1
10
100
1k
OUTPUT CURRENT (mA)
3106 G24
VOUT = 1.8V
VOUT = 2.2V
VOUT = 3.3V
VOUT = 5V
TEMPERATURE (°C)
–50
–30
–10
10
30
50
70
90
110
130
150
–12
–10
–8
–6
–4
–2
0
2
4
6
8
PERCENT CHANGE (%)
3106 G25
ILIMSEL = LO
INPUT VOLTAGE, V
IN
(V)
0
0.5
1
1.5
2
2.5
3
3.5
4
4.5
5
1
10
100
OUTPUT CURRENT (mA)
3106 G26
VOUT = 1.8V
VOUT = 2.2V
VOUT = 3.3V
VOUT = 5V
Normalized RUN Threshold
vs Temperature
Start-Up Into Resistive Load
L = 10µH
ILIMSEL = LO
INPUT VOLTAGE, V
STORE
/V
CAP
(V)
1.5
2
2.5
3
3.5
4
4.5
10
100
OUTPUT CURRENT (mA)
3106 G27
VOUT = 1.8V
VOUT = 2.2V
VOUT = 3.3V
VOUT = 5V
LTC3106
8
3106f
For more information www.linear.com/LTC3106
No Load Input Current vs Input
Voltage, MPP Enabled
5VIN to 3.3VOUT Load Step 10mA
to 300mA
5VIN to 3.3VOUT Load Step 100µA
to 40mA
Boost Mode at VIN = 1.5V
VOUT = 3.3V, 100mA
Buck-Boost Mode at VIN = 3.5V
VOUT = 3.3V 100mA
Buck Mode at VIN = 4.3V
VOUT = 3.3V, 100mA
Typical perForMance characTerisTics
TA = 25°C unless otherwise noted.
L = 10µH
COUT = 100µF
COUT = 47µF
LOAD CURRENT (mA)
0.001
0.01
0.1
1
10
100
500
–3.0
–2.5
–2.0
–1.5
–1.0
–0.5
0
0.5
1.0
LOAD REGULATION (%)
3106 G28
COUT = 47µF
ILIMSEL = HI
100µs/DIV
IL
200mA/DIV
I
LOAD
100mA/DIV
3106 G29
TEMPERATURE (°C)
–50
–30
–10
10
30
50
70
90
110
130
150
–4
–3
–2
–1
0
1
PERCENT CHANGE FROM 25°C (%)
3106 G30
INPUT VOLTAGE (V)
0.4
1.3
2.2
3.2
4.1
5
0
100
200
300
400
500
600
700
INPUT CURRENT (µA)
3106 G31
Normalized Output Voltage
Regulation vs Load Current Inductor Current vs Load Current
Normalized MPP Output vs
Temperature
ILIMSEL = HI
C
OUT
= 47µF
C
OUT
= 100µF
1ms/DIV
V
OUT
200mV/DIV
ILOAD
200mA/DIV
V
OUT
200mA/DIV
3106 G32
10mA
300mA
C
OUT
= 47µF, ILIMSEL = LO
5ms/DIV
V
OUT
100mV/DIV
I
LOAD
20mA/DIV
3106 G33
40mA
100µA
100µA
L = 10µH
COUT = 47µF
ILIMSEL = HI
50µs/DIV
V
OUT
50mV/DIV
V
AUX
50mV/DIV
IL
200mA/DIV
3106 G34
L = 10µH
COUT = 47µF
ILIMSEL = HI
50µs/DIV
V
OUT
100mV/DIV
V
AUX
20mV/DIV
IL
200mA/DIV
3106 G35
L = 10µH
COUT = 47µF
ILIMSEL = HI
50µs/DIV
V
OUT
100mV/DIV
V
AUX
50mV/DIV
IL
400mA/DIV
3106 G36
LTC3106
9
3106f
For more information www.linear.com/LTC3106
3.3V Output Voltage Ripple
vs Load Current (ILIMSEL High)
3.3V Output Voltage Ripple
vs Load Current (ILIMSEL Low)
5V Output Voltage Ripple
vs Load Current (ILIMSEL High)
Buck Mode at VIN = 5V
VOUT = 3.3V, 300mA
No-Load Start-Up from Low
Power Source VSTORE = 0V,
VIN = RUN
Typical perForMance characTerisTics
TA = 25°C unless otherwise noted.
P
IN
= 100µW
V
IN_OC
= 1.8V
V
AUX
CHARGING
V
OUT
CHARGING
5s/DIV
V
OUT
, 3.3V
2V/DIV
V
IN
1V/DIV
PGOOD
2V/DIV
3106 G38
I
LOAD
= 30mA
COUT = 47µF
500µs/DIV
V
OUT
, 3.3V
200mV/DIV
V
STORE
, 3V
100mV/DIV
V
IN
, 2V
100mV/DIV
RUN
2V/DIV
3106 G39
L = 10µH
VIN = 2V, COUT = 47µF
VIN = 5V, COUT = 47µF
VIN = 2V, COUT = 100µF
VIN = 5V, COUT = 100µF
LOAD CURRENT (mA)
0.0001
0.001
0.01
0.1
1
10
100
1k
0
20
40
60
80
100
120
140
160
180
200
RIPPLE VOTLAGE (mVP-P
)
3106 G40
L = 10µH
LOAD CURRENT (mA)
0.0001
0.001
0.01
0.1
1
10
100
0
25
50
75
100
125
150
RIPPLE VOTLAGE (mVP-P
)
3106 G41
VIN = 2V, COUT = 47µF
VIN = 5V, COUT = 47µF
VIN = 2V, COUT = 100µF
VIN = 5V, COUT = 100µF
L = 10µH
LOAD CURRENT (mA)
0.0001
0.001
0.01
0.1
1
10
100
1k
0
20
40
60
80
100
120
140
160
180
200
RIPPLE VOTLAGE (mV
pp
)
3106 G42
VIN = 2V, COUT = 47µF
VIN = 5V, COUT = 47µF
VIN = 2V, COUT = 100µF
VIN = 5V, COUT = 100µF
L = 10µH
LOAD CURRENT (mA)
0.0001
0.001
0.01
0.1
1
10
100
0
25
50
75
100
125
150
RIPPLE VOTLAGE (mV
P-P
)
3106 G43
VIN = 2V, COUT = 47µF
VIN = 5V, COUT = 47µF
VIN = 2V, COUT = 100µF
VIN = 5V, COUT = 100µF
L = 10µH
LOAD CURRENT (mA)
0.0001
0.001
0.01
0.1
1
10
100
1k
0
25
50
75
100
125
150
175
200
RIPPLE VOTLAGE (mVP-P
)
3106 G44
VIN = 2V, COUT = 47µF
VIN = 5V, COUT = 47µF
VIN = 2V, COUT = 100µF
VIN = 5V, COUT = 100µF
L = 10µH
LOAD CURRENT (mA)
0.0001
0.001
0.01
0.1
1
10
100
0
25
50
75
100
RIPPLE VOTLAGE (mVP-P
)
3106 G45
VIN = 2V, COUT = 47µF
VIN = 5V, COUT = 47µF
VIN = 2V, COUT = 100µF
VIN = 5V, COUT = 100µF
VSTORE to VIN Switchover
5V Output Voltage Ripple
vs Load Current (ILIMSEL Low)
1.8V Output Voltage Ripple
vs Load Current (ILIMSEL High)
1.8V Output Voltage Ripple
vs Load Current (ILIMSEL Low)
L = 10µH
COUT = 47µF
ILIMSEL = HI
50µs/DIV
V
OUT
50mV/DIV
V
AUX
100mV/DIV
IL
200mA/DIV
3106 G37
LTC3106
10
3106f
For more information www.linear.com/LTC3106
Typical perForMance characTerisTics
TA = 25°C unless otherwise noted.
