LTC4O70 [Linear Systems]
Ultralow Voltage Step-Up Converter and Power Manager; 超低电压，升压型转换器和电源管理器
| 型号： | LTC4O70 |
| 厂家： | 
Linear Systems |
| 描述： | Ultralow Voltage Step-Up Converter and Power Manager |
| 文件： | 总22页 (文件大小：224K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
LTC3108
Ultralow Voltage Step-Up
Converter and Power Manager
FEATURES
DESCRIPTION
TheLTC®3108isahighlyintegratedDC/DCconverterideal
forharvestingandmanagingsurplusenergyfromextremely
low input voltage sources such as TEGs (thermoelectric
generators),thermopilesandsmallsolarcells.Thestep-up
topology operates from input voltages as low as 20mV.
The LTC3108 is functionally equivalent to the LTC3108-1
n
Operates from Inputs of 20mV
n
Complete Energy Harvesting Power
Management System
- Selectable V
of 2.35V, 3.3V, 4.1V or 5V
OUT
- LDO: 2.2V at 3mA
- Logic Controlled Output
- Reserve Energy Output
Power Good Indicator
Uses Compact Step-Up Transformers
Small 12-Lead (3mm × 4mm) DFN or 16-Lead
SSOP Packages
except for its unique fixed V
options.
OUT
n
n
n
Usingasmallstep-uptransformer,theLTC3108providesa
completepowermanagementsolutionforwirelesssensing
and data acquisition. The 2.2V LDO powers an external
microprocessor, while the main output is programmed to
one of four fixed voltages to power a wireless transmitter
orsensors.Thepowergoodindicatorsignalsthatthemain
outputvoltageiswithinregulation.Asecondoutputcanbe
enabled by the host. A storage capacitor provides power
when the input voltage source is unavailable. Extremely
low quiescent current and high efficiency design ensure
the fastest possible charge times of the output reservoir
capacitor.
APPLICATIONS
n
Remote Sensors and Radio Power
n
Surplus Heat Energy Harvesting
n
HVAC Systems
n
Industrial Wireless Sensing
n
Automatic Metering
n
Building Automation
n
Predictive Maintenance
The LTC3108 is available in a small, thermally enhanced
12-lead (3mm × 4mm) DFN package and a 16-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.
TYPICAL APPLICATION
Wireless Remote Sensor Application Powered From a Peltier Cell
VOUT Charge Time
1nF
1:100
5V
1000
100
10
1
C1
VSTORE
LTC3108
V
C
= 3.3V
= 470μF
+
+
OUT
OUT
+
0.1F
6.3V
THERMOELECTRIC
GENERATOR
220μF
330pF
V
OUT2
C2
PGOOD
2.2V
PGD
VLDO
μP
20mV TO 500mV
SW
2.2μF
SENSORS
RF LINK
3.3V
VS2
V
OUT
+
470μF
1:100 Ratio
1:50 Ratio
1:20 Ratio
VS1
V
OUT2_EN
GND
3108 TA01a
VAUX
0
100 150 200 250 300 350 400
(mV)
0
50
1μF
V
IN
3108 TA01b
3108fb
1
LTC3108
ABSOLUTE MAXIMUM RATINGS (Note 1)
SW Voltage ..................................................–0.3V to 2V
C1 Voltage....................................................–0.3V to 6V
C2 Voltage (Note 5).........................................–8V to 8V
VS1, VS2, VAUX, V , PGD........................–0.3V to 6V
OUT
VLDO, VSTORE............................................–0.3V to 6V
Operating Junction Temperature Range
(Note 2)................................................. –40°C to 125°C
Storage Temperature Range.................. –65°C to 125°C
V
, V
...........................................–0.3V to 6V
OUT2 OUT2_EN
VAUX....................................................15mA into VAUX
PIN CONFIGURATION
TOP VIEW
TOP VIEW
GND
VAUX
1
2
3
4
5
6
7
8
16
15
14
13
12
11
10
9
GND
SW
C2
VAUX
1
2
3
4
5
6
12 SW
11 C2
10 C1
VSTORE
VSTORE
V
OUT
13
V
C1
OUT
GND
V
9
8
7
V
OUT2_EN
OUT2
V
V
OUT2
OUT2_EN
VLDO
PGD
VS1
VS2
VLDO
PGD
VS1
VS2
GND
GND
DE PACKAGE
12-LEAD (4mm s 3mm) PLASTIC DFN
GN PACKAGE
16-LEAD PLASTIC SSOP NARROW
T
= 125°C, θ = 43°C/W
JA
JMAX
EXPOSED PAD (PIN 13) IS GND, MUST BE SOLDERED TO PCB (NOTE 4)
T
= 125°C, θ = 110°C/W
JA
JMAX
ORDER INFORMATION
LEAD FREE FINISH
LTC3108EDE#PBF
LTC3108IDE#PBF
LTC3108EGN#PBF
LTC3108IGN#PBF
TAPE AND REEL
PART MARKING*
PACKAGE DESCRIPTION
TEMPERATURE RANGE
–40°C to 125°C
–40°C to 125°C
–40°C to 125°C
–40°C to 125°C
LTC3108EDE#TRPBF
LTC3108IDE#TRPBF
LTC3108EGN#TRPBF
LTC3108IGN#TRPBF
3108
3108
3108
3108
12-Lead (4mm × 3mm) Plastic DFN
12-Lead (4mm × 3mm) Plastic DFN
16-Lead Plastic SSOP
16-Lead Plastic SSOP
Consult LTC Marketing for parts specified for other fixed output voltages or 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/
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
20
3
MAX
UNITS
mV
Minimum Start-Up Voltage
No-Load Input Current
Using 1:100 Transformer Turns Ratio, VAUX = 0V
50
Using 1:100 Transformer Turns Ratio; V = 20mV,
mA
IN
V
= 0V; All Outputs Charged and in Regulation
OUT2_EN
l
Input Voltage Range
Using 1:100 Transformer Turns Ratio
V
500
mV
STARTUP
3108fb
2
LTC3108
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
l
l
l
l
Output Voltage
VS1 = VS2 = GND
2.30
3.234
4.018
4.90
2.350
3.300
4.100
5.000
2.40
3.366
4.182
5.10
V
V
V
V
VS1 = VAUX, VS2 = GND
VS1 = GND, VS2 = VAUX
VS1 = VS2 = VAUX
V
Quiescent Current
V
= 3.3V, V = 0V
OUT2_EN
0.2
6
μA
μA
V
OUT
OUT
VAUX Quiescent Current
LDO Output Voltage
LDO Load Regulation
LDO Line Regulation
LDO Dropout Voltage
LDO Current Limit
No Load, All Outputs Charged
0.5mA Load
9
2.266
1
l
2.134
2.2
0.5
0.05
100
11
For 0mA to 2mA Load
For VAUX from 2.5V to 5V
%
0.2
%
l
l
l
l
l
I
= 2mA
= 0V
200
mV
mA
mA
mA
V
LDO
V
4
LDO
OUT
V
Current Limit
V
= 0V
2.8
2.8
5
4.5
4.5
5.25
0.1
0.1
0.85
0.01
–7.5
–9
7
7
OUT
VSTORE Current Limit
VAUX Clamp Voltage
VSTORE Leakage Current
VSTORE = 0V
Current into VAUX = 5mA
VSTORE = 5V
5.55
0.3
μA
μA
V
V
Leakage Current
V
OUT2
= 0V, V
= 0V
OUT2
OUT2_EN
l
VS1, VS2 Threshold Voltage
VS1, VS2 Input Current
0.4
1.2
0.1
VS1 = VS2 = 5V
μA
%
PGOOD Threshold (Rising)
PGOOD Threshold (Falling)
Measured Relative to the V
Measured Relative to the V
Sink Current = 100μA
Source Current = 0
Voltage
Voltage
OUT
%
OUT
PGOOD V
PGOOD V
0.15
2.2
1
0.3
2.3
V
OL
OH
2.1
0.4
V
PGOOD Pull-Up Resistance
MΩ
V
l
V
V
V
V
V
V
V
Threshold Voltage
V
Rising
1
1.3
OUT2_EN
OUT2_EN
OUT2_EN
Pull-Down Resistance
5
MΩ
μs
μs
A
Turn-On Time
5
OUT2
OUT2
OUT2
OUT2
OUT2
Turn-Off Time
(Note 3)
= 3.3V
0.15
0.3
350
1.3
0.5
l
Current Limit
V
OUT
0.15
0.45
Current Limit Response Time
P-Channel MOSFET On-Resistance
(Note 3)
= 3.3V (Note 3)
ns
Ω
V
OUT
N-Channel MOSFET On-Resistance
C2 = 5V (Note 3)
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.
