LTC3112 Datasheet PDF - Linear Technology Corporation


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LTC3112
Linear Technology Corporation

Part Number LTC3112
Description 2.5A Synchronous Buck-Boost DC/DC Converter
Page 30 Pages

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Features
n Regulated Output with VIN Above, Below or Equal to VOUT
n 2.7V to 15V Input Voltage Range
n 2.5V to 14V Output Voltage Range
n 2.5A Continuous Output Current: VIN ≥ 5V,
VOUT = 5V, PWM Mode
n Output Current Monitor
n Up to 95% Efficiency
n 750kHz Switching Frequency, Synchronizable
Between 300kHz and 1.5MHz
n Internal N-Channel MOSFETs
n Selectable Burst Mode® Operation, IQ = 50µA
n Shutdown Current < 1µA
n Overvoltage Protection
n Output Disconnect in Shutdown
n Internal Soft-Start
n Small, Thermally Enhanced 16-Lead (4mm × 5mm ×
0.75mm) DFN and 20-Lead TSSOP Package
Applications
n 3.3V or 5V from 1, 2 or 3 Li-Ion, Backup Capacitor Stack
n Hand Held Inventory Terminals
n RF Transmitters
n 12V Synchronous Boost Converter
n Multiple Power Input Systems
n LED Lighting with Current Regulation
n 12V Lead Acid Battery to 12V
LTC3112
15V, 2.5A Synchronous
Buck-Boost DC/DC
Converter
Description
The LTC®3112 is a fixed frequency synchronous buck-boost
DC/DC converterwith an extended input and output range.
The unique 4-switch, single inductor architecture provides
low noise and seamless operation from input voltages
above, below or equal to the output voltage.
With an input range of 2.7V to 15V, the LTC3112 is well-
suited for a wide variety of single or multiple cell battery,
backup capacitor or wall adapter source applications. Low
RDS(ON) internal N-Channel MOSFET switches provide
highly efficient operation in applications with higher load
current requirements.
The LTC3112 features selectable PWM or Burst Mode
operation, an easily synchronized oscillator and output
disconnect in shutdown. An output current monitor circuit
allows the load current to be controlled or measured. Other
features include <1µA shutdown current, short circuit
protection, soft-start, current limit and thermal shutdown.
The LTC3112 is offered in both a 16-pin (4mm × 5mm ×
0.75mm) DFN and 20-pin TSSOP packages.
L, LT, LTC, LTM, Linear Technology Burst Mode, LTSpice and the Linear logo are registered
trademarks and No RSENSE and PowerPath are trademarks of Linear Technology Corporation.
All other trademarks are the property of their respective owners. Protected by U.S. Patents,
including 5481178.
Typical Application
5V, 750kHz Wide Input Voltage Range Buck-Boost Regulator
4.7µH
0.1µF
2.7V TO 15V
VIN
BURST PWM
10µF
OFF ON
1µF
SW1 SW2
BST1
BST2
VIN VOUT
VCC LTC3112 COMP
PWM/SYNC
RUN
GND
FB
IOUT
OVP
0.1µF
680pF 33k
22pF
845k
5V/2.5A, VIN > 5V
47pF
VOUT
10k
100pF
TO ADC
1V PER AMP
42.2k
158k
47µF
3112 TA01
For more information www.linear.com/LTC3112
Efficiency at 5VOUT
100 PWM
90
BURST
80
70
60
50
40
30
0.0001 0.001 0.01
0.1
LOAD CURRENT (A)
251..270VVVINIINN
1
3112 TA02
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LTC3112
Absolute Maximum Ratings
(Notes 1, 3)
VIN Voltage.................................................. – 0.3V to 16V
VOUT Voltage............................................... – 0.3V to 15V
SW1 Voltage (Note 4).................... – 0.3V to (VIN + 0.3V)
SW2 Voltage (Note 4)................. – 0.3V to (VOUT + 0.3V)
VBST1 Voltage.................... (VSW1 – 0.3V) to (VSW1 + 6V)
VBST2 Voltage....................(VSW2 – 0.3V) to (VSW2 + 6V)
RUN Voltage............................................... – 0.3V to 16V
PWM/SYNC, VCC, IOUT Voltage.....................– 0.3V to 6V
