LINER LTC3109EUF-PBF Auto-polarity, ultralow voltage step-up converter and power manager Datasheet

LTC3109
Auto-Polarity, Ultralow
Voltage Step-Up Converter
and Power Manager
Description
Features
n
n
n
n
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Operates from Inputs as Low as ±30mV
Less Than ±1°C Needed Across TEG to Harvest
Energy
Proprietary Auto-Polarity Architecture
Complete Energy Harvesting Power Management
System
– Selectable VOUT of 2.35V, 3.3V, 4.1V or 5V
– 2.2V, 5mA LDO
– Logic-Controlled Output
– Energy Storage Capability for Operation During Power Interruption
Power Good Indicator
Uses Compact Step-up Transformers
Small, 20-lead (4mm × 4mm) QFN Package or
20-Lead SSOP
The LTC®3109 is a highly integrated DC/DC converter ideal
for harvesting surplus energy from extremely low input
voltage sources such as TEGs (thermoelectric generators) and thermopiles. Its unique, proprietary autopolarity
topology* allows it to operate from input voltages as low
as 30mV, regardless of polarity.
Using two compact step-up transformers and external
energy storage elements, the LTC3109 provides a complete power management solution for wireless sensing
and data acquisition. The 2.2V LDO can power an external
microprocessor, while the main output can be programmed
to one of four fixed voltages. The power good indicator
signals that the main output is within regulation. A second
output can be enabled by the host. A storage capacitor (or
battery) can also be charged to provide power when the
input voltage source is unavailable. Extremely low quiescent current and high efficiency maximizes the harvested
energy available for the application.
Applications
n
n
n
n
n
n
Remote Sensor and Radio Power
HVAC Systems
Automatic Metering
Building Automation
Predictive Maintenance
Industrial Wireless Sensing
The LTC3109 is available in a small, thermally enhanced
20-lead (4mm × 4mm) QFN package and a 20-lead SSOP
package.
L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks of Linear
Technology Corporation. All other trademarks are the property of their respective owners.
*Patent pending.
Typical Application
•
•
C1A
•
1nF
•
VOUT2
470pF
47µF
1:100
VOUT Current vs TEG Voltage
1nF
C2A
VOUT
SWA
VINA
VLDO
OPTIONAL SWITCHED OUTPUT FOR SENSORS
+
2.2V
2.2µF
C1B
VAUX
700
470µF
LOW POWER
RADIO
SENSOR(S)
µP
470pF
600
500
400
300
PG00D
SWB VOUT2_EN
VINB
VS1
VSTORE
VAUX
VS2
GND
1:100 TRANSFORMERS
C1A = C1B = 1nF
VOUT = 3.3V
800
LTC3109
C2B
900
3.3V
IVOUT (µA)
TEG
(THERMOELECTRIC GENERATOR)
±30mV TO ±500mV
1:100
200
100
5.25V
1µF
+
CSTORE
3109 TA01a
0
–300
–200
–100
0
100
VTEG (mV)
200
300
3109 TA01b
3109f
LTC3109
Absolute Maximum Ratings
(Note 1)
SWA, SWB, VINA, VINB Voltage..................... –0.3V to 2V
C1A, C1B Voltage.......................................... –0.3V to 6V
C2A, C2B Voltage (Note 6)............................... –8V to 8V
VOUT2, VOUT2_EN........................................... –0.3V to 6V
VS1, VS2, VOUT, PGOOD............................... –0.3V to 6V
VLDO, VSTORE............................................. –0.3V to 6V
VAUX.......................................................15mA Into VAUX
Operating Junction Temperature Range
(Note 2)................................................... –40°C to 125°C
Storage Temperature Range................... –65°C to 125°C
Pin Configuration
TOP VIEW
GND
C2A
C1A
VS1
VS2
TOP VIEW
20 19 18 17 16
VS1
1
20 C1A
VS2
2
19 C2A
VSTORE 1
15 SWA
VSTORE
3
18 GND
VAUX 2
14 VINA
VAUX
4
17 SWA
13 VINB
VOUT
5
16 VINA
12 SWB
VOUT2
6
15 VINB
11 GND
VOUT2_EN
7
14 SWB
PGOOD
8
13 GND
VLDO
9
12 C2B
GND 10
11 C1B
21
GND
VOUT 3
VOUT2 4
8
VLDO
GND
9 10
C2B
7
C1B
6
PGOOD
VOUT2_EN 5
UF PACKAGE
20-LEAD (4mm s 4mm) PLASTIC QFN
GN PACKAGE
20-LEAD PLASTIC SSOP
TJMAX = 125°C, θJA = 37°C/W
EXPOSED PAD (PIN 21) IS GND (Note 5)
TJMAX = 125°C, θJA = 90°C/W
Order Information
LEAD FREE FINISH
TAPE AND REEL
PART MARKING*
PACKAGE DESCRIPTION
TEMPERATURE RANGE
LTC3109EUF#PBF
LTC3109EUF#TRPBF
3109
20-Lead (4mm × 4mm) Plastic QFN
–40°C to 125°C
LTC3109IUF#PBF
LTC3109IUF#TRPBF
3109
20-Lead (4mm × 4mm) Plastic QFN
–40°C to 125°C
LTC3109EGN#PBF
LTC3109EGN#TRPBF
LTC3109GN
20-Lead Plastic SSOP
–40°C to 125°C
LTC3109IGN#PBF
LTC3109IGN#TRPBF
LTC3109GN
20-Lead Plastic SSOP
–40°C to 125°C
Consult LTC Marketing for parts specified with wider operating temperature ranges. *The temperature grade is identified by a label on the shipping container.
Consult LTC Marketing for information on non-standard lead based finish parts.
For more information on lead free part marking, go to: http://www.linear.com/leadfree/
For more information on tape and reel specifications, go to: http://www.linear.com/tapeandreel/
3109f
LTC3109
Electrical Characteristics
The l denotes the specifications which apply over the full operating
junction temperature range, otherwise specifications are for TA = 25°C (Note 2). VAUX = 5V unless otherwise noted.
