LTC3115-2
40V, 2A Synchronous
Buck-Boost DC/DC Converter
FeaTures
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DescripTion
The
LTC
®
3115-2
is a high voltage monolithic synchronous
buck-boost DC/DC converter optimized for applications
subject to fast (<1ms) input voltage transients. For all other
applications, the LTC3115-1 is recommended. With its wide
2.7V to 40V input and output voltage ranges, the LTC3115-2
is well suited for use in a wide variety of automotive and
industrial power supplies. A proprietary low noise switch-
ing algorithm optimizes efficiency with input voltages that
are above, below or even equal to the output voltage and
ensures seamless transitions between operational modes.
Programmable frequency PWM mode operation provides
low noise, high efficiency operation and the ability to syn-
chronize switching to an external clock. Switching frequen-
cies up to 2MHz are supported to allow use of small value in-
ductors for miniaturization of the application circuit. Pin se-
lectable Burst Mode operation reduces standby current and
improves light load efficiency which, combined with a 3µA
shutdown current, make the LTC3115-2 ideally suited for
battery-powered applications. Additional features include
output disconnect in shutdown, short-circuit protection
and internal soft-start. The LTC3115-2 is available in ther-
mally enhanced 16-lead 4mm
×
5mm
×
0.75mm DFN and
20-lead TSSOP packages.
L,
LT, LTC, LTM, Burst Mode, LTspice, Linear Technology and the Linear logo are registered
trademarks and No R
SENSE
is a trademark of Linear Technology Corporation. All other
trademarks are the property of their respective owners. Protected by U.S. Patents including
6404251, 6166527 and others pending.
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Wide V
IN
Range: 2.7V to 40V
Wide V
OUT
Range: 2.7V to 40V
0.8A Output Current for V
IN
≥ 3.6V, V
OUT
= 5V
2A Output Current in Step-Down Operation
for V
IN
≥ 6V
Programmable Frequency: 100kHz to 2MHz
Synchronizable Up to 2MHz with an External Clock
Up to 95% Efficiency
30µA No-Load Quiescent Current in Burst Mode
®
Operation
Ultralow Noise Buck-Boost PWM
Internal Soft-Start
3µA Supply Current in Shutdown
Programmable Input Undervoltage Lockout
Small 4mm
×
5mm
×
0.75mm DFN Package
Thermally Enhanced 20-Lead TSSOP Package
applicaTions
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24V/28V Industrial Applications
Automotive Power Systems
Telecom, Servers and Networking Equipment
FireWire Regulator
Multiple Power Source Supplies
Typical applicaTion
5V, 750kHz Wide Input Voltage Range Buck-Boost Regulator
10µH
0.1µF
2.7V TO
40V
BST1 SW1
4.7µF
PV
IN
V
IN
SW2 BST2
PV
OUT
LTC3115-2
VC
FB
PV
CC
V
CC
GND
PGND
4.7µF
249k
(OPTIONAL)
31152 TA01a
Efficiency vs V
IN
95
I
LOAD
= 0.5A
90
EFFICIENCY (%)
5V
0.8A V
IN
> 3.6V
2A V
IN
≥ 6V
1M
33pF
15k
85
I
LOAD
= 1A
0.1µF
47µF
×
2
137k
3300pF
80
BURST PWM
OFF ON
PWM/SYNC
RUN
RT
75
V
OUT
= 5V
2
10
INPUT VOLTAGE (V)
40
31152 TA01b
47.5k
70
31152fa
For more information
www.linear.com/LTC3115-2
1
LTC3115-2
absoluTe MaxiMuM raTings
(Note 1)
V
IN
, PV
IN
, PV
OUT
........................................ –0.3V to 45V
V
SW1
DC........................................... –0.3V to (PV
IN
+ 0.3V)
Pulsed (<100ns) ......................–1.5V to (PV
IN
+ 1.5V)
V
SW2
DC.........................................–0.3V to (PV
OUT
+ 0.3V)
Pulsed (<100ns) .................... –1.5V to (PV
OUT
+ 1.5V)
V
RUN
............................................. –0.3V to (V
