LINER LTC3331 Nanopower buck-boost dc/dc with energy harvesting battery charger Datasheet

LTC3331
Nanopower Buck-Boost
DC/DC with Energy Harvesting
Battery Charger
DESCRIPTION
FEATURES
Dual Input, Single Output DC/DCs with Input
Prioritizer
nn Energy Harvesting Input: 3.0V to 19V Buck DC/DC
nn Battery Input: Up to 4.2V Buck-Boost DC/DC
nn 10mA Shunt Battery Charger with Programmable
Float Voltages: 3.45V, 4.0V, 4.1V, 4.2V
nn Low Battery Disconnect
nn Ultra Low Quiescent Current: 950nA at no Load
nn Integrated Supercapacitor Balancer
nn Up to 50mA of Output Current
nn Programmable DC/DC Output Voltage, Buck UVLO,
and Buck-Boost Peak Input Current
nn Integrated Low-Loss Full-Wave Bridge Rectifier
nn Input Protective Shunt: Up to 25mA at V ≥ 20V
IN
nn 5mm × 5mm QFN-32 Package
The LTC®3331 integrates a high voltage energy harvesting
power supply plus a buck-boost DC/DC powered from a
rechargeable battery to create a single output supply for
alternative energy applications. A 10mA shunt allows simple
charging of the battery with harvested energy while a low
battery disconnect function protects the battery from deep
discharge. The energy harvesting power supply, consisting
of an integrated full-wave bridge rectifier and a high voltage
buck DC/DC, harvests energy from piezoelectric, solar, or
magnetic sources. Either DC/DC converter can deliver energy to a single output. The buck operates when harvested
energy is available, reducing the quiescent current draw
on the battery to the 200nA required by the shunt charger,
thereby extending the life of the battery. The buck-boost
powers VOUT only when harvested energy is unavailable.
APPLICATIONS
A supercapacitor balancer is also integrated, allowing for
increased energy storage. Voltage and current settings
for both inputs and outputs are programmable via pinstrapped logic inputs. The LTC3331 is available in a 5mm
× 5mm QFN-32 package.
nn
Energy Harvesting
Solar Powered Systems with Battery Backup
nn Wireless HVAC Sensors and Security Devices
nn Mobile Asset Tracking
nn
nn
L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks and
PowerPath is a trademark of Linear Technology Corporation. All other trademarks are the
property of their respective owners.
TYPICAL APPLICATION
+
3V TO 19V
SOLAR
PANEL
–
AC1
AC2
VIN
SW
1µF
6.3V
22µF
25V
4.7µF, 6.3V
100k
LTC3331
SWB
VIN2
VOUT
CHARGE
SCAP
BAL
4.7µF
6.3V
PGVOUT
2
FLOAT[1:0]
OUT[2:0]
IPK[2:0]
LBSEL
SHIP
UV[3:0]
GND
VIN3
47µF
6.3V
10mF
2.7V
EH_ON
BAT_IN
Li-Ion
BATTERY
1.8V TO 5V
50mA
10mF
2.7V
BAT_OUT
Charging a Battery with Harvested Energy
VOUT
50mV/DIV
AC-COUPLED
BB_IN
4.7µF
6.3V
+
22µH
SWA
CAP
PIEZO
MIDE
V25W
22µH
3
OPTIONAL
EH_ON
4V/DIV
0V
IBB_IN
200mA/DIV
0A
0A
ICHARGE
1mA/DIV
ACTIVE ENERGY HARVESTER ENABLES
CHARGING OF THE BATTERY IN SLEEP
3
BAT = 3.6V
VOUT = 1.8V
ILOAD = 50mA
4
100µs/DIV
3331 TA01b
0.1µF
6.3V
3331 TA01a
3331fc
For more information www.linear.com/LTC3331
1
LTC3331
SHIP
VIN3
CHARGE
PGVOUT
EH_ON
OUT0
OUT1
TOP VIEW
OUT2
32 31 30 29 28 27 26 25
BAL 1
24 FLOAT0
SCAP 2
23 FLOAT1
VIN2 3
22 LBSEL
UV3 4
21 BAT_IN
33
GND
UV2 5
20 BAT_OUT
UV1 6
19 IPK2
UV0 7
18 IPK1
AC1 8
17 IPK0
BB_IN
SWA
SWB
VOUT
SW
9 10 11 12 13 14 15 16
CAP
VIN
Low Impedance Source...........................–0.3 to 19V*
Current-Fed, ISW = 0A.........................................25mA
AC1, AC2..............................................................0 to VIN
BB_IN, VOUT, VIN3, BAT_IN, SCAP, PGVOUT,
CHARGE, SHIP.................................................–0.3 to 6V
BAT_OUT..... –0.3V to [Lesser of (BAT_IN + 0.3V) or 6V]
VIN2.....................–0.3V to [Lesser of (VIN + 0.3V)] or 6V
CAP....................... [Higher of –0.3V or (VIN – 6V)] to VIN
BAL.............................................–0.3V to (SCAP + 0.3V)
OUT[2:0]........... –0.3V to [Lesser of (VIN3 + 0.3V) or 6V]
IPK[2:0]............ –0.3V to [Lesser of (VIN3 + 0.3V) or 6V]
EH_ON.............. –0.3V to [Lesser of (VIN3 + 0.3V) or 6V]
FLOAT[1:0].... –0.3V to [Lesser of (BB_IN + 0.3V) or 6V]
LBSEL............ –0.3V to [Lesser of (BB_IN + 0.3V) or 6V]
UV[3:0]............. –0.3V to [Lesser of (VIN2 + 0.3V) or 6V]
IAC1, IAC2...............................................................±50mA
ISWA, ISWB, IVOUT..................................................350mA
ISW........................................................................500mA
Operating Junction Temperature Range
(Notes 2, 3)............................................. –40°C to 125°C
Storage Temperature Range................... –65°C to 150°C
PIN CONFIGURATION
VIN
(Note 1)
AC2
ABSOLUTE MAXIMUM RATINGS
UH PACKAGE
32-LEAD (5mm × 5mm) PLASTIC QFN
TJMAX = 125°C, θJA = 44°C/W
EXPOSED PAD (PIN 33) IS GND, MUST BE SOLDERED TO PCB
*VIN has an internal 20V clamp
ORDER INFORMATION
LEAD FREE FINISH
TAPE AND REEL
PART MARKING*
PACKAGE DESCRIPTION
TEMPERATURE RANGE
LTC3331EUH#PBF
LTC3331EUH#TRPBF
3331
32-Lead (5mm × 5mm) Plastic QFN
–40°C to 85°C
LTC3331IUH#PBF
LTC3331IUH#TRPBF
3331
32-Lead (5mm × 5mm) Plastic QFN
–40°C to 125°C
Consult LTC Marketing for parts specified with wider operating temperature ranges. *The temperature grade is identified by a label on the shipping container.
For more information on lead free part marking, go to: http://www.linear.com/leadfree/
For more information on tape and reel specifications, go to: http://www.linear.com/tapeandreel/
2
3331fc
For more information www.linear.com/LTC3331
LTC3331
ELECTRICAL CHARACTERISTICS
The l denotes the specifications which apply over the specified operating
junction temperature range, otherwise specifications are at TA = 25°C (Note 2). VIN = 5V, BAT_IN = BAT_OUT = BB_IN = 3.6V,
SHIP = OV, SCAP = 0V unless otherwise specified.
SYMBOL
PARAMETER
VIN
Buck Input Voltage Range
VBB_IN
Buck-Boost Input Voltage Range
(Note 7)
IVIN
VIN Quiescent Current
VIN Input in UVLO
VIN Input in UVLO
Buck Enabled, Sleeping
Buck Enabled, Sleeping
Buck Enabled, Not Sleeping
VIN = 2.5V, VBB_IN = 0V
VIN = 16V, VBB_IN = 0V
VIN = 4V, VBB_IN = 0V
VIN = 18V, VBB_IN = 0V
VIN = 5V, VBB_IN = 0V, ISW = 0A (Note 4)
IBB_IN
BB_IN Quiescent Current (Note 6)
BB_IN Input with VIN Active
VBB_IN = 3.6V, VIN = 5V
Buck-Boost Enabled, Sleeping
VBB_IN = 3.6V, VIN = 0V
Buck-Boost Enabled, Not Sleeping VBB_IN = 3.6V, VIN = 0V, ISWA = ISWB = 0A (Note 4)
VOUT Leakage Current
5V Output Selected, Sleeping
IVOUT
CONDITIONS
MIN
TYP
UNITS
19
V
5.5
V
450
800
1300
1800
150
700
1400
2000
2700
225
nA
nA
nA
nA
µA
200
950
200
300
1500
300
nA
nA
µA
l
l
MAX
1.8
100
150
nA
VIN Undervoltage Lockout Thresholds 3V Level Selected
(Rising or Falling)
4V Level Selected
l
2.91
3.00
3.09
V
l
3.88
4.00
4.12
V
5V Level Selected
l
4.85
5.00
5.15
V
6V Level Selected
l
5.82
6.00
6.18
V
7V Level Selected
l
6.79
7.00
7.21
V
8V Level Selected
l
7.76
8.00
8.24
V
9V Level Selected
l
8.73
9.00
9.27
V
10V Level Selected
l
9.70
10.0
10.30
V
11V Level Selected
l
10.67
11.0
11.33
V
12V Level Selected
l
11.64
12.0
12.36
V
13V Level Selected
l
12.61
13.0
13.39
V
14V Level Selected
l
13.58
14.0
14.42
V
15V Level Selected
l
14.55
15.0
15.45
V
16V Level Selected
l
15.52
16.0
16.48
V
17V Level Selected
l
16.49
17.0
17.51
V
18V Level Selected
l
17.46
18.0
18.54
V
IVIN = 1mA
l
19.0
20.0
21.0
V
800
1550
900
1750
mV
mV
20
nA
VSHUNT
VIN Shunt Regulator Voltage
ISHUNT
Maximum Protective Shunt Current
25
Internal Bridge Rectifier Loss
(|VAC1 – VAC2| – VIN)
IBRIDGE = 10µA
IBRIDGE = 50mA
Internal Bridge Rectifier Reverse
Leakage Current
VREVERSE = 18V
Internal Bridge Rectifier Reverse
Breakdown Voltage
IREVERSE = 1µA
700
1350
VSHUNT
mA
30
V
3331fc
For more information www.linear.com/LTC3331
3
LTC3331
ELECTRICAL CHARACTERISTICS
The l denotes the specifications which apply over the specified operating
junction temperature range, otherwise specifications are at TA = 25°C (Note 2). VIN = 5V, BAT_IN = BAT_OUT = BB_IN = 3.6V,
SHIP = OV, SCAP = 0V unless otherwise specified.
SYMBOL
PARAMETER
CONDITIONS
VOUT
Regulated Buck/Buck-Boost Output
Voltage
1.8V Output Selected
Sleep Threshold
Wake-Up Threshold
IPEAK_BB
4
MIN
TYP
MAX
UNITS
l
l
1.728
1.806
1.794
1.872
V
V
2.5V Output Selected
Sleep Threshold
Wake-Up Threshold
l
l
2.425
2.508
2.492
2.575
V
V
2.8V Output Selected
Sleep Threshold
Wake-Up Threshold
l
l
2.716
2.809
2.791
2.884
V
V
3.0V Output Selected
Sleep Threshold
Wake-Up Threshold
l
l
2.910
3.010
2.990
3.090
V
V
3.3V Output Selected
Sleep Threshold
Wake-Up Threshold
l
l
3.200
3.311
3.289
3.400
V
V
3.6V Output Selected
Sleep Threshold
Wake-Up Threshold
l
l
3.492
3.612
3.588
3.708
V
V
4.5V Output Selected
Sleep Threshold
Wake-Up Threshold
l
l
4.365
4.515
4.485
4.635
V
V
5.0V Output Selected
Sleep Threshold
Wake-Up Threshold
l
l
4.850
5.017
4.983
5.150
V
V
PGVOUT Falling Threshold
As a Percentage of VOUT Target (Note 5)
l
88
92
96
%
Buck-Boost Peak Switch Current
250mA Target Selected
200
250
350
mA
150mA Target Selected
120
150
210
mA
100mA Target Selected
80
100
140
mA
50mA Target Selected
40
50
70
mA
25mA Target Selected
20
25
35
mA
15mA Target Selected
12
15
21
mA
10mA Target Selected
8
10
14
mA
5mA Target Selected
4
5
7
mA
50
Available Buck-Boost Current
IPEAK_BB = 250mA, VOUT = 3.3V
Buck-Boost PMOS Input and Output
Switch On-Resistance
IPK[2:0] = 111
IPK[2:0] = 110
IPK[2:0] = 101
IPK[2:0] = 100
IPK[2:0] = 011
IPK[2:0] = 010
IPK[2:0] = 001
IPK[2:0] = 000
0.8
1.0
1.4
2.4
4.5
7.3
10.7
20.5
mA
Ω
Ω
Ω
Ω
Ω
Ω
Ω
Ω
Buck-Boost NMOS Input and Output
Switch On-Resistance
IPK2 = 1
IPK2 = 0
0.6
3.9
Ω
Ω
3331fc
For more information www.linear.com/LTC3331
LTC3331
ELECTRICAL CHARACTERISTICS
The l denotes the specifications which apply over the specified operating
junction temperature range, otherwise specifications are at TA = 25°C (Note 2). VIN = 5V, BAT_IN = BAT_OUT = BB_IN = 3.6V,
SHIP = OV, SCAP = 0V unless otherwise specified.