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
±50
mV
Minimum Start-Up Voltage
Using 1:100 Transformer Turns Ratio, VAUX = 0V
±30
No-Load Input Current
Using 1:100 Transformer Turns Ratios,
VIN = 30mV, VOUT2_EN = 0V, All Outputs Charged
and in Regulation
6
Input Voltage Range
Using 1:100 Transformer Turns Ratios
l
VSTARTUP
Output Voltage
VS1 = VS2 = GND
VS1 = VAUX, VS2 = GND
VS1 = GND, VS2 = VAUX
VS1 = VS2 = VAUX
l
l
l
l
2.30
3.234
4.018
4.875
VAUX Quiescent Current
No Load, All Outputs Charged
VAUX Clamp Voltage
Current Into VAUX = 5mA
VOUT Quiescent Current
VOUT = 3.3V, VOUT2_EN = 0V
VOUT Current Limit
VOUT = 0V
N-Channel MOSFET On-Resistance
C2B = C2A = 5V (Note 3) Measured from VINA or
SWA, VINB or SWB to GND
LDO Output Voltage
0.5mA Load On VLDO
l
5.0
l
6
mA
±500
mV
2.350
3.300
4.100
5.000
2.40
3.366
4.182
5.10
V
V
V
V
7
10
µA
5.25
5.55
V
0.2
15
µA
26
mA
0.35
l
2.134
2.2
Ω
2.30
V
LDO Load Regulation
For 0mA to 2mA Load
0.5
1
%
LDO Line Regulation
For VAUX from 2.5V to 5V
0.05
0.2
%
LDO Dropout Voltage
ILDO = 2mA
l
100
200
mV
l
LDO Current Limit
VLDO = 0V
VSTORE Leakage Current
VSTORE = 5V
VSTORE Current Limit
VSTORE = 0V
VOUT2 Leakage Current
VOUT2 = 0V, VOUT2_EN = 0V
l
VS1, VS2 Threshold Voltage
VS1 = VS2 = 5V
PGOOD Threshold (Rising)
Measured Relative to the VOUT Voltage
PGOOD Threshold (Falling)
Measured Relative to the VOUT Voltage
PGOOD VOL
Sink Current = 100µA
PGOOD VOH
Source Current = 0
6
0.4
mA
0.3
µA
15
26
mA
nA
0.85
1.2
V
1
50
nA
–7.5
%
–9
%
0.12
0.3
V
2.1
2.2
2.3
V
0.4
1.0
PGOOD Pull-Up Resistance
VOUT2_EN Threshold Voltage
12
0.1
50
l
VS1, VS2 Input Current
5
1
VOUT2_EN Rising
l
VOUT2_EN Threshold Hysteresis
VOUT2_EN Pull-Down Resistance
VOUT2 Turn-On Time
MΩ
1.3
V
100
mV
5
MΩ
0.5
µs
VOUT2 Turn-Off Time
(Note 3)
VOUT2 Current Limit
VOUT = 3.3V
VOUT2 Current Limit Response Time
(Note 3)
350
ns
VOUT2 P-Channel MOSFET On-Resistance
VOUT = 5V (Note 3)
1.0
Ω
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 LTC3109 is tested under pulsed load conditions such that
TJ ≈ TA. The LTC3109E is guaranteed to meet specifications from
0.15
l
0.2
0.3
µs
0.5
A
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
LTC3109I is guaranteed over the full –40°C to 125°C operating junction
temperature range. Note that the maximum ambient temperature
is determined by specific operating conditions in conjunction with
3109f
LTC3109
Electrical Characteristics
Note 5: Failure to solder the exposed backside of the QFN package to the
PC board ground plane will result in a thermal resistance much higher
than 37°C/W.
Note 6: The Absolute Maximum Rating is a DC rating. Under certain
conditions in the applications shown, the peak AC voltage on the C2A and
C2B pins may exceed ±8V. This behavior is normal and acceptable because
the current into the pin is limited by the impedance of the coupling
capacitor.
board layout, the rated thermal package thermal resistance and other
environmental factors. 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 3: Specification is guaranteed by design and not 100% tested in
production.
Note 4: Current measurements are made when the output is not switching.
Typical Performance Characteristics TA = 25°C, unless otherwise noted.
IIN vs VIN
IVOUT vs VIN
10000
VOUT = 0V
1:100 RATIO, C1 = 1nF
1:50 RATIO, C1 = 4.7nF
1:20 RATIO, C1 = 10nF
VOUT = 3.3V
NO LOAD ON VLDO
1000
IIN (mA)
100
10
10
100
VIN (mV)
10
1000
10
100
VIN (mV)
Input Resistance vs VIN
50
VOUT = 0V
6.0
40
5.5
35
4.5
4.0
3.5
3.0
2.5
2.0
10
100
VIN (mV)
90
30
25
20
15
3109 G03
0
70
60
50
40
30
20
10
5
1000
1000
80
10
1:100 RATIO, C1 = 1nF
1:50 RATIO, C1 = 4.7nF
1:20 RATIO, C1 = 10nF
100
VIN (mV)
Open-Circuit Start-Up Voltage
vs Source Resistance
1:100 RATIO, C1 = 1nF
1:50 RATIO, C1 = 4.7nF
1:20 RATIO, C1 = 10nF
VOUT = 0V
45
5.0
10
3109 G18
Efficiency vs VIN
EFFICIENCY (%)
RIN (Ω)
6.5
1
3109 G02
3109 G01
7.0
VOUT = 5V
VOUT = 3.3V
0.1
1000
VSTARTUP (OPEN CIRCUIT) (mV)
1
1:100 RATIO, C1 = 1nF
1:50 RATIO, C1 = 4.7nF
1:20 RATIO, C1 = 10nF
1:50 RATIO
C1 = 4.7nF
10
IVOUT (µA)
100
PVOUT vs VIN
100
PVOUT (mW)
1000
10
100
VIN (mV)
1000
3109 G04
0
0
1
2 3 4 5 6 7 8
SOURCE RESISTANCE (Ω)
9
10
3109 G05
3109f
LTC3109
Typical Performance Characteristics TA = 25°C, unless otherwise noted.
5.5
3.0
0.75
VLDO
VOUT
0
–0.25
5.3
PVOUT (mW)
0.25
PVOUT vs dT and TEG Size,
1:100 Ratio, VOUT = 5V
2.5
5.4
0.50
VAUX (V)
CHANGE (%) (RELATIVE TO 25°C)
1.00
VAUX Clamp Voltage
vs Shunt Current
VOUT and VLDO vs Temperature
5.2
FERROTEC 9500/127/100B
40mm
2.0
1.5
1.0
–0.50
5.1
0.5
–0.75
–1.00
–50 –25
75
50
25
TEMPERATURE (°C)
0
100
5.0
125
3
9
12
6
VAUX SHUNT CURRENT (mA)
0
0
15
FERROTEC 9501/071/040B
22mm
0
1
3
2
4
5 6
dT (°K)
7
8
3109 G07
3109 G06
Resonant Switching Waveforms
9
10
3109 G08
LDO Load Regulation
LDO Dropout Voltage
0.00
0.20
0.18
C1 A OR B
2V/DIV
0.16
C2 A OR B
2V/DIV
DROPOUT VOLTAGE (V)
DROP IN VLDO (%)
–0.25
–0.50
–0.75
0.08
0.06
0.02
–1.00
0
0.5
1
1.5 2 2.5
LDO LOAD (mA)
3
3.5
4
0.00
VIN = 50mV
1:100 RATIO TRANSFORMER
COUT = 220µF
CSTORE = 470µF
CLDO = 2.2µF
CH2, VOUT
1V/DIV
CH3, VLDO
1V/DIV
3109 G12
0.5
1
1.5 2 2.5
LDO LOAD (mA)
3
3.5
4
3109 G11
VOUT Ripple
50mA LOAD STEP
COUT = 220µF
CH1
VSTORE
1V/DIV
0
3109 G10
VOUT and PGOOD Response
During a Step Load
Start-Up Voltage Sequencing
10SEC/DIV
0.10
0.04
3109 G9
20µs/DIV
0.14
0.12
30µA LOAD
COUT = 220µF
CH2
VOUT
1V/DIV
20mV/
DIV
CH1
PGD
1V/DIV
5ms/DIV
3109 G13
100ms/DIV
3109 G14
3109f
LTC3109
Typical Performance Characteristics TA = 25°C, unless otherwise noted.