IN
+ 0.3V)
V
BST1
.....................................V
SW1
– 0.3V to V
SW1
+ 6V
V
BST2
.....................................V
SW2
– 0.3V to V
SW2
+ 6V
V
PWM/SYNC
................................................... –0.3V to 6V
Voltage, All Other Pins ................................. –0.3V to 6V
Operating Junction Temperature Range (Notes 2, 4)
LTC3115E-2/LTC3115I-2..................... –40°C to 125°C
LTC3115H-2 ....................................... –40°C to 150°C
LTC3115MP-2 .................................... –55°C to 150°C
Storage Temperature Range .................. –65°C to 150°C
Lead Temperature (Soldering, 10 sec)
FE...................................................................... 300°C
pin conFiguraTion
TOP VIEW
TOP VIEW
RUN
SW2
PV
OUT
GND
GND
VC
FB
RT
1
2
3
4
5
6
7
8
PGND
17
16 PWM/SYNC
15 SW1
14 PV
IN
13 BST1
12 BST2
11 PV
CC
10 V
IN
9
V
CC
PGND
RUN
SW2
PV
OUT
GND
GND
VC
FB
RT
1
2
3
4
5
6
7
8
9
21
PGND
20 PGND
19 PWM/SYNC
18 SW1
17 PV
IN
16 BST1
15 BST2
14 PV
CC
13 V
IN
12 V
CC
11 PGND
PGND 10
DHD PACKAGE
16-LEAD (5mm
×
4mm) PLASTIC DFN
T
JMAX
= 125°C,
θ
JA
= 43°C/W,
θ
JC
= 4.3°C/W
EXPOSED PAD (PIN 17) IS PGND, MUST BE SOLDERED TO PCB
FE PACKAGE
20-LEAD PLASTIC TSSOP
T
JMAX
= 150°C,
θ
JA
= 38°C/W,
θ
JC
= 10°C/W
EXPOSED PAD (PIN 21) IS PGND, MUST BE SOLDERED
TO PCB FOR RATED THERMAL PERFORMANCE
orDer inForMaTion
LEAD FREE FINISH
LTC3115EDHD-2#PBF
LTC3115IDHD-2#PBF
LTC3115EFE-2#PBF
LTC3115IFE-2#PBF
LTC3115HFE-2#PBF
LTC3115MPFE-2#PBF
TAPE AND REEL
LTC3115EDHD-2#TRPBF
LTC3115IDHD-2#TRPBF
LTC3115EFE-2#TRPBF
LTC3115IFE-2#TRPBF
LTC3115HFE-2#TRPBF
LTC3115MPFE-2#TRPBF
PART MARKING*
31152
31152
LTC3115FE-2
LTC3115FE-2
LTC3115FE-2
LTC3115FE-2
PACKAGE DESCRIPTION
16-Lead (5mm
×
4mm) Plastic DFN
16-Lead (5mm
×
4mm) Plastic DFN
20-Lead Plastic TSSOP
20-Lead Plastic TSSOP
20-Lead Plastic TSSOP
20-Lead Plastic TSSOP
TEMPERATURE RANGE
–40°C to 125°C
–40°C to 125°C
–40°C to 125°C
–40°C to 125°C
–40°C to 150°C
–55°C to 150°C
Consult LTC Marketing for parts specified with wider operating temperature ranges. *The temperature grade is identified by a label on the shipping
container.Consult LTC Marketing for information on non-standard lead based finish parts.
For more information on lead free part marking, go to:
http://www.linear.com/leadfree/
For more information on tape and reel specifications, go to:
http://www.linear.com/tapeandreel/
2
31152fa
For more information
www.linear.com/LTC3115-2
LTC3115-2
elecTrical characTerisTics
PARAMETER
Input Operating Voltage
Output Operating Voltage
Input Undervoltage Lockout Threshold
Input Undervoltage Lockout Hysteresis
V
CC
Undervoltage Lockout Threshold
V
CC
Undervoltage Lockout Hysteresis
Input Current in Shutdown
Input Quiescent Current in Burst Mode Operation
Oscillator Frequency
Oscillator Operating Frequency
PWM/SYNC Clock Input Frequency
PWM/SYNC Input Logic Threshold
Soft-Start Duration
Feedback Voltage
Feedback Voltage Line Regulation
Feedback Pin Input Current
RUN Pin Input Logic Threshold
RUN Pin Comparator Threshold
RUN Pin Hysteresis Current
RUN Pin Hysteresis Voltage
Inductor Current Limit
Reverse Inductor Current Limit
Burst Mode Inductor Current Limit
Maximum Duty Cycle
Minimum Duty Cycle
SW1, SW2 Minimum Low Time
N-Channel Switch Resistance
The
l
denotes the specifications which apply over the specified operating
junction temperature range, otherwise specifications are for T
A
= 25°C (Note 2). PV
IN
= V
IN
= 24V, PV
OUT
= 5V, unless otherwise noted.