SYMBOL
IPEAK_BUCK
PARAMETER
CONDITIONS
MIN
PMOS Switch Leakage
Buck/Buck-Boost Regulators
–20
20
nA
NMOS Switch Leakage
Buck/Buck-Boost Regulators
–20
20
nA
Maximum Buck Duty Cycle
Buck/Buck-Boost Regulators
l
200
Available Buck Output Current
100
UNITS
%
250
500
mA
mA
Buck PMOS Switch On-Resistance
1.4
Ω
Buck NMOS Switch On-Resistance
1.2
Ω
Maximum Battery Shunt Current
10
Battery Disconnect Leakage Current
Battery Disconnected
SHIP Mode Engaged
VFLOAT
Shunt Charger Float Voltage
(BAT_OUT Voltage)
FLOAT[1:0] = 00, IBB_IN = 1mA
FLOAT[1:0] = 01, IBB_IN = 1mA
FLOAT[1:0] = 10, IBB_IN = 1mA
FLOAT[1:0] = 11, IBB_IN = 1mA
Low Battery Disconnect Threshold,
BAT_IN Voltage (Falling)
VLBC_BAT_IN Low Battery Connect Threshold,
BAT_IN Voltage (Rising)
VLBC_BAT_
OUT
MAX
100
Buck Peak Switch Current
IBAT_IN
VLBD
TYP
mA
–10
–10
0
0
10
10
nA
nA
3.415
3.960
4.059
4.158
3.45
4.0
4.1
4.2
3.485
4.040
4.141
4.242
V
V
V
V
FLOAT[1:0] = 00, IBB_IN = 1mA
FLOAT[1:0] = 01, IBB_IN = 1mA
FLOAT[1:0] = 10, IBB_IN = 1mA
FLOAT[1:0] = 11, IBB_IN = 1mA
l
l
l
l
3.381
3.920
4.018
4.116
3.45
4.0
4.1
4.2
3.519
4.080
4.182
4.284
V
V
V
V
LBSEL = 0, FLOAT[1:0] = 00, IBAT_IN = –1mA
LBSEL = 1, FLOAT[1:0] = 00, IBAT_IN = –1mA
LBSEL = 0, FLOAT[1:0] = 01, 10, 11, IBAT_IN = –1mA
LBSEL = 1, FLOAT[1:0] = 01, 10, 11, IBAT_IN = –1mA
l
l
l
l
1.98
2.43
2.62
3.10
2.04
2.51
2.70
3.20
2.10
2.59
2.78
3.30
V
V
V
V
2.26
2.74
2.91
3.39
2.35
2.85
3.03
3.53
2.44
2.96
3.15
3.67
V
V
V
V
LBSEL = 0, FLOAT[1:0] = 00, IBAT_IN = –1mA
LBSEL = 1, FLOAT[1:0] = 00, IBAT_IN = –1mA
LBSEL = 0, FLOAT[1:0] = 01, 10, 11, IBAT_IN = –1mA
LBSEL = 1, FLOAT[1:0] = 01, 10, 11, IBAT_IN = –1mA
Low Battery Connect Threshold,
BAT_OUT Voltage (Rising)
LBSEL = 0, FLOAT[1:0] = 00
LBSEL = 1, FLOAT[1:0] = 00
LBSEL = 0, FLOAT[1:0] = 01, 10, 11
LBSEL = 1, FLOAT[1:0] = 01, 10, 11
Battery Disconnect PMOS
On-Resistance
BAT_IN = 3.3V, IBAT_IN = 10mA
Charge Pin Current
Current Out of CHARGE Pin
CHARGE Pin Voltage PMOS
On-Resistance
2mA Out of CHARGE Pin
3.02
3.52
3.70
4.20
V
V
V
V
5
Ω
1
2
l
60
Ω
VSCAP
Supercapacitor Balancer Input Range
ISCAP
Supercapacitor Balancer Quiescent
Current
SCAP = 5.0V
Supercapacitor Balancer Source
Current
SCAP = 5.0V, BAL = 2.4V
10
mA
Supercapacitor Balancer Sink Current SCAP = 5.0V, BAL = 2.6V
10
mA
l
2.5
mA
mA
150
5.5
V
225
nA
3331fc
For more information www.linear.com/LTC3331
5
LTC3331
ELECTRICAL CHARACTERISTICS
The l denotes the specifications which apply over the specified operating
junction temperature range, otherwise specifications are at TA = 25°C (Note 2). VIN = 5V, BAT_IN = BAT_OUT = BB_IN = 3.6V,
SHIP = OV, SCAP = 0V unless otherwise specified.
SYMBOL
PARAMETER
CONDITIONS
VBAL
Supercapacitor Balance Point
Percentage of SCAP Voltage
VIH
Digital Input High Voltage
Pins: OUT[2:0], SHIP, FLOAT[1:0], LBSEL, IPK[2:0],
UV[3:0]
VIL
Digital Input Low Voltage
Pins: OUT[2:0], SHIP, FLOAT[1:0], LBSEL, IPK[2:0],
UV[3:0]
l
IIH
Digital Input High Current
Pins: OUT[2:0], SHIP, FLOAT[1:0], LBSEL, IPK[2:0],
UV[3:0]
IIL
Digital Input Low Current
Pins: OUT[2:0], SHIP, FLOAT[1:0], LBSEL, IPK[2:0],
UV[3:0]
VOH
PGVOUT, Output High Voltage
EH_ON Output High Voltage
BB_IN = 5V, 1µA Out of Pin
VIN = 6V, 1µA Out of Pin
VOL
PGVOUT, EH_ON Output Low Voltage BB_IN = 5V, 1µA into Pin
6000
VIN Quiescent Current in Sleep
vs VIN
IVIN (nA)
IVIN (nA)
85°C
800
25°C
–40°C
0
3
6
9
VIN (V)
12
85°C
25°C
1000
15
18
3331 G01
0.4
V
0
10
nA
0
10
nA
V
V
0.4
V
BAT_OUT TIED TO BB_IN
125°C
1750
3000
0
V
4.0
3.8
2500
3
6
12
9
VIN (V)
85°C
1250
1000
25°C
750
–40°C
250
18
15
1500
500
–40°C
200
0
%
Buck-Boost Quiescent Current in
Sleep vs BB_IN
125°C
2000
600
400
51
2000
4000
1400
1000
50
1.2
UNITS
TA = 25°C, unless otherwise noted.
5000
1600
1200
49
l
2250
125°C
1800
l
l
IBB_IN (nA)
2000
MAX
l
l
TYPICAL PERFORMANCE CHARACTERISTICS
2200
TYP
Note 3: TJ is calculated from the ambient TA and power dissipation PD
according to the following formula: TJ = TA + (PD • θJA).
Note 4: Dynamic supply current is higher due to gate charge being
delivered at the switching frequency.
Note 5: The PGVOUT Rising threshold is equal to the sleep threshold. See
VOUT specification.
Note 6: These quiescent currents include the contribution from the internal
resistor divider at the BAT_OUT pin as BAT_OUT must be tied to BB_IN for
all applications.
Note 7: The buck-boost operating voltage is further constrained to a
narrower range by the programmed float voltage and the selected low
battery disconnect and connect thresholds.
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 LTC3331 is tested under pulsed load conditions such that
TJ ≈ TA. The LTC3331E is guaranteed to meet specifications from 0°C to
85°C. The LTC3331I is guaranteed over the –40°C to 125°C operating
junction temperature range. Note that the maximum ambient temperature
consistent with these specifications is determined by specific operating
conditions in conjunction with board layout, the rated package thermal
impedance and other environmental factors.
VIN Quiescent Current in UVLO
vs VIN
MIN
3331 G02
0
2.1
2.4
2.7
3.3
3
BB_IN (V)
3.6
3.9
4.2
3331 G03
6
3331fc
For more information www.linear.com/LTC3331
LTC3331
TYPICAL PERFORMANCE CHARACTERISTICS
VOUT Quiescent Current
vs Temperature
UVLO Threshold vs Temperature
130
IVOUT (nA)
120
110
100
90
80
70
60
50
–50
0
25
50
75
TEMPERATURE (°C)
–25
100
APPLIES TO EACH UVLO SETTING
20.6
20.4
101
100
99
125
–25
0
25
50
75
TEMPERATURE (°C)
100
85°C
600
125°C
400
200
0
1µ
10µ
100µ
1m
BRIDGE CURRENT (A)
10m
1.6
1.4
12
1.2
10
8
0.6
0.4
2
0.2
WAKE-UP THRESHOLD
VOUT (V)
VOUT (V)
2.75
2.40
2.35
1.70
100
125
3331 G10
2.25
–50
2.70
2.65
2.30
PGVOUT FALLING
10M 100M
SLEEP THRESHOLD
WAKE-UP THRESHOLD
1.72
10k 100k 1M
FREQUENCY (Hz)
2.80
2.45
1.74
1k
2.8V Output vs Temperature
SLEEP THRESHOLD
1.76
0
25
50
75
TEMPERATURE (°C)
100
2.85
2.50
WAKE-UP THRESHOLD
–25
10
3331 G09
2.5V Output vs Temperature
1.80
VOUT (V)
0
170
35
80
125
TEMPERATURE (°C)
3331 G08
SLEEP THRESHOLD
1.66
0.8
4
2.55
1.68
1.0
6
1.8V Output vs Temperature
1.64
–50
4.8VP-P APPLIED TO AC1/AC2 INPUT
1.8 MEASURED IN UVLO
14
–10
125
Bridge Frequency Response
16
0
–55
1.84
1.78
100
2.0
VIN = 18V, LEAKAGE AT AC1 OR AC2
3331 G07
1.82
0
25
50
75
TEMPERATURE (°C)
3331 G06
VIN (V)
BRIDGE LEAKAGE (nA)
BRIDGE DROP (mV)
25°C
–25
3331 G05
18
1200
800
19.0
–50
125
Bridge Leakage vs Temperature
–40°C
ISHUNT = 1mA
19.8
19.2
|VAC1 – VAC2| – VIN
1000
20.0
19.4
97
–50
20
1400
ISHUNT = 25mA
20.2
19.6
98
Total Bridge Rectifier Drop
vs Bridge Current
1600
VSHUNT vs Temperature
20.8
102
3331 G04
1800
21.0
VSHUNT (V)
VOUT IN REGULATION, SLEEPING
140
103
PERCENTAGE OF TARGET SETTING (%)
150
TA = 25°C, unless otherwise noted.
2.60
PGVOUT FALLING
–25
0
25
50
75
TEMPERATURE (°C)
100
125
3331 G11
2.55
–50
PGVOUT FALLING
–25
0
25
50
75
TEMPERATURE (°C)
100
125
3331 G12
3331fc
For more information www.linear.com/LTC3331
7
LTC3331
TYPICAL PERFORMANCE CHARACTERISTICS
3V Output vs Temperature
3.3V Output vs Temperature
3.05
3.35
3.6V Output vs Temperature
3.65
SLEEP THRESHOLD
SLEEP THRESHOLD
WAKE-UP THRESHOLD
VOUT (V)
2.90
2.85
2.80
WAKE-UP THRESHOLD
3.25
3.20
3.15
2.75
–25
0
25
50
75
TEMPERATURE (°C)
100
3.00
–50
125
–25
0
25
50
75
TEMPERATURE (°C)
300
SLEEP THRESHOLD
SLEEP THRESHOLD
4.50
270
VOUT (V)
4.30
IPEAK_BB (mA)
4.90
4.35
4.80
4.70
4.25
4.10
–50
–25
210
0
25
50
75
TEMPERATURE (°C)
100
4.50
–50
125
–25
0
25
50
75
TEMPERATURE (°C)
3331 G16
200
–50
125
1.40
1.10
5.2
1.00
4.8
40
0.90
0.80
30
25
20
15
4.4
0.60
10
4.2
0.50
5
4.0
–50
0.40
–50
100
125
3331 G19
–25
50
25
0
75
TEMPERATURE (°C)
100
125
3331 G20
8
125
35
0.70
0
25
50
75
TEMPERATURE (°C)
100
PMOS, BB_IN = 2.1V
NMOS, BB_IN = 2.1V
PMOS, BB_IN = 4.2V
NMOS, BB_IN = 4.2V
45
4.6
–25
0
25
50
75
TEMPERATURE (°C)
RDS(ON) of Buck-Boost PMOS/NMOS
vs Temperature, 5mA IPEAK Setting
50
RDS(ON) (Ω)
5.4
RDS(ON) (Ω)
1.20
55
PMOS, BB_IN = 2.1V
NMOS, BB_IN = 2.1V
PMOS, BB_IN = 4.2V
NMOS, BB_IN = 4.2V
1.30
5.6
5.0
–25
3331 G18
RDS(ON) of Buck-Boost PMOS/NMOS
vs Temperature, 250mA IPEAK Setting
BB_IN = 3.6V
5.8
100
3331 G17
Buck-Boost Peak Current vs
Temperature, 5mA IPEAK Setting
6.0
250
240
220
4.60
PGVOUT FALLING
4.15
260
230
PGVOUT FALLING
4.20
125
280
WAKE-UP THRESHOLD
WAKE-UP THRESHOLD
100
BB_IN = 3.6V
290
5.00
4.40
0
25
50
75
TEMPERATURE (°C)
Buck-Boost Peak Current vs
Temperature, 250mA IPEAK Setting
5.10
4.45
–25
3331 G15
5V Output vs Temperature
4.60
VOUT (V)
3.25
–50
125
100
3331 G14
4.5V Output vs Temperature
4.55
PGVOUT FALLING
3.30
3331 G13
IPEAK_BB (mA)
3.45
3.35
PGVOUT FALLING
3.05
2.70
–50
3.50
3.40
3.10
PGVOUT FALLING
WAKE-UP THRESHOLD
3.55
VOUT (V)
2.95
SLEEP THRESHOLD
3.60
3.30
3.00
VOUT (V)
TA = 25°C, unless otherwise noted.
