FEATURES
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LTC3530
Wide Input Voltage
Synchronous Buck-Boost
DC/DC Converter
DESCRIPTION
The LTC
®
3530 is a wide V
IN
range, highly efficient, fixed
frequency, buck-boost DC/DC converter that operates
from input voltages above, below or equal to the output
voltage. The topology incorporated in the IC provides a
continuous transfer function through all operating modes,
making the product ideal for single lithium-ion, two-cell
alkaline or NiMH applications where the output voltage is
within the battery voltage range.
The LTC3530 is pin compatible with the LTC3440 buck-
boost DC/DC converter but adds programmable automatic
Burst Mode operation and extends the V
IN
/V
OUT
range to
1.8V. Switching frequencies up to 2MHz are programmed
with an external resistor. Automatic Burst Mode operation
allows the user to program the load current threshold for
Burst Mode operation using a single resistor from the
BURST pin to GND.
Other features include 1μA shutdown, short circuit pro-
tection, programmable soft-start control, current limit
and thermal shutdown. The LTC3530 is available in a
thermally enhanced 10-lead (3mm × 3mm) DFN or MSOP
package.
L,
LT, LTC, LTM and Burst Mode are registered trademarks of Linear Technology Corporation.
All other trademarks are the property of their respective owners. Patents Pending.
Regulated Output with Input Voltages Above, Below
or Equal to the Output
1.8V to 5.5V Input and 1.8V to 5.25V Output Range
250mA Continuous Output Current from 1.8V V
IN
600mA Continuous/1A Peak Output Current from
Li-Ion
Single Inductor
Synchronous Rectification: Up to 96% Efficiency
Programmable Automatic Burst Mode
®
Operation
Output Disconnect in Shutdown
Pin Compatible with the LTC3440
Programmable Frequency from 300kHz to 2MHz
<1μA Shutdown Current
Small Thermally Enhanced 10-Lead (3mm × 3mm)
DFN and 10-Lead MS Packages
APPLICATIONS
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MP3 Players
Handheld Instruments
Digital Cameras
Smart Phones
Portable GPS Units
Miniature Hard Disk Drive Power
TYPICAL APPLICATION
4.7μH
100
90
SW1
SW2
V
OUT
1.8V TO 5.5V
V
IN
LTC3530
SHDN/SS
FB
V
C
BURST
GND
100k
3530 TA01a
Efficiency
Burst Mode V
IN
= 3.6V
V
IN
= 4.2V
33pF
1M
15k
EFFICIENCY (%)
V
OUT
3.3V AT
250mA
80
70
60
50
40
30
V
IN
= 2.0V
V
IN
= 3.6V
OFF ON
22μF
10k
576k
560pF
10μF
33.2k
R
T
20
10
0.01μF
0
0.1
1
10
100
LOAD CURRENT (mA)
1000
3350 TA01b
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LTC3530
ABSOLUTE MAXIMUM RATINGS
(Note 1)
V
IN
, V
OUT
Voltage ......................................... –0.3V to 6V
SW1, SW2 Voltage
DC............................................................ –0.3V to 6V
Pulsed < 100ns ........................................ –0.3V to 7V
V
C
, R
T
, FB,
SHDN/SS,
BURST Voltage .......... –0.3V to 6V
Operating Temperature (Note 2)............... –40°C to 85°C
Maximum Junction Temperature (Note 4)............. 125°C
Storage Temperature Range................... –65°C to 150°C
PIN CONFIGURATION
TOP VIEW
R
T
BURST
SW1
SW2
GND
1
2
3
4
5
11
10 V
C
9 FB
8 SHDN/SS
7 V
IN
6 V
OUT
R
T
BURST
SW1
SW2
GND
1
2
3
4
5
TOP VIEW
10
9
8
7
6
V
C
FB
SHDN/SS
V
IN
V
OUT
DD PACKAGE
10-LEAD (3mm 3mm) PLASTIC DFN
T
JMAX
= 125°C,
θ
JA
= 43°C/W,
θ
JC
= 4.3°C/W
EXPOSED PAD IS GND (PIN 11) MUST BE SOLDERED TO PCB
MS PACKAGE
10-LEAD PLASTIC MSOP
T
JMAX
= 125°C,
θ
JA
= 120°C/W,
θ
JC
= 45°C/W
ORDER INFORMATION
LEAD FREE FINISH
LTC3530EDD#PBF
LTC3530EMS#PBF
TAPE AND REEL
LTC3530EDD#TRPBF
LTC3530EMS#TRPBF
PART MARKING
LCBH
LTCBJ
PACKAGE DESCRIPTION
10-Lead (3mm × 3mm) Plastic DFN
10-Lead Plastic MSOP
TEMPERATURE RANGE
–40°C to 85°C
–40°C to 85°C
Consult LTC Marketing for parts specified with wider operating temperature ranges.