temperature (T ) is calculated from the ambient temperature (T ) and
J A
power dissipation (P ) according to the formula: T = T + (P • θ °C/W),
D
J
A
D
JA
where θ is the package thermal impedance.
JA
Note 3: Specification is guaranteed by design and not 100% tested in
Note 2: The LTC3108 is tested under pulsed load conditions such that T ≈
production.
J
T . The LTC3108E is guaranteed to meet specifications from 0°C to 85°C
A
Note 4: Failure to solder the exposed backside of the package to the PC
board ground plane will result in a thermal resistance much higher than
43°C/W.
Note 5: The absolute maximum rating is a DC rating. Under certain
conditions in the applications shown, the peak AC voltage on the C2 pin
may exceed 8V. This behavior is normal and acceptable because the
current into the pin is limited by the impedance of the coupling capacitor.
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 LTC3108I 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 board layout, the rated thermal
package thermal resistance and other environmental factors. The junction
3108fb
3
LTC3108
TA = 25°C, unless otherwise noted.
TYPICAL PERFORMANCE CHARACTERISTICS
IVOUT and Efficiency vs VIN,
1:20 Ratio Transformer
IIN vs VIN, (VOUT = 0V)
4000
80
1000
100
10
C1 = 10nF
1:50 RATIO, C1 = 4.7n
1:100 RATIO, C1 = 1n
1:20 RATIO, C1 = 10n
3500
70
I
VOUT
OUT
(V
= 0V)
3000
60
50
40
30
20
10
0
2500
I
2000 EFFICIENCY
VOUT
OUT
(V
= 4.5V)
(V
= 4.5V)
OUT
1500
1000
500
0
1
100
200
V
300
(mV)
500
0
400
10
100
1000
V
(mV)
IN
IN
3108 G00
3108 G01
I
VOUT and Efficiency vs VIN,
IVOUT and Efficiency vs VIN,
1:50 Ratio Transformer
1:100 Ratio Transformer
3200
2800
2400
2000
1600
1200
800
80
70
60
50
40
30
20
10
0
70
1400
1200
1000
800
600
400
200
0
C1 = 4.7nF
C1 = 1nF
I
VOUT
OUT
(V
= 0V)
I
60
50
40
30
20
10
0
VOUT
OUT
(V
= 0V)
EFFICIENCY
(V = 4.5V)
EFFICIENCY
(V = 4.5V)
OUT
OUT
I
VOUT
OUT
(V
= 4.5V)
I
VOUT
OUT
(V
= 4.5V)
400
0
100
200
V
300
500
0
400
100
200
V
300
(mV)
500
0
400
(mV)
IN
IN
3108 G02
3108 G03
Input Resistance vs VIN
(VOUT Charging)
I
VOUT vs VIN and Source Resistance,
1:20 Ratio
10
9
8
7
6
5
4
3
2
1
0
10000
1000
100
10
C1 = 10nF
1:20 RATIO
1:50 RATIO
1Ω
2Ω
5Ω
10Ω
1:100 RATIO
400
0
100
200
300
(mV)
500
0
200 300 400 500 600 700 800
100
0
V
V
OPEN-CIRCUIT (mV)
IN
IN
3108 G05
3108 G04
3108fb
4
LTC3108
TA = 25°C, unless otherwise noted.
TYPICAL PERFORMANCE CHARACTERISTICS
I
VOUT vs VIN and Source Resistance,
IVOUT vs VIN and Source Resistance,
1:50 Ratio
1:100 Ratio
1000
10000
1000
100
10
C1 = 1nF
C1 = 4.7nF
100
1Ω
2Ω
5Ω
10Ω
1Ω
2Ω
5Ω
10Ω
10
0
100
200
300
400
500
0
200 300 400 500 600 700 800
100
0
V
OPEN-CIRCUIT (mV)
V
OPEN-CIRCUIT (mV)
IN
IN
3108 G07
3108 G06
IVOUT vs dT and TEG Size,
1:100 Ratio
Resonant Switching Waveforms
10000
1000
100
10
V
= 0V
V
= 20mV
OUT
IN
1:100 RATIO TRANSFORMER
40mm
TEG
C1 PIN
2V/DIV
C2 PIN
2V/DIV
15mm
TEG
SW PIN
50mV/
DIV
1:50 RATIO
1:100 RATIO
1:50 RATIO
1:100 RATIO
3108 G09
10μs/DIV
0
10
1
dT ACROSS TEG (°C)
100
0.1
3108 G08
LDO Load Regulation
LDO Dropout Voltage
0.00
–0.25
–0.50
–0.75
–1.00
0.20
0.18
0.16
0.14
0.12
0.10
0.08
0.06
0.04
0.02
0.00
0
0.5
1.5
2
2.5
3
3.5
4
1
0
0.5
1.5
2
2.5
3
3.5
4
1
LDO LOAD (mA)
LDO LOAD (mA)
3108 G11
3108 G10
3108fb
5
LTC3108
TA = 25°C, unless otherwise noted.
