Features
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LTC3533
2A Wide Input Voltage
Synchronous Buck-Boost
DC/DC Converter
Description
The
LTC
®
3533
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 cell lithium-ion/polymer
or multi-cell alkaline/NiMH applications where the output
voltage is within the input voltage range.
The LTC3533 features programmable Burst Mode oper-
ation, extended V
IN
and V
OUT
ranges down to 1.8V, and
increased output current. Switching frequencies up to
2MHz are programmed with an external resistor. The Burst
Mode threshold is programmed with a single resistor from
the BURST pin to GND.
Other features include 1µA shutdown current, short circuit
protection, programmable soft-start, current limit and
thermal shutdown. The LTC3533 is housed in the thermally
enhanced 14-lead (3mm
×
4mm
×
0.75mm) DFN package.
L,
LT, LTC, LTM, Linear Technology, BurstMode and the Linear logo are registered trademarks
of Linear Technology Corporation. All other trademarks are the property of their respective owners.
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Regulated Output with Input Voltages Above,
Below or Equal to the Output
1.8V to 5.5V (Input) and 5.25V (Output)
Voltage Range
0.8A Continuous Output Current: V
IN
> 1.8V
2A Continuous Output Current: V
IN
> 3V
Single Inductor
Synchronous Rectification: Up to 96% Efficiency
Programmable Burst Mode
®
Operation: I
Q
= 40µA
Output Disconnect in Shutdown
Programmable Frequency from 300kHz to 2MHz
<1µA Shutdown Current
Small Thermally Enhanced 14-Lead (3mm
×
4mm
×
0.75mm) DFN package
applications
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GSM Modems
Handheld Instruments
Digital Cameras
Smart Phones
Media Players
Miniature Hard Disk Drive Power
typical application
2.2μH
100
V
OUT
3.3V
1.5A
EFFICIENCY (%)
90
80
70
60
50
40
30
20
0.1μF
200k
200k
3533 TA01
Efficiency
SW2
V
IN
2.4V TO 4.2V
SW1
PV
IN
V
IN
LTC3533
OFF ON
RUN/SS
R
T
PV
OUT
V
OUT
FB
V
C
107k
4.7pF
340k
6.49k
47pF
330pF
Burst Mode
OPERATION
V
IN
= 2.9V
V
IN
= 2.2V
V
IN
= 3.9V
10μF
100μF
BURST
33.2k
SGND
PGND
10
0
0.1
1
10
100
1000
OUTPUT CURRENT (mA)
10000
3533 TA01b
3533fc
For more information
www.linear.com/LTC3533
1
LTC3533
absolute MaxiMuM ratings
(Note 1)
pin conFiguration
TOP VIEW
R
T
BURST
SGND
SW1
PGND
PGND
SW2
1
2
3
4
5
6
7
15
14 V
C
13 FB
12 RUN/SS
11 PV
IN
10 V
IN
9 PV
OUT
8 V
OUT
V
IN
, PV
IN
Voltages ...........................................–0.3 to 6V
V
OUT
, PV
OUT
Voltages......................................–0.3 to 6V
SW1, SW2 Voltages
DC...............................................................–0.3 to 6V
Pulsed < 100ns ...........................................–0.3 to 7V
V
C
, FB, RUN/SS, BURST Voltages ..................–0.3 to 6 V
Operating Temperature Range (Note 2).... –40°C to 85°C
Maximum Junction Temperature (Note 3)............. 125°C
Storage Temperature Range................... –65°C to 125°C
DE PACKAGE
14-LEAD (4mm
×
3mm) PLASTIC DFN
T
JMAX
= 125°C,
θ
JA
= 43°C/W,
θ
JC
= 4.3°C/W
EXPOSED PAD (PIN 15) IS GND, MUST BE SOLDERED TO PCB
orDer inForMation
LEAD FREE FINISH
LTC3533EDE#PBF
LEAD BASED FINISH
LTC3533EDE
TAPE AND REEL
LTC3533EDE#TRPBF
TAPE AND REEL
LTC3533EDE#TR
http://www.linear.com/product/LTC3533#orderinfo
PART MARKING*
3533
PART MARKING*
3533
PACKAGE DESCRIPTION
14-Lead (4mm
×
3mm) Plastic DFN
PACKAGE DESCRIPTION
14-Lead (4mm
×
3mm) Plastic DFN
TEMPERATURE RANGE
–40°C to 85°C
TEMPERATURE RANGE
–40°C to 85°C
Consult LTC Marketing for parts specified with wider operating temperature ranges.
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/.
Some packages are available i
designated sales channels with #TRMPBF suffix.
n 500 unit reels through
electrical characteristics
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
Peak Current Limit
Reverse Current Limit
NMOS Switch Leakage
PMOS Switch Leakage
NMOS Switch On Resistance
PMOS Switch On Resistance
V
FB
= 1.22V
CONDITIONS
The
l
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. V
IN
= 3.6V, V
OUT
= 3.3V, unless otherwise noted.
MIN
l
l
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TYP
MAX
5.5
5.25
UNITS
V
V
V
nA
µA
µA
µA
A
A
A
1.8
1.8
1.196
1.22
1
40
0.1
700
1.244
50
50
1
1100
V
C
= 0V, V
BURST
= 0V (Note 4)
V
RUN
= 0V, Not Including Switch Leakage
V
C
= 0V, BURST = 3.6V (Note 4)
l
3.5
4.5
7
0.5
Switches B and C
Switches A and D
Switches B and C
Switches A and D
0.1
0.1
60
80
5
10
µA
µA
mW
mW
3533fc
2
For more information
www.linear.com/LTC3533
LTC3533
electrical characteristics
PARAMETER
Maximum Duty Cycle
Minimum Duty Cycle
Frequency Accuracy
Error Amp AVOL
Error Amp Source Current
Error Amp Sink Current
Burst Threshold
Burst Input Current
RUN/SS Threshold
RUN/SS Input Current
V
BURST
= 5.5V, V
IN
= 5.5V
When IC is Enabled
When EA is at Maximum Boost Duty Cycle
V
RUN
= 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
= 3.6V, V
OUT
= 3.3V, unless otherwise noted.