0
–50
–25
50
25
0
75
TEMPERATURE (°C)
100
125
3331 G21
3331fc
For more information www.linear.com/LTC3331
LTC3331
TYPICAL PERFORMANCE CHARACTERISTICS
Buck Peak Current
vs Temperature
RDS(ON) of Buck PMOS/NMOS
vs Temperature
300
2.0
VIN = 5V
290
Buck-Boost Load Regulation,
VOUT = 3.3V
3.40
COUT = 100µF
3.38 L = 22µH
IPK[2:0] = 111
3.36
VIN = 5V
1.8
280
270
3.34
1.6
260
250
240
PMOS
1.4
NMOS
1.2
230
220
VOUT (V)
RDS(ON) (Ω)
IPEAK_BUCK (mA)
TA = 25°C, unless otherwise noted.
BB_IN = 4.1V
3.30
BB_IN = 2.1V
3.28
3.26
3.24
1.0
210
3.22
200
–50
–25
0
25
50
75
TEMPERATURE (°C)
100
125
0.8
–50
–25
0
25
50
75
TEMPERATURE (°C)
100
3.400
OUTPUT
VOLTAGE
50mV/DIV
AC-COUPLED
SWA
VOLTAGE 0V
2V/DIV
LOAD = 1mA
LOAD = 50mA
3.250
INDUCTOR
CURRENT 0mA
200mA/DIV
3.225
2.7
3.3
3
BB_IN (V)
3.6
10m
100m
3.350
SWB
VOLTAGE
2V/DIV
0V
3.300
2.4
100µ
1m
ILOAD (A)
3.9
8µs/DIV
BAT = 2.1V, VOUT = 3.3V
ILOAD = 10mA
L = 22µH, COUT = 100µF
4.2
VIN = 4V
COUT = 100µF
L = 22µH
3.375
VOUT (V)
COUT = 100µF
3.375 L = 22µH
IPK[2:0] = 111
3.350
3.200
2.1
10µ
Buck Load Regulation, 3.3V
Buck-Boost Switching Waveforms
3.400
3.275
1µ
3331 G24
Buck-Boost Line Regulation,
VOUT = 3.3V
3.325
3.20
125
3331 G23
3331 G22
VOUT (V)
3.32
3.325
3.300
3.275
3.250
3331 G26
3.225
3.200
1µ
10µ
100µ
1m
ILOAD (A)
10m
100m
3331 G27
3331 G25
Buck Line Regulation, 3.3V
3.400
COUT = 100µF
L = 22µH
3.375
VOUT (V)
3.350
3.325
OUTPUT
VOLTAGE
50mV/DIV
DC-COUPLED,
OFFSET = 3.3V
OUTPUT
VOLTAGE
50mV/DIV
AC-COUPLED
EH_ON
5V/DIV
SW VOLTAGE
10V/DIV 0V
LOAD = 1mA
3.300
0V
BUCK
INDUCTOR
CURRENT
200mA/DIV
BUCK-BOOST 0mA
INDUCTOR
CURRENT 0mA
200mA/DIV
LOAD = 100mA
3.275
INDUCTOR
CURRENT
200mA/DIV
3.250
3.225
3.200
Prioritizer Buck to Buck-Boost
Transition
Buck Switching Waveforms
4
6
8
10
12
VIN (V)
14
16
18
3331 G28
0mA
8µs/DIV
VIN = 18V, VOUT = 3.3V
ILOAD = 10mA
L = 22µH, COUT = 100µF
3331 G29
3331 G30
100µs/DIV
VIN TRANSITIONS 18V TO 17V, UV[3:0] = 1110
BB_IN = 4.1V, VOUT = 3.3V
ILOAD = 50mA, COUT = 100µF, LBUCK = 22µH,
LBUCK-BOOST = 22µH
3331fc
For more information www.linear.com/LTC3331
9
LTC3331
TYPICAL PERFORMANCE CHARACTERISTICS
Buck-Boost Load Step Response
LOAD
CURRENT
25mA/DIV 1mA
OUTPUT
VOLTAGE
50mV/DIV
DC-COUPLED,
OFFSET = 3.3V
LOAD
CURRENT
25mA/DIV 1mA
2ms/DIV
BB_IN = 3V, VOUT = 3.3V
COUT = 100µF, L = 22µH
LOAD STEP FROM 1mA TO 50mA
3331 G31
2ms/DIV
VIN = 18V, VOUT = 3.3V
COUT = 100µF, L = 22µH
LOAD STEP FROM 1mA TO 50mA
100
80
3331 G33
100µs/DIV
VIN TRANSITIONS 17V TO 18V, UV[3:0] = 1110
BB_IN = 4.1V, VOUT = 3.3V
ILOAD = 50mA, COUT = 100µF, LBUCK = 22µH,
LBUCK-BOOST = 22µH
VOUT = 1.8V
VOUT = 2.5V
VOUT = 2.8V
VOUT = 3V
95
Buck Efficiency vs VIN for
ILOAD = 100mA, L = 100µH
100
VOUT = 3.3V
VOUT = 3.6V
VOUT = 4.5V
VOUT = 5V
VOUT = 1.8V
VOUT = 2.5V
VOUT = 2.8V
VOUT = 3V
95
VOUT = 3.3V
VOUT = 3.6V
VOUT = 4.5V
VOUT = 5V
60
50
40
VOUT = 1.8V
VOUT = 2.5V
VOUT = 3.3V
VOUT = 5V
30
20
10
0
10µ
100µ
1m
ILOAD (A)
10m
90
85
80
VIN = 6V, L = 22µH, DCR = 0.19Ω
1µ
EFFICIENCY (%)
70
EFFICIENCY (%)
75
100m
DCR = 0.19Ω
4
6
3331 G34
Buck Efficiency vs VIN, for
VOUT = 3.3V
90
85
80
8
10
12
VIN (V)
14
16
75
18
Buck-Boost Efficiency vs ILOAD,
250mA IPEAK Setting
100
100
90
90
80
80
80
70
70
70
100
L = 22µH, DCR = 0.19Ω
EFFICIENCY (%)
90
60
50
40
30
ILOAD = 100mA
ILOAD =100µA
ILOAD =50µA
ILOAD =30µA
20
10
0
4
10
6
8
10
12
VIN (V)
ILOAD =20µA
ILOAD =10µA
ILOAD =5µA
14
16
60
50
40
30
VOUT = 1.8V
VOUT = 2.5V
VOUT = 3.3V
VOUT = 5.0V
20
18
3331 G37
BAT = 3.6V
10 L = 22µH
RL = 0.36Ω
0
1µ
10µ
1m
100µ
ILOAD (A)
DCR = 0.45Ω
4
6
8
3331 G35
EFFICIENCY (%)
EFFICIENCY (%)
3331 G32
EH_ON
5V/DIV 0V
BUCK
INDUCTOR
CURRENT
200mA/DIV 0mA
BUCK-BOOST
INDUCTOR
CURRENT 0mA
200mA/DIV
Buck Efficiency vs VIN for
ILOAD = 100mA, L = 22µH
Buck Efficiency vs ILOAD
90
EFFICIENCY (%)
Prioritizer Buck-Boost to Buck
Transition
Buck Load Step Response
OUTPUT
VOLTAGE
20mV/DIV
AC-COUPLED
OUTPUT
VOLTAGE
20mV/DIV
AC-COUPLED
100
TA = 25°C, unless otherwise noted.
10m
3331 G39
10
12
VIN (V)
14
16
18
3331 G36
Buck-Boost Efficiency vs ILOAD,
5mA IPEAK Setting
60
50
40
30
VOUT = 1.8V
VOUT = 2.5V
VOUT = 3.3V
VOUT = 5.0V
20
BAT = 3.6V
10 L = 22µH
DCR = 5.1Ω
0
10µ
1µ
100µ
ILOAD (A)
1m
3331 G38
3331fc
For more information www.linear.com/LTC3331
LTC3331
TYPICAL PERFORMANCE CHARACTERISTICS
90
80
70
ILOAD = 50mA
ILOAD = 100µA
ILOAD = 50µA
ILOAD = 20µA
ILOAD = 10µA
ILOAD = 5µA
60
50
40
2.1
2.4
2.7
3.3
3
BB_IN (V)
3.9
90
70
ILOAD = 50mA
ILOAD = 100µA
ILOAD = 50µA
ILOAD = 20µA
ILOAD = 10µA
ILOAD = 5µA
60
50
3.6
40
2.1
4.2
2.4
2.7
3.3
3
BB_IN (V)
3.6
3.9
90
80
70
ILOAD = 1mA
ILOAD = 100µA
ILOAD = 50µA
ILOAD = 20µA
ILOAD = 10µA
ILOAD = 5µA
60
50
40
2.1
2.4
2.7
3.3
3
BB_IN (V)
3.9
100
L = 1000µH
DCR = 5.1Ω
90
ILOAD = 1mA
ILOAD = 100µA
ILOAD = 50µA
ILOAD = 20µA
ILOAD = 10µA
ILOAD = 5µA
60
40
2.1
4.25
3.55
4.20
2.4
2.7
3.3
3
BB_IN (V)
3.6
3.9
3.95
75
50
25
TEMPERATURE (°C)
100
125
3331 G46
2.4
2.7
3.3
3
BB_IN (V)
3.9
3.6
3.90
–50 –25
75
50
25
TEMPERATURE (°C)
0
4.2
3331 G45
8
IBB_IN = 1mA
4.05
3.30
0
ILOAD = 1mA
ILOAD = 100µA
ILOAD = 50µA
ILOAD = 20µA
ILOAD = 10µA
ILOAD = 5µA
60
Shunt Float Voltage Load
Regulation
4.10
4.00
4.2
70
40
2.1
4.2
4.15
3.35
3.25
–50 –25
3.9
3.6
L = 1000µH
DCR = 5.1Ω
50
FLOAT VOLTAGE DEVIATION (mV)
3.60
FLOAT VOLTAGE (V)
FLOAT VOLTAGE (V)
4.30
IBB_IN = 1mA
3.40
3.3
3
BB_IN (V)
80
4V, 4.1V, 4.2V Float Voltage
vs Temperature
3.45
2.7
3331 G44
3.45V Float Voltage
vs Temperature
3.50
2.4
Buck-Boost Efficiency vs BB_IN for
VOUT = 5V, 5mA IPEAK Setting
3331 G43
3.65
ILOAD = 50mA
ILOAD = 100µA
ILOAD = 50µA
ILOAD = 20µA
ILOAD = 10µA
ILOAD = 5µA
60
Buck-Boost Efficiency vs BB_IN for
VOUT = 3.3V, 5mA IPEAK Setting
70
4.2
70
3331 G42
50
3.6
80
3331 G41
80
EFFICIENCY (%)
EFFICIENCY (%)
90
100
L = 1000µH
DCR = 5.1Ω
L = 22µH
DCR = 0.36Ω
40
2.1
4.2
EFFICIENCY (%)
100
Buck-Boost Efficiency vs BB_IN for
VOUT = 5V, 250mA IPEAK Setting
50
3331 G40
Buck-Boost Efficiency vs BB_IN for
VOUT = 1.8V, 5mA IPEAK Setting
100
L = 22µH
DCR = 0.36Ω
80
EFFICIENCY (%)
EFFICIENCY (%)
90
100
L = 22µH
DCR = 0.36Ω
Buck-Boost Efficiency vs BB_IN for
VOUT = 3.3V, 250mA IPEAK Setting
EFFICIENCY (%)
100
Buck-Boost Efficiency vs BB_IN for
VOUT = 1.8V, 250mA IPEAK Setting
TA = 25°C, unless otherwise noted.
100
125
3331 G47
ALL FLOAT SETTINGS IN SLEEP
7
6
5
4
3
2
1
0
1µ
10µ
100µ
IBB_IN (A)
1m
10m
3331 G48
3331fc
For more information www.linear.com/LTC3331
11
LTC3331
TYPICAL PERFORMANCE CHARACTERISTICS
Battery Connect Voltage at
BAT_IN vs IBAT_OUT
4.2
800
4.0
700
3.8
BAT_IN VOLTAGE (V)
4.4
900
PMOS BODY DIODE DROP (mV)
1000
–40°C
25°C
500
85°C
400
300
200
125°C
Battery Connect Voltage at
BAT_OUT vs IBAT_OUT
4.4
4.0, 4.1, 4.2 FLOAT, LBSEL = 1
4.0, 4.1, 4.2 FLOAT, LBSEL = 0
3.45 FLOAT, LBSEL = 1
3.45 FLOAT, LBSEL = 0
4.2
4.0
BAT_OUT VOLTAGE (V)
Disconnect PMOS Body Diode
Drop vs Current
600
TA = 25°C, unless otherwise noted.
