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 opera-
tion, 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.
, LT, LTC, LTM and Burst Mode are registered trademarks of Linear Technology
Corporation. All other trademarks are the property of their respective owners.
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
SW1
V
IN
2.4V TO 4.2V
PV
IN
V
IN
SW2
PV
OUT
V
OUT
LTC3533
OFF ON
RUN/SS
R
T
FB
107k
10µF
V
C
4.7pF
330pF
100µF
340k
6.49k
47pF
V
OUT
3.3V
1.5A
EFFICIENCY (%)
90
80
70
60
50
40
30
20
BURST
33.2k
SGND
PGND
0.1µF
200k
200k
3533 TA01
Efficiency
Burst Mode
OPERATION
V
IN
= 2.9V
V
IN
= 2.2V
V
IN
= 3.9V
10
0
0.1
1
10
100
1000
OUTPUT CURRENT (mA)
10000
3533 TA01b
3533f
1
LTC3533
ABSOLUTE MAXIMUM RATINGS
(Note 1)
PACKAGE/ORDER INFORMATION
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 PART NUMBER
LTC3533EDE
DE PART MARKING
3533
Order Options
Tape and Reel: Add #TR
Lead Free: Add #PBF Lead Free Tape and Reel: Add #TRPBF
Lead Free Part Marking:
http://www.linear.com/leadfree/
Consult LTC Marketing for parts specified with wider operating temperature ranges.
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
Maximum Duty Cycle
Minimum Duty Cycle
V
FB
= 1.22V
CONDITIONS
The
●
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
●
●
●
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)
●
3.5
4.5
7
0.5
Switches B and C
Switches A and D
Switches B and C
Switches A and D
Boost (% Switch C On)
Buck (% Switch A On)
●
●
●
0.1
0.1
60
80
80
100
90
5
10
µA
µA
mΩ
mΩ
%
%
0
%
3533f
2
LTC3533
ELECTRICAL CHARACTERISTICS
PARAMETER
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
●
The
●
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
R
T
= 33.2k
●
MIN
0.7
TYP
1
80
–20
250
1
MAX
1.3
UNITS
MHz
dB
µA
µA
V
8
0.4
0.7
1.3
0.01
1.4
1
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.
3533f
3
LTC3533
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
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
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
–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
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
75
TEMPERATURE (°C)
15
35
55
95 115
3533 G05
–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
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
FEEDBACK VOLTAGE (V)
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
3533f
4
LTC3533
TYPICAL PERFORMANCE CHARACTERISTICS
Switch Pins in Buck-Boost Mode
SW1
2V/DIV
T
A
= 25°C, unless otherwise specified.
Switch Pins Entering Buck-Boost
Mode
Output Ripple at 1A Load
SW1
2V/DIV
SW2
2V/DIV
V
IN
= 2.7V
V
IN
= 3.3V
SW2
2V/DIV
V
IN
= 4.2V
1µs/DIV
V
OUT
= 3.3V, 20mV/DIV
C
OUT
= 100µF CERAMIC
3533 G12
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
Load Transient Response in Fixed
Frequency Mode, No Load to 1.5A
V
OUT
100mV/DIV
V
OUT
100mV/DIV
Load Transient Response in Auto
Burst Mode, No Load to 600mA
I
L
0.5A/DIV
LOAD
0.5A/DIV
100µs/DIV
V
IN
= 3.6V
V
OUT
= 3.3V
C
OUT
= 100µF X5R CERAMIC
3533 G13
100µs/DIV
V
IN
= 3.6V
V
OUT
= 3.3V
C
OUT
= 100µF X5R CERAMIC +
100µF LOW ESR TANTALUM
3533 G14
Burst Mode Operation
Transition from Burst Mode
Operation to Fixed Frequency Mode
V
OUT
50mV/DIV
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
3533f
5
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