5V VIN to 1.8V VOUT Load Step
10µA to 50mA
5V VIN to 1.8V VOUT Load Step
10µA to 200mA
Output Voltage Ripple
5V VIN, 3.3V VOUT 200mA
Maximum Slew Rate vs Input
Voltage
Maximum Output Current vs
Input Voltage (VSTORE Shelf Mode)
Normalized Average Minimum
Operating VSTORE vs Temperature
Maximum Output Current vs
Input Voltage (VSTORE Shelf Mode)
INPUT VOLTAGE V
IN
(V)
2.5
3
3.5
4
4.5
5
0
0.1
0.2
0.4
0.5
0.6
0.7
0.8
1.0
1.1
1.2
INPUT VOLTAGE SLEW RATE (V/µs)
3106 G49
ILIMSEL = LO
INPUT VOLTAGE, V
STORE
(V)
2
2.5
3
3.5
4
4.5
10
100
OUTPUT CURRENT (mA)
3106 G51
VOUT = 1.8V
VOUT = 2.2V
VOUT = 3.3V
VOUT = 5V
PRI = HI
TEMPERATURE (°C)
–50
–30
–10
10
30
50
70
90
110
130
150
–5.0
–2.5
0
2.5
5.0
7.5
10.0
12.5
15.0
CHANGE IN V
STORE
(%)
3106 G52
ILIMSEL = HI
INPUT VOLTAGE, V
STORE
(V)
1.5
2
2.5
3
3.5
4
4.5
0.1
1
10
100
1k
OUTPUT CURRENT (mA)
3106 G50
VOUT = 1.8V
VOUT = 2.2V
VOUT = 3.3V
VOUT = 5V
ILIMSEL = HIGH
COUT = 100µF
100µs/DIV
IL
500mA/DIV
V
OUT
100mV/DIV
V
AUX
100mV/DIV
3106 G46
VAUX CHARGING
ILIMSEL = LOW
C
OUT
= 47µF
C
OUT
= 100µF
10µA
10µA
50mA
500µs/DIV
I
LOAD
50mA/DIV
VOUT (AC)
50mV/DIV
VOUT (AC)
50mV/DIV
3106 G47
ILIMSEL = HIGH
C
OUT
= 47µF
C
OUT
= 100µF
10µA
10µA
200mA
500µs/DIV
I
LOAD
200mA/DIV
100mV/DIV
VOUT (AC)
VOUT (AC)
100mV/DIV
3106 G48
LTC3106
11
3106f
For more information www.linear.com/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 program-
ming 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 Pro-
gramming 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 bat-
tery 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 imped-
ance 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 Con-
verter 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
LTC3106
12
3106f
For more information www.linear.com/LTC3106
block DiagraM
+
–
START LOGIC,
CONTROL LOGIC
AND STATE MACHINE
VBEST
CNTRL
THERMAL
SHUTDOWN
VSTORE
COMP
VCAP
SS1
VIN
VSTORE
VCAP
SS2
RUN
PRI
ENVSTR
ILIMSEL
GND
600mV
600mV
400mV
600mV
VOLTAGE
REFERENCE
PWR ADJ
+
–
+
–
UVLO
COMP
600mV
VIN
600mV
FB
1.5µA
MPP
OUTPUT
CURRENT
VCC
ADJ
MPP
OS2
OS1
VOUT
VIN
+
–
PGOOD
COMP
MPP
COMP
VOUT
VREF
+
–
RUN
COMP
SLEEP
COMP
+
–
ACCURATE RUN
COMP
VCC
VBEST
SWD1
SWB
SWA1
VSTR_EN
VOUT
VAUX
SWA2
VSTR_EN VBEST
SWD2
VBEST
VCAP
VIN VOUT
AUXSW
PGOOD
3106 BD
+
–
VIN
ADJ
IPEAK
DETECT
IVAL/IZERO
DETECT ADJ
VAUX
VSTORE
DRIVERS
+
–
+
–
SW1 SW2
VBEST
SWC
or high capacity secondary battery applications. For low
capacity sources only tie VSTORE directly to the battery.
Tie to GND if unused.
VCAP (Pin 20/Pin 2): VSTORE Isolation Pin. Isolates VSTORE
from the decoupling capacitor for low capacity backup
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.