3.6
3.4
3.2
3.0
2.8
3.4
3.2
3.0
2.8
2.6
100
2.4
2.4
0
2.2
1µ
100µ
ID (A)
10µ
1m
10m
1µ
100µ
10µ
1m
3.4
BAT_IN VOLTAGE (V)
7
BAT_IN = 3.1V
5
BAT_IN = 4.1V
0
–50 –25
50
25
75
0
TEMPERATURE (°C)
100
3.4
3.0
2.8
2.6
2.4
2.0
100µ
IBAT_IN (A)
10µ
1m
10m
CONNECT, BAT_OUT
CONNECT, BAT_IN
0
25
50
75
TEMPERATURE (°C)
3.2
1m
10m
100
125
BAT_IN
BATTERY
CONNECTED
1V/DIV
CONNECT, BAT_IN
2.8
0V
2.6
2.2
3331 G55
12
100µ
IBAT_IN (A)
3331 G54
4.2V
3.0
2.4
DISCONNECT, BAT_OUT, BAT_IN
–25
10µ
Battery Connect Transient
3.4
2.6
2.0
–50
1µ
CONNECT, BAT_OUT
3.6
2.8
2.2
1.8
3.8
3.0
2.4
2.4
Battery Connect/Disconnect
vs Temperature
3.45 FLOAT
LBSEL = 0
IBAT_OUT = 1mA
3.2
2.6
3331 G53
VOLTAGE (V)
3.4
2.8
2.2
Battery Connect/Disconnect
vs Temperature
3.6
3.0
2.0
1µ
10m
3.2
2.2
3331 G50
3.8
1m
4.0, 4.1, 4.2 FLOAT, LBSEL = 1
4.0, 4.1, 4.2 FLOAT, LBSEL = 0
3.45 FLOAT, LBSEL = 1
3.45 FLOAT, LBSEL = 0
3.6
3.2
1.8
125
3.8
BAT_OUT VOLTAGE (V)
BAT_IN = 2.1V
8
100µ
IBAT_OUT (A)
Battery Disconnect Voltage at
BAT_OUT vs IBAT_IN
4.0, 4.1, 4.2 FLOAT, LBSEL = 1
4.0, 4.1, 4.2 FLOAT, LBSEL = 0
3.45 FLOAT, LBSEL = 1
3.45 FLOAT, LBSEL = 0
3.6
4
10µ
3331 G52
Battery Disconnect Voltage at
BAT_IN vs IBAT_IN
3.8
6
1µ
3331 G51
10
9
2.2
10m
4.0, 4.1, 4.2 FLOAT, LBSEL = 1
4.0, 4.1, 4.2 FLOAT, LBSEL = 0
3.45 FLOAT, LBSEL = 1
3.45 FLOAT, LBSEL = 0
IBAT_OUT (A)
RDS(ON) of Disconnect PMOS
vs Temperature
RDS(ON) (Ω)
3.6
2.6
3331 G49
VOLTAGE (V)
3.8
BAT_OUT
DISCONNECT, BAT_OUT, BAT_IN
3.45 FLOAT
LBSEL = 1
IBAT_OUT = 1mA
2.0
–50
–25
0
25
50
75
TEMPERATURE (°C)
100
125
3331 G57
2.5ms/DIV
VIN = 18V, VOUT IN REGULATION, SLEEPING
10mA CHARGES BB_IN/BAT_OUT
CBB_IN = 22µF
FLOAT[1:0] = 11, LBSEL = 0
3331 G56
3331fc
For more information www.linear.com/LTC3331
LTC3331
TYPICAL PERFORMANCE CHARACTERISTICS
Battery Connect/Disconnect
vs Temperature
4.4
4.2
Battery Connect/Disconnect
vs Temperature
4.4
4.0, 4.1, 4.2 FLOAT
LBSEL = 0
IBAT_OUT = 1mA
3.6
3.4
3.2
CONNECT, BAT_IN
3.0
2.8
2.6
–50
3.8
0
25
50
75
TEMPERATURE (°C)
DISCONNECT, BAT_OUT, BAT_IN
3.2
0V
4.0, 4.1, 4.2 FLOAT
LBSEL = 1
IBAT_OUT = 1mA
2.6
–50
125
–25
0
25
50
75
TEMPERATURE (°C)
500ms/DIV
CBAT_IN = 1mF
CBB_IN = 22µF, BB_IN TIED TO BAT_OUT
1mA LOAD AT VOUT
FLOAT[1:0] = 11, LBSEL = 0
3331 G60
3331 G59
Supercapacitor Balancer
Quiescent Current vs VSCAP
Supercapacitor Balancer
Source/Sink Current
50
BALANCER SOURCE/SINK CURRENT (mA)
250
125°C
200
85°C
ISCAP (nA)
125
100
3331 G58
150
25°C
100
–40°C
50
0
BAT_OUT
3.4
2.8
100
VOUT
500mV/DIV
CONNECT, BAT_IN
3.6
3.0
DISCONNECT, BAT_OUT, BAT_IN
–25
BATTERY
DISCONNECTED
BAT_IN
4.0
CONNECT, BAT_OUT
3.8
Battery Connect Transient
CONNECT, BAT_OUT
4.2
VOLTAGE (V)
VOLTAGE (V)
4.0
TA = 25°C, unless otherwise noted.
2
2.5
3
3.5
4
VSCAP (V)
4.5
5
5.5
3330 G61
40
SCAP = 5V
30
20
10
SCAP = 2.5V
0
–10
–20
0
10 20 30 40 50 60 70 80 90 100
VBAL/VSCAP (%)
3330 G62
PIN FUNCTIONS
BAL (Pin 1): Supercapacitor Balance Point. The common
node of a stack of two supercapacitors is connected to
BAL. A source/sink balancing current of up to 10mA is
available. Tie BAL along with SCAP to GND to disable the
balancer and its associated quiescent current.
SCAP (Pin 2): Supply and Input for Supercapacitor
Balancer. Tie the top of a 2-capacitor stack to SCAP and
the middle of the stack to BAL to activate balancing. Tie
SCAP along with BAL to GND to disable the balancer and
its associated quiescent current.
VIN2 (Pin 3): Internal Low Voltage Rail to Serve as Gate
Drive for Buck NMOS Switch. Connect a 4.7µF (or larger)
capacitor from VIN2 to GND. This pin is not intended for
use as an external system rail.
UV3, UV2, UV1, UV0 (Pins 4, 5, 6, 7): UVLO Select Bits
for the Buck Switching Regulator. Tie high to VIN2 or low to
GND to select the desired UVLO rising and falling thresholds
(see Table 4). The UVLO falling threshold must be greater
than the selected VOUT regulation level. Do not float.
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13
LTC3331
PIN FUNCTIONS
AC1 (Pin 8): Input Connection for piezoelectric element,
other AC source, or current limited DC source (used in
conjunction with AC2 for differential AC inputs).
LBSEL (Pin 22): Low Battery Disconnect Select Pin. Connect LBSEL high to BB_IN or low to GND to select the low
battery disconnect level. See Table 2. Do not float.
AC2 (Pin 9): Input Connection for piezoelectric element,
other AC source, or current limited DC source (used in
conjunction with AC1 for differential AC inputs).
FLOAT1, FLOAT0 (Pins 23, 24): Float Voltage Select Pins.
Connect high to BB_IN or low to GND to select battery
float voltages of 3.45V, 4.0V, 4.1V, and 4.2V (see Table 2).
Do not float.
VIN (Pin 10): Rectified Input Voltage. A capacitor on this
pin serves as an energy reservoir and input supply for the
buck regulator. The VIN voltage is internally clamped to a
maximum of 20V (typical).
CAP (Pin 11): Internal Rail Referenced to VIN to Serve
as Gate Drive for Buck PMOS Switch. Connect a 1μF (or
larger) capacitor between CAP and VIN. This pin is not
intended for use as an external system rail.
SW (Pin 12): Switch Node for the Buck Switching Regulator. Connect a 22µH or greater external inductor between
this node and VOUT.
VOUT (Pin 13): Regulated Output Voltage Derived from the
Buck or Buck-Boost Switching Regulator.
SWB (Pin 14): Switch Node for the Buck-Boost Switching
Regulator. Connect an external inductor (value in Table 3)
between this node and SWA.
SWA (Pin 15): Switch Node for the Buck-Boost Switching
Regulator. Connect an external inductor (value in Table 3)
between this node and SWB.
BB_IN (Pin 16): Input for the Buck-Boost Switching Regulator. BB_IN must be tied to BAT_OUT for proper operation.
SHIP (Pin 25): Input to select SHIP mode. Tie SHIP to
at least 1.2V to select SHIP mode in which the battery
disconnect switch will be forced off, ensuring there is no
drain on the battery. Do not float.
VIN3 (Pin 26): Internal Low Voltage Rail Used by the
Prioritizer. Logic high reference for IPK[2:0] and OUT[2:0].
Connect a 0.1µF capacitor from VIN3 to GND. This pin is
not intended for use as an external system rail.
CHARGE (Pin 27): Connect a resistor from CHARGE to
the common BAT_OUT = BB_IN node to enable charging
of the battery. The CHARGE pin is controlled to provide
excess energy from the energy harvesting input when
the output is in regulation and the BUCK converter is in
SLEEP mode.
PGVOUT (Pin 28): Power Good Output for VOUT. Logic
level output referenced to an internal maximum rail (see
Operation). PGVOUT transitioning high indicates regulation has been reached on VOUT (VOUT = Sleep Rising).
PGVOUT remains high until VOUT falls to 92% (typical)
of the programmed regulation point.
IPK0, IPK1, IPK2 (Pins 17, 18, 19): IPEAK_BB Select Bits
for the Buck-Boost Switching Regulator. Tie high to VIN3
or low to GND to select the desired IPEAK_BB (see Table 3).
Do not float.
EH_ON (Pin 29): Switcher Status. Logic level output referenced to VIN3. EH_ON is high when the buck switching
regulator is in use (energy harvesting input). It is pulled
low when the buck-boost switching regulator is in use
(battery input).
BAT_OUT (Pin 20): This is the output side of the battery
disconnect switch. BAT_OUT must be connected to BB_IN
to power the buck-boost regulator.
OUT0, OUT1, OUT2 (Pins 30, 31, 32): VOUT Voltage Select
Bits. Tie high to VIN3 or low to GND to select the desired
VOUT (see Table 1). Do not float.
BAT_IN (Pin 21): Input for backup battery and the input
side to the battery disconnect switch. When the battery
is disconnected there will be less than 10nA of quiescent
current draw at BAT_IN.
GND (Exposed Pad Pin 33): Ground. The Exposed Pad
should be connected to a continuous ground plane on the
second layer of the printed circuit board by several vias
directly under the LTC3331.
14
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LTC3331
BLOCK DIAGRAM
10
VIN
20V
INTERNAL
RAIL
GENERATION
UVLO
AC1
8
UVLO_SET
CAP
SW
AC2
9
26
VIN2
BANDGAP
REFERENCE
VREF
PRIORITIZER
GND
SWA
BB_IN
VIN3
EH_ON
ILIM_SET
27
3
BUCK
CONTROL
SWB
29
12
VIN3
SLEEP
16
11
CHARGE
–
VREF
VIN2
VOUT
BUCK-BOOST
CONTROL
33
15
14
13
SLEEP
+
SLEEP-UVLO
VIN2 BB_IN VOUT
+
SHUNT
PMOS
20
VREF
SLEEP
0.925*VREF
–
+
PGVOUT
–
BAT_OUT
SCAP
BODY
DIODE
+
–
+
21
EA
–
VREF
BAT_IN
UVLO_SET
BB_IN
VIN3
BB_IN
2
SHIP
25
23, 24
VIN2
3
FLOAT[1:0]
BAL
LBSEL
22
32, 31, 30
4, 5, 6, 7
2
1
ILIM_SET
VIN3
4
OUT[2:0]
28
3
UV[3:0]
19, 18, 17
IPK[2:0]
3331 BD
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15
LTC3331
OPERATION
Modes of Operation
Table 3. IPEAK_BB Selection
The following four tables detail all programmable settings
on the LTC3331.
Table 1. Output Voltage Selection
OUT2
OUT1
OUT0
VOUT
0
0
0
1.8V
0
0
1
2.5V
0
1
0
2.8V
0
1
1
3.0V
1
0
0
3.3V
1
0
1
3.6V
1
1
0
4.5V
1
1
1
5.0V
FLOAT1 FLOAT0
FLOAT
CONNECT
IPK1
IPK0
ILIM
LMIN
0
0
0
5mA
1000µH
0
0
1
10mA
470µH
0
1
0
15mA
330µH
0
1
1
25mA
220µH
1
0
0
50mA
100µH
1
0
1
100mA
47µH
1
1
0
150mA
33µH
1
1
1
250mA
22µH
Table 4.UVLO Selection
UV3
UV2
UV1
UV0
UVLO
RISING
UVLO
FALLING
0
0
0
0
4V
3V
0
0
0
1
5V
4V
DISCONNECT
0
0
1
0
6V
5V
0
1
1
7V
6V
8V
7V
Table 2. FLOAT Selection
LBSEL
IPK2
0
0
0
3.45V
2.35V
2.04V
0
0
0
1
4.0V
3.03V
2.70V
0
1
0
0
0
1
0
4.1V
3.03V
2.70V
0
1
0
1
8V
5V
1
1
0
10V
9V
0
1
1
4.2V
3.03V
2.70V
0
1
0
0
3.45V
2.85V
2.51V
0
1
1
1
10V
5V
0
0
0
12V
11V
1
0
1
4.0V
3.53V
3.20V
1
1
1
0
4.1V
3.53V
3.20V
1
0
0
1
12V
5V
1
1
1
4.2V
3.53V
3.20V
1
0
1
0
14V
13V
1
0
1
1
14V
5V
1
1
0
0
16V
15V
1
1
0
1
16V
5V
1
1
1
0
18V
17V
1
1
1
1
18V
5V
16
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LTC3331
OPERATION
Overview
The LTC3331 combines a buck switching regulator and
a buck-boost switching regulator to produce an energy
harvesting solution with battery backup. The converters
are controlled by a prioritizer that selects which converter
to use based on the availability of a battery and/or harvestable energy. If harvested energy is available the buck
regulator is active and the buck-boost is OFF. An onboard
10mA shunt battery charger with low battery disconnect
enables charging of the backup battery to greatly extend
the life of the battery. An optional supercapacitor balancer
allows for significant energy storage at the output to handle
a variety of load requirements.