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/
The
l
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. V
IN
= V
OUT
= 3.6V, R
T
= 33.2k, unless otherwise noted.
PARAMETER
Input Operating Range
Output Voltage Adjust Range
Feedback Voltage
Feedback Input Current
Quiescent Current, Burst Mode Operation
Quiescent Current, Shutdown
Quiescent Current, Active
Input Current Limit
V
FB
= 1.215V
V
FB
= 1.215V, BURST = 0V (Note 3)
SHDN
= 0V, Not Including Switch Leakage
V
C
= 0V, BURST = 3V (Note 3)
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ELECTRICAL CHARACTERISTICS
CONDITIONS
MIN
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TYP
MAX
5.5
5.25
UNITS
V
V
V
nA
μA
μA
μA
A
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1.8
1.8
1.191
1.215
1
40
0.1
700
1
2
1.239
50
60
1
1200
2
LTC3530
ELECTRICAL CHARACTERISTICS
PARAMETER
NMOS Switch Leakage
PMOS Switch Leakage
NMOS Switch On Resistance
PMOS Switch On Resistance
Maximum Duty Cycle
Minimum Duty Cycle
Frequency
Error Amp AVOL
Error Amp Source Current
Error Amp Sink Current
Burst Threshold
Burst Input Current
SHDN/SS
Threshold
SHDN/SS
Input Current
V
BURST
= 5.5V
When IC is Enabled
When EA is at Maximum Boost Duty Cycle
V
SHDN
= 5.5V
l
The
l
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. V
IN
= V
OUT
= 3.6V, R
T
= 33.2k, unless otherwise noted.
CONDITIONS
Switches B and C
Switches A and D
Switches B and C
Switches A and D
Boost (% Switch C On)
Buck (% Switch A On)
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MIN
TYP
0.1
0.1
0.21
0.24
MAX
5
10
UNITS
μA
μA
Ω
Ω
%
%
80
100
0.7
90
0
1
90
300
300
1
2
1.3
%
MHz
dB
μA
μA
V
μA
V
V
μA
0.4
0.85
1.6
0.01
1.4
1
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 LTC3530E is guaranteed to meet performance specifications
from 0°C to 85°C. Specifications over the –40°C to 85°C operating
temperature range are assured by design, characterization and correlations
with statistical process controls.
Note 3:
Current measurements are performed when the outputs are not
switching.
Note 4:
This IC includes overtemperature protection that is intended
to protect the device during momentary overload conditions. Junction
temperature will exceed 125°C when overtemperature protection is active.
Continuous operation above the specified maximum operating junction
temperature may result in device degradation or failure.
TYPICAL PERFORMANCE CHARACTERISTICS
Quiescent Current vs V
IN
(Fixed Frequency Mode)
4.0
V
IN
QUIESCENT CURRENT (mA)
3.5
3.0
1.5 MHz
2.5
2.0
1.5
1.0
0.5
0.0
2.5
3.0
3.5
4.0
V
IN
(V)
4.5
5.0
5.5
3530 G01
T
A
= 25°C, unless otherwise specified.
Peak Current Clamp vs V
IN
3.5
3.0
INPUT CURRENT (A)
2.5
2.0
1.5
1.0
0.5
0.0
2.5
Burst Mode Quiescent Current
50
45
V
IN
QUIESCENT CURRENT (μA)
2.0 MHz
40
35
30
25
20
15
10
5
0
2.5
3.0
3.5
4.0
V
IN
(V)
4.5
5.0
5.5
3530 G02
1.0 MHz
0.5 MHz
NO SWITCHING
3.0
3.5
4.0
V
IN
(V)
4.5
5.0
5.5
3530 G03
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LTC3530
TYPICAL PERFORMANCE CHARACTERISTICS
Automatic Burst Mode Threshold
vs R
BURST
90
80
MINIMUM START VOLTAGE (V)
70
LOAD CURRENT (mA)
60
50
40
30
20
10
0
125 175 225 275 325 375 425 475 500
R
BURST
(kΩ)
3530 G04
T
A
= 25°C, unless otherwise specified.