CONDITIONS
l
l
MIN
2.7
2.7
TYP
V
IN
Falling
V
IN
Rising
V
IN
Rising (0°C to 125°C)
V
CC
Falling
V
RUN
= 0V
V
FB
= 1.1V (Not Switching), V
PWM/SYNC
= Low
R
T
= 35.7k, V
PWM/SYNC
= High
V
PWM/SYNC
= High
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l
2.4
2.6
100
2.4
200
3
50
1000
MAX
40
40
2.7
2.8
2.725
2.6
10
1100
2000
2000
1.5
1017
50
1.1
1.26
l
l
l
l
l
l
900
100
100
0.5
977
V
IN
= 2.7V to 40V
l
V
RUN
Rising
l
0.3
1.16
N-Channel Switch Leakage
PV
CC
/V
CC
External Forcing Voltage
V
CC
Regulation Voltage
V
CC
Load Regulation
V
CC
Line Regulation
V
CC
Current Limit
V
CC
Dropout Voltage
V
CC
Reverse Current
(Note 3)
Current into PV
OUT
(Note 3)
(Note 3)
Percentage of Period SW2 is Low in Boost Mode,
R
T
= 35.7k (Note 5)
Percentage of Period SW1 is High in Buck Mode,
R
T
= 35.7k (Note 5)
R
T
= 35.7k (Note 5)
Switch A (From PV
IN
to SW1)
Switch B (From SW1 to PGND)
Switch C (From SW2 to PGND)
Switch D (From PV
OUT
to SW2)
PV
IN
= PV
OUT
= 40V
I
VCC
= 1mA
I
VCC
= 1mA to 20mA
I
VCC
= 1mA, V
IN
= 5V to 40V
V
CC
= 2.5V
I
VCC
= 5mA, V
IN
= 2.7V
V
CC
= 5V, V
IN
= 3.6V
l
2.4
0.65
90
l
l
1.0
9
1000
0.1
1
0.8
1.21
500
100
3.0
1.5
1.0
95
3.7
1.35
UNITS
V
V
V
V
V
mV
V
mV
µA
µA
kHz
kHz
kHz
V
ms
mV
%
nA
V
V
nA
mV
A
A
A
%
%
ns
mΩ
mΩ
mΩ
mΩ
µA
V
V
%
%
mA
mV
µA
0
100
150
150
150
150
0.1
4.58
4.33
4.45
1.2
0.5
110
50
10
10
5.5
4.58
50
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 LTC3115-2 is tested under pulsed load conditions such
that T
J
≈ T
A
. The LTC3115E-2 is guaranteed to meet specifications
from 0°C to 85°C junction temperature. Specifications over the –40°C
to 125°C operating junction temperature range are ensured by design,
characterization and correlation with statistical process controls. The
LTC3115I-2 specifications are guaranteed over the –40°C to 125°C
operating junction temperature range. The LTC3115H-2 specifications are
guaranteed over the –40°C to 150°C operating junction temperature range.
The LTC3115MP-2 specifications are guaranteed over the –55°C to 150°C
operating junction temperature range. High junction temperatures degrade
31152fa
For more information
www.linear.com/LTC3115-2
3
LTC3115-2
elecTrical characTerisTics
operating lifetime; operating lifetime is derated for junction temperatures
greater than 125°C. The maximum ambient temperature consistent with
these specifications is determined by specific operating conditions in
conjunction with board layout, the rated package thermal resistance and
other environmental factors.
The junction temperature (T
J
in °C) is calculated from the ambient
temperature (T
A
in °C) and power dissipation (P
D
in Watts) according to
the following formula:
T
J
= T
A
+ (P
D
•
θ
JA
)
where
θ
JA
is the thermal impedance of the package.
Note 3:
Current measurements are performed when the LTC3115-2 is
not switching. The current limit values measured in operation will be
somewhat higher due to the propagation delay of the comparators.
Note 4:
This IC includes overtemperature protection that is intended to
protect the device during momentary overload conditions. The maximum
rated junction temperature will be exceeded when this protection is active.
Continuous operation above the specified absolute maximum operating
junction temperature may impair device reliability or permanently damage
the device.
Note 5:
Switch timing measurements are made in an open-loop test
configuration. Timing in the application may vary somewhat from these
values due to differences in the switch pin voltage during the non-overlap
durations when switch pin voltage is influenced by the magnitude and
direction of the inductor current.