TYPICAL PERFORMANCE CHARACTERISTICS
VOUT and PGD Response
During a Step Load
Start-Up Voltage Sequencing
50mA LOAD STEP
OUT
V
= 50mV
IN
CH1
VSTORE
1V/DIV
C
= 220μF
1:100 RATIO TRANSFORMER
= 220μF
C
OUT
CSTORE = 470μF
= 2.2μF
C
CH2
OUT
1V/DIV
LDO
CH2, V
1V/DIV
OUT
V
CH3, V
1V/DIV
LDO
CH1
PGD
1V/DIV
3108 G13
3108 G12
5ms/DIV
10sec/DIV
VOUT Ripple
LDO Step Load Response
30μA LOAD
C
= 220μF
OUT
V
LDO
20mV/
DIV
20mV/DIV
I
LDO
5mA/DIV
3108 G14
3108 G15
100ms/DIV
200μs/DIV
0mA TO 3mA LOAD STEP
C
= 2.2μF
LDO
Enable Input and VOUT2
Running on Storage Capacitor
CSTORE = 470μF
LOAD = 100μA
CH3
VSTORE
1V/DIV
V
OUT
CH2, V
OUT
CH2, V
OUT2
1V/DIV
1V/DIV
CH4, V
LDO
1V/DIV
CH1
OUT2_EN
1V/DIV
CH1, V
IN
V
50mV/DIV
3108 G16
3108 G17
1ms/DIV
5sec/DIV
10mA LOAD ON V
OUT
OUT2
C
= 220μF
3108fb
6
LTC3108
PIN FUNCTIONS (DFN/SSOP)
VAUX (Pin 1/Pin 2): Output of the Internal Rectifier Cir-
VS1 (Pin 8/Pin 11): V
Select Pin 1. Connect this pin
OUT
cuit and V for the IC. Bypass VAUX with at least 1μF of
to ground or VAUX to program the output voltage (see
CC
capacitance. An active shunt regulator clamps VAUX to
Table 1).
5.25V (typical).
V
(Pin 9/Pin 12): Enable Input for V
. V
OUT2 OUT2
OUT2_EN
VSTORE (Pin 2/Pin 3): Output for the Storage Capacitor
or Battery. A large 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.
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.
C1(Pin10/Pin13):InputtotheChargePumpandRectifier
Circuit. Connect a capacitor from this pin to the secondary
winding of the step-up transformer.
V
OUT
(Pin 3/Pin 4): Main Output of the Converter. The
C2 (Pin 11/Pin 14): Input to the N-Channel Gate Drive
Circuit. Connect a capacitor from this pin to the secondary
winding of the step-up transformer.
voltage at this pin is regulated to the voltage selected by
VS1 and VS2 (see Table 1). Connect this pin to an energy
storage capacitor or to a rechargeable battery.
SW (Pin 12/Pin 15): Drain of the Internal N-Channel
Switch. Connect this pin to the primary winding of the
transformer.
V
(Pin 4/Pin 5): Switched Output of the Converter.
OUT2
Connect this pin to a switched load. This output is open
until V is driven high, then it is connected to
OUT2_EN
GND (Pins 1, 8, 9, 16) SSOP Only: Ground
V
OUT
through a 1.3ꢀ P-channel switch. If not used, this
pin should be left open or tied to V . The peak current
OUT
GND (Exposed Pad Pin 13) DFN Only: Ground. The DFN
exposed pad must be soldered to the PCB ground plane.
It serves as the ground connection, and as a means of
conducting heat away from the die.
in this output is limited to 0.3A typical.
VLDO (Pin 5/Pin 6): 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.
Table 1. Regulated Voltage Using Pins VS1 and VS2
VS2
GND
GND
VAUX
VAUX
VS1
GND
VAUX
GND
VAUX
V
OUT
PGD (Pin 6/Pin 7): Power Good Output. When V
is
OUT
2.35V
3.3V
4.1V
5V
within 7.5% of its programmed value, PGD will be pulled
up to VLDO through a 1MΩ resistor. If V drops 9%
OUT
below its programmed value PGD will go low. This pin
can sink up to 100μA.
VS2 (Pin 7/Pin 10): V
Select Pin 2. Connect this pin
OUT
to ground or VAUX to program the output voltage (see
Table 1).
3108fb
7
LTC3108
BLOCK DIAGRAM
LTC3108
1.2V
V
OUT2
1.3Ω
V
ILIM
OUT2
V
OUT2_EN
OFF ON
SYNC RECTIFY
REFERENCE
V
REF
5M
C1
V
OUT
1:100
C1
V
V
OUT
IN
C
C
IN
5.25V
OUT
C2
+
C2
VS1
VS2
–
V
SW
SW
OUT
CHARGE
CONTROL
V
OUT
PROGRAM
VSTORE
0.5Ω
V
REF
VLDO
1M
PGD
–
+
PGOOD
VAUX
VSTORE
V
LDO
BEST
V
V
REF
OUT
C
1μF
STORE
VLDO
GND (SSOP)
EXPOSED PAD (DFN)
3108 BD
2.2V
2.2μF
OPERATION (Refer to the Block Diagram)
The LTC3108 is designed to use a small external step-up
transformer to create an ultralow input voltage step-up
DC/DC converter and power manager. It is ideally suited
for low power wireless sensors and other applications in
whichsurplusenergyharvestingisusedtogeneratesystem
power because traditional battery power is inconvenient
or impractical.
average power draw is very low, but there may be periodic
pulses of higher load current required. This is typical of
wireless sensor applications, where the quiescent power
drawisextremelylowmostofthetime,exceptfortransmit
bursts when circuitry is powered up to make measure-
ments and transmit data.
The LTC3108 can also be used to trickle charge a standard
capacitor, supercapacitor or rechargeable battery, using
energy harvested from a Peltier or photovoltaic cell.
The LTC3108 is designed to manage the charging and
regulation of multiple outputs in a system in which the
3108fb
8
LTC3108
OPERATION
Oscillator
Synchronous Rectifiers
The LTC3108 utilizes a MOSFET switch to form a resonant
step-up oscillator using an external step-up transformer
andasmallcouplingcapacitor.Thisallowsittoboostinput
voltages as low as 20mV high enough to provide multiple
regulated output voltages for powering other circuits. The
frequencyofoscillationisdeterminedbytheinductanceof
the transformer secondary winding and is typically in the
range of 10kHz to 100kHz. For input voltages as low as
20mV, a primary-secondary turns ratio of about 1:100 is
recommended. For higher input voltages, this ratio can be
lower. See the Applications Information section for more
information on selecting the transformer.
Once VAUX exceeds 2V, synchronous rectifiers in parallel
with each of the internal diodes take over the job of rectify-
ing the input voltage, improving efficiency.
Low Dropout Linear Regulator (LDO)
The LTC3108 includes a low current LDO to provide a
regulated 2.2V output for powering low power proces-
sors or other low power ICs. The LDO is powered by the
higher of VAUX or V . This enables it to become active
OUT
as soon as VAUX has charged to 2.3V, while the V
stor-
OUT
age capacitor is still charging. In the event of a step load
on the LDO output, current can come from the main V
OUT
capacitor if VAUX drops below V . The LDO requires
OUT
Charge Pump and Rectifier
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 4mA minimum.
The AC voltage produced on the secondary winding of
the transformer is boosted and rectified using an external
chargepumpcapacitor(fromthesecondarywindingtopin
C1) and the rectifiers internal to the LTC3108. The rectifier
circuit feeds current into the VAUX pin, providing charge
to the external VAUX capacitor and the other outputs.