Energy Harvester
The energy harvester is an ultralow quiescent current power
supply designed to interface directly to a piezoelectric or
alternative A/C power source, rectify the input voltage,
and store harvested energy on an external capacitor
while maintaining a regulated output voltage. It can also
bleed off any excess input power via an internal protective
shunt regulator. It consists of an internal bridge rectifier,
an undervoltage lockout circuit, and a synchronous buck
DC/DC.
offers UVLO rising thresholds from 4V to 18V with large
or small hysteresis windows. This allows for programming of the UVLO window near the peak power point of
the input source. Extremely low quiescent current (450nA
typical) in UVLO allows energy to accumulate on the input
capacitor in situations where energy must be harvested
from low power sources.
Internal Rail Generation (CAP, VIN2, VIN3)
Two internal rails, CAP and VIN2, are generated from VIN
and are used to drive the high side PMOS and low side
NMOS of the buck converter, respectively. Additionally the
VIN2 rail serves as logic high for the UVLO threshold select
bits UV[3:0]. The VIN2 rail is regulated at 4.8V above GND
while the CAP rail is regulated at 4.8V below VIN. These are
not intended to be used as external rails. Bypass capacitors are connected to the CAP and VIN2 pins to serve as
energy reservoirs for driving the buck switches. When VIN
is below 4.8V, VIN2 is equal to VIN and CAP is held at GND.
Figure 1 shows the ideal VIN, VIN2 and CAP relationship.
VIN3 is an internal rail used by the buck and the buck-boost.
When the LTC3331 runs the buck VIN3 will be a Schottky
diode drop below VIN2. When it runs the buck-boost VIN3
is equal to BB_IN.
18
Internal Bridge Rectifier
Buck Undervoltage Lockout (UVLO)
16
14
VOLTAGE (V)
An internal full-wave bridge rectifier accessible via the differential AC1 and AC2 inputs rectifies AC sources such as
those from a piezoelectric element. The rectified output is
stored on a capacitor at the VIN pin and can be used as an
energy reservoir for the buck converter. The bridge rectifier
has a total drop of about 800mV at typical piezo-generated
currents (~10μA), but is capable of carrying up to 50mA.
Either side of the bridge can be operated independently
as a single-ended AC or DC input.
VIN
12
10
8
6
VIN2
4
CAP
2
0
0
5
10
VIN (V)
15
3331 F01
Figure 1. Ideal VIN, VIN2 and CAP Relationship
When the voltage on VIN rises above the UVLO rising
threshold the buck converter is enabled and charge is
transferred from the input capacitor to the output capacitor.
When the input capacitor voltage is depleted below the
UVLO falling threshold the buck converter is disabled.
These thresholds can be set according to Table 4 which
Buck Operation
The buck regulator uses a hysteretic voltage algorithm
to control the output through internal feedback from the
VOUT sense pin. The buck converter charges an output
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17
LTC3331
OPERATION
capacitor through an inductor to a value slightly higher
than the regulation point. It does this by ramping the
inductor current up to IPEAK_BUCK through an internal
PMOS switch and then ramping it down to 0mA through
an internal NMOS switch. This efficiently delivers energy
to the output capacitor. The ramp rate is determined by
VIN, VOUT, and the inductor value. When the buck brings
the output voltage into regulation the converter enters a
low quiescent current sleep state that monitors the output
voltage with a sleep comparator. During sleep load current is provided by the output capacitor. When the output
voltage falls below the regulation point the buck regulator
wakes up and the cycle repeats. This hysteretic method
of providing a regulated output reduces losses associated
with FET switching and maintains the output at light loads.
The buck delivers a minimum of 100mA of average load
current when it is switching. VOUT can be set from 1.8V to
5V via the output voltage select bits, OUT[2:0] (see Table 1).
When the sleep comparator senses that the output has
reached the sleep threshold the buck converter may be
in the middle of a cycle with current still flowing through
the inductor. Normally both synchronous switches would
turn off and the current in the inductor would freewheel to
zero through the NMOS body diode. Instead, the NMOS
switch is kept on to prevent the conduction loss that would
occur in the diode if the NMOS were off. If the PMOS is
on when the sleep comparator trips the NMOS will turn
on immediately in order to ramp down the current. If the
NMOS is on it will be kept on until the current reaches zero.
Though the quiescent current when the buck is switching
is much greater than the sleep quiescent current, it is still
a small percentage of the average inductor current which
results in high efficiency over most load conditions. The
buck operates only when sufficient energy has been accumulated in the input capacitor and the length of time the
converter needs to transfer energy to the output is much
less than the time it takes to accumulate energy. Thus, the
buck operating quiescent current is averaged over a long
period of time so that the total average quiescent current
is low. This feature accommodates sources that harvest
small amounts of ambient energy.
18
Buck-Boost Converter
The buck-boost uses the same hysteretic voltage algorithm
as the buck to control the output, VOUT, with the same sleep
comparator. The buck-boost has three modes of operation:
buck, buck-boost, and boost. An internal mode comparator
determines the mode of operation based on BB_IN and
VOUT. Figure 2 shows the four internal switches of the
buck-boost converter. In each mode the inductor current
is ramped up to IPEAK_BB, which is programmable via the
IPK[2:0] bits and ranges from 5mA to 250mA (see Table 3).
BB_IN
M1
SWA
M2
SWB
M4
VOUT
M3
3331 F02
Figure 2: Buck-Boost Power Switches
In BUCK mode M4 is always on and M3 is always off. The
inductor current is ramped up through M1 to IPEAK_BB and
down to 0mA through M2. In boost mode M1 is always on
and M2 is always off. The inductor current is ramped up
to IPEAK_BB when M3 is on and is ramped down to 0mA
when M4 is on as VOUT is greater than BB_IN in boost
mode. Buck-boost mode is very similar to boost mode in
that M1 is always on and M2 is always off. If BB_IN is less
than VOUT the inductor current is ramped up to IPEAK_BB
through M3. When M4 turns on the current in the inductor
will start to ramp down. However, because BB_IN is close
to VOUT and M1 and M4 have finite on-resistance the current ramp will exhibit a slow exponential decay, potentially
lowering the average current delivered to VOUT. For this
reason the lower current threshold is set to IPEAK_BB/2 in
buck-boost mode to maintain high average current to the
load. If BB_IN is greater than VOUT in buck-boost mode
the inductor current still ramps up to IPEAK_BB and down
to IPEAK_BB/2. It can still ramp down if BB_IN is greater
than VOUT because the final value of the current in the
inductor would be (VIN – VOUT)/(RON1 + RON4). If BB_IN
is exactly IPEAK_BB/2 • (RON1 + RON4) above VOUT the
inductor current will not reach the IPEAK_BB/2 threshold
and switches M1 and M4 will stay on all the time. For
higher BB_IN voltages the mode comparator will switch
the converter to buck mode. M1 and M4 will remain on for
BB_IN voltages up to VOUT + IPEAK_BB • (RON1 + RON4). At
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LTC3331
OPERATION
this point the current in the inductor is equal to IPEAK_BB
and the IPEAK_BB comparator will trip turning off M1 and
turning on M2 causing the inductor current to ramp down
to IZERO, completing the transition from buck-boost mode
to buck mode.
VOUT Power Good
A power good comparator is provided for the VOUT output.
It transitions high the first time the LTC3331 goes to sleep,
indicating that VOUT has reached regulation. It transitions
low when VOUT falls to 92% (typical) of its regulation value.
The PGVOUT output is referenced to an internal rail that
is generated to be the highest of VIN2, BB_IN, and VOUT
less a Schottky diode drop.
Shunt Battery Charger
The LTC3331 provides a reliable low quiescent current
shunt battery charger to facilitate charging a battery
with harvested energy. A low battery disconnect feature
provides protection to the battery from overdischarge by
disconnecting the battery from the buck-boost input at a
programmable level.
To use the charger connect the battery to the BAT_IN
pin. An internal low battery disconnect PMOS switch is
connected between the BAT_IN pin and the BAT_OUT
pin. The BAT_OUT pin must be connected to BB_IN for
proper operation. A charging resistor connected from VIN
to BAT_OUT or from CHARGE to BAT_OUT will charge the
battery through the body diode of the disconnect PMOS
until the battery voltage rises above the low-battery connect threshold. Depending on the capacity of the battery
and the input decoupling capacitor, the common BAT_OUT
= BB_IN node voltage generally rises or falls to VBAT_IN
when the PMOS turns on. Once the PMOS is on the charge
current is determined by the charging resistor, the battery
voltage, and the voltage of the charging source.
As the battery voltage approaches the float voltage, the
LTC3331 shunts current away from the battery thereby
reducing the charging current. The LTC3331 can shunt
up to 10mA. Float voltages of 3.45V, 4.0V, 4.1V, and 4.2V
are programmable via the FLOAT[1:0] pins (see Table 2).
Charging can occur through a resistor connected to VIN
or the CHARGE pin. An internal set of back to back PMOS
switches are connected between CHARGE and VIN2 and are
turned on only when the energy harvesting buck converter
is sleeping. In this way charging of the battery only happens when there is excess harvested energy available and
the VOUT output is prioritized over charging of the battery.
The charge current available from this pin is limited by the
strength of the VIN2 LDO and an appropriate charging resistor must be selected to limit this current. The on resistance
of the internal charge switches combined is approximately
60Ω. To charge with higher currents connect a resistor
directly to VIN. Note that when charging from VIN the battery is always being charged. Care must be taken to ensure
that enough power is available to bring up the VOUT output.
Low Battery Disconnect/Connect: LBD/LBC
The low battery disconnect (VLBD) and connect (VLBC) voltage levels are programmed by the LBSEL and FLOAT[1:0]
pins (see Table 2). As shown in the Block Diagram the battery disconnects from the common BAT_OUT = BB_IN node
by shutting off the PMOS switch when the BAT_IN voltage
falls below VLBD. This disconnect function protects Li-Ion
batteries from permanent damage due to deep discharge.
Disconnecting the battery from the common BAT_OUT
= BB_IN node prevents the load as well as the LTC3331
quiescent current from further discharging the battery.
Once disconnected the common BAT_OUT = BB_IN node
voltage collapses towards ground. When an input supply is
reconnected the battery charges through the internal body
diode of the disconnect PMOS. The input supply voltage
should be larger than VLBC_BAT_OUT to ensure that the PMOS
is turned on. When the voltage reaches VLBC_BAT_OUT, the
PMOS turns on and connects the common BAT_OUT =
BB_IN node to BAT_IN. While disconnected, the BAT_IN
pin voltage is indirectly sensed through the PMOS body
diode. Therefore VLBC_BAT_IN varies with charge current
and junction temperature. See the Typical Performance
Characteristics section for more information.
Low Battery Select
The low battery disconnect voltage level is programmed by
the LBSEL pin for each float setting. The LBSEL pin allows
the user to trade-off battery run time and maximum shelf
life. A lower battery disconnect threshold maximizes run
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3331fc
19
LTC3331
OPERATION
time by allowing the battery to fully discharge before the
disconnect event. Conversely, by increasing the low battery
disconnect threshold more capacity remains following the
disconnect event which extends the shelf life of the battery.
For maximum run time, tie LBSEL to GND. For extended
shelf life, tie LBSEL to the common BAT_OUT = BB_IN
node. If a high peak current event is expected, users may
temporarily select the lower disconnect threshold. This
avoids disconnecting the battery too early when the load
works against the battery series resistance and temporarily
reduces the common BAT_OUT = BB_IN node.
Ship Mode
A ship mode is provided which manually disconnects the
battery. This may be useful to prevent discharge of the battery in situations when no harvestable energy is expected
for a long period of time such as during shipping. Bring
the SHIP pin high to engage ship mode. The low battery
disconnect PMOS will turn off, disconnecting the battery
at BAT_IN from the common BAT_OUT = BB_IN node. If
no harvestable energy is present to hold up the common
BAT_OUT = BB_IN node that voltage will collapse. Typically an additional 1µA of quiescent current will appear
on BB_IN while SHIP mode is engaged.
To exit SHIP mode first bring the SHIP pin low. If the
BB_IN voltage had collapsed while in SHIP mode it must
now be brought above the LBC threshold to reconnect
the battery. This can be done manually or from an energy
harvesting charging source. If harvestable energy had
been propping up the common BAT_OUT = BB_IN node
voltage above the LBC threshold then the battery will be
connected immediately.
Prioritizer
The input prioritizer on the LTC3331 decides whether to use
the energy harvesting input or the battery input to power
VOUT. If a battery is powering the buck-boost converter
and harvested energy causes a UVLO rising transition on
VIN, the prioritizer will shut off the buck-boost and turn on
the buck, orchestrating a smooth transition that maintains
regulation of VOUT.
20
When harvestable energy disappears, the prioritizer will
first poll the BB_IN voltage. If the BB_IN voltage is above
1.8V the prioritizer will switch back to the buck-boost while
maintaining regulation. If the BB_IN voltage is below 1.8V
the buck-boost is not enabled and VOUT cannot be supported
until harvestable energy is again available. If the battery
is connected then the BB_IN voltage will be above 1.8V
for every float and LBSEL combination. If the battery is
disconnected the BB_IN voltage will have collapsed below
1.8V and the prioritizer will not switch to the buck-boost
when harvestable energy goes away. In the event that the
battery is depleted and is disconnected while powering
the buck-boost the prioritizer will not switch back to VIN
until harvested energy is again available.