Typical perForMance characTerisTics
(T
A
= 25°C unless otherwise specified)
PWM Mode Efficiency, V
OUT
= 5V,
f
SW
= 500kHz, Non-Bootstrapped
100
90
80
EFFICIENCY (%)
EFFICIENCY (%)
70
60
50
40
30
20
0.01
0.10
LOAD CURRENT (A)
V
IN
= 3.6V
V
IN
= 5V
V
IN
= 12V
V
IN
= 24V
V
IN
= 36V
1
31152 G01
PWM Mode Efficiency,
V
OUT
= 12V, f
SW
= 500kHz
100
90
80
70
60
50
40
30
0.01
0.1
LOAD CURRENT (A)
V
IN
= 5V
V
IN
= 12V
V
IN
= 24V
V
IN
= 36V
1
31152 G02
PWM Mode Efficiency,
V
OUT
= 24V, f
SW
= 500kHz
100
90
80
EFFICIENCY (%)
70
60
50
40
30
0.01
0.1
LOAD CURRENT (A)
V
IN
= 12V
V
IN
= 18V
V
IN
= 24V
V
IN
= 36V
1
31152 G03
PWM Mode Efficiency, V
OUT
= 5V,
f
SW
= 1MHz, Non-Bootstrapped
100
90
80
EFFICIENCY (%)
EFFICIENCY (%)
70
60
50
40
30
20
0.01
0.1
LOAD CURRENT (A)
V
IN
= 3.6V
V
IN
= 5V
V
IN
= 12V
V
IN
= 24V
V
IN
= 36V
1
31152 G04
PWM Mode Efficiency,
V
OUT
= 12V, f
SW
= 1MHz
100
90
80
70
60
50
40
30
0.01
0.1
LOAD CURRENT (A)
V
IN
= 5V
V
IN
= 12V
V
IN
= 24V
V
IN
= 36V
1
31152 G05
PWM Mode Efficiency,
V
OUT
= 24V, f
SW
= 1MHz
100
90
80
EFFICIENCY (%)
70
60
50
40
30
0.01
0.1
LOAD CURRENT (A)
V
IN
= 12V
V
IN
= 18V
V
IN
= 24V
V
IN
= 36V
1
31152 G06
4
31152fa
For more information
www.linear.com/LTC3115-2
LTC3115-2
Typical perForMance characTerisTics
Burst Mode Efficiency, V
OUT
= 5V,
L = 15µH, Non-Bootstrapped
90
85
80
EFFICIENCY (%)
75
70
65
60
55
50
0.1
1
10
LOAD CURRENT (mA)
V
IN
= 3.6V
V
IN
= 12V
V
IN
= 24V
V
IN
= 36V
100
31152 G07
(T
A
= 25°C unless otherwise specified)
Burst Mode Efficiency,
V
OUT
= 24V, L = 15µH
90
85
80
EFFICIENCY (%)
75
70
65
60
55
50
0.1
1
10
LOAD CURRENT (mA)
V
IN
= 12V
V
IN
= 18V
V
IN
= 24V
V
IN
= 36V
100
31152 G09
Burst Mode Efficiency,
V
OUT
= 12V, L = 15µH
95
90
85
EFFICIENCY (%)
80
75
70
65
60
55
50
0.1
1
10
LOAD CURRENT (mA)
V
IN
= 5V
V
IN
= 12V
V
IN
= 24V
V
IN
= 36V
100
31152 G08
400
350
INPUT CURRENT (µA)
300
250
200
150
100
50
0
Burst Mode No-Load Input
Current vs V
IN
V
OUT
= 24V
V
OUT
= 15V
V
OUT
= 5V
V
OUT
= 5V, BOOTSTRAPPED
50
45
40
INPUT CURRENT (mA)
35
30
25
20
15
10
5
2
10
INPUT VOLTAGE (V)
40
31152 G10
PWM Mode No-Load Input
Current vs V
IN
f
SW
= 1MHz
V
OUT
= 24V
V
OUT
= 12V
V
OUT
= 5V
LOAD CURRENT (A)
2.5
2.0
1.5
Maximum Load Current
vs V
IN
, PWM Mode
L = 22µH
f
SW
= 500kHz
1.0
0.5
0
2
10
INPUT VOLTAGE (V)
40
31152 G11
0
V
OUT
= 24V
V
OUT
= 12V
V
OUT
= 5V
2
10
INPUT VOLTAGE (V)
40
31152 G12
Maximum Load Current
vs V
IN
, PWM Mode
2.5
2.0
LOAD CURRENT (A)
1.5
LOAD CURRENT (A)
L = 15µH
f
SW
= 1MHz
2.5
2.0
1.5
Maximum Load Current
vs V
IN
, PWM Mode
L = 5.2µH
f
SW
= 2MHz
1000
Maximum Load Current
vs V
IN
, Burst Mode Operation
L = 22µH
LOAD CURRENT (mA)
100
1.0
1.0
0.5
0
V
OUT
= 24V
V
OUT
= 12V
V
OUT
= 5V
2
10
INPUT VOLTAGE (V)
40
31152 G47
0.5
V
OUT
= 12V
V
OUT
= 5V
2
10
INPUT VOLTAGE (V)
40
31152 G48
0
10
V
OUT
= 32V
V
OUT
= 12V
V
OUT
= 5V
2
10
INPUT VOLTAGE (V)
40
31152 G13
31152fa
For more information
www.linear.com/LTC3115-2
5
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