V
OUT
ThemainoutputvoltageonV ischargedfromtheVAUX
OUT
supply, and is user programmed to one of four regulated
voltages using the voltage select pins VS1 and VS2, ac-
cording 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.
VAUX
The active circuits within the LTC3108 are powered from
VAUX, which should be bypassed with a 1μF capacitor.
Larger capacitor values are recommended when using
turns ratios of 1:50 or 1:20 (refer to the Typical Applica-
tion examples). Once VAUX exceeds 2.5V, the main V
is allowed to start charging.
Table 2. Regulated Voltage Using Pins VS1 and VS2
VS2
GND
GND
VAUX
VAUX
VS1
GND
VAUX
GND
VAUX
V
OUT
OUT
2.35V
3.3V
4.1V
5V
An internal shunt regulator limits the maximum voltage
on VAUX to 5.25V typical. It shunts to GND 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.
Whentheoutputvoltagedropsslightlybelowtheregulated
value,thechargingcurrentwillbeenabledaslongasVAUX
is greater than 2.5V. Once V
has reached the proper
OUT
Voltage Reference
value, the charging current is turned off.
The LTC3108 includes a precision, micropower reference,
for accurate regulated output voltages. This reference
becomes active as soon as VAUX exceeds 2V.
The internal programmable resistor divider sets V
eliminating the need for very high value external resistors
that are susceptible to board leakage.
,
OUT
3108fb
9
LTC3108
OPERATION
In a typical application, a storage capacitor (typically a few
The V
enable input has a typical threshold of 1V
OUT2
hundred microfarads) is connected to V . As soon as
with 100mV of hysteresis, making it logic-compatible. If
(which has an internal pull-down resistor) is
OUT
V
VAUX exceeds 2.5V, the V
capacitor will be allowed to
OUT2_EN
OUT
low, V
the V
will be off. Driving V
output.
high will turn on
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 4.5mA
typical.
OUT2
OUT2
OUT2_EN
Note that while V
cuitry for V
is high, the current limiting cir-
OUT2_EN
draws an extra 8μA of quiescent current
OUT2
from V . This added current draw has a negligible effect
OUT
PGOOD
on the application and capacitor sizing, since the load on
A power good comparator monitors the V
voltage.
the V
output, when enabled, is likely to be orders of
OUT
OUT2
The PGD pin is an open-drain output with a weak pull-up
magnitude higher than 8μA.
(1MΩ)totheLDOvoltage.OnceV haschargedtowithin
OUT
VSTORE
7.5% of its regulated voltage, the PGD output will go high.
If V
drops more than 9% from its regulated voltage,
OUT
The VSTORE output can be used to charge a large storage
PGD will go low. The PGD 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. Pulling PGD
up externally to a voltage greater than VLDO will cause a
small current to be sourced into VLDO. PGD can be pulled
low in a wire-OR configuration with other circuitry.
capacitor or rechargeable battery after V
has reached
OUT
regulation.OnceV hasreachedregulation,theVSTORE
OUT
output will be allowed to charge up to the VAUX voltage.
The storage element on VSTORE can 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 V
,
OUT
V
OUT2
and LDO outputs. If VAUX drops below VSTORE,
V
OUT2
the LTC3108 will automatically draw current from the stor-
age element. Note that it may take a long time to charge
a large capacitor, depending on the input energy available
V
is an output that can be turned on and off by the
OUT2
host, using the V
connected to V
pin. When enabled, V
is
OUT2_EN
OUT2
and the loading on V
and VLDO.
through a 1.3ꢀ P-channel MOSFET
OUT
OUT
switch. This output, controlled by a host processor, can
be used to power external circuits such as sensors and
amplifiers,thatdonothavealowpowersleeporshutdown
Since the maximum current from VSTORE is limited to a
few milliamps, it can safely be used to trickle-charge NiCd
or NiMH rechargeable batteries for energy storage when
the input voltage is lost. Note that the VSTORE capacitor
capability. V
can be used to power these circuits only
OUT2
when they are needed.
cannotsupplylargepulsecurrentstoV .Anypulseload
OUT
on V
must be handled by the V
capacitor.
Minimizing the amount of decoupling capacitance on
OUT
OUT
V
OUT2
willallowittobeswitchedonandofffaster, allowing
Short-Circuit Protection
shorter burst times and, therefore, smaller duty cycles in
pulsed applications such as a wireless sensor/transmit-
All outputs of the LTC3108 are current limited to protect
against short-circuits to ground.
ter. A small V
capacitor will also minimize the energy
OUT2
that will be wasted in charging the capacitor every time
V
OUT2
is enabled.
Output Voltage Sequencing
V
has a soft-start time of about 5μs to limit capacitor
A timing diagram showing the typical charging and
voltage sequencing of the outputs is shown in Figure 1.
Note: time not to scale.
OUT2
chargingcurrentandminimizeglitchingofthemainoutput
whenV
isenabled. Italsohasacurrentlimitingcircuit
OUT2
that limits the peak current to 0.3A typical.
3108fb
10
LTC3108
OPERATION
5.0
2.5
0
VSTORE (V)
PGD (V)
3.0
2.0
1.0
0
5.0
2.5
0
V
(V)
OUT
3.0
2.0
1.0
0
VLDO (V)
VAUX (V)
5.0
2.5
0
0
50
60
80
10
20
30
40
TIME (ms)
70
3108 F01a
Figure 1. Output Voltage Sequencing with VOUT Programmed for 3.3V (Time Not to Scale)
3108fb
11
LTC3108
APPLICATIONS INFORMATION
Introduction
Refer to the I vs V curves in the Typical Performance
IN IN
Characteristicssectiontoseewhatinputcurrentisrequired
from the source for a given input voltage.
The LTC3108 is designed to gather energy from very low
input voltage sources and convert it to usable output volt-
agestopowermicroprocessors,wirelesstransmittersand
analog sensors. Such applications typically require much
more peak power, and at higher voltages, than the input
voltage source can produce. The LTC3108 is designed to
accumulate and manage energy over a long period of time
to enable short power bursts for acquiring and transmit-
ting data. The bursts must occur at a low enough duty
cycle such that the total output energy during the burst
does not exceed the average source power integrated
over the accumulation time between bursts. For many
applications, this time between bursts could be seconds,
minutes or hours.
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 bulk decoupling capacitor will usually
berequiredacrosstheinputsourcetopreventlargevoltage
droop and ripple caused by the source’s ESR and the peak
primary switching current (which can reach hundreds of
milliamps). The time constant of the filter capacitor and
the ESR of the voltage source should be much longer than
the period of the resonant switching frequency.
The PGD signal can be used to enable a sleeping micro-
processororothercircuitrywhenV reachesregulation,
Peltier Cell (Thermoelectric Generator)
OUT
indicating that enough energy is available for a burst.
A Peltier cell (also known as a thermoelectric cooler) is
made up of a large number of series-connected P-N junc-
tions, sandwiched between two parallel ceramic plates.