LDO Step Load Response
Enable Input and VOUT2
Running on Storage Capacitor
CSTORE = 470µF
VOUT LOAD = 100µA
VLDO
20mV/DIV
CH3
VSTORE
1V/DIV
CH2
VOUT2
1V/DIV
ILDO
5mA/DIV
CH2, VOUT
1V/DIV
CH4, VLDO
1V/DIV
CH1, VIN
50mV/DIV
CH1
VOUT2_EN
1V/DIV
200µs/DIV
3109 G15
3109 G17
5SEC/DIV
10mA LOAD ON VOUT2
COUT = 220µF
0mA TO 3mA LOAD STEP
CLDO = 2.2µF
Pin Functions
3109 G16
1ms/DIV
(QFN/SSOP)
VSTORE (Pin 1/Pin 3): Output for the Storage Capacitor or
Battery. A large storage capacitor may be connected from
this pin to GND for powering the system in the event the
input voltage is lost. It will be charged up to the maximum
VAUX clamp voltage. If not used, this pin should be left
open or tied to VAUX.
VAUX (Pin 2/Pin 4): Output of the Internal Rectifier Circuit and VCC for the IC. Bypass VAUX with at least 1µF of
capacitance to ground. An active shunt regulator clamps
VAUX to 5.25V (typical).
VOUT (Pin 3/Pin 5): Main Output of the Converter. The
voltage at this pin is regulated to the voltage selected by
VS1 and VS2 (see Table 1). Connect this pin to a reservoir
capacitor or to a rechargeable battery. Any high current
pulse loads must be fed by the reservoir capacitor on
this pin.
VOUT2 (Pin 4/ Pin 6): Switched Output of the Converter.
Connect this pin to a switched load. This output is open
until VOUT_EN is driven high, then it is connected to VOUT
through a 1Ω PMOS switch. If not used, this pin should
be left open or tied to VOUT .
VOUT2_EN (Pin 5/Pin 7): Enable Input for VOUT2. VOUT2
will be enabled when this pin is driven high. There is an
internal 5M pull-down resistor on this pin. If not used,
this pin can be left open or grounded.
PGOOD (Pin 6/Pin 8): Power Good Output. When VOUT
is within 7.5% of its programmed value, this pin will be
pulled up to the LDO voltage through a 1M resistor. If
VOUT drops 9% below its programmed value PGOOD will
go low. This pin can sink up to 100µA.
VLDO (Pin 7/Pin 9): Output of the 2.2V LDO. Connect a
2.2µF or larger ceramic capacitor from this pin to GND.
If not used, this pin should be tied to VAUX.
GND (Pins 8, 11, 16, Exposed Pad Pin 21/Pins 10, 13,
18): Ground Pins. Connect these pins directly to the ground
plane. The exposed pad serves as a ground connection and
as a means of conducting heat away from the die.
VS2 (Pin 20/Pin 2): VOUT Select Pin 2. Connect this
pin to ground or VAUX to program the output voltage
(see Table 1).
VS1 (Pin 19/Pin 1): VOUT Select Pin 1. Connect this
pin to ground or VAUX to program the output voltage
(see Table 1).
Table 1. Regulated Output Voltage Using Pins VS1 and VS2
VS2
VS1
VOUT
GND
GND
2.35V
GND
VAUX
3.3V
VAUX
GND
4.1V
VAUX
VAUX
5.0V
3109f
LTC3109
Pin Functions
(DFN/SSOP)
C1B (Pin 9/Pin 11): Input to the Charge Pump and Rectifier
Circuit for Channel B. Connect a capacitor from this pin
to the secondary winding of the “B” step-up transformer.
See the Applications Information section for recommended
capacitor values.
C1A (Pin 18/Pin 20): Input to the Charge Pump and Rectifier Circuit for Channel A. Connect a capacitor from this pin
to the secondary winding of the “A” step-up transformer.
See the Applications Information section for recommended
capacitor values.
C2B (Pin 10/Pin 12): Input to the Gate Drive Circuit for
SWB. Connect a capacitor from this pin to the secondary
winding of the “B” step-up transformer. See the Applications
Information section for recommended capacitor values.
SWA (Pin 15/Pin 17): Connection to the Internal N-Channel Switch for Channel A. Connect this pin to the primary
winding of the “A” transformer.
SWB (Pin 12/Pin 14): Connection to the Internal N-Channel Switch for Channel B. Connect this pin to the primary
winding of the “B” transformer.
VINA (Pin 14/Pin 16): Connection to the Internal N-Channel
Switch for Channel A. Connect this pin to one side of the
input voltage source (see Typical Applications).
VINB (Pin 13/Pin 15): Connection to the Internal N-Channel
Switch for Channel B. Connect this pin to the other side of
the input voltage source (see Typical Applications).
C2A (Pin 17/Pin 19): Input to the Gate Drive Circuit for
SWA. Connect a capacitor from this pin to the secondary
winding of the “A” step-up transformer. See the Applications
Information section for recommended capacitor values.
3109f
LTC3109
Block Diagram
SYNC
RECTIFY
C1B
REFERENCE
VREF
1.2V
VOUT2
1Ω
SYNC
RECTIFY
•
•
VOUT2_EN
VOUT
C1A
5.25V
+
C2A
VIN
C2B
VOUT
VINA
•
•
SWB
+
–
POWER
SWITCHES
VREF
COUT
VOUT
PROGRAM
VS2
CHARGE
CONTROL
VOUT
VS1
VLDO
VSTORE
SWA
VOUT2
1M
+
PG00D
PG00D
–
VINB
VSTORE
VOUT
VREF
VAUX
CAUX
1µF
+
LDO
VLDO
CSTORE
GND
3109 BD
2.2V
CLDO
2.2µF
3109f
LTC3109
Operation (Refer to the Block Diagram)
The LTC3109 is designed to use two small external
step-up transformers to create an ultralow input voltage
step-up DC/DC converter and power manager that can
operate from input voltages of either polarity. This unique
capability enables energy harvesting from thermoelectric
generators (TEGs) in applications where the temperature
differential across the TEG may be of either (or unknown)
polarity. It can also operate from low level AC sources. It
is ideally suited for low power wireless sensors and other
applications in which surplus energy harvesting is used to
generate system power because traditional battery power
is inconvenient or impractical.
The LTC3109 is designed to manage the charging and
regulation of multiple outputs in a system in which the
average power draw is very low, but where periodic pulses
of higher load current may be required. This is typical of
wireless sensor applications, where the quiescent power
draw is extremely low most of the time, except for transmit
pulses when circuitry is powered up to make measurements and transmit data.
The LTC3109 can also be used to trickle charge a standard
capacitor, super capacitor or rechargeable battery, using
energy harvested from a TEG or low level AC source.
Resonant Oscillator
The LTC3109 utilizes MOSFET switches to form a resonant step-up oscillator that can operate from an input of
either polarity using external step-up transformers and
small coupling capacitors. This allows it to boost input
voltages as low as 30mV high enough to provide multiple
regulated output voltages for powering other circuits. The
frequency of oscillation is determined by the inductance
of the transformer secondary winding, and is typically
in the range of 10kHz to 100kHz. For input voltages as
low as 30mV, transformers with a turns ratio of about
1:100 is recommended. For operation from higher input
voltages, this ratio can be lower. See the Applications
Information section for more information on selecting
the transformers.
Charge Pump and Rectifier
The AC voltage produced on the secondary winding of
the transformer is boosted and rectified using an external
charge pump capacitor (from the secondary winding to
pin C1A or C1B) and the rectifiers internal to the LTC3109.
The rectifier circuit feeds current into the VAUX pin, providing charge to the external VAUX capacitor and the other
outputs.
