FEATURES
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LTC3532
Micropower Synchronous
Buck-Boost DC/DC Converter
DESCRIPTIO
The LTC
®
3532 is a high efficiency, 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, multicell alkaline or NiMH ap-
plications where the output voltage is within the battery
voltage range.
The device includes two 0.36Ω N-channel MOSFET
switches and two 0.42Ω P-channel switches. Switching
frequencies up to 2MHz are programmed with an external
resistor. Quiescent current is only 35μA in Burst Mode
operation, maximizing battery life in portable applica-
tions. Automatic Burst Mode operation allows the user
to program the load current for Burst Mode operation or
to control it manually.
Other features include a 1μA shutdown, soft-start control,
thermal shutdown, and peak current limit. The LTC3532 is
available in a low profile (0.75mm) 10-lead (3mm × 3mm)
DFN and 10-lead MSOP packages.
, LT, LTC and LTM are registered trademarks of Linear Technology Corporation.
Burst Mode is a registered trademark of Linear Technology Corporation.
All other trademarks are the property of their respective owners.
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Single Inductor
Regulated Output with Input Voltages Above, Below
or Equal to the Output
Wide V
IN
Range: 2.4V to 5.5V
V
OUT
Range: 2.4V to 5.25V
Up to 500mA Peak Output Current
Synchronous Rectification: Up to 95% Efficiency
Manual or Programmable Automatic Burst Mode
®
Operation
Output Disconnect in Shutdown
Programmable Oscillator: 300kHz to 2MHz
Pin Compatible with LTC3440
Small Thermally Enhanced 10-Lead (3mm × 3mm)
DFN and 10-Lead MSOP Packages
APPLICATIO S
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Miniature Hard Disk Drive Power Supply
MP3 Players
Handheld Instruments
Digital Cameras
Handheld Terminals
TYPICAL APPLICATIO
Miniature Hard Disk Drive Power Supply
4.7μH
V
OUT
3.3V
100mA
TO 500mA
(PEAK)
V
OUT
200mV/DIV
SW1
V
IN
Li-Ion
2.5V TO 4.2V
V
IN
SHDN/SS LTC3532
BURST
R
T
200k
4.7μF
0.01μF
43.2k
SW2
V
OUT
FB
12.1k
V
C
GND
220pF
340k
1k
33pF
I
LOAD
100mA/DIV
100μs/DIV
3532 TA01b
200k
10μF
3532 TA01
U
U
U
V
IN
= 3V
V
OUT
= 3.3V
I
LOAD
= 50mA TO 300mA
3532fc
1
LTC3532
ABSOLUTE
AXI U RATI GS
(Note 1)
Maximum Junction Temperature (Note 4)............. 125°C
Storage Temperature Range
DD ..................................................... –65°C to 125°C
MSOP ................................................ –65°C to 150°C
Lead Temperature (Soldering,10 sec)
MSOP ............................................................... 300°C
BURST, V
IN
, V
OUT
, V
C
, FB
...................................
–0.3V to 6V
R
T
..................................................................... 0V to 5V
SHDN/SS
..................................................... –0.3V to 6V
SW1, SW2
DC............................................................ –0.3V to 6V
Pulsed < 100ns ........................................ –0.3V to 7V
Operating Temperature Range (Note 2).... –40°C to 85°C
PI CO FIGURATIO
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
DD PACKAGE
10-LEAD (3mm × 3mm) PLASTIC DFN
T
JMAX
= 125°C,
θ
JA
= 43°C/W
EXPOSED PAD (PIN 11) IS GND, MUST BE CONNECTED TO PCB
ORDER I FOR ATIO
LEAD FREE FINISH
LTC3532EDD#PBF
LTC3532EMS#PBF
TAPE AND REEL
PART MARKING
LBXR
LTBXS
LTC3532EDD#TRPBF
LTC3532EMS#TRPBF
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
●
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
= 64.9k, unless otherwise specified.
