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LTC3245
Features
Wide VIN Range,
Low Noise, 250mA Buck-Boost
Charge Pump
Description
n 2.7V to 38V VIN Range
n IQ = 18µA Operating; 4μA in Shutdown
n 12V to 5V Efficiency = 81%
n Multimode Operation (2:1, 1:1, 1:2) with Automatic
Mode Switching
n Low Noise, Constant Frequency Operation
n Pin Selectable Burst Mode® Operation
n VOUT: Fixed 3.3V, 5V or Adjustable (2.5V to 5V)
n IOUT Up to 250mA
n Overtemperature and Short-Circuit Protection
n Operating Junction Temperature: 150°C Maximum
n Thermally Enhanced 12-Pin MSOP and Low Profile
12-Pin (3mm × 4mm) DFN Packages
Applications
n Automotive ECU/CAN Transceiver Supplies
n Industrial Housekeeping Supplies
n Low Power 12V to 5V Conversion
L, LT, LTC, LTM, Burst Mode, Linear Technology and the Linear logo are registered trademarks
and ThinSOT is a trademark of Linear Technology Corporation. All other trademarks are the
property of their respective owners.
The LTC®3245 is a switched capacitor buck-boost DC/DC
converter that produces a regulated output (3.3V, 5V or
adjustable) from a 2.7V to 38V input. The device uses
switched capacitor fractional conversion to maintain
regulation over a wide range of input voltage. Internal
circuitry automatically selects the conversion ratio to
optimize efficiency as input voltage and load conditions
vary. No inductors are required.
The unique constant frequency architecture provides a
lower noise output than conventional charge pump regu-
lators. To optimize efficiency at the expense of slightly
higher output ripple, the device has pin selectable Burst
Mode operation.
Low operating current (20μA with no load, 4μA in shut-
down) and low external parts count (three small ceramic
capacitors) make the LTC3245 ideally suited for low power,
space constrained automotive/industrial applications. The
device is short-circuit and overtemperature protected, and
is available in thermally enhanced 12-pin MSOP and low
profile 3mm × 4mm 12-pin DFN packages.
Typical Application
Efficient Regulated 5V Output
1µF
C+ C
LTC3245
VIN = 2.7V TO 38V
VIN VOUT
SEL2 OUTS/ADJ
1µF
BURST
PGOOD
SEL1
GND
3245 TA01a
500k
VOUT = 5V
IOUT UP TO 250mA
10µF
5VOUT Efficiency vs Output Current
90
VIN = 12V
80
70
EFFICIENCY
400
350
300
60 250
50 200
40 150
PLOSS
30 100
20 50
10
0.1
0
1 10 100 1000
IOUT (mA)
3245 TA01b
For more information www.linear.com/LTC3245
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LTC3245
Absolute Maximum Ratings
(Note 1)
VIN, SEL1, SEL2, BURST............................. –0.3V to 38V
VOUT, OUTS/ADJ, PGOOD............................. –0.3V to 6V
IPGOOD.......................................................................2mA
VOUT Short-Circuit Duration.............................. Indefinite
Operating Junction Temperature Range (Notes 2, 3)
(E-/I-Grade)......................................... –40°C to 125°C
(H-Grade)............................................ –40°C to 150°C
(MP-Grade)......................................... –55°C to 150°C
Storage Temperature Range................... –65°C to 150°C
Lead Temperature (Soldering, 10 sec)
(MSE Only) ........................................................... 300°C
Pin Configuration
TOP VIEW
VIN
VIN
VIN
BURST
SEL1
SEL2
1
2
3
4
5
6
12 GND
11 C
13 10 VOUT
GND 9 C+
8 PGOOD
7 OUTS/ADJ
DE PACKAGE
12-LEAD (3mm × 4mm) PLASTIC DFN
TJMAX = 150°C, θJA = 43°C/W
EXPOSED PAD (PIN 13) IS GND, MUST BE SOLDERED TO PCB GND
TOP VIEW
VIN 1
VIN 2
12 GND
11 C
VIN 3
BURST 4
13
GND
10
9
VCO+ UT
SEL1 5
8 PGOOD
SEL2 6
7 OUTS/ADJ
MSE PACKAGE
12-LEAD PLASTIC MSOP
TJMAX = 150°C, θJA = 40°C/W
EXPOSED PAD (PIN 13) IS GND, MUST BE SOLDERED TO PCB GND
Order Information
LEAD FREE FINISH
TAPE AND REEL
PART MARKING*
PACKAGE DESCRIPTION
TEMPERATURE RANGE
LTC3245EDE#PBF
LTC3245EDE#TRPBF
3245
12-Lead (3mm × 4mm) Plastic DFN
–40°C to 125°C
LTC3245IDE#PBF
LTC3245IDE#TRPBF
3245
12-Lead (3mm × 4mm) Plastic DFN
–40°C to 125°C
LTC3245EMSE#PBF
LTC3245EMSE#TRPBF 3245
12-Lead Plastic MSOP
–40°C to 125°C
LTC3245IMSE#PBF
LTC3245IMSE#TRPBF 3245
12-Lead Plastic MSOP
–40°C to 125°C
LTC3245HMSE#PBF
LTC3245HMSE#TRPBF 3245
12-Lead Plastic MSOP
–40°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.