VAUX
The active circuits within the LTC3109 are powered from
VAUX, which should be bypassed with a 1µF minimum
capacitor. Once VAUX exceeds 2.5V, the main VOUT is allowed to start charging.
An internal shunt regulator limits the maximum voltage
on VAUX to 5.25V typical. It shunts to ground any excess
current into VAUX when there is no load on the converter
or the input source is generating more power than is
required by the load. This current should be limited to
15mA max.
Voltage Reference
The LTC3109 includes a precision, micropower reference,
for accurate regulated output voltages. This reference
becomes active as soon as VAUX exceeds 2V.
Synchronous Rectifiers
Once VAUX exceeds 2V, synchronous rectifiers in parallel with each of the internal rectifier diodes take over the
job of rectifying the input voltage at pins C1A and C1B,
improving efficiency.
Low Dropout Linear Regulator (LDO)
The LTC3109 includes a low current LDO to provide a
regulated 2.2V output for powering low power processors or other low power ICs. The LDO is powered by
the higher of VAUX or VOUT . This enables it to become
active as soon as VAUX has charged to 2.3V, while the
3109f
LTC3109
Operation (Refer to the Block Diagram)
VOUT storage capacitor is still charging. In the event of a
step load on the LDO output, current can come from the
main VOUT reservoir capacitor. The LDO requires a 2.2µF
ceramic capacitor for stability. Larger capacitor values
can be used without limitation, but will increase the time
it takes for all the outputs to charge up. The LDO output
is current limited to 5mA minimum.
VOUT
The main output voltage on VOUT is charged from the VAUX
supply, and is user-programmed to one of four regulated
voltages using the voltage select pins VS1 and VS2, according to Table 2. Although the logic-threshold voltage
for VS1 and VS2 is 0.85V typical, it is recommended that
they be tied to ground or VAUX.
Table 2
VS2
VS1
VOUT
GND
GND
2.35V
GND
VAUX
3.3V
VAUX
GND
4.1V
VAUX
VAUX
5V
When the output voltage drops slightly below the regulated
value, the charging current will be enabled as long as VAUX
is greater than 2.5V. Once VOUT has reached the proper
value, the charging current is turned off. The resulting
ripple on VOUT is typically less than 20mV peak to peak .
The internal programmable resistor divider, controlled by
VS1 and VS2, sets VOUT , eliminating the need for very
high value external resistors that are susceptible to noise
pickup and board leakages.
In a typical application, a reservoir capacitor (typically a
few hundred microfarads) is connected to VOUT . As soon
as VAUX exceeds 2.5V, the VOUT capacitor will begin to
charge up to its regulated voltage. The current available
to charge the capacitor will depend on the input voltage
and transformer turns ratio, but is limited to about 15mA
typical. Note that for very low input voltages, this current
may be in the range of 1µA to 1000µA.
PGOOD
A power good comparator monitors the VOUT voltage.
The PGOOD pin is an open-drain output with a weak pullup (1MΩ) to the LDO voltage. Once VOUT has charged
to within 7.5% of its programmed voltage, the PGOOD
output will go high. If VOUT drops more than 9% from its
programmed voltage, PGOOD will go low. The PGOOD
output is designed to drive a microprocessor or other
chip I/O and is not intended to drive a higher current load
such as an LED. The PGOOD pin can also be pulled low in
a wire-OR configuration with other circuitry.
VOUT2
VOUT2 is an output that can be turned on and off by the
host using the VOUT2_EN pin. When enabled, VOUT2 is connected to VOUT through a 1Ω P-channel MOSFET switch.
This output, controlled by a host processor, can be used
to power external circuits such as sensors and amplifiers,
that don’t have a low power “sleep” or shutdown capability. VOUT2 can be used to power these circuits only when
they are needed.
Minimizing the amount of decoupling capacitance on
VOUT2 enables it to be switched on and off faster, allowing shorter pulse times and therefore smaller duty cycles
in applications such as a wireless sensor/transmitter. A
small VOUT2 capacitor will also minimize the energy that
will be wasted in charging the capacitor every time VOUT2
is enabled.
VOUT2 has a current limiting circuit that limits the peak
current to 0.3A typical.
The VOUT2 enable input has a typical threshold of 1V
with 100mV of hysteresis, making it logic compatible. If
VOUT2_EN (which has an internal 5M pull-down resistor)
is low, VOUT2 will be off. Driving VOUT2_EN high will turn
on the VOUT2 output.
Note that while VOUT2_EN is high, the current limiting circuitry for VOUT2 draws an extra 8µA of quiescent current
from VOUT . This added current draw has a negligible effect
3109f
10
LTC3109
Operation (Refer to the Block Diagram)
on the application and capacitor sizing, since the load on
the VOUT2 output, when enabled, is likely to be orders of
magnitude higher than 8µA.
VSTORE
The VSTORE output can be used to charge a large storage
capacitor or rechargeable battery. Once VOUT has reached
regulation, the VSTORE output will be allowed to charge
up to the clamped VAUX voltage (5.25V typical). The
storage element on VSTORE can then be used to power
the system in the event that the input source is lost, or
is unable to provide the current demanded by the VOUT ,
VOUT2 and LDO outputs.
VOLTAGE (V)
If VAUX drops below VSTORE, the LTC3109 will automatically draw current from the storage element. Note that it
may take a long time to charge a large storage capacitor,
depending on the input energy available and the loading
on VOUT and VLDO.
5.0
2.5
0
3.0
2.0
1.0
0
5.0
Note that VSTORE is not intended to supply high pulse
load currents to VOUT . Any pulse load on VOUT must be
handled by the VOUT reservoir capacitor.
Short-Circuit Protection
All outputs of the LTC3109 are current limited to protect
against short circuits to ground.
Output Voltage Sequencing
A timing diagram showing the typical charging and voltage
sequencing of the outputs is shown in Figure 1. Note that
the horizontal (time) axis is not to scale, and is used for
illustration purposes to show the relative order in which
the output voltages come up.
VSTORE
PGOOD
2.5
VOUT
0
3.0
2.0
1.0
0
5.0
2.5
0
Since the maximum charging current available at the
VSTORE output is limited to about 15mA, it can safely be
used to trickle charge NiCd or NiMH batteries for energy
storage when the input voltage is lost.
VLDO
VAUX
0
10
20
30
40
TIME (ms)
50
60
70
80
3109 F01
Figure 1. Output Voltage Sequencing
(with VOUT Programmed for 3.3V). Time Not to Scale
3109f
11
LTC3109
Applications Information
The LTC3109 is designed to gather energy from very low
input voltage sources and convert it to usable output
voltages to power microprocessors, wireless transmitters and analog sensors. Its architecture is specifically
tailored to applications where the input voltage polarity is
unknown, or can change. This “auto-polarity” capability
makes it ideally suited to energy harvesting applications
using a TEG whose temperature differential may be of
either polarity.
Applications such as wireless sensors typically require
much more peak power, and at higher voltages, than
the input voltage source can produce. The LTC3109 is
designed to accumulate and manage energy over a long
period of time to enable short power pulses for acquiring
and transmitting data. The pulses must occur at a low
enough duty cycle that the total output energy during the
pulse does not exceed the average source power integrated
over the accumulation time between pulses. For many
applications, this time between pulses could be seconds,
minutes or hours.
The PGOOD signal can be used to enable a sleeping
microprocessor or other circuitry when VOUT reaches
regulation, indicating that enough energy is available for
a transmit pulse.