If either BB_IN or VIN is grounded, the prioritizer allows
the other input to run if its input is high enough for operation. The specified quiescent current in UVLO is valid
upon start-up of the VIN input and when the battery has
taken over regulation of the output. If the battery is less
than 1.8V when UVLO is entered and the prioritizer does
not enable the buck-boost several hundred nanoamperes
of additional quiescent current will appear on VIN.
When the prioritizer selects the VIN input the current on the
BB_IN input drops to 200nA. However, if the voltage on
BB_IN is higher than VIN2, a fraction of the VIN quiescent
current will appear on BB_IN due to internal level shifting.
This only affects a small range of battery voltages and
UVLO settings.
A digital output, EH_ON, is low when the prioritizer has
selected the BB_IN input and is high when the prioritizer
has selected the VIN input. The EH_ON output is referenced
to VIN3.
Supercapacitor Balancer
An integrated supercapacitor balancer with 150nA of
quiescent current is available to balance a stack of two
supercapacitors. Typically the input, SCAP, will tie to
VOUT to allow for increased energy storage at VOUT with
supercapacitors. The BAL pin is tied to the middle of the
stack and can source and sink 10mA to regulate the BAL
pin’s voltage to half that of the SCAP pin’s voltage. To
disable the balancer and its associated quiescent current
the SCAP and BAL pins can be tied to ground.
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LTC3331
APPLICATIONS INFORMATION
When harvestable energy is available, it is transferred
through the bridge rectifier where it accumulates on the VIN
capacitor. A low quiescent current UVLO mode allows the
voltage on the capacitor to increase towards a programmed
UVLO rising threshold. When the voltage rises to this level,
the buck converter turns on and transfers energy to VOUT.
As energy is transferred the voltage at VIN may decrease
to the UVLO falling threshold. If this happens, the buck
converter turns off and the buck-boost then turns on to
service the load from the battery input while more energy
is harvested. When the buck is running the quiescent current on the BB_IN pin drops to the 200nA required by the
shunt battery charger.
The LTC3331 is well suited to wireless systems which
consume low average power but occasionally need a
higher concentrated burst of power to accomplish a task. If
these bursts occur with a low duty cycle such that the total
energy needed for a burst can be accumulated between
bursts then the output can be maintained entirely by the
harvester. If the bursts need to happen more frequently or
if harvestable energy goes away the battery will be used. If
enough energy is available the energy harvester will bring
the output up and enter the low quiescent current sleep
state and excess energy can be used to charge the battery.
Piezo Energy Harvesting
Ambient vibrational energy can be harvested with a
piezoelectric transducer which produces a voltage and
current in response to strain. Common piezoelectric
elements are PZT (lead zirconate titanate) ceramics, PVDF
(polyvinylidene fluoride) polymers, or other composites.
Ceramic piezoelectric elements exhibit a piezoelectric effect
when the crystal structure of the ceramic is compressed
and internal dipole movement produces a voltage. Polymer
elements comprised of long-chain molecules produce
a voltage when flexed as molecules repel each other.
Ceramics are often used under direct pressure while a
polymer is commonly used as a cantilevered beam.
A wide range of piezoelectric elements are available and
produce a variety of open-circuit voltages and short-circuit
currents. Typically the open-circuit voltage and short-circuit
currents increase with available vibrational energy as shown
in Figure 3. Piezoelectric elements can be placed in series
or in parallel to achieve desired open-circuit voltages.
12
9
PIEZO VOLTAGE (V)
The LTC3331 allows for energy harvesting from a variety
of alternative energy sources in order to power a wireless
sensor system and charge a battery. The extremely low
quiescent current of the LTC3331 facilitates harvesting
from sources generating only microamps of current. The
onboard bridge rectifier is suitable for AC piezoelectric
or electromagnetic sources as well as providing reverse
protection for DC sources such as solar and thermoelectric
generators. The LTC3331 powers the VOUT output continuously by seamlessly switching between the energy
harvesting and battery inputs.
INCREASING
VIBRATION ENERGY
6
3
0
0
10
20
PIEZO CURRENT (µA)
30
3331 F03
Figure 3. Typical Piezoelectric Load Lines for Piezo Systems
T220-A4-503X
Piezos produce the most power when they operate at
approximately half the open circuit voltage for a given
vibration level. The UVLO window can be programmed to
straddle this voltage so that the piezo operates near the
peak power point. In addition to the normal configuration
of connecting the piezo across the AC1 and AC2 inputs, a
piezo can be connected from either AC1 or AC2 to ground.
The resulting configuration is a voltage doubler as seen
in Figure 4 where the intrinsic capacitance of the piezo is
used as the doubling capacitor.
3331fc
For more information www.linear.com/LTC3331
21
LTC3331
APPLICATIONS INFORMATION
500
AC1
IP sin(ωt)
VIN
CP
1500
SANYO 1815 SOLAR PANEL
1800 LUX
400
1200
CIN
Figure 4. LTC3331 Voltage Doubler Configuration
A second piezo may be connected from AC2 to ground. This
may be of use if the second piezo is mechanically tuned
to a different resonant frequency present in the system
than the first piezo. To achieve maximum power transfer
from the piezo with the doubler the UVLO window should
be set to the open circuit voltage of the piezo.
Piezoelectric elements are available from the manufacturers listed in Table 5.
Table 5. Piezoelectric Element Manufacturers
Advanced Cerametrics
www.advancedcerametrics.com
Piezo Systems
www.piezo.com
Measurement Specialties
www.meas-spec.com
PI (Physik Instrumente)
www.pi-usa.us
MIDE Technology Corporation
www.mide.com
Morgan Technical Ceramics
www.morganelectroceramics.com
Electromagnetic Energy Harvesting
Another alternative AC source is an electromagnetic vibration harvester in which a magnet vibrating inside a coil
induces an AC voltage and current in the coil that can then
be rectified and harvested by the LTC3331. The vibration
could be ambient to the system or it could be caused by
an impulse as in a spring loaded switch.
Solar Energy Harvesting
The LTC3331 can harvest solar energy as the bridge rectifier can be used to provide reverse protection for a solar
panel. A solar cell produces current in proportion to the
amount of light falling on it. Figure 5 shows the relationship
between current and voltage for a solar panel illuminated
with several levels of light. The maximum power output
occurs near the knee of each curve where the cell transitions from a constant current device to a constant voltage
IPANEL (µA)
3331 F04
300
900
1000 LUX
200
600
WPANEL (µW)
GND
22
PANEL CURRENT
PANEL POWER
LTC3331
PIEZO MODEL
500 LUX
100
0
300
200 LUX
0
1
2
3
VPANEL (V)
4
5
6
0
3331 F05
Figure 5. Typical Solar Panel Characteristics
device. Fortunately, the peak power point doesn’t change
much with illumination and an appropriate UVLO window
can be selected so that the panel operates near the peak
power point for a majority of light conditions.
Two solar panels can be connected to the LTC3331, one
from AC1 to ground and another from AC2 to ground. Each
panel could be aimed in a different direction to capture
light from different angles or at different times of the day
as the sun moves. The panels should be similar so that
the selected UVLO window is optimal for both panels.
BB_IN/BAT_OUT, BAT_IN, VIN, and VOUT Capacitors
The input to the buck-boost, BB_IN, must be connected to
BAT_OUT for proper operation. BAT_OUT is the output side
of the low battery disconnect switch. The series resistance
of this switch must be considered when selecting a bypass
capacitor for the common BAT_OUT = BB_IN node. At least
4.7μF to GND or greater should be used. For the higher
IPEAK_BB settings the capacitor may need to be larger to
smooth the voltage at the common BAT_OUT = BB_IN
node. The goal is to average the input current to the buck
boost so that the voltage droop at the common BAT_OUT
= BB_IN node is minimized.
A bypass capacitor of 1µF or greater can also be placed
at the BAT_IN pin. In cases where the series resistance of
the battery is high, a larger capacitor may be desired to
handle transients.
3331fc
For more information www.linear.com/LTC3331
LTC3331
APPLICATIONS INFORMATION
The input capacitor to the buck on VIN and the VOUT
capacitor can vary widely and should be selected to optimize the use of an energy harvesting source depending
on whether storage of the harvested energy is needed at
the input or the output. Storing energy at the input takes
advantage of the high input voltage as the energy stored
in a capacitor increases with the square of its voltage.
Storage at the output may be necessary to handle load
transients greater than the 100mA the buck can provide.
The input or output capacitor should be sized to store
enough energy to provide output power for the length
of time required. If enough energy is stored so that the
buck does not reach the UVLO falling threshold during
a load transient then the battery current will always be
zero. Spacing load transients so that the average power
required to service the application is less than or equal
to the power available from the energy harvesting source
will then greatly extend the life of the battery. The VIN
capacitor should be rated to withstand the highest voltage
ever present at VIN.
The following equation can be used to size the input
capacitor to meet the power requirements of the output
for the desired duration:
1
PLOAD t LOAD = ηCIN ( VIN2 – VUVLOFALLING2)
2
VUVLOFALLING ≤ VIN ≤ VSHUNT
Here η is the average efficiency of the buck converter over
the input voltage range and VIN is the input voltage when
the buck begins to switch. Typically VIN will be the UVLO
rising threshold. This equation may overestimate the input
capacitor necessary as it may be acceptable to allow the
load current to deplete the output capacitor all the way to
the lower PGVOUT threshold. It also assumes that the input
source charging has a negligible effect during this time.
The duration for which the buck or buck-boost regulator
sleeps depends on the load current and the size of the VOUT
capacitor. The sleep time decreases as the load current
increases and/or as the output capacitor decreases. The
DC sleep hysteresis window is ±6mV for the 1.8V output
and scales linearly with the output voltage setting (±12mV
for the 3.6V setting, etc.). Ideally this means that the sleep
time is determined by the following equation:
tSLEEP = COUT
12mV •
VOUT
1.8V
I LOAD
This is true for output capacitors on the order of 100μF
or larger, but as the output capacitor decreases towards
10μF, delays in the internal sleep comparator along with
the load current itself may result in the VOUT voltage slewing past the DC thresholds. This will lengthen the sleep
time and increase VOUT ripple. A capacitor less than 10μF
is not recommended as VOUT ripple could increase to an
undesirable level. If transient load currents above 100mA
are required then a larger capacitor should be used at the
output. This capacitor will be continuously discharged
during a load condition and the capacitor can be sized for
an acceptable drop in VOUT:
COUT = (ILOAD – IDC/DC )
tLOAD
+
VOUT – VOUT –
Here VOUT+ is the value of VOUT when PGVOUT goes high
and VOUT– is the acceptable lower limit of VOUT. IDC/DC is
the average current being delivered from either the buck
converter or the buck-boost converter. The buck converter
typically delivers 125mA on average to the output as the
inductor current is ramped up to 250mA and down to zero.
The current the buck-boost delivers depends on the mode of
operation and the IPEAK_BB setting. In buck mode the deliverable current is IPEAK_BB/2. In buck-boost and boost modes
the deliverable current also depends on the VIN to VOUT ratio:
Buck-boost mode:
3
V
I DC/DC = I PEAK_BB IN
4
VOUT
Boost mode:
1
V
I DC/DC = I PEAK_BB IN
2
VOUT
A standard surface mount ceramic capacitor can be used for
COUT, though some applications may be better suited to a low
leakage aluminum electrolytic capacitor or a supercapacitor.
These capacitors can be obtained from manufacturers such
as Vishay, Illinois Capacitor, AVX, or CAP-XX.
3331fc
For more information www.linear.com/LTC3331
23
LTC3331
APPLICATIONS INFORMATION
CAP, VIN2, and VIN3 Capacitors
A 1μF or larger capacitor must be connected between VIN
and CAP and a 4.7μF capacitor must be connected between
VIN2 and GND. These capacitors hold up the internal rails
during buck switching and compensate the internal rail
generation circuits. In applications where the voltage at VIN
is limited to less than 6V, the CAP pin can be tied to GND
and the VIN2 pin can be tied to VIN as shown in Figure 6.
An optional 5.6V Zener diode can be connected to VIN
to clamp VIN in this scenario. The leakage of the Zener
diode below its clamping voltage should be considered
as it could be comparable to the quiescent current of the
LTC3331. This circuit does not require the capacitors on
VIN2 and CAP, saving two components and allowing for a
lower voltage rating for the single VIN capacitor.
A 0.1µF bypass capacitor must be connected from VIN3
to ground. VIN3 is an internal rail that is shared by both
the buck and buck-boost. It is not intended for use as a
system rail. It is used as a the logic high reference level
for the IPK[2:0] and OUT[2:0] digital inputs. In the event
that these pins are dynamically driven in the application,
external inverters may be needed and they must use VIN3
as a rail. However, care must be taken not to overload
VIN3 and the quiescent current of such logic should be
kept minimal. The output resistance of the VIN3 pin is
typically 15kΩ.