pin FuncTions
(QFN/TSSOP)
LTC3106
13
3106f
For more information www.linear.com/LTC3106
Simplified Operational Flow Chart Using Accurate RUN with Primary Battery Backup
operaTion
3106 SD01
VBEST* > 1.5V (MAX)
VIN > VIN START-UP VOLTAGE
(0.85V TYP)
ENVSTR > 0.8V AND/OR
RUN > ENABLE THRESHOLD (0.4V TYP)
ENVSTR = VSTORE = VCAP
RUN = VIN OR EXTERNAL DIVIDER TAP
PRI = HI
VAUX > VAUX THRESHOLD
VOUT > 1.2V (TYP)
* VBEST IS THE GREATER OF VAUX,
VIN, VSTORE, VOUT
** VIN(TURNON) = 0.6V • (1 +R1/R2)
SYNCHRONOUS
SWITCHING
VSTORE > VSTORE(MIN)
YES YES
NO
VIN > ACC. RUN THRESHOLD
OR VIN > VIN(TURNON)**
ASYNCHRONOUS
START-UP
SHUTDOWN
NO
NO
1
START
COMPLETE/SLEEP
YESYES
YES
NO
VAUX > 5.2V (TYP)
VOUT IN REGULATION
NO
YES
NO
1
LTC3106
14
3106f
For more information www.linear.com/LTC3106
Simplified Operational Flow Chart Using VIN UVLO with Primary Battery Backup
operaTion
3106 SD02
VBEST* > 1.5V (MAX)
VIN > VIN START-UP VOLTAGE
(0.85V TYP)
ENVSTR > 0.8V AND/OR
RUN > ENABLE THRESHOLD (0.4V TYP)
ENVSTR = VSTORE = VCAP
RUN > 0.6V (TYPICALLY TIED TO VSTORE)
PRI = HI
VAUX = VAUX THRESHOLD
VOUT > 1.2V (TYP)
* VBEST IS THE GREATER OF VAUX,
VIN, VSTORE, VOUT
SYNCHRONOUS
SWITCHING
VSTORE > VSTORE(MIN)
YES
NO
VIN > VIN(UVLO)
0.3V (TYP)
ASYNCHRONOUS
START-UP
SHUTDOWN
NO
NO
1
START
COMPLETE/SLEEP
YESYES
YES
NO
VAUX > 5.2V (TYP)
VOUT IN REGULATION
NO
YES
NO
1
LTC3106
15
3106f
For more information www.linear.com/LTC3106
operaTion
Simplified Operational Flow Chart Using Accurate RUN with Rechargeable Battery Backup
3106 SD03
VBEST* > 1.5V (MAX)
VIN > VIN START-UP VOLTAGE
(0.85V TYP)
ENVSTR > 0.8V AND/OR
RUN > ENABLE THRESHOLD (0.4V TYP)
ENVSTR = VSTORE = VCAP
RUN = VIN OR EXTERNAL DIVIDER TAP
PRI = GND
VAUX = VAUX THRESHOLD
VOUT > 1.2V (TYP)
* V
BEST IS THE GREATER OF VAUX,
V
IN, VSTORE, VOUT
** V
IN(TURNON) = 0.6V • (1 + R1/R2)
*** V
STORE IS LOCKED OUT AS AN INPUT UNTIL
V
AUX = VAUX TH, IF VSTORE IS LESS THAN
V
STORE(UV) WHEN LTC3106 IS FIRST ENABLED
SYNCHRONOUS
SWITCHING
VSTORE(UV) < VSTORE < VSTORE(OV)
OR NO IF VSTORE LOCKED OUT***
YES YES
NO
VIN > ACC. RUN THRESHOLD
OR VIN > VIN(TURNON)**
CHARGE VSTORE
ASYNCHRONOUS
START-UP
SHUTDOWN
NO
NO
1
START
COMPLETE/SLEEP
YESYES
YES
NO
VAUX > 5.2V (TYP)
VOUT IN REGULATION
NO
YES
YES
VSTORE > VSTORE(OV)
NO
1
NO
LTC3106
16
3106f
For more information www.linear.com/LTC3106
operaTion
3106 SD04
VBEST* > 1.5V (MAX)
VIN > VIN START-UP VOLTAGE
(0.85V TYP)
ENVSTR > 0.8V AND/OR
RUN > ENABLE THRESHOLD (0.4V TYP)
ENVSTR = VSTORE = VCAP
RUN > 0.6V (TYPICALLY TIED TO VSTORE)
PRI = HI
VAUX = VAUX THRESHOLD
VOUT > 1.2V (TYP)
* VBEST IS THE GREATER OF VAUX,
VIN, VSTORE, VOUT
*** VSTORE IS LOCKED OUT AS AN INPUT UNTIL
VAUX = VAUX TH, IF VSTORE IS LESS THAN
VSTORE(UV) WHEN LTC3106 IS FIRST ENABLED
SYNCHRONOUS
SWITCHING
VSTORE(UV) < VSTORE < VSTORE(OV)
OR NO IF VSTORE LOCKED OUT***
YES YES
NO
VIN > VIN(UVLO)
0.3V (TYP)
CHARGE VSTORE
ASYNCHRONOUS
START-UP
SHUTDOWN
NO
NO
1
START
COMPLETE/SLEEP
YESYES
YES
NO
VAUX > 5.2V (TYP)
VOUT IN REGULATION
NO
YES
YES
VSTORE > VSTORE(OV)
NO
1
NO
Simplified Operational Flow Chart Using VIN UVLO with Rechargeable Battery Backup
LTC3106
17
3106f
For more information www.linear.com/LTC3106
operaTion
Introduction
The LTC3106 is a high performance two input, synchro-
nous 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.
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 im-
pedance 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 appli-
cations 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.
Both configurations are shown in Figure1. In either con-
figuration, 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).
Figure 1. VSTORE/VCAP Configurations
Shutdown
Either input source can be enabled independently or to-
gether. Bring ENVSTR below the worst-case logic thresh-
old 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 com-
parator 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.
VSTORE
VCAP
ILIMSEL
BACKUP
POWER
VCC FOR IPEAK = 170mA
GND FOR IPEAK
= 100mA
LTC3106
NONISOLATED
VSTORE/VCAP
ISHDN = 100nA
VSTORE
VCAP
ILIMSEL
BACKUP
POWER
LTC3106
ISOLATED
VSTORE/VCAP
ISHDN = 0.1nA IPEAK = 100mA
3106 F01
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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 undervolt-
age 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.
operaTion
VOUT. When the VAUX voltage drops to 5.1V typical, input
power is briefly diverted to recharge VAUX.
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
OS1 OS2 OUTPUT VOLTAGE
0 0 1.8V
0 VCC 2.2V
VCC 0 3.3V
VCC VCC 5V
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
BATTERY TYPE
0 0 0 4V 2.78V Li Carbon
0 0 VCC 2.9V 1.9V 2x Rechargeable NiMH
0 VCC 0 3V 2.15V Rechargeable Li Coin Cell
0 VCC VCC 4V 3V Li Polymer/Graphite
VCC 0 0 4.2V 2.1V Primary, Non-Rechargeable
VIN 0.6V ENABLE VIN
ACCURATE RUN COMP
LTC3106
3106 F02
LOW VOLTAGE LOGIC THRESH
RUN
R1
R2 ENABLE VREF,
CLEAR SHUTDOWN
0.4V
+
–
+
–
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:
VIN(TURNON) =0.6V •1+
R1
R2
The RUN comparator includes a built-in hysteresis of ap-
proximately 100mV, so that the typical turn-off threshold
will be;
VIN(TURNOFF) =0.5V •1+
R1
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
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operaTion
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.
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.