Input Voltage Sources
For a given transformer turns ratio, there is a maximum
recommended input voltage to avoid excessively high
secondary voltages and power dissipation in the shunt
regulator. It is recommended that the maximum input
voltage times the turns ratio be less than 50.
Note that a low ESR decoupling capacitor may be required
across a DC input source to prevent large voltage droop and
Peltier Cell (ThermoElectric Generator)
A Peltier cell 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.
When used in this manner, they are referred to as thermoelectric generators (TEGs). The polarity of the output voltage
will depend on the polarity of the temperature differential
between the TEG plates. The magnitude of the output voltage is proportional to the magnitude of the temperature
differential between the plates.
The low voltage capability of the LTC3109 design allows it
to operate from a typical TEG with temperature differentials
as low as 1°C of either polarity, making it ideal for harvesting energy in applications where a temperature difference
exists between two surfaces or between a surface and
the ambient temperature. The internal resistance (ESR)
of most TEGs is in the range of 1Ω to 5Ω, allowing for
reasonable power transfer. The curves in Figure 2 show the
open-circuit output voltage and maximum power transfer
for a typical TEG with an ESR of 2Ω, over a 20°C range of
temperature differential (of either polarity).
1000
100
TEG: 30mm SQUARE
127 COUPLES
R = 2Ω
100
10
VOC
MAX POUT
(IDEAL)
10
1
1
1
10
dT (°C)
TEG MAXIMUM POUT – IDEAL (mW)
The LTC3109 can operate from a number of low input
voltage sources, such as Peltier cells (thermoelectric
generators), or low level AC sources. The minimum input
voltage required for a given application will depend on the
transformer turns ratios, the load power required, and the
internal DC resistance (ESR) of the voltage source. Lower
ESR sources will allow operation from lower input voltages,
and provide higher output power capability.
ripple caused by the source’s ESR and the peak primary
switching current (which can reach hundreds of milliamps).
Since the input voltage may be of either polarity, a ceramic
capacitor is recommended.
TEG VOPEN-CIRCUIT (mV)
Introduction
0.1
100
3109 F02
Figure 2. Typical Performance of a Peltier Cell
Acting as a Power Generator (TEG)
3109f
12
LTC3109
Applications Information
TEG Load Matching
Unipolar Applications
The LTC3109 was designed to present an input resistance
(load) in the range of 2Ω to 10Ω, depending on input voltage, transformer turns ratio and the C1A and C2A capacitor
values (as shown in the Typical Performance curves). For
a given turns ratio, as the input voltage drops, the input
resistance increases. This feature allows the LTC3109 to
optimize power transfer from sources with a few Ohms
of source resistance, such as a typical TEG. Note that a
lower source resistance will always provide more output
current capability by providing a higher input voltage
under load.
The LTC3109 can also be configured to operate from two
independent unipolar voltage sources, such as two TEGs
in different locations. In this configuration, energy can be
harvested from either or both sources simultaneously. See
the Typical Applications for an example.
Table 3. Peltier Cell Manufacturers
The LTC3109 can also be configured to operate from a
single unipolar source, using a single step-up transformer,
by ganging its VIN and SW pins together. In this manner,
it can extract the most energy from very low resistance
sources. See Figure 3 for an example of this configuration,
along with the performance curves.
Peltier Cell (TEG) Suppliers
CUI Inc
www.cui.com
Ferrotec
www.ferrotec.com/products/thermal/modules/
Fujitaka
www.fujitaka.com/pub/peltier/english/thermoelectric_power.html
Hi-Z Technology
www.hi-z.com
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 some Peltier cell manufacturers is given in Table 3 and
some recommended part numbers in Table 4.
Kryotherm
www.kryotherm
COMPONENT SELECTION
Laird Technologies
www.lairdtech.com
Step-Up Transformer
Micropelt
www.micropelt.com
Nextreme
www.nextreme.com
TE Technology
www.tetech.com/Peltier-Thermoelectric-Cooler-Modules.html
Tellurex
www.tellurex.com/
The turns ratio of the step-up transformers will determine
how low the input voltage can be for the converter to start.
Due to the auto-polarity architecture, two identical step-up
transformers should be used, unless the temperature drop
across the TEG is significantly different in one polarity, in
which case the ratios may be different.
Table 4. Recommended TEG Part Numbers by Size
MANUFACTURER
CUI Inc. (Distributor)
15mm
20mm
30mm
40mm
CP60133
CP60233
CP60333
CP85438
Ferrotec
9501/031/030 B
9501/071/040 B
9500/097/090 B
9500/127/100 B
Fujitaka
FPH13106NC
FPH17106NC
FPH17108AC
FPH112708AC
Kryotherm
TGM-127-1.0-0.8
LCB-127-1.4-1.15
Laird Technology
PT6.7.F2.3030.W6
PT8.12.F2.4040.TA.W6
Marlow Industries
Tellurex
TE Technology
RC3-8-01
RC6-6-01
RC12-8-01LS
C2-15-0405
C2-20-0409
C2-30-1505
C2-40-1509
TE-31-1.0-1.3
TE-31-1.4-1.15
TE-71-1.4-1.15
TE-127-1.4-1.05
3109f
13
LTC3109
Applications Information
VIN
+
•
T1
CIN
C1
•
C1A
1nF
VOUT2
VOUT2
LTC3109
330k
VOUT
SET
C2A
VOUT
+
VLDO
SWA
VINA
C1B
C2B
PG00D
SWB
VINB VOUT2_EN
VS1
VSTORE
VAUX
VS2
GND
VLDO
2.2µF
VOUT
COUT
PG00D
VOUT2_ENABLE
10µF
NOTE: VALUES FOR CIN, T1, C1 AND COUT
ARE DETERMINED BY THE APPLICATION
3109 F03a
Figure 3. Unipolar Application
Typical PVOUT vs dT for Unipolar
Configuration
10000
FERROTEC 9500/127/100B, 40mm TEG
C1 = 33nF,
T1 = COILCRAFT LPR6235-123QML
1:50 RATIO
VOUT = 5V
55
50
45
EFFICIENCY (%)
1000
VOUT = 3.3V
1
60
VOUT = 3.3V
IVOUT (µA)
POUT (mW)
10
Typical Efficiency vs VIN for
Unipolar Configuration
Typical IVOUT vs VIN for Unipolar
Configuration
100
40
35
30
25
20
15
0.1
100
10
10
1:100, C1 = 6.8nF
1:50, C1 = 33nF
1:20, C1 = 68nF
10
100
VIN (mV)
dT (°K)
1000
0
10
100
VIN (mV)
1000
3109 F03c
Typical RIN vs VIN for Unipolar
Configuration
Typical Input Current vs VIN for
Unipolar Configuration
600
4.0
1:100, C1 = 6.8nF
1:50, C1 = 33nF
1:20, C1 = 68nF
550
500
450
3.5
INPUT RESISTANCE (Ω)
INPUT CURRENT (mA)
5
3109 F03b
3109 F03f
400
350
300
250
200
150
100
3.0
2.5
2.0
1.5
1.0
1:100, C1 = 6.8nF
1:50, C1 = 33nF
1:20, C1 = 68nF
0.5
50
0
1:100, C1 = 6.8nF
1:50, C1 = 33nF
1:20, C1 = 68nF
10
10
100
VIN (mV)
1000
3109 F03d
0
10
100
VIN (mV)
1000
3109 F03e
3109f
14
LTC3109
Applications Information
Using a 1:100 primary-secondary ratio yields start-up
voltages as low as 30mV. Other factors that affect performance are the resistance of the transformer windings
and the inductance of the windings. Higher DC resistance
will result in lower efficiency and higher start-up voltages. The secondary winding inductance will determine
the resonant frequency of the oscillator, according to the
formula below.