+
+
SOLAR
PANEL
SOLAR
PANEL
–
–
AC2
AC1
VIN
5.6V
(OPTIONAL)
22µF
6.3V
VIN2
CAP
UV3
UVLO RISING = 4V
UVLO FALLING = 3V
IPEAK_BB = 150mA
SWA
33µH
SWB
LTC3331
SW
22µH
VOUT
UV2
SCAP
UV1
BAL
UV0
PGVOUT
1.8V
22µF
6.3V
EH_ON
4.2V
+
BAT_IN
Li-ION
1µF
6.3V
VIN3
IPK2
IPK1
CHARGE
12k
22µF
6.3V
IPK0
OUT2
BAT_OUT
OUT1
BB_IN
OUT0
FLOAT1 FLOAT0 LBSEL SHIP GND
0.1µF
6.3V
3331 F06
Figure 6. Low Voltage Solar Harvester with Reduced Component Count (VIN < 6V)
24
3331fc
For more information www.linear.com/LTC3331
LTC3331
APPLICATIONS INFORMATION
Inductor Selection
The buck is optimized to work with a 22µH inductor in
typical applications. A larger inductor will benefit high
voltage applications by increasing the on-time of the PMOS
switch and improving efficiency by reducing gate charge
loss. Choose an inductor with a DC current rating greater
than 500mA. The DCR of the inductor can have an impact
on efficiency as it is a source of loss. Tradeoffs between
price, size, and DCR should be evaluated.
The buck-boost is optimized to work with a minimum inductor of 22μH for the 250mA IPEAK_BB setting. For the other
seven IPEAK_BB settings the inductor value should increase
as the IPEAK_BB selection decreases to maintain the same
IPEAK_BB • L product. The minimum inductor values for the
buck-boost for each IPEAK_BB setting are listed in Table 3.
Larger inductors may increase efficiency. Choose an
inductor with an ISAT rating at least 50% greater than the
selected IPEAK value. Table 6 lists several inductors that
work well with both the buck and the buck-boost.
Table 6. Recommended Inductors for the LTC3331
PART NUMBER
744043102
LPS5030-105ML
LPS4018-105ML
LPS3314-105ML
B82442T1105K050
L(µH)
1000
744043471
LPS4018-474ML
LPS3314-474ML
B82442T147K050
744042331
LPS4018-334ML
LPS3314-334ML
B82442T1334K050
744042221
LPS4018-224ML
LPS3314-224ML
B82442T1224K050
744031101
LPS4018-104ML
LPS3314-104ML
B82442T1104K050
744031470
LPS4018-473ML
LPS3314-473ML
B82442T1473K050
744031330
LPS4018-333ML
LPS3314-333ML
1070BS-330ML
B82442T1333K050
744031220
LPS5030-223ML
LPS4018-223ML
LPS3314-223ML
1070AS-220M
B82442T1223K050
744029220
1069BS-220M
470
330
220
100
47
33
22
22
MANUFACTURER
Würth Elektronik
Coilcraft
Coilcraft
Coilcraft
EPCOS
Würth Elektronik
Coilcraft
Coilcraft
EPCOS
Würth Elektronik
Coilcraft
Coilcraft
EPCOS
Würth Elektronik
Coilcraft
Coilcraft
EPCOS
Würth Elektronik
Coilcraft
Coilcraft
EPCOS
Würth Elektronik
Coilcraft
Coilcraft
EPCOS
Würth Elektronik
Coilcraft
Coilcraft
Toko
EPCOS
Würth Elektronik
Coilcraft
Coilcraft
Coilcraft
Toko
EPCOS
Würth Elektronik
Toko
SIZE (mm) (L × W × H)
4.8 × 4.8 × 2.8
5.51 × 5.51 × 2.9
3.9 × 3.9 × 1.7
3.3 × 3.3 × 1.3
5.6 × 5 × 5
4.8 × 4.8 × 2.8
3.9 × 3.9 × 1.7
3.3 × 3.3 × 1.3
5.6 × 5 × 5
4.8 × 4.8 × 1.8
3.9 × 3.9 × 1.7
3.3 × 3.3 × 1.3
5.6 × 5 × 5
4.8 × 4.8 × 1.8
3.9 × 3.9 × 1.7
3.3 × 3.3 × 1.3
5.6 × 5 × 5
3.8 × 3.8 × 1.65
3.9 × 3.9 × 1.7
3.3 × 3.3 × 1.3
5.6 × 5 × 5
3.8 × 3.8 × 1.65
3.9 × 3.9 × 1.7
3.3 × 3.3 × 1.3
5.6 × 5 × 5
3.8 × 3.8 × 1.65
3.9 × 3.9 × 1.7
3.3 × 3.3 × 1.3
3.2 × 3.2 × 2
5.6 × 5 × 5
3.8 × 3.8 × 1.65
5.51 × 5.51 × 2.9
3.9 × 3.9 × 1.7
3.3 × 3.3 × 1.3
3.2 × 3.2 × 2
5.6 × 5 × 5
2.8 × 2.8 × 1.35
3.2 × 3.2 × 1.8
MAX IDC
(mA)
80
110
98
99
150
125
160
110
240
130
190
110
280
160
260
160
330
180
360
230
510
250
550
330
700
320
640
380
230
840
360
750
800
450
410
1040
300
290
MAX DCR
(Ω)
7
5.1
18
31
9.5
2.6
7.8
12
4.73
4.5
5.9
9.3
3.29
3.2
3.7
6
2.2
2.4
1.4
2.75
0.99
1
0.65
1.4
0.519
0.66
0.42
0.92
0.61
0.36
0.45
0.19
0.36
0.72
0.64
0.238
0.97
0.495
3331fc
For more information www.linear.com/LTC3331
25
LTC3331
APPLICATIONS INFORMATION
Supercapacitor Balancer
Battery Considerations
If supercapacitors are used at VOUT the onboard
supercapacitor balancer can be used to balance them
with ±10mA of balance current. A list of supercapacitor
suppliers is provided in Table 7.
The shunt battery charger is designed to work with any
single Li-Ion, LiFeP04, or other chemistry with a termination
voltage compatible with the available levels. Table 9 lists
some batteries, their capacities and their equivalent series
resistance (ESR). The ESR causes BAT_OUT and BAT_IN
to droop by the product of the load current amplitude
multiplied by the ESR. This droop may trigger the low
battery disconnect while the battery itself may still have
ample capacity. An appropriate bypass capacitor placed
at BAT_OUT will help prevent large, low duty cycle load
transients from pulling down on BAT_OUT. The bypass
capacitor used at BB_IN, which is tied to BAT_OUT, to
bypass the buck-boost may be sufficient.
Table 7. Supercapacitor Manufacturers
CAP-XX
www.cap-xx.com
NESS CAP
www.nesscap.com
Maxwell
www.maxwell.com
Bussman
www.cooperbussman.com
AVX
www.avx.com
Illinois Capacitor
www.illcap.com
Tecate Group
www.tecategroup.com
By seamlessly combining a battery source and an energy harvesting source, the LTC3331 enables the use of
supercapacitors in energy harvesting applications. The
battery provides the initial current required to overcome
the effects of the diffusion current when voltage is first
applied to the supercapacitors. The energy harvesting
source can then support the lower steady state leakage
current and average load current.
Summary of Digital inputs and outputs
There are 14 digital pin-strapped logic inputs to the
LTC3331 and two digital logic outputs. These and the rails
they are referenced to are summarized in Table 8.
Table 8. Digital Pin Summary
INPUT PIN
UV[3:0]
IPK[2:0]
OUT[2:0]
FLOAT[1:0], LBSEL
SHIP
LOGIC HIGH LEVEL
VIN2
VIN3
VIN3
BAT_OUT = BB_IN
≥ 1.2V
OUTPUT PIN
PGVOUT
EH_ON
LOGIC HIGH LEVEL
MAX (BB_IN, VIN2, VOUT)
VIN3
26
Table 9. Low Capacity Li-Ion and Thin-Film Batteries
MANUFACTURER
P/N
CAPACITY
RESISTANCE
VMIN
CYMBET
CBC012
CYMBET
CBC050
12μAh
5k to 10k
3.0V
50μAh
1500Ω to 3k
3.0V
GM Battery
GMB031009
8mAh
10Ω to 20Ω
2.75V
GS NanoTech
N/A
500μAh
40Ω
3.0V
Power Stream
LIR2032
40mAh
0.6Ω
3.0V
Charging the Battery
Charging the battery with the CHARGE pin allows the
battery to be charged only when the energy harvester is
sleeping, which prioritizes the VOUT output over the battery.
The current that the CHARGE pin can supply is limited to
2mA and an appropriately chosen current limiting resistor
should be used. Use the following equation to calculate
the value of this resistor:
RCHARGE =
4.8V – VLBD
– 60Ω
ICHARGE
Here 4.8V is the output of the VIN2 LDO which is the supply to the CHARGE pin, VLBD is the selected low battery
disconnect threshold, 60Ω is the resistance of the CHARGE
pin PMOS, and ICHARGE is the desired charge current. For
high charging currents approaching 2mA, a larger VIN2
capacitor may improve transient behavior.
3331fc
For more information www.linear.com/LTC3331
LTC3331
APPLICATIONS INFORMATION
For applications where more charging current is available a resistor tied to VIN or the circuit of Figure 7 can
be used to provide up to 10mA to the battery. The circuit
of Figure 7 uses the CHARGE pin to only allow charging
when the energy harvester is sleeping. For applications
VIN
LTC3331
R1
56.2Ω
Q2
CMPT3906E
R2
1M
Q1A
NDC7001C
CHARGE
R3
1M
R4
100k
BB_IN
Q1B
NDC7001C
Higher Efficiency Battery Powered Buck
3331 F07
MIDE V25W
22µF
25V
AC2
VIN
VIN2
4.7µF
6.3V
UVLO RISING = 12V**
UVLO FALLING = 11V
IPEAK_BB = 250mA
AC1
SWA
CAP
22µH
SW
UV3
VOUT
UV2
SCAP
UV1
BAL
UV0
PGVOUT
+
BAT_IN
1µF
6.3V
Li-ION
22µH
5V
22µF
6.3V
1µF
6.3V
VIN3
4.7µF
6.3V
22µF
6.3V
BB_IN
OUT0
FLOAT1 FLOAT0 LBSEL SHIP GND
22µH
EN
VOUT
22µF
6.3V
D1
D0
OUT2
OUT1
PGOOD
SW
VIN2
IPK0
BAT_OUT
LTC3388-3*
CAP
IPK1
CHARGE
VIN
2.2µF
10V
IPK2
68k
If the battery voltage will always be higher than the regulated output of the LTC3331 then the battery powered
buck-boost will always run in buck mode. In this case the
inductor that is usually placed between SWA and SWB
can go directly to VOUT from SWA, bypassing internal
switch M4 of the buck-boost (Figure 9). This will reduce
conduction losses in the converter and improve the efficiency at higher loads.
SWB
LTC3331
EH_ON
4.1V
LTC3331 System Solutions
The LTC3331 can be paired with other Linear Technology low
quiescent current integrated circuits to form a multirail system. Figure 8 shows an LTC3331 powering an LTC3388-3
from its 5V output. The LTC3388-3, an 800nA Buck
converter, is configured here to produce a negative 5V
rail by tying the VOUT pin to ground and tying its GND pin
to the regulated –5V output. The result is a ±5V energy
harvesting power supply with battery backup.
CMOSH-3
Figure 7
1µF
6.3V
requiring even more charging current, the LTC3331 can be
paired with the LTC4071 shunt battery charger connected
at the BB_IN pin.
GND
STBY
–5V
3331 F08
0.1µF
6.3V
*EXPOSED PAD MUST BE ELECTRICALLY ISOLATED FROM
SYSTEM GROUND AND CONNECTED TO THE –5V RAIL
**FOR PEAK POWER TRANSFER, CENTER THE UVLO WINDOW
AT HALF THE RECTIFIED OPEN CIRCUIT VOLTAGE OF THE PIEZO
Figure 8. Dual ±5V Power Supply
3331fc
For more information www.linear.com/LTC3331
27
LTC3331
APPLICATIONS INFORMATION
MIDE V25W
22µF
25V 4.7µF
AC2
VIN2
UVLO RISING = 12V*
UVLO FALLING = 11V
IPEAK_BB = 250mA
4.0V
+
Li-ION
1µF
6.3V
LTC3331
SW
UV3
UV2
BAL
UV1
PGVOUT
UV0
EH_ON
BAT_IN
22µH
VOUT
SCAP
22µF
6.3V
100
1.8V
95
VIN3
VOUT = 1.8V, BYPASS SWB
VOUT = 1.8V, INCLUDE SWB
VOUT = 3.3V, BYPASS SWB
VOUT = 3.3V, INCLUDE SWB
90
85
IPK2
80
IPK1
CHARGE
68k
22µF
6.3V
22µH
SWA
SWB
CAP
6.3V
AC1
EFFICIENCY (%)
1µF
6.3V
VIN
IPK0
75
2.6
OUT2
BAT_OUT
OUT1
BB_IN
OUT0
FLOAT0
0.1µF
6.3V
FLOAT1 LBSEL SHIP GND
2.8
3
3.2 3.4 3.6
BB_IN (V)
3.8
4
4.2
3331 F09b
Figure 9b. Efficiency Comparison Between
Normal Buck-Boost and Bypassed SWB
Configuration
3331 F09a
*FOR PEAK POWER TRANSFER, CENTER THE UVLO WINDOW
AT HALF THE RECTIFIED OPEN CIRCUIT VOLTAGE OF THE PIEZO
Figure 9a. Higher Efficiency Battery-Powered Buck Regulator
Alternative Power Sources
The LTC3331 can accommodate a wide variety of input
sources. Figure 10 shows the LTC3331 internal bridge
rectifier connected to a 120V RMS AC line in series with
four 3.9k current limiting resistors. This produces a peak
current of 10mA with the LTC3331 shunt holding VIN
at 20V. This current may be increased by reducing the
resistor values since the shunt can sink 25mA and the
bridge is rated for 50mA. An optional external Zener diode
(shown) may be required if the current exceeds 25mA. A
transformer may also be used to step down the voltage
and reduce the power loss in the current limiting resistors.