Although Peltier cells are often used as coolers by apply-
ing 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 tem-
perature differential between the plates. The magnitude of
the output voltage is proportional to the magnitude of the
temperature differential between the plates. When used in
Input Voltage Sources
The LTC3108 can operate from a number of low input
voltagesources, suchasPeltiercells, photovoltaiccellsor
thermopilegenerators.Theminimuminputvoltagerequired
for a given application will depend on the transformer
turns ratio, the load power required, and the internal DC
resistance (ESR) of the voltage source. Lower ESR will
allow the use of lower input voltages, and provide higher
output power capability.
1000
100
10
1
TEG: 30mm
127 COUPLES
R = 2Ω
V
OC
100
MAX P
(IDEAL)
OUT
10
1
0.1
100
1
10
dT (°C)
3108 F02
Figure 2. Typical Performance of a Peltier Cell Acting as a Thermoelectric Generator
3108fb
12
LTC3108
APPLICATIONS INFORMATION
this manner, a Peltier cell is referred to as a thermoelectric
generator (TEG).
current capability by providing a higher input voltage
under load.
The low voltage capability of the LTC3108 design allows
it to operate from a TEG with temperature differentials
as low as 1°C, making it ideal for harvesting energy in
applications in which a temperature difference exists
between two surfaces or between a surface and the am-
bient temperature. The internal resistance (ESR) of most
cells 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 Peltier cell (with an ESR of 2Ω) over a 20°C range
of temperature differential.
Peltier Cell (TEG) Suppliers
Peltiercellsareavailableinawiderangeofsizesandpower
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 3.
Table 3. Peltier Cell Manufacturers
CUI, Inc.
www.cui.com (Distributor)
Fujitaka
www.fujitaka.com/pub/peltier/english/thermoelectric_power.html
Ferrotec
www.ferrotec.com/products/thermal/modules
TEG Load Matching
Kryotherm
www.kryothermusa.com
The LTC3108 was designed to present a minimum input
resistance (load) in the range of 2Ω to 10Ω, depending
on input voltage and transformer turns ratio (as shown
in the Typical Performance Characteristics curves). For
a given turns ratio, as the input voltage drops, the input
resistance increases. This feature allows the LTC3108 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
Laird Technologies
www.lairdtech.com
Marlow Industries
www.marlow.com
Micropelt
www.micropelt.com
Nextreme
www.nextreme.com
TE Technology
www.tetech.com/Peltier-Thermoelectric-Cooler-Modules.html
Tellurex
www.tellurex.com
Table 4. Recommended TEG Part Numbers by Size
MANUFACTURER
CUI Inc. (Distributor)
Ferrotec
15mm × 15mm
CP60133
20mm × 20mm
CP60233
30mm × 30mm
CP60333
40mm × 40mm
CP85438
9501/031/030 B
FPH13106NC
9501/071/040 B
FPH17106NC
9500/097/090 B
FPH17108AC
9500/127/100 B
FPH112708AC
Fujitaka
Kryotherm
TGM-127-1.0-0.8
PT6.7.F2.3030.W6
RC6-6-01
LCB-127-1.4-1.15
PT8.12.F2.4040.TA.W6
RC12-8-01LS
Laird Technology
Marlow Industries
Tellurex
RC3-8-01
C2-15-0405
C2-20-0409
TE-31-1.4-1.15
C2-30-1505
C2-40-1509
TE Technology
TE-31-1.0-1.3
TE-71-1.4-1.15
TE-127-1.4-1.05
3108fb
13
LTC3108
APPLICATIONS INFORMATION
Thermopile Generator
these applications the C2 and SW pins are not used and
can be grounded or left open.
Thermopile generators (also called powerpile generators)
are made up of a number of series-connected thermo-
couples enclosed in a metal tube. They are commonly
used in gas burner applications to generate a DC output
of hundreds of millivolts when exposed to the high tem-
perature of a flame. Typical examples are the Honeywell
CQ200 and Q313. These devices have an internal series
resistance of less than 3Ω, and can generate as much as
750mVopen-circuitattheirhighestratedtemperature.For
applications in which the temperature rise is too high for
a solid-state thermoelectric device, a thermopile can be
used as an energy source to power the LTC3108. Because
of the higher output voltages possible with a thermopile
generator, a lower transformer turns ratio can be used
(typically 1:20, depending on the application).
Examples of such input sources would be piezoelectric
transducers, vibration energy harvesters, low current
generators, a stack of low current solar cells or a 60Hz
AC input.
A series resistance of at least 100Ω/V should be used
to limit the maximum current into the VAUX shunt
regulator.
COMPONENT SELECTION
Step-Up Transformer
The step-up transformer turns ratio will determine how
low the input voltage can be for the converter to start.
Using a 1:100 ratio can yield start-up voltages as low as
20mV. Other factors that affect performance are the DC
resistanceofthetransformerwindingsandtheinductance
of the windings. Higher DC resistance will result in lower
efficiency. The secondary winding inductance will deter-
mine the resonant frequency of the oscillator, according
to the following formula.
Photovoltaic Cell
The LTC3108 converter can also operate from a single
photovoltaic cell (also known as a PV or solar cell) at light
levels too low for other low input voltage boost convert-
ers to operate. However, many variables will affect the
performance in these applications. Light levels can vary
over several orders of magnitude and depend on light-
ing conditions (the type of lighting and indoor versus
outdoor). Different types of light (sunlight, incandescent,
fluorescent) also have different color spectra, and will
producedifferentoutputpowerlevelsdependingonwhich
type of photovoltaic cell is being used (monocrystalline,
polycrystalline or thin-film). Therefore, the photovoltaic
cell must be chosen for the type and amount of light avail-
able. Note that the short-circuit output current from the
cell must be at least a few milliamps in order to power
the LTC3108 converter
1
Frequency =
Hz
2 • π • L(sec)•C
Where L is the inductance of the transformer secondary
winding and C is the load capacitance on the secondary
winding. This is comprised of the input capacitance at pin
C2,typically30pF,inparallelwiththetransformersecondary
winding’s shunt capacitance. The recommended resonant
frequency is in the range of 10kHz to 100kHz. See Table 5
for some recommended transformers.
Table 5. Recommended Transformers
VENDOR
PART NUMBER
Non-Boost Applications
Coilcraft
www.coilcraft.com
LPR6235-752SML (1:100 Ratio)
LPR6235-253PML (1:20 Ratio)
LPR6235-123QML (1:50 Ratio)
The LTC3108 can also be used as an energy harvester
and power manager for input sources that do not require
boosting. In these applications the step-up transformer
can be eliminated.
Würth
www.we-online
S11100034 (1:100 Ratio)
S11100033 (1:50 Ratio)
S11100032 (1:20 Ratio)
Any source whose peak voltage exceeds 2.5V AC or 5V
DC can be connected to the C1 input through a current-
limiting resistor where it will be rectified/peak detected. In
3108fb
14
LTC3108
APPLICATIONS INFORMATION
C1 Capacitor
Using External Charge Pump Rectifiers
The charge pump capacitor that is connected from the
transformer’s secondary winding to the C1 pin has an ef-
fect on converter input resistance and maximum output
current capability. Generally, a minimum value of 1nF is
recommended when operating from very low input volt-
ages using a transformer with a ratio of 1:100. Too large
a capacitor value 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
schematic examples for the recommended value for a
given turns ratio.