Freq =
1
Hz
2 • π • L SEC • C
where LSEC is the inductance of one of the secondary
windings and C is the load capacitance on the secondary winding. This is comprised of the input capacitance
at pin C2A or C2B, typically 70pF each, in parallel with
the transformer secondary winding’s shunt capacitance.
The recommended resonant frequency is in the range of
10kHz to 100kHz. Note that loading will also affect the
resonant frequency. See Table 5 for some recommended
transformers.
Table 5. Recommended Transformers
VENDOR
Coilcraft
www.coilcraft.com
TYPICAL STARTUP VOLTAGE
25mV
35mV
85mV
PART NUMBER
LPR6235-752SML (1:100 ratio)
LPR6235-123QML (1:50 ratio)
LPR6235-253PML (1:20 ratio)
Using External Charge Pump Rectifiers
The synchronous rectifiers in the LTC3109 have been
optimized for low frequency, low current operation, typical
of low input voltage applications. For applications where
the resonant oscillator frequency exceeds 100kHz, or a
transformer turns ratio of less than 1:20 is used, or the
C1A and C1B capacitor values are greater than 68nF, the
use of external charge pump rectifiers (1N4148 or 1N914
or equivalent) is recommended. See the Typical Application
circuits for an example. Avoid the use of Schottky rectifiers, as their low forward voltage increases the minimum
start-up voltage.
C1 Capacitor
The charge pump capacitor that is connected from each
transformer’s secondary winding to the corresponding
C1A and C1B pins has an effect on converter input resistance and maximum output current capability. Generally
a minimum value of 1nF is recommended when operating
from very low input voltages using a transformer with
a ratio of 1:100. Capacitor values of 2.2nF to 10nF will
provide higher output current at higher input voltages,
however larger capacitor values can compromise performance when operating at low input voltage or with high
resistance sources. For higher input voltages and lower
turns ratios, the value of the C1 capacitor can be increased
for higher output current capability. Refer to the Typical
Applications examples for the recommended value for a
given turns ratio.
C2 Capacitor
The C2 capacitors connect pins C2A and C2B to their
respective transformer secondary windings. For most
applications a capacitor value of 470pF is recommended.
Smaller capacitor values tend to raise the minimum
start-up voltage, and larger capacitor values can lower
efficiency.
Note that the C1 and C2 capacitors must have a voltage
rating greater than the maximum input voltage times the
transformer turns ratio.
VOUT and VSTORE Capacitor
For pulsed load applications, the VOUT capacitor should
be sized to provide the necessary current when the load
is pulsed on. The capacitor value required will be dictated
by the load current (ILOAD), the duration of the load pulse
(tPULSE), and the amount of VOUT voltage droop the application can tolerate (∆VOUT). The capacitor must be
rated for whatever voltage has been selected for VOUT by
VS1 and VS2:
COUT (µF) ≥
ILOAD(mA ) • tPULSE(ms)
∆VOUT ( V)
3109f
15
LTC3109
Applications Information
Note that there must be enough energy available from the
input voltage source for VOUT to recharge the capacitor
during the interval between load pulses (as discussed in
Design Example 1). Reducing the duty cycle of the load
pulse will allow operation with less input energy.
Note that storage capacitors requiring voltage balancing
resistors are not recommended due to the steady-state
current draw of the resistors.
The VSTORE capacitor may be of very large value (thousands of microfarads or even Farads), to provide energy
storage at times when the input voltage is lost. Note that
this capacitor can charge all the way to the VAUX clamp
voltage of 5.25V typical (regardless of the settings for
VOUT), so be sure that the holdup capacitor has a working voltage rating of at least 5.5V at the temperature that
it will be used.
Due to the rather low switching frequency of the resonant
converter and the low power levels involved, PCB layout
is not as critical as with many other DC/DC converters.
There are however, a number of things to consider.
The VSTORE input is not designed to provide high pulse
load currents to VOUT . The current path from VSTORE to
VOUT is limited to about 26mA max.
The VSTORE capacitor can be sized using the following
formula:
CSTORE ≥
(7µA + IQ + ILDO + (IPULSE • tPULSE • f)) • tSTORE
5.225 – VOUT
PCB Layout Guidelines
Due to the very low input voltages the circuit operates from,
the connections to VIN, the primary of the transformers
and the SW, VIN and GND pins of the LTC3109 should be
designed to minimize voltage drop from stray resistance,
and able to carry currents as high as 500mA. Any small
voltage drop in the primary winding conduction path will
lower efficiency and increase start-up voltage and capacitor charge time.
Also, due to the low charge currents available at the outputs of the LTC3109, any sources of leakage current on
the output voltage pins must be minimized. An example
board layout is shown in Figure 4.
where 7µA is the quiescent current of the LTC3109, IQ is
the load on VOUT in between pulses, ILDO is the load on
the LDO between pulses, IPULSE is the total load during the
pulse, tPULSE is the duration of the pulse, f is the frequency
of the pulses, tSTORE is the total storage time required
and VOUT is the output voltage required. Note that for a
programmed output voltage of 5V, the VSTORE capacitor
cannot provide any beneficial storage time to VOUT .
To minimize losses and capacitor charge time, all capacitors used for VOUT and VSTORE should be low leakage.
See Table 6 for recommended storage capacitors.
Table 6. Recommended Storage Capacitors
VENDOR
PART NUMBER/SERIES
AVX
www.avx.com
BestCap Series
TAJ and TPS Series Tantalum
Cap-XX
www.cap-xx.com
GZ Series
Figure 4. Example Component Placement for 2-Layer PC Board
(QFN Package). Note That VSTORE and VOUT Capacitor Sizes
are Application Dependent
Cooper/Bussman
KR Series
www.bussmann.com/3/PowerStor.html P Series
Vishay/Sprague
www.vishay.com/capacitors
Tantamount 592D
595D Tantalum
3109f
16
LTC3109
Applications Information
Design example 1
This design example will explain how to calculate the
necessary reservoir capacitor value for VOUT in pulsedload applications, such as a wireless sensor/transmitter.
In these types of applications, the load is very small for a
majority of the time (while the circuitry is in a low power
sleep state), with pulses of load current occurring periodically during a transmit burst.
The reservoir capacitor on VOUT supports the load during
the transmit pulse; the long sleep time between pulses
allows the LTC3109 to accumulate energy and recharge
the capacitor (either from the input voltage source or the
storage capacitor). A method for calculating the maximum
rate at which the load pulses can occur for a given output
current from the LTC3109 will also be shown.
In this example, VOUT is set to 3.3V, and the maximum
allowed voltage droop during a transmit pulse is 10%, or
0.33V. The duration of a transmit pulse is 5ms, with a total
average current requirement of 20mA during the pulse.
Given these factors, the minimum required capacitance
on VOUT is:
20mA • 5ms
COUT (µF ) ≥
= 303µF
0.33V
Note that this equation neglects the effect of capacitor ESR
on output voltage droop. For ceramic capacitors and low
ESR tantalum capacitors, the ESR will have a negligible
effect at these load currents. However, beware of the voltage
coefficient of ceramic capacitors, especially those in small
case sizes. This greatly reduces the effective capacitance
when a DC bias is applied.