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/
E lectrical 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 = 12V, VOUT = 5V, CFLY = 1µF unless otherwise
noted.
SYMBOL
VIN
VUVLO
PARAMETER
Operating Input Voltage Range
VIN Undervoltage Lockout Threshold
CONDITIONS
VVIINN
Rising
Falling
MIN TYP MAX UNITS
l 2.7
38 V
l
2.4 2.7
V
2.2 V
2 For more information www.linear.com/LTC3245
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LTC3245
E lectrical Characteristics The l denotes the specifications which apply over the specified operating
junction
noted.
temperature
range,
otherwise
specifications
are
at
TA
=
25°C,
(Note
2).
VIN
=
12V,
VOUT
=
5V,
CFLY
=
1µF
unless
otherwise
SYMBOL PARAMETER
CONDITIONS
MIN TYP MAX UNITS
IVIN
VOUT5_BM
VOUT5_LN
VOUT33_BM
VOUT33_LN
VADJ
RCL
VPG_RISE
VPG_FALL
VPG_LOW
IPG_HIGH
VLOW
VHIGH
ILOW
IHIGH
ISHORT_CKT
ROUT
VIN
Quiescent Current
SEL1 = SEL2 = 0V
VVOOUUTT
Enabled,
Enabled,
BURST
BURST
=
=
0V
VIN
Fixed 5V Burst Mode Output Regulation
(OUTS/ADJ Connected to
BURST =
(Note 5)
0V,
SEL2
=
VIN,
SVEOLU1T,=
VIN)
Fixed 5V Low Noise Output Regulation
(B(ONUUoRtTeSST5/A)=DVJINC,oSnEnLe2ct=edVtINo,VSOEULT1, = VIN)
Fixed 3.3V Burst Mode Output Regulation
(OUTS/ADJ Connected to
BURST =
(Note 5)
0V,
SEL2
=
VIN,
SVEOLU1T,=
VIN)
Fixed 3.3V Low Noise Output Regulation
(B(ONUUoRtTeSST5/A)=DVJINC,oSnEnLe2ct=edVtINo,VSOEULT1, = VIN)
OUTS/ADJ Reference Voltage (Note 4)
Load Regulation (Referred to ADJ)
PGOOD Rising Threshold
PGOOD Falling Threshold
PGOOD Output Low Voltage
PGOOD Output High Leakage
BURST, SEL1, SEL2 Input Voltage
BURST, SEL1, SEL2 input Voltage
BURST, SEL1, SEL2 Input Current
BURST, SEL1, SEL2 Input Current
IVOUT Short-Circuit Current
Charge Pump Output Impedance
fOSC Oscillator Frequency
SChPuEtdnoabwlned, ,VOOUuTtp=ut0iVn Regulation
CP Enabled, Output in Regulation
5V ≤
4V ≤
3.3V
3V ≤
≤VVVIIIVNNNI<<<N
353<8V.34,VVV,I,,OIIIUOOOTUUUTTT≤≤≤1257450550mmmmAAAA
5V ≤
4V ≤
3.3V
3V ≤
≤VVVIIIVNNNI<<<N
353<8V.34,VVV,I,,OIIIUOOOTUUUTTT≤≤≤1226300050mmmmAAAA
5V ≤
4V ≤
3.3V
2.7V
≤≤VVIIVVNNII<<NN
35<<8V43,VV.,I3,OIVIUO,OTUIUTOTU≤≤1T27≤15510m60m0mAmAAA
5V ≤
4V ≤
3.3V
2.7V
≤≤VVIIVVNNII<<NN
35<<8V43,VV.,I3,OIVIUO,OTUIUTOTU≤≤1T42≤9020m05mm0AmAAA
SEL2 = 0V, SEL1 = VIN, IOUT = 0mA
SEL2 = 0V, SEL1 = VIN
VOUT% of Final Regulation Voltage
VOUT% of Final Regulation Voltage
IPGOOD = 0.2mA
VPGOOD = 5V
VPIN = 0V
VPIN = 38V
VOUT = GND
2:1 Step-Down Mode
1:1 Step-Down Mode
1:2 Step-Up Mode (VIN = 3.3V)
l 4.8
l 4.8
l 4.8
l 4.8
l 4.8
l 4.8