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 (<1nA) on VSTORE. As shown
in Figure 4, simply connect VCAP to a bulk capacitor and
VSTORE to the isolated source. Tie ENVSTR to ground to
isolate VSTORE. Although adequate for most low capacity
sources such as solid state or small Li-Ion Polymer bat-
teries, the current available to the output from VSTORE in
this configuration will be reduced. To enable VSTORE as an
input and prevent a significant increase in the quiescent
current, it is recommended that ENVSTR terminate to
VSTORE or to a voltage greater than VSTORE.
Primary Battery
The LTC3106 PRI input allows the user to disable secondary
battery features such as trickle charging on VSTORE so that
a primary battery may be used in the absence of sufficient
power from the harvested source on VIN. The SW2 to VAUX
Schottky diode is NOT required or recommended with the
primary function enabled. With PRI tied to VCC, the VSTORE
input voltage range ignores the state of the SS1 and SS2
pins and operates over the wide voltage range of 2.1V to
4.3V. To use the highest peak current capability VSTORE
should be tied to VCAP in this configuration. To start the
LTC3106 from VSTORE/VCAP, VSTORE/VCAP must be greater
than 2.1V nominally. During an output short (VOUT < 1.1V)
a small VSTORE reverse current of 20µA (typical) will be
Figure 3. High Capacity Battery Configuration
(Shown with VSTORE Enabled)
Figure 4. Low Capacity Battery Configuration
(Shown with VSTORE Disabled, ENVSTR Tied to Ground)
Figure 5. Rechargeable Battery Configuration with
Inrush Current Limiting
+
+
INPUT
SOURCE
RECHARGEABLE
BACKUP
SOURCE
LTC3106
VIN
VCAP
VAUX
PRI
SW1 SW2
VSTORE
ENVSTR
3106 F03
C1
C2
C3
D1
L1
+
+
INPUT
SOURCE
RECHARGEABLE
LOW CAPACITY
SOURCE
LTC3106
VIN
VCAP
VSTORE
ENVSTR
3106 F04
C1
EN
DIS
C2
VAUX
PRI
SW1 SW2
C3
D1
L1
+
+
INPUT
SOURCE
BACKUP
SOURCE
LTC3106
VIN
VCAP
VSTORE
ENVSTR
3106 F05
C1
C2
VAUX
PRI
SW1 SW2
4.7µF
D1
Q1
L1
0.1µF
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operaTion
present. If an extended duration output short is expected,
protection for the primary battery should be considered.
Start-Up
The LTC3106 will start up from either input voltage source
but gives priority to VIN. The AUX output is initially charged
with the synchronous rectifiers disabled. Once VAUX has
reached its terminal voltage the output voltage is then also
charged asynchronously until VOUT reaches approximately
1.2V. The converter then leaves the asynchronous mode in
favor of a more efficient synchronous start-up mode until
VOUT is in regulation and the part enters normal operation.
It is normal for the output voltage to rise as VAUX is charging.
The AUXSW switch and the SWDI switch are in parallel so
even when switched off there is still some asynchronous
body diode conduction to the output. The rate at which
this occurs is related to the VAUX/VOUT output capacitor
ratio and operating conditions at start-up (i.e., any static
load on VOUT). A minimum 10:1 ratio of VOUT to VAUX cap
is recommended to allow for proper start-up.
Starting from Very Low Current Input Sources
Many solar cells that are optimized for indoor use have
very low available power at low light levels and therefore
very low output current, often less than 100µA at 200Lux.
If the LTC3106 is to start up using only a weak source on
VIN and with no back up battery on VSTORE the input capaci-
tance must be sized larger than that for normal operation.
Although dependent on the specific operating conditions
for the application, in general, starting from low current
sources on VIN at low light levels alone will require larger
input capacitances than those calculated using the CVIN
equation in the VIN and VOUT Capacitor Selection section.
For example if the LTC3106 application in Figure 14 needs
to start from the AM-1454 solar cell without the benefit
of a battery on VSTORE, the required input capacitance
increases from 470µF to 2.2mF minimum.
If a battery is connected to VSTORE but is disabled by
bringing ENVSTR low and is therefore not used to start the
LTC3106, the input source on VIN needs to have an output
current equal to or greater than 100µA (typ) regardless
of the input capacitor size for the internal VCC decision
circuit to run properly during start up. If the input source
has less than a 100µA capability, startup could stall until
more input current is available from the source or until
the VSTORE battery is enabled. The 100µA limitation also
applies where the LTC3106’s output is used to charge a
battery or a large super capacitor. For typical applications
where the input capacitance is greater than the output
capacitance the 100µA limitation does not apply.
Operating from a Low Power VIN
Controlling the minimum input voltage is essential when
using high impedance or intermittent input sources. The
LTC3106 has several options for VIN voltage control during
start-up and during normal operation.
If a valid VSTORE voltage exists or if VAUX is in regulation,
there are several LTC3106 configurations allowing accu-
rate control at lower input voltages on VIN. The accurate
RUN comparator can be used to control the VIN turn-on
threshold at any arbitrary voltage equal to or above 600mV
as discussed in the Accurate RUN Pin section of this
data sheet. The 300mV UVLO on VIN could also be used
to maintain VIN but is fixed at the 300mV threshold. If a
higher sleep current can be tolerated, the MPP pin can
be used to control VIN at any arbitrary threshold above
300mV. These latter two methods of controlling VIN are
discussed in later sections of the data sheet.
Even if no other input source is present (VSTORE/VCAP
disabled, not used or too low), a crude VIN comparator
will control VIN during start-up. If the RUN pin is tied to
VIN or held above the RUN enable threshold (>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.
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BOOST MODE BUCK-BOOST MODE BUCK MODE
VOUT
IMAX
IPEAK
IVALLEY
IZERO
VIN
VIN
tOFF tOFF
tOFF
AC AC AC AD AD ADADAD AD AD ACAC BD BDBD BD BD
3106 F06
V
IN VOUT
A
B C
D1
SW1 SW2
L
Figure 6. Operating Voltage and Current Waveforms
operaTion
Normal Operation
When VAUX is in regulation (~5.2V) and VOUT is greater
than 1.2V typical, the converter will enter normal operation.
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 volt-
age 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.
Boost Mode
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 induc-
tor) 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.
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
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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 opera-
tion, 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 pow-
ering 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
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 ac-
curate 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.
operaTion
Figure 7. MPP Configurations
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 con-
trol 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
1.2µA
R3
3106 F07
LTC3106
IQ = 10.5µA
MPP FUNCION
ENABLED
MPPVCC
LTC3106
IQ = 1.5µA
MPP FUNCION
DISABLED
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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Figure 8. Inductor Current Changing as a Function of Load
operaTion
will turn off and PGOOD will go high if an external pull-
up resistor has been provided. An internal deglitch filter
prevents nuisance trips of PGOOD due to short transients
(<15µs typically) on VOUT. Note that PGOOD can be pulled
up to any voltage, as long as the absolute maximum rat-
ing of 6V is not exceeded, and as long as the maximum
sink current rating is not exceeded when PGOOD is low.