The synchronous charge pump rectifiers in the LTC3108
(connectedtotheC1pin)areoptimizedforoperationfrom
very low input voltage sources, using typical transformer
step-up ratios between 1:100 and 1:50, and typical C1
charge pump capacitor values less than 10nF.
Operation from higher input voltage sources (typically
250mV or greater, under load), allows the use of lower
transformer step-up ratios (such as 1:20 and 1:10) and
larger C1 capacitor values to provide higher output cur-
rent capability from the LTC3108. However, due to the
resulting increase in rectifier currents and resonant oscil-
lator frequency in these applications, the use of external
charge pump rectifiers is recommended for optimal
performance.
Squegging
In applications where the step-up ratio is 1:20 or less, and
the C1 capacitor is 10nF or greater, the C1 pin should be
grounded and two external rectifiers (such as 1N4148 or
1N914 diodes) should be used. These are available as
dual diodes in a single package. Avoid the use of Schottky
rectifiers, as their lower forward voltage drop increases
theminimumstart-upvoltage.SeetheTypicalApplications
schematics for an example.
Certaintypesofoscillators,includingtransformer-coupled
oscillators such as the resonant oscillator of the LTC3108,
can exhibit a phenomenon called squegging. This term
refers to a condition that can occur which blocks or stops
the oscillation for a period of time much longer than the
period of oscillation, resulting in bursts of oscillation. An
exampleofthisistheblockingoscillator,whichisdesigned
to squegg to produce bursts of oscillation. Squegging
is also encountered in RF oscillators and regenerative
receivers.
V
and VSTORE Capacitor
OUT
For pulsed load applications, the V
capacitor should
OUT
In the case of the LTC3108, squegging can occur when a
charge builds up on the C2 gate coupling capacitor, such
thattheDCbiaspointshiftsandoscillationisextinguished
foracertainperiodoftime,untilthechargeonthecapacitor
bleeds off, allowing oscillation to resume. It is difficult to
predict when and if squegging will occur in a given ap-
plication. While squegging is not harmful, it reduces the
average output current capability of the LTC3108.
be sized to provide the necessary current when the load
is pulsed on. The capacitor value required will be dictated
by the load current, the duration of the load pulse, and
the amount of voltage droop the circuit can tolerate. The
capacitor must be rated for whatever voltage has been
selected for V
by VS1 and VS2.
OUT
ILOAD(mA)• tPULSE(ms)
COUT(μF) ≥
ΔVOUT(V)
Squegging can easily be avoided by the addition of a
bleeder resistor in parallel with the coupling capacitor on
the C2 pin. Resistor values in the range of 100k to 1MΩ
are sufficient to eliminate squegging without having any
negative impact on performance. For the 330pF capacitor
used for C2 in most applications, a 499k bleeder resistor
isrecommended. SeetheTypicalApplicationsschematics
for an example.
Note that there must be enough energy available from
theinputvoltagesourceforV torechargethecapacitor
OUT
during the interval between load pulses (to be discussed
in the next example). Reducing the duty cycle of the load
pulse will allow operation with less input energy.
3108fb
15
LTC3108
APPLICATIONS INFORMATION
The VSTORE capacitor may be of very large value (thou-
sands of microfarads or even Farads), to provide holdup
at times when the input power may be lost. Note that this
capacitor can charge all the way to 5.25V (regardless of
Due to the very low input voltage the circuit may operate
from, the connections to V , the primary of the trans-
IN
former and the SW and GND pins of the LTC3108 should
bedesignedtominimizevoltagedropfromstrayresistance
and able to carry currents as high as 500mA. Any small
voltage drop in the primary winding conduction path will
lower efficiency and increase capacitor charge time.
the settings for V ), so ensure that the holdup capacitor
OUT
has a working voltage rating of at least 5.5V at the tem-
perature for which it will be used. The VSTORE capacitor
can be sized using the following:
Also, due to the low charge currents available at the out-
puts of the LTC3108, any sources of leakage current on
the output voltage pins must be minimized. An example
board layout is shown in Figure 3.
6μA+I +ILDO+(IBURST • t • f) • TSTORE
[
]
Q
CSTORE
≥
5.25− VOUT
Where 6μA is the quiescent current of the LTC3108, I is
Q
V
IN
the load on V
in between bursts, I
is the load on the
OUT
LDO
LDO between bursts, I
is the total load during the
BURST
burst, t is the duration of the burst, f is the frequency of
the bursts, TSTORE is the storage time required and V
OUT
istheoutputvoltagerequired. Notethatforaprogrammed
outputvoltageof5V,theVSTOREcapacitorcannotprovide
any beneficial storage time.
SW
C2
VAUX
1
2
3
4
5
6
12
11
10
9
To minimize losses and capacitor charge time, all capaci-
VSTORE
V
OUT
tors used for V
and VSTORE should be low leakage.
V
C1
V
OUT
OUT
V
OUT2
OUT2_EN
See Table 6 for recommended storage capacitors.
V
OUT2
VLDO
PGD
VS1
VS2
8
Table 6. Recommended Storage Capacitors
VLDO
PGOOD
7
VENDOR
PART NUMBER/SERIES
AVX
www.avx.com
BestCap Series
TAJ and TPS Series Tantalum
GND
3108 FO3
Cap-XX
GZ Series
KR Series
VIAS TO GROUND PLANE
www.cap-xx.com
Cooper/Bussmann
www.bussmann.com/3/PowerStor.html P Series
Figure 3. Example Component Placement
for Two-Layer PC Board (DFN Package)
Vishay/Sprague
www.vishay.com/capacitors
Tantamount 592D
595D Tantalum
150CRZ/153CRV Aluminum
013 RLC (Low Leakage)
Design Example 1
This design example will explain how to calculate the
necessary storage capacitor value for V in pulsed load
applications,suchasawirelesssensor/transmitter.Inthese
types of applications, the load is very small for a major-
ity of the time (while the circuitry is in a low power sleep
state), with bursts of load current occurring periodically
Storage capacitors requiring voltage balancing are not
recommended due to the current draw of the balancing
resistors.
OUT
PCB Layout Guidelines
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.
during a transmit burst. The storage capacitor on V
OUT
supports the load during the transmit burst, and the long
sleeptimebetweenburstsallowstheLTC3108torecharge
the capacitor. A method for calculating the maximum rate
3108fb
16
LTC3108
APPLICATIONS INFORMATION
at which the load pulses can occur for a given output cur-
rent from the LTC3108 will also be shown.
Therefore, in this application example, the circuit can sup-
port a 1ms transmit burst every 1.5 seconds.
In this example, V
is set to 3.3V, and the maximum
It can be determined 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 current is low. Even if the available
charge current in the example above was only 10μA and
the sleep current was only 5μA, it could still transmit a
burst every ten seconds.
OUT
allowed voltage droop during a transmit burst is 10%, or
0.33V. The duration of a transmit burst is 1ms, with a total
average current requirement of 40mA during the burst.