The 3.3k charging resistor charges the battery from VIN
with approximately 5mA. This is a high voltage application
and minimum spacing between the line, neutral, and any
high voltage components should be maintained per the
applicable UL specification. For general off-line applications refer to UL Regulation 1012.
28
Figure 11 shows an application where copper panels
are placed near a standard fluorescent room light to
capacitively harvest energy from the electric field around
the light. The frequency of the emission will be double the
line frequency for magnetic ballasts but could be higher
if the light uses electronic ballast. The peak AC voltage
and the total available energy will scale with the size of
the panels used and with the proximity of the panels to
the electric field of the light.
The LTC3331 could also be used to wirelessly harvest
energy and charge a battery by using a transmitter and
receiver consisting of loosely coupled tuned resonant
tanks as shown in Figure 12.
Using EH_ON to Program VOUT
The EH_ON output indicates whether the energy harvesting
input or the battery is powering the output. The application
3331fc
For more information www.linear.com/LTC3331
LTC3331
APPLICATIONS INFORMATION
DANGEROUS AND LETHAL POTENTIALS ARE PRESENT IN OFFLINE CIRCUITS! BEFORE PROCEEDING ANY FURTHER, THE READER IS WARNED THAT
CAUTION MUST BE USED IN THE CONSTRUCTION, TESTING AND USE OF OFFLINE CIRCUITS. EXTREME CAUTION MUST BE USED IN WORKING
WITH AND MAKING CONNECTIONS TO THESE CIRCUITS. REPEAT: OFFLINE CIRCUITS CONTAIN DANGEROUS, AC LINE-CONNECTED HIGH VOLTAGE
POTENTIALS, USE CAUTION. ALL TESTING PERFORMED ON AN OFFLINE CIRCUIT MUST BE DONE WITH AN ISOLATION TRANSFORMER CONNECTED
BETWEEN THE OFFLINE CIRCUIT’S INPUT AND THE AC LINE. USERS AND CONSTRUCTORS OF OFFLINE CIRCUITS MUST OBSERVE THIS PRECAUTION
WHEN CONNECTING TEST EQUIPMENT TO THE CIRCUIT TO AVOID ELECTRIC SHOCK. REPEAT: AN ISOLATION TRANSFORMER MUST BE CONNECTED
BETWEEN THE CIRCUIT INPUT AND THE AC LINE IF ANY TEST EQUIPMENT IS TO BE CONNECTED.
DANGER HIGH VOLTAGE
3.9k
3.9k
120VAC
60Hz
3.9k
3.9k
1µF
6.3V
22µF
25V
18V
(OPTIONAL)
VIN
AC2
VIN2
UV3
4.0V
+
LTC3331
3.3V
VOUT
22µF
6.3V
SCAP
BAL
UV1
PGVOUT
UV0
EH_ON
BAT_IN
VIN3
1µF
6.3V
Li-ION
22µH
SW
UV2
UVLO RISING = 18V
UVLO FALLING = 5V
IPEAK_BB = 250mA
3.3k
SWA
SWB
CAP
4.7µF
6.3V
22µH
AC1
IPK2
IPK1
IPK0
22µF
6.3V
CHARGE
OUT2
BAT_OUT
OUT1
BB_IN
OUT0
FLOAT0
0.1µF
6.3V
FLOAT1 LBSEL SHIP GND
3331 F10
Figure 10. AC Line Powered 5V UPS
on the last page of this data sheet shows the EH_ON output
tied to the OUT2 input. When EH_ON is low the output is
programmed to 2.5V and the battery powers the output.
When energy harvesting is available EH_ON is high and
the output is programmed to 3.6V allowing for increased
storage of harvested energy. If energy harvesting goes
away, the output is again programmed to 2.5V and the
buck-boost converter will be in sleep until the output is
discharged to the wake-up threshold. If the energy stored
at 3.6V is enough to ride through a temporary loss of
energy harvesting then the only drain on the battery will
be the quiescent current in sleep.
3331fc
For more information www.linear.com/LTC3331
29
LTC3331
APPLICATIONS INFORMATION
COPPER PANEL
(12" × 24")
AC2
AC1
VIN
1µF
6.3V
22µF
25V
COPPER PANEL
(12" × 24")
CAP
VIN2
4.7µF
6.3V
LTC3331
UV2
UV1
UV0
4.2V
+
SWB
UV3
UVLO RISING = 14V
UVLO FALLING = 5V
IPEAK_BB = 5mA
1µF
6.3V
Li-ION
BAT_IN
SW
22µH
2.5V
VOUT
100mF
2.7V
SCAP
22µF
6.3V
BAL
PGVOUT
EH_ON
VIN3
100mF
2.7V
IPK2
IPK1
CHARGE
300k
22µF
6.3V
100µH
SWA
IPK0
OUT2
BAT_OUT
BB_IN
FLOAT1 FLOAT0
OUT1
OUT0
LBSEL SHIP GND
0.1µF
6.3V
3331 F10
Figure 11. Electric Field Energy Harvester
30
3331fc
For more information www.linear.com/LTC3331
LTC3331
APPLICATIONS INFORMATION
TX
+
–
DC
130kHz
SOURCE TRANSMITTER
GND
300nF
5µH
50V
270Ω
100nF
25V
47µH
POWER
TY
LINEAR TECHNOLOGY
DC1968A
PART OF DC1969A-B KIT
1µF
6.3V
22µF
25V
VIN
AC2
CAP
VIN2
4.7µF
6.3V
UVLO RISING = 14V
UVLO FALLING = 5V
IPEAK_BB = 5mA
AC1
SWB
LTC3331
PGVOUT
22µF
6.3V
100mF
2.7V
EH_ON
VIN3
BAT_IN
IPK2
IPK1
IPK0
CHARGE
4.3k
22µF
6.3V
2.5V
100mF
2.7V
BAL
UV1
1µF
6.3V
200F
22µH
SCAP
UV2
3.45V
SW
VOUT
UV3
UV0
Li-ION CAPACITOR
TAIYO YUDEN
100µH
SWA
OUT2
BAT_OUT
BB_IN
FLOAT1 FLOAT0
OUT1
OUT0
LBSEL SHIP GND
0.1µF
6.3V
3331 F12
Figure 12. Wireless Battery Charger
3331fc
For more information www.linear.com/LTC3331
31
LTC3331
PACKAGE DESCRIPTION
Please refer to http://www.linear.com/designtools/packaging/ for the most recent package drawings.
UH Package
32-Lead Plastic QFN (5mm × 5mm)
(Reference LTC DWG # 05-08-1693 Rev D)
0.70 ±0.05
5.50 ±0.05
4.10 ±0.05
3.50 REF
(4 SIDES)
3.45 ±0.05
3.45 ±0.05
PACKAGE OUTLINE
0.25 ±0.05
0.50 BSC
RECOMMENDED SOLDER PAD LAYOUT
APPLY SOLDER MASK TO AREAS THAT ARE NOT SOLDERED
5.00 ±0.10
(4 SIDES)
BOTTOM VIEW—EXPOSED PAD
0.75 ±0.05
R = 0.05
TYP
0.00 – 0.05
R = 0.115
TYP
PIN 1 NOTCH R = 0.30 TYP
OR 0.35 × 45° CHAMFER
31 32
0.40 ±0.10
PIN 1
TOP MARK
(NOTE 6)
1
2
3.50 REF
(4-SIDES)
3.45 ±0.10
3.45 ±0.10
(UH32) QFN 0406 REV D
0.200 REF
NOTE:
1. DRAWING PROPOSED TO BE A JEDEC PACKAGE OUTLINE
M0-220 VARIATION WHHD-(X) (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 0.20mm 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
32
0.25 ±0.05
0.50 BSC
3331fc
For more information www.linear.com/LTC3331
LTC3331
REVISION HISTORY
REV
DATE
DESCRIPTION
PAGE NUMBER
A
07/14
Clarified IQ on the LTC3330 in the Related Parts list
34
B
11/14
Clarified Description
Clarified Available Buck-Boost Current Conditions
Replaced PGOOD with PGVOUT in Graphs
Clarified Table 2
Replaced PGOOD with PGVOUT in Text
Clarified tSLEEP Formula
Clarified Figure 6 Schematic
Clarified Inductor Selection Paragraph
Clarified Typical Application Schematic
Clarified LTC3330 Comments in Related Parts
1
4
7, 8
16
23
23
24
25
34
34
C
08/15
Changed COUT Equation
23
3331fc
Information furnished by Linear Technology Corporation is believed to be accurate and reliable.
However, no responsibility is assumed for its use. Linear Technology Corporation makes no representaFor more
information
www.linear.com/LTC3331
tion that the interconnection
of its circuits
as described
herein will not infringe on existing patent rights.
33
LTC3331
TYPICAL APPLICATION
UPS System for Wireless Mesh Networks with Output Supercapacitor Energy Storage
MIDE V25W
AC2
1µF
6.3V
22µF
25V
AC1
VIN
SWA
SWB
CAP
UVLO RISING = 12V*
UVLO FALLING = 11V
IPEAK_BB = 50mA
3.45V
+
1µF
6.3V
LiFePO4
VOUT = 3.6V FOR EH_ON = 1
VOUT = 2.5V FOR EH_ON = 0
22µH
SW
LTC3331
VIN2
4.7µF
6.3V
100µH
VOUT
UV3
SCAP
UV2
BAL
UV1
PGVOUT
UV0
EH_ON
1F
2.7V
1F
2.7V
VIN3
BAT_IN
IPK2
PGOOD
IPK1
VSUPPLY
TX
IPK0
CHARGE
EHORBAT
OUT2
130k
OUT1
BAT_OUT
OUT0
BB_IN
22µF
6.3V
22µF
6.3V
FLOAT1 FLOAT0
LBSEL
0.1µF
6.3V
SHIP GND
3331 TA02
GND
LINEAR TECHNOLOGY DC9003A-AB
DUST MOTE FOR WIRELESS MESH NETWORKS
*FOR PEAK POWER TRANSFER, CENTER THE UVLO WINDOW
AT HALF THE RECTIFIED OPEN CIRCUIT VOLTAGE OF THE PIEZO
RELATED PARTS
PART NUMBER
DESCRIPTION
COMMENTS
LTC3330
Nanopower Buck-Boost DC/DC with Energy
Harvesting Battery Life Extender
VIN: 3.0V to 19V; BAT: 1.8V to 5.5V, 750nA IQ
5mm × 5mm QFN-32 Package
LTC3588-1/
LTC3588-2
Nanopower Energy Harvesting Power Supply with
Up to 100mA of Output Current
VIN: 2.7V to 20V; VOUT: Fixed 1.8V to 5V; IQ = 950nA; ISD = 450nA;
MSOP-10, 3mm × 3mm DFN-10 Packages
LT1389
Nanopower Precision Shunt Voltage Reference
VREF: 1.25V, 2.25V, 4.096V; IQ = 800nA; ISD < 1µA; SO-8 Package
LTC1540
Nanopower Comparator with Reference
VIN: 2V to 11V; IQ = 0.3µA; ISD < 1µA; 3mm × 3mm DFN-8 Package
LT3009
3μA IQ, 20mA Low Dropout Linear Regulator
VIN: 1.6V to 20V; VOUT: 0.6V, Fixed 1.2V to 5V; IQ = 3µA; ISD < 1µA;
SC-70-8, 2mm × 2mm DFN-8 Packages
LTC3105
400mA Step-Up Converter with MPPC and 250mV VIN: 0.2V to 5V; VOUT: Max 5.25V; IQ = 22µA; ISD < 1µA; 3mm × 3mm DFN-10,
MSOP-12 Package
Start-Up
LTC3108
Ultralow Voltage Step-Up Converter and Power
Manager
VIN: 0.02V to 1V; VOUT: Fixed 2.35V to 5V; IQ = 7µA; ISD < 1µA;
TSSOP-16, 3mm × 4mm DFN-12 Packages
LTC3109
Auto-Polarity, Ultralow Voltage Step-Up Converter
and Power Manager
VIN: 0.03V to 1V; VOUT: Fixed 2.35V to 5V; IQ = 7µA; ISD < 1µA;
SSOP-20, 4mm × 4mm QFN-20 Packages
LTC3388-1/
LTC3388-3
20V, 50mA High Efficiency Nanopower
Step-Down Regulator
VIN: 2.7V to 20V; VOUT: Fixed 1.1V to 5.5V; IQ = 720nA; ISD = 400nA;
MSOP-10, 3mm × 3mm DFN-10 Packages
LTC4070
50mA Micropower Shunt Li-Ion Charger
VOUT(MIN): 4V, 4.1V, 4.2V; IQ = 450nA; ISD = 45nA; MSOP-8, 2mm × 3mm DFN-8
Packages
LTC4071
50mA Micropower Shunt Li-Ion Charger with
PowerPath™ Control
VOUT(MIN): 4V, 4.1V, 4.2V; IQ = 450nA; ISD = 45nA; MSOP-8, 2mm × 3mm DFN-8
Packages
LTC3129/
LTC3129-1
Micropower 200mA Synchronous Buck-Boost
DC/DC Converter
VIN: 2.42V to 15V; VOUT: 1.4V to 15V; IQ = 1.3µA; ISD = 10nA;
MSOP-16E, 3mm × 3mm QFN-16 Packages
34 Linear Technology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
For more information www.linear.com/LTC3331
(408) 432-1900 ● FAX: (408) 434-0507
●
www.linear.com/LTC3331
3331fc
LT 0815 REV C • PRINTED IN USA
 LINEAR TECHNOLOGY CORPORATION 2014