The PGOOD pin is not actively pulled low in shutdown. If
pulled high the PGOOD pin will float high and will not be
valid until 3.5ms after the part is enabled.
Power Adjust Feature
The LTC3106 ILIMSEL option enables a feature that maxi-
mizes efficiency at light load while providing increased
power capability at heavy load by adjusting the peak and
valley of the inductor current as a function of load. Lowering
the peak inductor current for either input source at light
load optimizes efficiency by reducing conduction losses
in the internal MOSFET switches. As the load increases,
the peak inductor current is automatically increased to a
maximum of 650mA for VIN and 150mA for VSTORE/VCAP.
At intermediate loads, the peak inductor current may vary
from 90mA to 650mA. Figure 8 shows an example of how
the inductor current changes as the load increases.
The valley of the inductor current is automatically adjusted
as well to maintain a relatively constant inductor ripple
current. This keeps the switching frequency relatively
constant with load. The “burst” frequency (how often the
LTC3106 delivers a burst of current pulses to the load)
is determined by the internal hysteresis (output voltage
ripple), the load current and the amount of output capaci-
tance. All Burst Mode operation, or hysteretic converters,
will enter the audible frequency range when the load is light
enough. However, due to the low peak inductor current
at light load, circuits using the LTC3106 do not typically
generate any audible noise. Note that the power adjust
feature is overridden by the MPP function.
To maximize efficiency for very high impedance input
sources, low frequency pulsed load or low load current
applications, the power adjust feature may be disabled
using the ILIMSEL pin keeping the peak currents limited
to 90mA. See Table 3 for ILIMSEL configurations.
Table 3. Current Limit Adjustment
ILIMSEL VIN PEAK ILIMIT (mA) VSTORE PEAK ILIMIT (mA)
0 100 100
VCC 650 170
Energy Storage
Harvested energy can be stored on the input capacitor,
the output capacitor or if enabled, on the backup storage
element on VSTORE. The wide input voltage range takes
advantage of the fact that energy storage on the input
capacitor is proportional to the square of the capacitor
voltage. After the output voltage is brought into regulation
any excess energy is stored on the input capacitor and its
voltage increases. If VSTORE charging is enabled (PRI pin
grounded) excess energy will first be used to recharge
the backup power source before storing energy on the
input capacitor.
C
OUT
= 47µF, ILIMSEL = HI
100µs/DIV
IL
200mA/DIV
I
LOAD
100mA/DIV
3106 F08
The VOUT capacitor should be a minimum of 47μF. A larger
output capacitor can be used if lower peak to peak output
voltage ripple is desired. A larger output capacitor will also
improve load regulation on VOUT but will result in higher
peak currents than necessary at light load lowering the
light load efficiency.
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applicaTions inForMaTion
A standard application circuit for the LTC3106 is shown on
the front page of this data sheet, although the LTC3106 can
be configured to work from a variety of alternative energy
and backup battery sources. The appropriate selection
of external components is dependent upon the required
performance of the IC in each particular application. This
section of the data sheet provides some basic guidelines
and considerations to aid in the selection of external com-
ponents and the design of the applications circuit, as well
as a few other application circuit examples.
VSTORE/VCAP Capacitor Selection
If there is insufficient power on VIN, the VSTORE/VCAP
input carries the full inductor current and provides power
to internal control circuits in the IC. To minimize VSTORE
voltage ripple and ensure proper operation of the IC, a low
ESR bypass capacitor with a value of at least 4.7μF should
be located as close to the VCAP pin as possible. The traces
connecting this capacitor to VCAP and the ground plane
should be made as short as possible. In cases where the
series resistance of the battery is high or the LTC3106 is
powered by long traces or leads, a larger value bulk input
capacitor may be required and is generally recommended.
In such applications a 47μF to 100μF low ESR electrolytic
capacitor in parallel with a 1μF ceramic capacitor generally
yields a high performance, low cost solution. Note that
if there is sufficient power on VIN only capacitor leakage
current and shutdown current will be drawn from the
VSTORE/VCAP source. When using the Shelf Mode feature,
the VSTORE pin should be isolated from the VCAP pin and
no capacitor is needed on the VSTORE pin. Instead the
bypass capacitor should be located only on the VCAP pin.
VIN and VOUT Capacitor Selection
The LTC3106 has no maximum capacitance limitation on
VIN or VOUT but there is a slew rate limitation on VIN that
drives the need for a minimum input capacitance. Refer
to the plot of Maximum Slew Rate vs Input Voltage in the
Typical Performance Characteristics section. For general
applications where the input source has a low impedance
and relatively high output power, a minimum 22μF ceramic
capacitor is recommended between VIN and GND. In ap-
plications where the input has a high impedance and may
be intermittent, such as in energy harvesting applications,
the total VIN capacitor value will be selected to optimize the
use of the harvested source and will typically be greater
than 100μF.
In energy harvesting applications the VIN and VOUT capaci-
tors should be selected to optimize the use of the harvested
source. Input capacitor selection is highly important if the
LTC3106 must start from a, high source resistance system
on VIN. When using bulk input capacitors that have high
ESR, a small valued parallel ceramic capacitor should be
placed between VIN and GND as close to the converter pins
as possible. After VAUX and the output voltage are brought
into regulation any excess energy is stored on the input
capacitor and its voltage will increase. Care should be
taken to ensure the open-circuit voltage of the harvested
source does not exceed or is appropriately clamped to
the maximum operating voltage VIN and that the input
capacitor is rated for that voltage.
For pulsed load applications, even low power pulsed load
applications such as Eterna
®
BLE, ZigBee as well as other
proprietary low power RF protocols, the input capacitor
should be sized to store enough energy to provide out-
put power for the duration of the load profile. If enough
energy is stored so that VIN does not reach the chosen
falling threshold during a load transient then the VSTORE/
VCAP current will be minimized thereby maximizing battery
life. Spacing load transients so that the average power
required to service the application is less than or equal
to the power available from the energy harvesting source
will also greatly extend the life of the battery. The following
equation can be used to size the input capacitor to meet the
power requirements of the output for the desired duration:
CVIN =2/
η
•VOUT •
Σ
InTn
( )
VINOV 2– VINUV 2
( )
µF
( )
Here η is the average efficiency of the converter over the
input voltage range and VIN is the input voltage when the
converter begins to switch. Typically VIN(OV) will be the
selected input voltage rising threshold. VIN(UV) is the VIN(OV)
minus the hysteresis voltage. ∑InTn is the area under each
of the load pulses for given load profile. This equation
may overestimate the input capacitor necessary. It may be
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applicaTions inForMaTion
acceptable to allow the load current to deplete the output
capacitor all the way to the lower PGOOD threshold. The
equation also assumes that the input source charging
has a negligible effect during this time. Example uses of
this equation to size input capacitors are included in the
design examples later in this section.