l 4.8
l 4.8
l 3.17
l 3.17
l 3.17
l 3.17
l 3.17
l 3.17
l 3.17
l 3.17
l 1.176
88
l
–1
l 0.4
l
–1
0.5
l
4
18
20
1.200
0.2
95
91
0.1
0
0.9
1.2
0
1
900
3
3.5
14
450
8
35
40
5.2
5.2
5.2
5.2
5.2
5.2
5.2
5.2
3.43
3.43
3.43
3.43
3.43
3.43
3.43
3.43
1.224
98
0.4
1
2
1
3
500
µA
µA
µA
V
V
V
V
V
V
V
V
V
V
V
V
V
V
V
V
V
mV/mA
%
%
V
µA
V
V
µA
µA
mA
Ω
Ω
Ω
kHz
Note 1: Stresses beyond those listed under Absolute Maximum Ratings
temperature consistent with these specifications is determined by specific
may cause permanent damage to the device. Exposure to any Absolute
operating conditions in conjunction with board layout, the rated package
Maximum Rating condition for extended periods may affect device
thermal resistance and other environmental factors.
reliability and lifetime. This IC has overtemperature protection that is
intended to protect the device during momentary overload conditions.
Junction temperatures will exceed 150°C when overtemperature is active.
Continuous operation above the specified maximum operating junction
temperature may impair device reliability.
Note 2: The LTC3245E is guaranteed to meet performance specifications
from 0°C to 85°C. Specifications over the –40°C to 125°C operating junction
temperature range are assured by design, characterization and correlation
with statistical process controls. The LTC3245I is guaranteed over the –40°C
to 125°C operating junction temperature range. The LTC3245H is guaranteed
over the –40°C to 150°C operating junction temperature range. High junction
temperatures degrade operating lifetimes; operating lifetime is derated for
junction temperatures greater than 125°C. Note that the maximum ambient
Note 3: The junction temperature (TJ, in °C) is calculated from the ambient
temperature (TA, in °C) and power dissipation (PD, in Watts) according to
the formula:
TJ = TA + (PD θJA) where θJA (in °C/W) is the package thermal
impedance.
Note 4: VOUT programming range is from 2.5V to 5V. See the
Programming the Output Voltage section for more detail.
Note 5: The maximum operating junction temperature of 150°C must be
followed. Certain combinations of input voltage and output current will
cause the junction temperature to exceed 150°C and must be avoided. See
Thermal Management section for information on calculating maximum
operating conditions.
For more information www.linear.com/LTC3245
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LTC3245
Typical Performance Characteristics TA = 25°C, unless otherwise noted.