A standard value of 330µF could be used for COUT in
this case. Note that the load current is the total current
draw on VOUT , VOUT2 and VLDO, since the current for all
of these outputs must come from VOUT during a pulse.
Current contribution from the capacitor on VSTORE is not
considered, since it may not be able to recharge between
pulses. Also, it is assumed that the harvested charge
current from the LTC3109 is negligible compared to the
magnitude of the load current during the pulse.
To calculate the maximum rate at which load pulses can
occur, you must know how much charge current is available from the LTC3109 VOUT pin given the input voltage
source being used. This number is best found empirically,
since there are many factors affecting the efficiency of the
converter. You must also know what the total load current is on VOUT during the sleep state (between pulses).
Note that this must include any losses, such as storage
capacitor leakage.
Let’s assume that the charge current available from the
LTC3109 is 150µA and the total current draw on VOUT and
VLDO in the sleep state is 17µA, including capacitor leakage.
We’ll also use the value of 330µF for the VOUT capacitor.
The maximum transmit rate (neglecting the duration of
the transmit pulse, which is very short compared to the
period) is then given by:
T=
330µF • 0.33V
= 0.82 sec or fMAX = 1.2Hz
150µA – 17µA
Therefore, in this application example, the circuit can support a 5ms transmit pulse of 20mA every 0.82 seconds.
It can be seen that for systems that only need to transmit
every few seconds (or minutes or hours), the average
charge current required is extremely small, as long as
the sleep or standby current is low. Even if the available
charge current in the example above was only 21µA, if the
sleep current was only 5µA, it could still transmit a pulse
every seven seconds.
The following formula will allow you to calculate the time
it will take to charge the LDO output capacitor and the
VOUT capacitor the first time, from zero volts. Here again,
the charge current available from the LTC3109 must be
known. For this calculation, it is assumed that the LDO
output capacitor is 2.2µF:
tLDO =
2.2V • 2.2µF
ICHG – ILDO
If there was 150µA of charge current available and a 5µA
load on the LDO (when the processor is sleeping), the time
for the LDO to reach regulation would be only 33ms.
3109f
17
LTC3109
Applications Information
The time for VOUT to charge and reach regulation can be
calculated by the formula below, which assumes VOUT is
programmed to 3.3V and COUT is 330µF:
t VOUT =
3.3V • 330µF
+t
ICHG – IVOUT – ILDO LDO
With 150µA of charge current available and 5µA of load on
both VOUT and VLDO, the time for VOUT to reach regulation after the initial application of power would be 7.81
seconds.
Design example 2
In most pulsed-load applications, the duration, magnitude
and frequency of the load current pulses are known and
fixed. In these cases, the average charge current required
from the LTC3109 to support the average load must be
calculated, which can be easily done by the following:
ICHG ≥ IQ +
IPULSE • tPULSE
T
In this example, IQ is 5µA, IPULSE is 100mA, tPULSE is 5ms
and T is one hour. The average charge current required
from the LTC3109 would be:
ICHG ≥ 5µA +
100mA • 0.005 sec
= 5.14µA
3600 sec
Therefore, if the LTC3109 has an input voltage that allows
it to supply a charge current greater than just 5.14µA, the
application can support 100mA pulses lasting 5ms every
hour. It can be seen that the sleep current of 5µA is the
dominant factor in this example, because the transmit
duty cycle is so small (0.00014%). Note that for a VOUT
of 3.3V, the average power required by this application is
only 17µW (not including converter losses).
Keep in mind that the charge current available from the
LTC3109 has no effect on the sizing of the VOUT capacitor,
and the VOUT capacitor has no effect on the maximum
allowed pulse rate.
where IQ is the sleep current supplied by VOUT and VLDO
to the external circuitry in-between load pulses, including
output capacitor leakage, IPULSE is the total load current
during the pulse, tPULSE is the duration of the load pulse
and T is the pulse period (essentially the time between
load pulses).
3109f
18
LTC3109
Typical Applications
Energy Harvester Operates from Small Temperature Differentials of Either Polarity
TEG
(THERMOELECTRIC GENERATOR) T1
±30mV TO ±500mV
1:100
•
•
T2
1:100
1nF
•
1nF
•
C1A
VOUT2
C2A
VOUT
SWA
VINA
VLDO
470pF
OPTIONAL SWITCHED OUTPUT FOR SENSORS
3.3V
+
2.2V
2.2µF
LOW POWER
RADIO
LTC3109
C1B
C2B
SENSOR(S)
µP
470pF
470µF
PG00D
SWB VOUT2_EN
VINB
VS1
VSTORE
VAUX
VS2
GND
5.25V
1µF
+
CSTORE
3109 TA02
T1, T2: COILCRAFT LPR6235-752SML
3109f
19
LTC3109
Typical Applications
Li-Ion Battery Charger and LDO Operates from a Low Level AC Input
50mV TO
300mV RMS
•
T1
1:100
1nF
•
AC 60Hz
•
T2
1:100
C1A
VOUT2
C2A
VOUT
470pF
1nF
SWA
VINA
VLDO
LTC3109
TO LOAD
2.2V
VLDO
FAIRCHILD
2.2µF
FDG328P
4.1V
C1B
•
+
470pF
C2B
Li-Ion
BATTERY
PG00D
SWB VOUT2_EN
VINB
VS1
VSTORE
VAUX
VS2
GND
T1, T2: COILCRAFT
LPR6235-752SML
NC
1µF
LTC4070*
HBO
LBO
NC
NTC
DRV
NC
VCC
NTCBIAS
NC
ADJ
GND
*THE LTC4070 IS A PRECISION BATTERY
CHARGER OFFERING UNDERVOLTAGE
PROTECTION, WITH A TYPICAL SUPPLY
CURRENT OF ONLY 0.45µA