PARAMETER
Input Start-Up Voltage
Input Operating Range
Output Voltage Adjust Range
Feedback Voltage
Feedback Input Current
Quiescent Current, Burst Mode Operation
Quiescent Current, Shutdown
Quiescent Current, Active
NMOS Switch Leakage
V
FB
= 1.22V
BURST = 0V
SHDN
= 0V, Not Including Switch Leakage, V
OUT
= 0V
V
C
= 0V, BURST = V
IN
(Note 3)
Switches B and C
CONDITIONS
●
●
●
●
ELECTRICAL CHARACTERISTICS
2
U
U
W W
U
W
W
U
U
U
TOP VIEW
R
T
BURST
SW1
SW2
GND
1
2
3
4
5
10
9
8
7
6
V
C
FB
SHDN/SS
V
IN
V
OUT
MS PACKAGE
10-LEAD PLASTIC MSOP
T
JMAX
= 125°C
θ
JA
= 130°C/W 1 LAYER BOARD
θ
JA
= 100°C/W 4 LAYER BOARD
θ
JC
= 45°C/W
PACKAGE DESCRIPTION
10-Lead (3mm × 3mm) Plastic DFN
10-Lead Plastic MSOP
TEMPERATURE RANGE
–40°C to 85°C
–40°C to 85°C
MIN
2.4
2.4
1.19
TYP
2.3
MAX
2.4
5.5
5.25
UNITS
V
V
V
V
nA
μA
μA
μA
μA
3532fc
1.22
1
35
0.1
600
0.1
1.25
50
60
1
1000
5
LTC3532
ELECTRICAL CHARACTERISTICS
PARAMETER
PMOS Switch Leakage
NMOS Switch On Resistance
PMOS Switch On Resistance
Input Current Limit
Maximum Duty Cycle
Minimum Duty Cycle
Frequency Accuracy
Burst Threshold (Falling)
Burst Threshold (Rising)
Burst Current Ratio
Error Amp AVOL
Error Amp Source Current
Error Amp Sink Current
SHDN/SS
Threshold
SHDN/SS
Input Current
V
C
= 1.4V
V
C
= 2V
When IC is Enabled
When EA is at Maximum Boost Duty Cycle
V
SHDN
= 5.5V
●
The
●
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
= 64.9k, unless otherwise specified.
CONDITIONS
Switches A and D
Switches B and C
Switches A and D
0.8
Boost (% Switch C On)
Buck (% Switch A On)
●
●
●
●
MIN
TYP
0.1
0.36
0.42
1.1
88
MAX
10
UNITS
μA
Ω
Ω
1.45
A
%
%
70
100
575
0
740
0.88
1.12
885
%
kHz
V
V
dB
μA
μA
Ratio of I
OUT
to I
BURST
8000
90
15
310
0.4
1
2.2
0.01
1.5
1
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.
Note 2:
The LTC3532E 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 PERFOR A CE CHARACTERISTICS
Efficiency and Power Loss
vs Load Autoburst Mode
100
90
EFFICIENCY (%)
80
10
70
60
50
V
= 3.3V
40
OUT
1
0.1
3V
3.6V
4.2V
10
100
LOAD CURRENT (mA)
0.1
POWER LOSS
1
EFFICIENCY
100
POWER LOSS (mW)
EFFICIENCY (%)
1000
100
90 BURST EFFICIENCY
V
IN
QUIESCENT CURRENT (mA)
U W
3532 G01
T
A
= 25°C, unless otherwise specified.
Fixed Frequency and Burst Mode
Quiescent Current vs V
IN
1000
3.0
2.5
2000kHz
2.0
1000kHz
1.5
1.0
0.5
0
BURST MODE
2.5
3.5
V
IN
(V)
NOT SWITCHING
4.5
5.5
3532 G03
Efficiency and Power Loss
vs Load
80
75
70
65
60
55
50
500kHz
45
40
V
IN
QUIESCENT CURRENT BURST MODE (μA)
100
POWER LOSS (mW)
80
70
60
50
40
0.1
FIXED FREQUENCY
EFFICIENCY
1
10
100
LOAD CURRENT (mA)
0.1
1000
3532 G02
1500kHz
10
BURST
POWER LOSS
FIXED FREQUENCY
POWER LOSS
1
0.01
1000
3532fc
3
LTC3532
TYPICAL PERFOR A CE CHARACTERISTICS
Efficiency vs Frequency
100
98
96
INPUT CURRENT (A)
EFFICIENCY (%)
94
92
90
88
86
84
82 V
IN
= 3.6V
V
OUT
= 3.3V
80
1500
500
1000
FREQUENCY (kHz)
0.2
2000
3532 G04
I
LIMIT
I
CLAMP
LOAD CURRENT (mA)
Frequency vs Temperature
1200
1150
FEEDBACK VOLTAGE (V)
1100
FREQUENCY (MHz)
1050
1000
950
900
850
800
–55
V
IN
= 3.6V
–5
95
45
TEMPERATURE (°C)
3532 G07
Burst Mode to Fixed Frequency
Transition
V
OUT
200mV/DIV
SW1
2V/DIV
BURST PIN
2V/DIV
400μs/DIV
C
OUT
= 22μF
V
IN
= 3.6V
V
OUT
= 3.3V
4
U W
T
A
= 25°C, unless otherwise specified.