The duration for which the regulator sleeps depends
on the load current and the size of the VOUT capacitor.
The sleep time decreases as the load current increases
and/or as the output capacitor decreases. The VOUT capaci-
tor should be a minimum of 47μF. A larger output capacitor
can be used if lower peak-to-peak output voltage ripple
is desired. A larger output capacitor will also improve
load regulation on VOUT. Multilayer ceramic or low ESR
electrolytic capacitors are both excellent options.
Proper sizing of the input capacitor to optimize energy
storage at the input utilizes the potential for higher input
voltages and higher efficiency. Ultimately the output current
is limited by what the converter can supply from its input.
If a larger peak transient load needs to be serviced, the
output capacitor should be sized to support the larger cur-
rent for the duration of the load transient by the following:
COUT ≥ILOAD •
t
PULSE
VDROOP
COUT is the output capacitor value (µF) required, ILOAD is
the peak transient load current (mA), tPULSE is the duration
of that transient (ms) and VDROOP is the amount of voltage
droop the circuit can tolerate (both in V).
For many of the LTC3106 applications, the input capaci-
tor values can be quite large (>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 great-
est 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 capaci-
tor 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 (<500nA) the parasitic current
from VAUX to VOUT could force VOUT to regulate up to 5%
higher than typical.
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Use of Ceramic Capacitors
To minimize losses in low power systems all capacitors
should have low leakage current. Ceramic capacitors are
recommended for use in LTC3106 applications due to their
small size, low ESR and low leakage currents. However,
many ceramic capacitors intended for power applications
experience a significant loss in capacitance from their rated
value as the DC bias voltage on the capacitor increases.
It is not uncommon for a small surface mount capacitor
to lose more than 50% of its rated capacitance when
operated at even half of its maximum rated voltage. This
effect is generally reduced as the case size is increased for
the same nominal value capacitor. As a result, it is often
necessary to use a larger value capacitance or a higher
voltage rated capacitor than would ordinarily be required
to actually realize the intended capacitance at the operating
voltage of the application. X5R and X7R dielectric types are
recommended as they exhibit the best performance over
the wide operating range and temperature of the LTC3106.
To verify that the intended capacitance is achieved in the
application circuit, be sure to consult the capacitor vendor’s
curve of capacitance versus DC bias voltage.
PGOOD Output
The PGOOD output can also help with power manage-
ment. PGOOD transitions high the first time the output
reaches regulation and stays high until the output falls
to 92% of the regulation point. PGOOD can be used to
trigger a system load. For example, a current burst could
begin when PGOOD goes high and would continuously
deplete the output capacitor until PGOOD went low. Note
the PGOOD pin will remain high if the output is still within
92% of the regulation point, even if the input falls below
the lower UVLO threshold.
Inductor Selection
Low DCR power inductors with values between 4.7μH and
10μH are suitable for use with the LTC3106. Inductor vendor
information can be found in Table 5. For most applications,
a 10μH inductor is recommended. In applications where
the input voltage is very low, a larger value inductor can
provide higher efficiency and a lower start-up voltage.
In applications where the input voltage is relatively high
(VIN > 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 draw-
ing 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
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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:
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
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 cur-
rent 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.
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.
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 appli-
cation 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.
Figure 9. Solar Harvester with Primary Battery Backup
+
10µH
VSTORE
VCAP
ENVSTR
VCC
PRI
ILIMSEL
VAUX
CR2032
LITHIUM
COIN CELL
3V
VOUT
MPP
OS1
OS2
SS1
SS2
GND
SW1 SW2
LTC3106
VIN
RUN
10M
365k
2M
V
OC = 4.9V
ISC = 82µA
VIN VCC
3106 F09
2.2µF
47µF
3.3V, ~200µW
VIN THRESHOLD = 3.8V MIN
47µF
10µF
0.01µF
100µF
6.3V
×3
+
SANYO
AM1816
VDD
EN
GND
Tx
PGOOD
LTC3106
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Table 6. Typical Light Conditions
LOCATION ILLUM. (Lux)
Meeting Room 200
Corridor 200
Office Desk 400 to 700
Lab 500 to 1000
Outdoors (Overcast) 1000 to 2000
Outdoors (Clear) >2000
Table 7. Small Photovoltaic Panel Manufacturers
Sanyo 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
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 depen-
dent load on the input source. The divider current would
be equal to:
IINDIV(STATIC)
4V
2.21M+432k
( )
=1.6µA
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.
Figure 10. Measured I-V and P-V Curves
Under Variable Light Conditions
Table 8. Application Load Profile Power Budget for Figure 11
INTERVAL
MCU
FUNCTION
PEAK
CURRENT In
(mA)
INTERVAL Tn
(ms)
CHARGE InTn
(µC)
REGION
DUTY CYCLE
(%)
INTERVAL
OUTPUT
POWER
(mW)
AVERAGE
OUTPUT
POWER (µW)
LTC3106
POWER
LOSS (FROM
CURVES)
(mW)
LTC3106
AVERAGE
POWER
LOSS (µW)
Region 1 Wake 0.3 1 0.3 0.1 1.0 1 0.2 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
1800 LUX
1000 LUX
500
LUX
200 LUX
Sanyo 1816
V
PANEL
(V)
0
0.7
1.5
2.2
3.0
3.7
4.4
5.2
5.9
0
0.1
0.3
0.4
0.5
0.6
0.8
0.9
1.0
I
PANEL
(mA)
P
PANEL
(mW)
3106 F10
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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 di-
vider 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 condi-
tions 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.
Figure10 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.
TIME
TIME
3106 F11
T6T5T4T3T2T1
IBACK
IPK1
IPK2
REGION 6REGION 5
REGION
4
REGION 3
REGION
2
REGION 1
CURRENT
CURRENT
ACTIVE ACTIVE ACTIVE ACTIVE
TBTA
INACTIVE/
SLEEPING
INACTIVE/
SLEEPING
INACTIVE/
SLEEPING
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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:
CVIN =2/
η
•VOUT •
Σ
lnTn
( )
VIN(OV)2– VIN(UV)2
( )
µF
( )
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 dif-
ferential between the plates. In this manner, a Peltier cell
is referred to as a thermoelectric generator (TEG).