FB, COMP, OVP Voltage................................– 0.3V to 6V
Operating Junction Temperature Range (Notes 2, 6)
............................................................... –55°C to 150°C
Storage Temperature Range...................– 65°C to 150°C
Lead Temperature (Soldering, 10sec) TSSOP........ 300°C
Pin Configuration
TOP VIEW
COMP
FB
OVP
VIN
VIN
RUN
IOUT
VOUT
1
2
3
4
5
6
7
8
16 PWM/SYNC
15 VCC
14 BST1
17 13 SW1
GND 12 SW1
11 BST2
10 SW2
9 SW2
DHD16 PACKAGE
16-LEAD (5mm × 4mm) PLASTIC DFN
TJMAX=150 °C, qJA = 43°C/W, qJC = 4°C/W
EXPOSED PAD (PIN 17) IS GND, MUST BE SOLDERED TO PCB
GND 1
COMP 2
FB 3
OVP 4
VIN 5
VIN 6
RUN 7
IOUT
VOUT
GND
8
9
10
TOP VIEW
21
GND
20 GND
19 PWM/SYNC
18 VCC
17 BST1
16 SW1
15 SW1
14 BST2
13 SW2
12 SW2
11 GND
FE PACKAGE
20-LEAD PLASTIC TSSOP
TJMAX = 150°C, qJA = 38°C/W, qJC = 4°C/W
EXPOSED PAD (PIN 21) IS GND, MUST BE SOLDERED TO PCB
Order Information
LEAD FREE FINISH
TAPE AND REEL
PART MARKING*
PACKAGE DESCRIPTION
TEMPERATURE RANGE
LTC3112EDHD#PBF
LTC3112EDHD#TRPBF 3112
16-Lead (5mm × 4mm) Plastic DFN
–40°C to 125°C
LTC3112IDHD#PBF
LTC3112IDHD#TRPBF 3112
16-Lead (5mm × 4mm) Plastic DFN
–40°C to 125°C
LTC3112HDHD#PBF
LTC3112HDHD#TRPBF 3112
16-Lead (5mm × 4mm) Plastic DFN
–40°C to 150°C
LTC3112MPDHD#PBF
LTC3112MPDHD#TRPBF 3112
16-Lead (5mm × 4mm) Plastic DFN
–55°C to 150°C
LTC3112EFE#PBF
LTC3112EFE#TRPBF
3112FE
20-Lead Plastic TSSOP
–40°C to 125°C
LTC3112IFE#PBF
LTC3112IFE#TRPBF
3112FE
20-Lead Plastic TSSOP
–40°C to 125°C
LTC3112HFE#PBF
LTC3112HFE#TRPBF
3112FE
20-Lead Plastic TSSOP
–40°C to 150°C
LTC3112MPFE#PBF
LTC3112MPFE#TRPBF 3112FE
20-Lead Plastic TSSOP
–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/
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LTC3112
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 = VOUT = PWM/SYNC = RUN = 5V unless otherwise noted.
PARAMETER
CONDITIONS
MIN TYP MAX UNITS
Input Operating Range
0°C to 150°C
–55°C to 0°C
2.7 15 V
2.85 15 V
VIN UVLO Threshold
VIN UVLO Hysteresis
VCC UVLO Threshold
VCC UVLO Hysteresis
Output Voltage Adjust Range
Rising
Rising
2.0 2.3 2.7
300
l 2.2 2.35 2.5
150
l 2.5
14
V
mV
V
mV
V
INTVCC Clamp Voltage
VCC Voltage in Dropout
Quiescent Current – Burst Mode Operation
Quiescent Current – Shutdown
Feedback Voltage = PWM Mode Operation
VIN = 5V or 15V
VIN = 2.7V, IVCC = 10mA
VFB = 1V, VPWM/SYNC = 0V
RUN = VOUT = VCC = 0V, Not Including Switch Leakage
l 3.8 4.2 4.6
2.6
50 75
01
l 0.778 0.8 0.818
V
V
µA
µA
V
Feedback Leakage
OVP Threshold
VFB = 0.8V
Rising Threshold
0 50
0.78 0.83 0.88
nA
V
OVP Hysteresis
Measured at OVP Pin
20 mV
OVP Leakage
OVP = 0.8V
0 100
nA
NMOS Switch Leakage
NMOS Switch On Resistance
Switch A, B, C, D, VIN = VOUT = 12V
Switch A
1 10
40
µA
NMOS Switch On Resistance
Switch B, C
50 mΩ
NMOS Switch On Resistance
Switch D
60 mΩ
Input Current Limit
L = 4.7µH
l 4.5 6 8.5
A
Peak Current Limit
L = 4.7µH
7 10 12
A
Burst Current Limit
L = 4.7µH
0.7 1.3
2
A
Burst Zero Current Threshold
L = 4.7µH
0.3 A
Reverse Current Limit
L = 4.7µH
–0.5 –1 –1.5
A
IOUT Accuracy (Note 5)
Maximum Duty Cycle
SW2 to VOUT Current = 1.5A
SW2
SW2
to
to
VVOOUUTT
Current
Current
=
=
1.0A
0.5A
Buck (Switch A On)
32 36 40
20 24 28
8 12 16
l 80
87
µA
µA
µA
%
Boost (Switch C On)
l 75
82
%
Minimum Duty Cycle
Buck (Switch A On)
l 0%
Boost (Switch C On)
l5
12
%
Frequency
SYNC Frequency Range (Note 7)
PWM/SYNC = 5V, VIN = VOUT = 12V
l 675
l 300
750 825
1500
kHz
kHz
PWM/SYNC Threshold
RUN Threshold
VCC = 2.7V or 5V
VIN = 2.7V or 15V
l 0.5
l 0.35
0.9
0.75
1.5
1.5
V
V
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 LTC3112 is tested under pulsed load conditions such that TJ ≈ TA.