Automatic Burst Threshold
vs R
BURST
70
60
50
40
LEAVE BURST
30
20
Peak Current Clamp and Limit
vs V
IN
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0
2.4
V
OUT
= 3.3V
3.4
V
IN
(V)
3532 G05
4.4
5.4
10
150
V
OUT
= 3.3V
V
IN
= 3.6V
ENTER BURST
550
3532 G06
250
350
450
BURST RESISTOR (kΩ)
Feedback Voltage vs Temperature
1.241
1.236
1.231
1.226
1.221
1.216
1.211
1.206
1.201
1.196
–55
–5
45
TEMPERATURE (°C)
95
3532 G08
Load Transient Response in
Fixed Frequency Mode
V
OUT
200mV/DIV
I
LOAD
100mA/DIV
100μs/DIV
C
OUT
= 10μF
V
IN
= 3.6V
V
OUT
= 3.3V
3535 G09
Switch Pins in Buck-Boost Mode
SW1
2V/DIV
Switch Pins Before Entering
Boost Mode
SW2
2V/DIV
SW2
2V/DIV
3532 G10
40ns/DIV
V
IN
= 3.3V
V
OUT
= 3.3V
I
LOAD
= 100mA
3532 G11
40ns/DIV
V
IN
= 2.9V
V
OUT
= 3.3V
I
LOAD
= 100mA
3532 G12
3532fc
LTC3532
TYPICAL PERFOR A CE CHARACTERISTICS
Switch Pins Before Entering
Buck Mode
SW1
2VDIV
SW2
2VDIV
40ns/DIV
V
IN
= 4V
VOUT = 3.3V
I
LOAD
= 100mA
Burst Mode, Buck-Boost
SW1
5V/DIV
SW2
5V/DIV
V
OUT
100mV/DIV
INDUCTOR
CURRENT
500mA/DIV
4μs/DIV
V
IN
= 3.75V
V
OUT
= 3.3V
I
LOAD
= 20mA
C
OUT
= 22μF
340612 G16
PI FU CTIO S
RT (Pin 1):
Timing Resistor to Program the Oscillator
Frequency. The programming range is 300kHz to 2MHz.
48,000
f(kHz)
=
R
T
(kΩ)
BURST (Pin 2):
Used to Set the Automatic Burst Mode Op-
eration Threshold. Place 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
OUT
to force fixed frequency 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 connected from SW1
to ground. Minimize trace length to minimize EMI.
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 SW2 does not exhibit excess voltage.
GND (Pin 5):
Signal and Power Ground for the IC.
V
OUT
(Pin 6):
Output of the Synchronous Rectifier. A filter
capacitor is placed from V
OUT
to GND.
V
IN
(Pin 7):
Input Supply Pin. Supplies current to the
inductor through SW1 and supplies internal V
CC
for the
IC. A ceramic bypass capacitor as close to the V
IN
pin and
GND (Pin 5) is required.
3532fc
U W
T
A
= 25°C, unless otherwise specified.
Output Ripple at 100mA Load
V
IN
= 2.4V
V
IN
= 3.6V
V
OUT
50mV/DIV
V
IN
= 4.5V
V
OUT
50mV/DIV
SW1
5V/DIV
SW2
5V/DIV
V
OUT
100mV/DIV
INDUCTOR
CURRENT
500mA/DIV
400ns/DIV
V
OUT
= 3.6V
I
OUT
= 100mA
C
OUT
= 10μF
3535 G14
Burst Mode, Boost
V
OUT
50mV/DIV
3535 G13
4μs/DIV
V
IN
= 2.4V
V
OUT
= 3.3V
I
LOAD
= 20mA
C
OUT
= 22μF
3535 G15
Burst Mode, Buck
SW1
5V/DIV
SW2
5V/DIV
V
OUT
100mV/DIV
INDUCTOR
CURRENT
500mA/DIV
4μs/DIV
V
IN
= 4.2V
V
OUT
= 3.3V
I
LOAD
= 20mA
C
OUT
= 22μF
3535 G17
U
U
U
5
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