Input Operating Current
vs Input Voltage
50 BURST = 0V
45
40
35
30
25
20 VOUT = 5V
15 VOUT = 3.3V
10
5
0
0 5 10 15 20 25 30 35 40
VIN (V)
3245 G01
5V Fixed Output Voltage
vs Input Voltage (Burst Mode
Operation)
5.20
5.15
5.10
5.05 IOUT = 0mA
5.00
4.95 IOUT = 150mA
4.90
IOUT = 250mA
4.85
4.80
2 3 4 5 6 7 8 9 10 11 12 13 14 15
VIN (V)
3245 G04
3.3V Fixed Output Voltage
vs Input Voltage (Burst Mode
Operation)
3.50
3.45
3.40
3.35 IOUT = 0mA
3.30
3.25
3.20
IOUT = 250mA
IOUT = 150mA
3.15
3.10
2 3 4 5 6 7 8 9 10 11 12 13 14 15
VIN (V)
3245 G07
4
Input Shutdown Current
vs Input Voltage
20
18
16
14 150°C
12
10
125°C
8
6
25°C
4
2 –55°C
0
0 5 10 15 20 25 30 35 40
VIN (V)
5V Fixed Output Voltage
vs Input Voltage (Low Noise
Operation)
3245 G02
5.20
5.15
5.10
5.05 IOUT = 0mA
5.00 IOUT = 150mA
4.95
IOUT = 250mA
4.90
4.85
4.80
2 3 4 5 6 7 8 9 10 11 12 13 14 15
VIN (V)
3245 G05
3.3V Fixed Output Voltage
vs Input Voltage (Low Noise
Operation)
3.50
3.45
3.40
3.35 IOUT = 0mA
3.30 IOUT = 150mA
3.25
3.20 IOUT = 250mA
3.15
3.10
2 3 4 5 6 7 8 9 10 11 12 13 14 15
VIN (V)
3245 G08
For more information www.linear.com/LTC3245
Oscillator Frequency
vs Temperature
500
475
450
425
400
375
350
325
300
–60 –30
0 30 60 90
TEMPERATURE (°C)
120 150
3245 G03
5V Fixed Efficiency
vs Output Current
100
90
VIN = 12V
80 Burst Mode OPERATION
70
60 LOW NOISE
50
40
30
20
10
0
0.1 1 10 100 1000
IOUT (mA)
3245 G06
3.3V Fixed Output Efficiency
vs Output Current
100
90
VIN = 9V
80 Burst Mode OPERATION
70
60
50 LOW NOISE
40
30
20
10
0
0.1 1 10 100
IOUT (mA)
1000
3245 G09
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LTC3245
Typical Performance Characteristics TA = 25°C, unless otherwise noted.
5V Fixed Output Voltage
vs Falling Input Voltage
(Burst Mode Operation)
5.100
3.3V Fixed Output Voltage
vs Falling Input Voltage
(Burst Mode Operation)
3.400
ADJ Regulation Voltage
vs Temperature
1.220
5.075
5.050
5.025
IOUT = 1mA
3.375
3.350
3.325
IOUT = 1mA
1.215
1.210
1.205
5.000
3.300
1.200
4.975
4.950
IOUT = 250mA
4.925
–55°C
25°C
4.900
125°C
2 3 4 5 6 7 8 9 10 11 12 13 14 15
VIN (V)
3245 G10
3.275
3.250
IOUT = 250mA
3.225
–55°C
25°C
125°C
3.200
2 3 4 5 6 7 8 9 10 11 12 13 14 15
VIN (V)
3245 G11
1.195
1.190
1.185
1.180
–60 –30
0 30 60 90
TEMPERATURE (°C)
120 150
3245 G12
5V Output Impedance
vs Temperature (Boost Mode)
30
VIN = 2.7V
25
VIN = 3.3V
20
LOW NOISE
15
10
Burst Mode OPERATION
5
0
–60 –30
0 30 60 90
TEMPERATURE (°C)
120 150
3245 G13
3.3V Output Impedance
vs Temperature (Boost Mode)
40
35 VIN = 3.3V VIN = 2.7V
30
LOW NOISE
25
20
15
10 Burst Mode OPERATION
5
0
–60 –30
0 30 60 90
TEMPERATURE (°C)
120 150
3245 G14
Output Current vs Input Voltage
(VOUT 5% Below Regulation)
800
5V Burst Mode
700 OPERATION
5V LOW NOISE
600
500
400
3.3V LOW NOISE
300
3.3V Burst Mode
200 OPERATION
100
0
2 3 4 5 6 7 8 9 10 11 12 13 14
VIN (V)
3245 G15
Operating Mode Transition
Voltage vs Input Voltage
12
11
IOUT = 1mA
10
9
8
7
6
RISING
FALLING
5 RISING
4
3 FALLING
2
BUCK
LDO
BOOST
1
0
2.5 3 3.5 4 4.5 5
VOUT (V)
3245 G16
Operating Mode Transition
Voltage vs Input Voltage
12
11
IOUT = 150mA
10
9
8 RISING
7 FALLING
6
5 RISING
4
3 FALLING
2
BUCK
LDO
BOOST
1
0
2.5 3 3.5 4 4.5 5
VOUT (V)
3245 G17
Operating Mode Transition
Voltage vs Input Voltage
12
11
IOUT = 250mA
10 RISING
9
8
7 FALLING
6
5
RISING
4
3
FALLING
2
BUCK
LDO
BOOST
1
0
2.5 3 3.5 4 4.5 5
VOUT (V)
3245 G18
For more information www.linear.com/LTC3245
3245f
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