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)
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 recharge-
able (secondary) battery, both configured to deliver power
to a low power pulsed load output. With the RUN pin con-
nected 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.
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I
n 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 exces-
sive 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.
Figure 12. TEG Harvester with Secondary Battery Backup
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 capaci-
tor to handle the average power load for the load profile
at the lowest temperature differential. Referring again to
+
10µH
VSTORE
VCAP
ENVSTR
RUN
VCC
PRI
ILIMSEL
VAUX
PANASONIC NCR18650B
LITHIUM ION
CELL
VOUT
MPP
OS2
OS1
SS2
SS1
GND
SW1 SW2
LTC3106
VIN
10M
VCC
VCC
3106 F12
2.2µF
ZLLS400
SCHOTTKY
47µF
3.3V, ~50µW
0.3V TO 3.5V
47µF
10µF
MARLOW TEG
RC12-2.5-01LS
WITH 40MM
× 40MM × 35MM
FINNED HEATSINK
+
0.01µF
470µF
6.3V
×2
+VDD
EN
GND
Tx
PGOOD
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Table 11 to sum the required charge for the load and using
the input capacitor sizing equation:
CVIN =2/
η
•VOUT •
Σ
lnTn
( )
VINOV2– VINUV2
( )
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
The average efficiency (η) with VIN(OV) = 0.3V and VIN(UV)
= 0.25V, the input UVLO upper and lower thresholds re-
spectively, 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.
Large value storage capacitor manufactures are listed
in Table4. The application in Figure 12 uses 2× 470µF
Tantalum chip capacitors.
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.
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.
Figure 13. Application Load Profile
TIME
3106 F13
T5T4T3T2T1
I
BACK
IPK1
IPK3
IPK2
REGION 5
REGION
4
REGION 3REGION 2REGION 1
CURRENT
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Table 10. Application Load Profile Power Budget for Figure 11
INTERVAL MCU FUNCTION
PEAK
CURRENT In
(mA)
INTERVAL Tn
(ms)
CHARGE InTn
(µC)
REGION
DUTY CYCLE
(%)
INTERVAL
OUTPUT
POWER
(mW)
AVERAGE
OUTPUT
POWER (µW)
LTC3106
POWER
LOSS (FROM
CURVES)
(mW)
LTC3106
AVERAGE
POWER LOSS
(µW)
Region 1 Sleep/Idle 0.002 2000 4 99.85 0.007 7 0.2 20.0
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
applicaTions inForMaTion
If conditions become more favorable the input capacitor
will charge to a higher voltage terminating at the open-
circuit 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.
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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.
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.
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
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.
Typical applicaTions
Figure 14. Portable Medical Device with Ambient Light Harvester or USB Powered Charging
10µH
PRI
VAUX
VOUT
ILIMSEL
MPP
OS2
SS1
OS1
SS2
GND
SW1 SW2
LTC3106
VIN
5V
RUN
10M
432k
D1: DIODES INC ZLLS400
Q1: ZETEX ZMX61P03F
2.21M
VCC
3106 F15
2.2µF
0.1µF
47µF
2.2V (300mA)
(3.7V TURN ON)
47µF
22µF
0.01µF
PGOOD
VCC
+VSTORE
VCAP
ENVSTR
Li RECHARGEABLE
BATTERY
Q1
D1
10µH
VSTORE
VCAP
ENVSTR
VCC
PRI
VAUX
VOUT
MPP
OS1
SS2
OS2
SS1
GND
SW1 SW2
LTC3106
VIN
RUN
10M
1.33M
2.21M
V
OC = 2.4V
ISC = 35µA
VIN VCC
3106 F14
2.2µF
NiMH
×2
47µF
GND
SENSOR(S)
USB I/O
USB
POWER
VDD
EN
DO1
3.3V (90mA/300mA)
MONITOR PROCESSING
10µF
0.1µF
4700µF
6.3V
+
SANYO
AM1454 PGOOD
ILMSEL
MCU
DATA
DISPLAY
USB BUS
POWER
+
4.7µF
ZLLS400
SCHOTTKY
Figure 15. 5V to 2.2V Converter with Rechargeable Battery
Backup and Inrush Current Limiting
LTC3106
35
3106f
For more information www.linear.com/LTC3106
Figure 16. Remote Outdoor Solar Powered Harvester with Thin Film Battery Backup
Figure 17. Extended Life Battery Powered Mote for Wireless Mesh Network
+
10µH
VSTORE
ENVSTR
VCAP
PRI
ILIMSEL
VAUX
THINERGY
MEC201-10STR
VOUT
MPP
OS2
OS1
SS2
SS1
GND
SW1 SW2
LTC3106
VIN
RUN
1M
432k
2.21M
VIN VCC
3106 F16
4.7µF
ZLLS400
SCHOTTKY
47µF
VDD
EN
3.3V, (180µW)
WIRELESS SENSOR NODE
VIN THRESHOLD = 3.6V
1µF
0.01µF
100µF
6.3V
×2
+
POWERFILM
MPT3.6-75 PGOOD
VCC
GND
SENSOR(S)
MCU
47µF
SHELF
MODE
10µH
PRI
ILIMSEL
VAUX
VOUT
MPP
OS2
OS1
SS2
SS1
GND
SW1 SW2
LTC3106
VIN
RUN
1M
402k
2.21M VCC
3106 F17
4.7µF
47µF
3V
VCELL
1µF
1µF
0.1µF
100µF
6.3V
×2
+
SANYO
AM-1815 PGOOD
VCC
VSUPPLY
LNA_EN
GND
ANTENNA
+
VSTORE
VCAP
ENVSTR
LITHIUM THIONYL
CHLORIDE AA CELL
3.6V
47µF
LTC5800
Typical applicaTions
LTC3106
36
3106f
For more information www.linear.com/LTC3106
package DescripTion
Please refer to http://www.linear.com/product/LTC3106#packaging for the most recent package drawings.