Given these factors, the minimum required capacitance
on V
is:
OUT
40mA •1ms
0.33V
COUT(μF) ≥
= 121μF
The following formula enables the user to calculate the
time it will take to charge the LDO output capacitor and
Note that this equation neglects the effect of capacitor
ESR on output voltage droop. For most ceramic or low
ESR tantalum capacitors, the ESR will have a negligible
effect at these load currents.
the V
capacitor the first time, from 0V. Here again,
OUT
the charge current available from the LTC3108 must be
known. For this calculation, it is assumed that the LDO
output capacitor is 2.2μF.
A standard value of 150μF or larger could be used for C
OUT
2.2V • 2.2μF
ICHG −ILDO
tLDO
=
in this case. Note that the load current is the total current
draw on V , V
and VLDO, since the current for all of
OUT OUT2
theseoutputsmustcomefromV duringaburst.Current
OUT
If there were 50μA of charge current available and a 5μA
loadontheLDO(whentheprocessorissleeping), thetime
for the LDO to reach regulation would be 107ms.
contribution from the holdup capacitor on VSTORE is not
considered, since it may not be able to recharge between
bursts. Also, it is assumed that the charge current from
the LTC3108 is negligible compared to the magnitude of
the load current during the burst.
If V
were programmed to 3.3V and the V
capacitor
OUT
OUT
was 150μF, the time for V
to reach regulation would be:
OUT
To calculate the maximum rate at which load bursts can
occur, determine how much charge current is available
3.3V •150μF
ICHG −IVOUT −ILDO
tVOUT
=
+ tLDO
fromtheLTC3108V
pingiventheinputvoltagesource
OUT
If there were 50μA of charge current available and 5μA of
load on V , the time for V to reach regulation after
the initial application of power would be 12.5 seconds.
being used. This number is best found empirically, since
there are many factors affecting the efficiency of the
converter. Also determine what the total load current is
OUT
OUT
on V
during the sleep state (between bursts). Note
OUT
Design Example 2
that this must include any losses, such as storage ca-
pacitor leakage.
Inmanypulsedloadapplications, theduration, magnitude
and frequency of the load current bursts are known and
fixed. In these cases, the average charge current required
from the LTC3108 to support the average load must be
calculated, which can be easily done by the following:
Assume, for instance, that the charge current from the
LTC3108 is 50μA and the total current drawn on V
in
OUT
the sleep state is 17μA, including capacitor leakage. In
addition, use the value of 150μF for the V capacitor.
OUT
The maximum transmit rate (neglecting the duration of
the transmit burst, which is typically very short) is then
given by:
IBURST • t
ICHG ≥IQ +
T
Where I is the sleep current on V
required by the ex-
Q
OUT
150μF • 0.33V
t =
= 1.5sec or fMAX = 0.666Hz
ternal circuitry in between bursts (including cap leakage),
(50μA −17μA)
I
is the total load current during the burst, t is the
BURST
3108fb
17
LTC3108
APPLICATIONS INFORMATION
duration of the burst and T is the period of the transmit
burst rate (essentially the time between bursts).
hour. It can be determined that the sleep current of 5μA
is the dominant factor because the transmit duty cycle is
so small (0.00014%). Note that for a V
average power required by this application is only 17μW
(not including converter losses).
of 3.3V, the
OUT
In this example, I = 5μA, I
T = one hour. The average charge current required from
the LTC3108 would be:
= 100mA, t = 5ms and
BURST
Q
Note that the charge current available from the LTC3108
100mA • 0.005sec
ICHG ≥ 5μA+
= 5.14μA
has no effect on the sizing of the V
capacitor (if it is
OUT
3600sec
assumedthattheloadcurrentduringaburstismuchlarger
Therefore, if the LTC3108 has an input voltage that allows
it to supply a charge current greater than 5.14μA, the
application can support 100mA bursts lasting 5ms every
than the charge current), and the V capacitor has no
effect on the maximum allowed burst rate.
OUT
TYPICAL APPLICATIONS
Peltier-Powered Energy Harvester for Remote Sensor Applications
COOPER BUSSMAN PB-5ROH104-R
OR KR-5R5H104-R
5V
1nF
1:100
T1
VSTORE
C
0.1F
6.3V
+
STORE
C1
3.3V
+
+
THERMOELECTRIC
GENERATOR
V
OUT2
μP
V
OUT2
C
IN
330pF
PGOOD
PGD
SENSORS
XMTR
C2
LTC3108
2.2V
ΔT = 1°C TO 20°C
VLDO
SW
2.2μF
3.3V
+
V
OUT
VS2
VS1
C
*
OUT
V
OUT2_EN
VAUX
GND
OFF ON
T1: COILCRAFT LPR6235-752SML
*C VALUE DEPENDENT ON
THE MAGNITUDE AND DURATION
OF THE LOAD PULSE
OUT
1μF
3108 TA02
3108fb
18
LTC3108
TYPICAL APPLICATIONS
Li-Ion Battery Charger and LDO Powered by a Solar Cell
T1
1:20
0.01μF
C1
VSTORE
+
–
+
V
SOLAR CELL*
OUT2
220μF
330pF
LTC3108
PGD
C2
2.2V
OUT
SW
VLDO
VLDO
2.2μF
4.1V
V
OUT
V
VS2
VS1
Li-Ion
* 2 DIAMETER MONOCRYSTALLINE CELL
"
V
GND
OUT2_EN
LIGHT LEVEL ≥ 900 LUX
VAUX
T1: COILCRAFT LPR6235-253PML
4.7μF
3108 TA03
Supercapacitor Charger and LDO Powered by a Thermopile Generator
HONEYWELL
CQ200
THERMOPILE
T1
1:50
4.7nF
C1
VSTORE
+
V
OUT2
220μF
330pF
LTC3108
PGD
PGOOD
C2
2.2V
SW
VLDO
VLDO
2.2μF
2.35V
V
V
OUT
OUT
+
VS2
VS1
150mF
2.5V
T1: COILCRAFT LPR6235-123QML
V
OUT2_EN
VAUX
GND
CAP-XX GZ115F
2.2μF
3108 TA04
DC Input Energy Harvester and Power Manager
AC Input Energy Harvester and Power Manager
R
R
IN
C
IN
IN
R
> 100Ω/V
R
> 100Ω/V
IN
IN
5V
5V
C1
VSTORE
C1
VSTORE
+
+
C
C
STORE
STORE
V
V
V
+
IN
IN
IN
AC
V
OUT2
V
V
OUT2
V
OUT2
OUT2
–
> 5V
V
> 5V
IN
P-P
- PIEZO
- 60Hz
PGD
PGOOD
PGD
PGOOD
C2
LTC3108
LTC3108
2.2V
2.2V
SW
VS2
VLDO
C2
VLDO
VLDO
2.2μF
VLDO
2.2μF
3.3V
5V
+
V
V
V
V
SW
OUT
OUT
OUT
OUT
+
C
C
OUT
OUT
VS2
VS1
VS1
V
V
V
V
OUT2_EN
OUT2_ENABLE
OUT2_ENABLE
OUT2_EN
VAUX
GND
VAUX
GND
3108 TA05
3108 TA06
2.2μF
2.2μF
3108fb
19
LTC3108
PACKAGE DESCRIPTION
Please refer to http://www.linear.com/designtools/packaging/ for the most recent package drawings.