The LTC3112E 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 assured by design, characterization and correlation with
statistical process controls. The LTC3112I is guaranteed to meet specifications
over the –40°C to 125°C operating junction temperature, the LTC3112H is
guaranteed to meet specifications over the –40°C to 150°C operating junction
temperature range and the LTC3112MP is guaranteed and tested to meet
specifications over the full –55°C to 150°C operating junction temperature
range. High junction temperatures degrade operating lifetimes; operating
lifetime is derated for temperature greater than 125°C. 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.
For more information www.linear.com/LTC3112
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LTC3112
Electrical Characteristics
Note 3: This IC includes overtemperature protection that is intended
to protect the device during momentary overload conditions. Junction
temperature will exceed 150°C when overtemperature protection is active.
Continuous operation above the specified maximum operating junction
temperature may impair device reliability.
Note 4: Voltage transients on the switch pins beyond the DC limit specified
in the Absolute Maximum Ratings, are non disruptive to normal operation
when using good layout practices, as shown on the demo board or
described in the data sheet and application notes.
Note 5: IOUT current is tested in a non-switching DC state. In a switching
environment IOUT accuracy may exhibit variation with factors such as
switching frequency, load current, input/output voltage, and temperature.
See typical performance characteristic curves for predicted variation.
Note 6: 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 qJA), where qJA (in °C/W) is the package thermal
impedance.
Note 7: SYNC frequency range is tested with a square wave. Operation
with 100ns minimum high or low times is assured by design.
Typical Performance Characteristics
TA = 25°C, VIN = 5.0V, VOUT = 5.0V unless otherwise specified
Wide VIN to 5VOUT Efficiency
100 PWM
90
BURST
80
70
60
50
40
30
0.0001 0.001 0.01
0.1
LOAD CURRENT (A)
251..270VVVINIINN
1
3112 G01a
Wide VIN to 5VOUT Power Loss
1 PWM
0.1
0.01 BURST
0.001
0.0001
0.0001
512.2.07VVVINIINNLLLOOOSSSSSS
0.001 0.01 0.1
1
LOAD CURRENT (A)
3112 G01b
Wide VIN to 3.3VOUT Efficiency
100 PWM
90
BURST
80
70
60
50
40
30
0.0001 0.001 0.01
0.1
LOAD CURRENT (A)
251..270VVVINIINN
1
3112 G02a
Wide VIN to 3.3VOUT Power Loss
PWM
1
0.1
0.01 BURST
0.001
0.0001
0.0001
512.2.07VVVINIINNLLLOOOSSSSSS
0.001 0.01 0.1
1
LOAD CURRENT (A)
3112 G02b
Wide VIN to 12VOUT Efficiency
100 PWM
90
BURST
80
70
60
50
40
30
0.0001 0.001 0.01
0.1
LOAD CURRENT (A)
351..260VVVINIINN
1
3112 G03a
Wide VIN to 12VOUT Power Loss
1 PWM
0.1
0.01 BURST
0.001
0.0001
0.0001
513.2.06VVVINIINNLLLOOOSSSSSS
0.001 0.01 0.1
1
LOAD CURRENT (A)
3112 G03b
3112fc
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