CONDITIONS
Boost (% Switch C On)
Buck (% Switch A On)
R
T
= 33.2k
l
l
l
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MIN
80
100
0.7
TYP
90
MAX
UNITS
%
%
0
1
80
–20
250
1
8
0.4
0.7
1.3
0.01
1.4
1
1.3
%
MHz
dB
µA
µA
V
µA
V
V
µA
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.
Note2:
The LTC3533EDE is guaranteed to meet performance specifications
from 0ºC to 85ºC. Specifications over the –40ºC to 85ºC operating
temperature range are assured by design, characterization and correlation
with statistical process controls.
Note 3:
This IC includes over-temperature protection that is intended
to protect the device during momentary overload conditions. Junction
temperature will exceed 125°C when over-temperature protection is active.
Continuous operation above the specified maximum operating junction
temperature may result in device degradation or failure.
Note 4:
Current Measurements are performed when the outputs are not
switching.
3533fc
For more information
www.linear.com/LTC3533
3
LTC3533
typical perForMance characteristics
Quiescent Current vs V
IN
(Fixed Frequency Mode)
4.0
V
IN
QUIESCENT CURRENT (mA)
V
IN
QUIESCENT CURRENT (μA)
3.5
3.0
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
3533 G01
T
A
= 25°C, unless otherwise specified.
Peak Current Limit vs
Temperature
5
4
CURRENT LIMIT CHANGE (%)
3
2
1
0
–1
–2
–3
–4
Burst Mode Quiescent Current
50
45
2.0 MHz
1.5 MHz
1.0 MHz
0.5 MHz
NO SWITCHING
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
–5
–55 –35 –15
5 25 45 65 85 105 125
TEMPERATURE (°C)
3533 G03
Automatic Burst Mode Threshold
vs R
BURST
200
MINIMUM START VOLTAGE (V)
1.84
1.82
1.80
1.78
1.76
1.74
1.72
Minimum Start Voltage vs
Temperature
5
4
3
CHANGE FROM 25°C (%)
2
1
0
–1
–2
–3
–4
75
TEMPERATURE (°C)
15
35
55
95 115
3533 G05
Average Input Current Limit vs
Temperature
LOAD CURRENT (mA)
150
LEAVE Burst Mode
OPERATION
100
ENTER Burst Mode
OPERATION
50
0
100
125
150
175
200
R
BURST
(kΩ)
225
250
3533 G04
1.70
–45 –25 –5
–5
–55 –35 –15
5 25 45 65 85 105 125
TEMPERATURE (°C)
3533 G06
Frequency Change vs
Temperature
1.076
1.074
1.072
FEEDBACK VOLTAGE (V)
FREQUENCY (MHz)
1.070
1.068
1.066
1.064
1.062
1.060
1.058
1.056
–55 –35 –15
5 25 45 65 85 105 125
TEMPERATURE (°C)
3533 G07
Feedback Voltage vs Temperature
1.2250
Switch Pins Before Entering
Boost Mode
1.2200
SW1
2V/DIV
1.2150
SW2
2V/DIV
1.2100
–55 –35 –15
5 25 45 65 85 105 125
TEMPERATURE (°C)
3533 G08
50ns/DIV
V
IN
= 2.9V
V
OUT
= 3.3V AT 500mA
3533 G09
4
3533fc
For more information
www.linear.com/LTC3533
LTC3533
typical perForMance characteristics
Switch Pins in Buck-Boost Mode
SW1
2V/DIV
SW2
2V/DIV
SW1
2V/DIV
T
A
= 25°C, unless otherwise specified.
Switch Pins Entering Buck-Boost
Mode
V
IN
= 2.7V
V
IN
= 3.3V
SW2
2V/DIV
V
IN
= 4.2V
Output Ripple at 1A Load
50ns/DIV
V
IN
= 3.3V
V
OUT
= 3.3V AT 500mA
3533 G10
50ns/DIV
V
IN
= 4.2V
V
OUT
= 3.3V AT 500mA
3533 G11
1μs/DIV
V
OUT
= 3.3V, 20mV/DIV
C
OUT
= 100μF CERAMIC
3533 G12
Load Transient Response in Fixed
Frequency Mode, No Load to 1.5A
V
OUT
100mV/DIV
I
L
0.5A/DIV
100μs/DIV
V
IN
= 3.6V
V
OUT
= 3.3V
C
OUT
= 100μF X5R CERAMIC
3533 G13
Load Transient Response in Auto
Burst Mode, No Load to 600mA
V
OUT
100mV/DIV
LOAD
0.5A/DIV
100μs/DIV
V
IN
= 3.6V
V
OUT
= 3.3V
C
OUT
= 100μF X5R CERAMIC +
100μF LOW ESR TANTALUM
3533 G14
Burst Mode Operation
V
OUT
50mV/DIV
Transition from Burst Mode
Operation to Fixed Frequency Mode
V
OUT
50mV/DIV
INDUCTOR
CURRENT
0.5A/DIV
20μs/DIV
C
OUT
= 100μF CERAMIC
3533 G15
INDUCTOR
CURRENT
0.5A/DIV
200μs/DIV
C
OUT
= 100μF CERAMIC
3533 G16
3533fc
For more information
www.linear.com/LTC3533
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