3.00 ±0.10 1.50 REF
4.00 ±0.10
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
PIN 1
TOP MARK
(NOTE 6)
0.40 ±0.10
19 20
1
2
BOTTOM VIEW—EXPOSED PAD
2.50 REF
0.75 ±0.05
R = 0.115
TYP
PIN 1 NOTCH
R = 0.20 OR 0.25
× 45° CHAMFER
0.25 ±0.05
0.50 BSC
0.200 REF
0.00 – 0.05
(UDC20) QFN 1106 REV Ø
RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS
APPLY SOLDER MASK TO AREAS THAT ARE NOT SOLDERED
0.70 ±0.05
0.25 ±0.05
2.50 REF
3.10 ±0.05
4.50 ±0.05
1.50 REF
2.10 ±0.05
3.50 ±0.05
PACKAGE OUTLINE
R = 0.05 TYP
1.65 ±0.10
2.65 ±0.10
1.65 ±0.05
2.65 ±0.05
0.50 BSC
UDC Package
20-Lead Plastic QFN (3mm × 4mm)
(Reference LTC DWG # 05-08-1742 Rev Ø)
LTC3106
37
3106f
For more information www.linear.com/LTC3106
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 representa-
tion that the interconnection of its circuits as described herein will not infringe on existing patent rights.
package DescripTion
Please refer to http://www.linear.com/product/LTC3106#packaging for the most recent package drawings.
FE20(CC) TSSOP REV Ø 0413
0.09 – 0.20
(.0035 – .0079)
0° – 8°
0.25
REF
RECOMMENDED SOLDER PAD LAYOUT
0.50 – 0.75
(.020 – .030)
4.30 – 4.50*
(.169 – .177)
1 3 4 5678 9 10
111214 13
6.40 – 6.60*
(.252 – .260)
2.74
(.108)
2.74
(.108)
20 1918 17 16 15
1.20
(.047)
MAX
0.05 – 0.15
(.002 – .006)
0.65
(.0256)
BSC 0.195 – 0.30
(.0077 – .0118)
TYP
2
2.74
(.108)
0.45 ±0.05
0.65 BSC
4.50 ±0.10
6.60
±0.10
1.05 ±0.10
2.74
(.108)
MILLIMETERS
(INCHES) *DIMENSIONS DO NOT INCLUDE MOLD FLASH. MOLD FLASH
SHALL NOT EXCEED 0.150mm (.006") PER SIDE
NOTE:
1. CONTROLLING DIMENSION: MILLIMETERS
2. DIMENSIONS ARE IN
3. DRAWING NOT TO SCALE
SEE NOTE 4
4. RECOMMENDED MINIMUM PCB METAL SIZE
FOR EXPOSED PAD ATTACHMENT
6.40
(.252)
BSC
FE Package
20-Lead Plastic TSSOP (4.4mm)
(Reference LTC DWG # 05-08-1950 Rev Ø)
Exposed Pad Variation CC
LTC3106
38
3106f
For more information www.linear.com/LTC3106
LINEAR TECHNOLOGY CORPORATION 2015
LT 1115 • PRINTED IN USA
Linear Technology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408) 432-1900 ● FAX: (408) 434-0507 ● www.linear.com/LTC3106
relaTeD parTs
Typical applicaTion
PART NUMBER DESCRIPTION COMMENTS
LTC3103 15V, 300mA Synchronous Step-Down DC/DC Converter
with Ultralow Quiescent Current
VIN: 2.5V to 15V, VOUT(MIN) = 0.6V, IQ = 1.8μA, ISD = 1μA
3mm × 3mm DFN-10, MSOP-10
LTC3105 400mA Step-Up DC/DC Converter with Maximum Power
Point Control and 250mV Start-Up
VIN: 0.225V to 5V, VOUT(MIN) Adj. 1.5V to 5V, IQ = 24μA, ISD < 1μA,
3mm × 3mm DFN-12, MSOP-12
LTC3107 Ultralow Voltage Energy Harvester and Primary Battery
Life Extender
VIN = 0.02V to 1V, VOUT Tracks VBAT, VBAT = 2V to 4V, IQ = 80nA,
VLDO = 2.2V, 3mm × 3mm DFN-10
LTC3108/LTC3108-1 Ultralow Voltage Step-Up Converter and Power
Managers
VIN: 0.02V to 1V, VOUT(MIN) Fixed 2.35V to 5V, IQ = 6μA, ISD < 1μA,
3mm × 4mm DFN-12, SSOP-16
LTC3109 Auto-Polarity, Ultralow Voltage Step-Up Converter and
Power Manager
VIN: 0.03V to 1V, VOUT(MIN) Fixed 2.35V to 5V, IQ = 7μA, ISD < 1μA,
4mm × 4mm QFN-20, SSOP-20
LTC4070 Li-Ion/Polymer Shunt Battery Charger System 450nA IQ, 1% Float Voltage Accuracy, 50mA Shunt Current
4.0V/4.1V/4.2V
LTC4071 Li-Ion/Polymer Shunt Battery Charger System with Low
Battery Disconnect
550nA IQ, 1% Float Voltage Accuracy, <10nA Low Battery
Disconnect, 4.0V/4.1V/4.2V, 8-Lead 2mm × 3mm DFN and MSOP
Packages
LTC3129/LTC3129-1 Micropower 200mA Synchronous Buck-Boost
DC/DC Converter
VIN: 2.42V to 15V, VOUT: 1.4V to 15V, IQ = 1.3μA, ISD = 10nA,
MSOP-16E, 3mm × 3mm QFN-16 Packages
LTC3330/LTC3331 Nanopower Buck-Boost DC/DC with Energy Harvesting
Battery Life Extender
VIN: 2.7V to 20V, VOUT: 1.2V to 5.0V, Enable and Standby Pins,
IQ = 750nA, 5mm × 5mm QFN-32 Package
LTC3388-1/LTC3388-3 20V High Efficiency Nanopower Step-Down Regulator VIN: 2.7V to 20V, VOUT: 1.2V to 5.0V, Enable and Standby Pins,
IQ = 720nA, ISD = 400nA, 3mm × 3mm DFN-10, MSOP-10
LTC3588-1 Nanopower Energy Harvesting Power Supply 950nA IQ in Sleep, VOUT: 1.8V, 2.5V, 3.3V, 3.6V, Integrated Bridge
Rectifier, MSE-10 and 3mm × 3mm QFN-10 Packages
LTC3588-2 Nanopower Energy Harvesting Power Supply <1μA IQ in Regulation, UVLO Rising = 16V, UVLO Falling = 14V, VOUT
= 3.45V, 4.1V, 4.5V 5.0, MSE-10 and 3mm × 3mm QFN-10 Packages
LTC5800-IPMA IP Wireless Mote-On-Chip Ultralow Power Mote, 72-Lead, 10mm × 10mm QFN
10µH
VSTORE
VCAP
ENVSTR
VCC
PRI
ILIMSEL
VAUX
VOUT
MPP
OS2
OS1
SS2
SS1
GND
SW1 SW2
LTC3106
RUN
10M 47µF
1.8V
300mA
VCC
3106 TAo2
2.2µF
22µF
0.01µF
PGOOD
VIN
0.6V TO 5V
(0.85V TO START)
Simple Wide Input Voltage Buck-Boost Converter