GN Package
16-Lead Plastic SSOP (Narrow .150 Inch)
(Reference LTC DWG # 05-08-1641 Rev B)
.189 – .196*
.045 .005
(4.801 – 4.978)
.009
(0.229)
REF
16 15 14 13 12 11 10 9
.254 MIN
.150 – .165
.229 – .244
.150 – .157**
(5.817 – 6.198)
(3.810 – 3.988)
.0165 .0015
.0250 BSC
RECOMMENDED SOLDER PAD LAYOUT
1
2
3
4
5
6
7
8
.015 .004
(0.38 0.10)
= 45$
.0532 – .0688
(1.35 – 1.75)
.004 – .0098
(0.102 – 0.249)
.007 – .0098
(0.178 – 0.249)
0° – 8° TYP
.016 – .050
(0.406 – 1.270)
.0250
(0.635)
BSC
.008 – .012
GN16 REV B 0212
(0.203 – 0.305)
TYP
NOTE:
1. CONTROLLING DIMENSION: INCHES
INCHES
2. DIMENSIONS ARE IN
(MILLIMETERS)
*DIMENSION DOES NOT INCLUDE MOLD FLASH. MOLD FLASH
SHALL NOT EXCEED 0.006" (0.152mm) PER SIDE
3. DRAWING NOT TO SCALE
4. PIN 1 CAN BE BEVEL EDGE OR A DIMPLE
**DIMENSION DOES NOT INCLUDE INTERLEAD FLASH. INTERLEAD
FLASH SHALL NOT EXCEED 0.010" (0.254mm) PER SIDE
DE/UE Package
12-Lead Plastic DFN (4mm × 3mm)
(Reference LTC DWG # 05-08-1695 Rev D)
0.40 0.10
4.00 0.10
(2 SIDES)
R = 0.115
TYP
7
12
0.70 0.05
R = 0.05
TYP
3.30 0.10
3.30 0.05
3.60 0.05
2.20 0.05
3.00 0.10
(2 SIDES)
1.70 0.10
1.70 0.05
PIN 1
PIN 1 NOTCH
TOP MARK
(NOTE 6)
R = 0.20 OR
0.35 × 45°
PACKAGE
OUTLINE
CHAMFER
(UE12/DE12) DFN 0806 REV D
6
1
0.25 0.05
0.75 0.05
0.200 REF
0.25 0.05
0.50 BSC
0.50 BSC
2.50 REF
2.50 REF
BOTTOM VIEW—EXPOSED PAD
0.00 – 0.05
RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS
APPLY SOLDER MASK TO AREAS THAT ARE NOT SOLDERED
NOTE:
1. DRAWING PROPOSED TO BE A VARIATION OF VERSION
(WGED) IN JEDEC PACKAGE OUTLINE M0-229
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
3108fb
20
LTC3108
REVISION HISTORY
REV
DATE
DESCRIPTION
PAGE NUMBER
A
04/10 Updated front page text and Typical Appliction
Updated Absolute Maximum Ratings and Order Information sections
Updated Electrical Characteristics
1
2
3
Added graph (3108 G00) to Typical Performance Characteristics
Updated Block Diagram
4
8
9
Text added to Operation section
Changes to Applications Information section
Updated Typical Applications
12-18
18, 19, 22
22
Updated Related Parts
B
Added vendor information to Table 5
14
3108fb
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.
21
LTC3108
TYPICAL APPLICATION
Dual TEG Energy Harvester Operates from Temperature Differentials of Either Polarity
1nF
1:100
5V
C1
HOT
VSTORE
+
+
C
STORE
THERMOELECTRIC
GENERATOR
V
V
OUT2
OUT2
330pF
LTC3108
PGD
PGOOD
3.3V
C2
COLD
2.2V
VLDO
SW
VS2
VS1
VLDO
2.2μF
V
V
OUT
OUT
+
LPR6235-752SML
V
OUT2_EN
C
OUT
VAUX
GND
OFF
ON
1μF
VAUX
1nF
1:100
C1
C2
VSTORE
COLD
HOT
+
THERMOELECTRIC
GENERATOR
V
OUT2
PGD
330pF
LTC3108
SW
VLDO
V
VS2
VS1
OUT
V
LPR6235-752SML
OUT2_EN
VAUX
GND
3108 TA07
RELATED PARTS
PART NUMBER
LTC1041
DESCRIPTION
COMMENTS
Bang-Bang Controller
Nanopower Precision Shunt Voltage Reference
V : 2.8V to 16V; I = 1μA; SO-8 Package
IN
Q
LTC1389
V = 1.25V; I = 0.8μA; SO-8 Package
OUT(MIN) Q
LT1672/LT1673/
LT1674
Single-/Dual-/Quad-Precision 2μA Rail-to-Rail Op Amps SO-8, SO-14 and MSOP-8 Packages
LT3009
3μA I , 20mA Linear Regulator V : 1.6V to 20V; V : 0.6V to Adj, 1.2V, 1.5V, 1.8V, 2.5V, 3.3V,
Q
IN
OUT(MIN)
5V to Fixed; I = 3μA; I < 1μA; 2mm × 2mm DFN-8 and SC70 Packages
Q
SD
LTC3108-1
Ultralow Voltage Step-Up Converter and Power Manager V : 0.02V to 1V; V
= 2.5V, 3V, 3.7V, 4.5V Fixed; I = 6μA;
OUT Q
IN
3mm × 4mm DFN-12 and SSOP-16 Packages
LTC3525L-3/
LTC3525L-3.3/
LTC3525L-5
400mA (I ), Synchronous Step-Up DC/DC Converter
V : 0.7V to 4V; V = 5V ; I = 7μA; I < 1μA; SC70 Package
SW
IN
OUT(MIN)
MAX
Q
SD
with Output Disconnect
LTC3588-1
LTC3642
LTC6656
Piezoelectric Energy Generator with Integrated High
Efficiency Buck Converter
V : 2.7V to 20V; V
: Fixed to 1.8V, 2.5V, 3.3V, 3.6V; I = 0.95μA;
OUT(MIN) Q
IN
3mm × 3mm DFN-10 and MSOP-10E Packages
45V, 50mA Synchronous MicroPower Buck Converter
V : 4.5V to 45V, 60V ; V : 0.8V to Adj, 3.3V Fixed, 5V Fixed;
IN
MAX OUT(MIN)
I = 12μA; I < 1μA; 3mm × 3mm DFN-8 and MSOP-8E Packages
Q
SD
850mA Precision Reference
Series Low Dropout Precision
LT8410/ LT8410-1 MicroPower 25mA/8mA Low Noise Boost Converter
with Integrated Schottky Diode and Output Disconnect
V : 2.6V to 16V; V = 40V
; I = 8.5μA; I < 1μA;
MAX Q SD
IN
OUT(MIN)
2mm × 2mm DFN-8 Package
LTC4O70
Micropower Shunt Li-Ion Charge
Controls Charging with μA Source
3108fb
LT 0612 REV B • PRINTED IN USA
LinearTechnology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
22
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