3109 TA03
Unipolar Energy Harvester Charges Battery Backup
THERMOELECTIC
GENERATOR
FERROTEC 9500/127/100B
+
–
47µF
•
T1
1:50
33nF
•
330k
T1: COILCRAFT
LPR6235-123QML
Typical PVOUT vs dT for Unipolar
Configuration
5.0
4.0
POUT (mW)
3.5
VOUT2
C2A
VOUT
+
330µF
4V
LTC3109
VLDO
SWA
VINA
C1B
C2B
PG00D
SWB VOUT2_EN
VINB
VS1
VSTORE
VAUX
VS2
GND
2.2V
VOUT
3.3V
VLDO
2.2µF
PGOOD
1µF
FAIRCHILD
FDG328P
4.1V
+
FERROTEC 9500/127/100B
C1 = 33nF
T1 = COILCRAFT LPR6235-123QML
1:50 RATIO
VOUT = 3.3V
4.5
C1A
1nF
NC
Li-Ion
BATTERY
LTC4070
HBO
LBO
NC
NTC
DRV
NC
VCC
NTCBIAS
NC
ADJ
GND
3109 TA06a
3.0
2.5
2.0
1.5
1.0
0.5
0
0
1
2
3
4
5 6
dT (°K)
7
8
9
10
3109 TA06b
3109f
20
LTC3109
Typical Applications
Dual-Input Energy Harvester Generates 5V and 2.2V from Either or Both TEGs,
Operating at Different Temperatures of Fixed Polarity
THERMOELECTRIC
GENERATOR
25mV TO 500mV
THERMOELECTRIC
GENERATOR OR
THERMOPILE
35mV TO 1000mV
+
COILCRAFT
LPR6235-752SML
1:100
•
•
–
+
–
1nF
C1A
470pF
VOUT2
LTC3109
C2A
COILCRAFT
LPR6235-123QML 4.7nF
1:50
•
•
VOUT
5V
+
SWA
VINA
VLDO
VOUT
COUT*
2.2V
2.2µF
C1B
VLDO
470pF
C2B
PG00D
SWB VOUT2_EN
VINB
VS1
VS2
PG00D
VSTORE
VAUX
1µF
GND
3109 TA04
*THE VALUE OF THE COUT CAPACITOR IS
DETEMINED BY THE LOAD CHARACTERISTICS
3109f
21
LTC3109
Package Description
UF Package
20-Lead Plastic QFN (4mm × 4mm)
(Reference LTC DWG # 05-08-1710 Rev A)
0.70 p0.05
4.50 p 0.05
3.10 p 0.05
2.00 REF
2.45 p 0.05
2.45 p 0.05
PACKAGE OUTLINE
0.25 p0.05
0.50 BSC
RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS
APPLY SOLDER MASK TO AREAS THAT ARE NOT SOLDERED
4.00 p 0.10
0.75 p 0.05
R = 0.05
TYP
R = 0.115
TYP
19 20
0.40 p 0.10
PIN 1
TOP MARK
(NOTE 6)
4.00 p 0.10
PIN 1 NOTCH
R = 0.20 TYP
OR 0.35 s 45o
CHAMFER
BOTTOM VIEW—EXPOSED PAD
1
2.00 REF
2.45 p 0.10
2
2.45 p 0.10
(UF20) QFN 01-07 REV A
0.200 REF
0.00 – 0.05
0.25 p 0.05
0.50 BSC
NOTE:
1. DRAWING IS PROPOSED TO BE MADE A JEDEC PACKAGE OUTLINE MO-220
VARIATION (WGGD-1)—TO BE APPROVED
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
3109f
22
LTC3109
Package Description
GN Package
20-Lead Plastic SSOP (Narrow .150 Inch)
(Reference LTC DWG # 05-08-1641)
.337 – .344*
(8.560 – 8.738)
.045 p.005
20 19 18 17 16 15 14 13 12
.254 MIN
.150 – .165
.0165 p.0015
11
.229 – .244
(5.817 – 6.198)
.058
(1.473)
REF
.150 – .157**
(3.810 – 3.988)
.0250 BSC
1
RECOMMENDED SOLDER PAD LAYOUT
.015 p .004
s 45o
(0.38 p 0.10)
.0075 – .0098
(0.19 – 0.25)
2 3
4
5 6
7
8
.0532 – .0688
(1.35 – 1.75)
9 10
.004 – .0098
(0.102 – 0.249)
0o – 8o TYP
.016 – .050
(0.406 – 1.270)
NOTE:
1. CONTROLLING DIMENSION: INCHES
INCHES
2. DIMENSIONS ARE IN
(MILLIMETERS)
.008 – .012
(0.203 – 0.305)
TYP
.0250
(0.635)
BSC
3. DRAWING NOT TO SCALE
*DIMENSION DOES NOT INCLUDE MOLD FLASH. MOLD FLASH
SHALL NOT EXCEED 0.006" (0.152mm) PER SIDE
**DIMENSION DOES NOT INCLUDE INTERLEAD FLASH. INTERLEAD
FLASH SHALL NOT EXCEED 0.010" (0.254mm) PER SIDE
GN20 (SSOP) 0204
3109f
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 representation that the interconnection of its circuits as described herein will not infringe on existing patent rights.
23
LTC3109
Typical Application
IVOUT vs VIN
16
1:20 RATIO
C1 = 1µF
EXTERNAL DIODES
14
Unipolar TEG Energy Harvester for Low Resistance/High Current Inputs,
Using External Charge Pump Rectifiers
+
•
IVOUT (mA)
VAUX
BAS31
C1A
•
1nF
70mV TO 1V
VOUT2
LTC3109
C2A
SWA
VINA
C1B
VOUT
VLDO
C2B
VAUX
12
PG00D
SWB VOUT2_EN
VINB
VS1
VSTORE
VAUX
VS2
GND
SWITCHED VOUT GOES HIGH
WHEN PGOOD IS HIGH
VOUT2
0.1µF
3.3V
+
10
8
6
4
2
0
VOUT
0
COUT
100 200 300 400 500 600 700 800
VIN (mV)
3109 TA05b
2.2V
2.2µF
Efficiency vs VIN
VLDO
50
45
PG00D
40
10µF
+
CSTORE
3109 TA05
EFFICIENCY (%)
COILCRAFT
LPR6235-253PML 1.0µF
1:20
TYPICAL
35
30
25
20
15
10
5
0
100
VIN (mV)
10
1000
3109 TA05c
Related Parts
PART NUMBER
DESCRIPTION
COMMENTS
LTC3108/
LTC3108-1
Ultralow Voltage Step-Up Converter and
Power Manager
VIN: 0.02V to 1V, VOUT = 2.2V, 2.35V, 3.3V, 4.1V, 5V, IQ = 6µA,
4mm × 3mm DFN-12, SSOP-16; LTC3108-1 VOUT = 2.2V, 2.5V, 3V, 3.7V, 4.5V
LTC4070
Micropower Shunt Battery Charger
1% Float Voltage Accuracy, 50mA Max Shunt Current, VOUT = 4.0V, 4.1V, 4.2V,
IQ = 450nA, 2mm × 3mm DFN-8, MSOP-8
LTC1041
Bang-Bang Controller
VIN: 2.8V to 16V; VOUT(MIN) = Adj; IQ = 1.2mA; ISD < 1µA; SO-8 Package
LTC1389
Nanopower Precision Shunt Voltage Reference
VOUT(MIN) = 1.25V; IQ = 0.8µA; SO-8 Package
LT1672/LT1673/
LT1674
Single-/Dual-/Quad-Precision 2µA Rail-to-Rail
Op Amps
SO-8, SO-14 and MSOP-8 Packages
LT3009
3µA IQ, 20mA Linear Regulator
VIN: 1.6V to 20V; VOUT(MIN): 0.6V to Adj, 1.2V, 1.5V, 1.8V, 2.5V, 3.3V,
5V to Fixed; IQ = 3µA; ISD < 1µA; 2mm × 2mm DFN-8 and SC70 Packages
LTC3588-1
Piezoelectric Energy Generator with Integrated
High Efficiency Buck Converter
VIN: 2.7V to 20V; VOUT(MIN): Fixed to 1.8V, 2.5V, 3.3V, 3.6V; IQ = 0.95µA;
3mm × 3mm DFN-10 and MSOP-10E Packages
LT8410/LT8410-1
Micropower 25mA/8mA Low Noise Boost Converter VIN: 2.6V to 16V; VOUT(MIN) = 40VMAX; IQ = 8.5µA; ISD < 1µA;
2mm × 2mm DFN-8 Package
with Integrated Schottky Diode and Output
Disconnect
3109f
24 Linear Technology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408) 432-1900
●
FAX: (408) 434-0507 ● www.linear.com
LT 0610 • PRINTED IN USA
 LINEAR TECHNOLOGY CORPORATION 2010
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