Average Input Current Limit
vs Temperature
5%
4%
3%
CHANGE FROM 25°C
V
IN
= V
OUT
= 3.3V
Minimum Start Voltage
vs Temperature
1.84
1.82
1.80
1.78
1.76
1.74
1.72
1.70
–45 –25 –5
LEAVE Burst Mode
OPERATION
2%
1%
0%
–1%
–2%
–3%
–4%
ENTER Burst Mode
OPERATION
75
TEMPERATURE (°C)
15
35
55
95 115
3530 G05
–5%
–55 –35 –15
5 25 45 65 85 105 125
TEMPERATURE (°C)
3530 G06
Frequency Change vs Temperature
1.25
1.23
1.21
FREQUENCY (MHz)
1.19
1.17
1.15
1.13
1.11
1.09
1.07
1.05
–45 –25 –5
15 35 55 75
TEMPERATURE (°C)
95 115
3530 G07
Feedback Voltage vs Temperature
1.225
Switch Pins Before Entering
Boost Mode
1.220
FEEDBACK VOLTAGE (V)
SW1
2V/DIV
1.215
1.210
SW2
2V/DIV
1.205
1.200
–45 –25 –5
15 35 55 75
TEMPERATURE (°C)
95 115
3530 G08
50ns/DIV
V
IN
= 2.9V
V
OUT
= 3.3V AT 500mA
3530 G09
Switch Pins in Buck-Boost Mode
SW1
2V/DIV
SW2
2V/DIV
SW1
2V/DIV
Switch Pins Entering
Buck-Boost Mode
LTC3530 Output Ripple
500mA Load
V
IN
= 2.7V
SW2
2V/DIV
V
IN
= 3.3V
V
IN
= 4.2V
50ns/DIV
V
IN
= 3.3V
V
OUT
= 3.3V AT 500mA
3530 G10
50ns/DIV
V
IN
= 4.2V
V
OUT
= 3.3V AT 500mA
3530 G11
1μs/DIV
V
OUT
= 3.3V
20mV/DIV
AC COUPLED
C
OUT
= 22μF, X5R CERAMIC
3530 G12
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LTC3530
TYPICAL PERFORMANCE CHARACTERISTICS
Load Transient Response in Fixed
Frequency Mode, No Load to 300mA
V
OUT
100mV/DIV
V
OUT
100mV/DIV
T
A
= 25°C, unless otherwise specified.
Load Transient Response in
Auto Burst Mode Operation,
No Load to 500mA
Typical Burst Mode Waveforms
V
OUT
50mV/DIV
LOAD
0.25A/DIV
100μs/DIV
V
IN
= 3.6V
V
OUT
= 3.3V
,
C
OUT
= 22μF X5R CERAMIC
3530 G13
LOAD
0.25A/DIV
100μs/DIV
V
IN
= 3.6V
V
OUT
= 3.3V
,
C
OUT
= 47μF X5R CERAMIC + 100μF
LOW ESR TANTALUM
3530 G14
INDUCTOR
CURRENT
0.25A/DIV
22μs/DIV
C
OUT
= 22μF X5R CERAMIC
,
3530 G15
Transition from Burst Mode
Operation to Fixed Frequency Mode
V
OUT
200mV/DIV
2000
1800
1600
CURRENT (mA)
BURST
2V/DIV
INDUCTOR
CURRENT
0.5A/DIV
200μs/DIV
C
OUT
= 22μF X5R CERAMIC
,
3530 G16
Maximum Output Current vs V
IN
1400
1200
1000
800
600
400
250mA AT 1.8V
200
1.5
2.5
3.5
V
IN
(V)
4.5
5.5
3530 G17
I
OUT
PIN FUNCTIONS
R
T
(Pin 1):
Programs the Frequency of the Internal Oscil-
lator. Connect a resister from R
T
to ground.
f(kHz) = 33,170/R
T
(kΩ)
BURST (Pin 2):
Used to Set the Automatic Burst Mode
Threshold. Connect a resistor and capacitor in parallel
from this pin to ground. See the Applications Information
section for component value selection. For manual control,
ground the pin to force Burst Mode operation, connect to
V
IN
to force fixed frequency PWM mode.
SW1 (Pin 3):
Switch Pin Where the Internal Switches A and
B are Connected. Connect inductor from SW1 to SW2. An
optional Schottky diode can be connnected from SW1 to
ground for a moderate efficiency improvement. Minimize
trace length to keep EMI down.
SW2 (Pin 4):
Switch Pin Where the Internal Switches C
and D are Connected. For applications with output voltages
over 4.3V, a Schottky diode is required from SW2 to V
OUT
to ensure the SW pin does not exhibit excessive voltage.
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