LTC3531/
LTC3531-3.3/LTC3531-3
200mA Buck-Boost
Synchronous DC/DC
Converters
FEATURES
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DESCRIPTIO
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Regulated Output with Input Above, Below or Equal
to the Output
Single Inductor
Up to 90% Efficiency
V
IN
Range: 1.8V to 5.5V
200mA at 3.3V
OUT
from 3.6V Input
125mA at 3V
OUT
from 2.5V Input
Fixed V
OUT
Versions (TSOT, DFN): 3.3V, 3V
Adjustable V
OUT
Version (DFN): 2V to 5V
Burst Mode
®
Operation, No External Compensation
Ultra Low Quiescent Current: 16μA, Shutdown
Current <1μA
Only 3 External Components Required
(Fixed Voltage Versions)
Short-Circuit Protection
Output Disconnect in Shutdown
Available in 6-Pin ThinSOT and 3mm
×
3mm DFN
Packages
The LTC
®
3531/LTC3531-3.3/LTC3531-3 are synchronous
buck-boost DC/DC converters that operate from input
voltages above, below or equal to the output voltage. The
topology incorporated in the ICs provides a continuous
transfer through all operating modes, making the product
ideal for single cell Li-Ion and multicell alkaline or nickel
applications. The converters operate in Burst Mode, mini-
mizing solution footprint and component count as well as
providing high conversion efficiency over a wide range of
load currents.
The devices include two 0.5Ω N-channel MOSFET switches
and two P-channel switches (0.5Ω, 0.8Ω). Quiescent
current is typically 16μA, making the parts ideal for bat-
tery power applications. Other features include a <1μA
shutdown current, current limiting, thermal shutdown
and output disconnect. The parts are offered in a 6-pin
ThinSOT
TM
package for fixed voltage versions or a 3mm
×
3mm DFN package for fixed and adjustable versions.
, LT, LTC and LTM are registered trademarks of Linear Technology Corporation.
Burst Mode is a registered trademark of Linear Technology Corporation.
ThinSOT is a trademark of Linear Technology Corporation.
All other trademarks are the property of their respective owners.
Protected by U.S. Patents including 6166527.
APPLICATIO S
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Handheld Instruments
MP3 Players
Handheld computers
PDA/GPS
TYPICAL APPLICATIO
10μH
SW1
V
IN
100
95
90
EFFICIENCY (%)
V
IN
3.1V TO
4.2V
Li-Ion
SW2
V
OUT
V
OUT
3.3V
160mA
10μF
SHDN
GND
70
3531 TA01a
85
80
75
+
LTC3531-3.3
2.2μF
65
ON OFF
60
1.5
2
2.5
3.3V
OUT
AT 100mA
3 3.5 4 4.5
INPUT VOLTAGE (V)
5
5.5
U
Efficiency vs V
IN
BOOST
MODE
BUCK
MODE
4SW
MODE
3531 TA01b
U
U
3531fb
1
LTC3531/
LTC3531-3.3/LTC3531-3
ABSOLUTE
(Note 1)
AXI U RATI GS
Storage Temperature Range................... –65°C to 125°C
Lead Temperature (TS6, Soldering, 10 sec) .......... 300°C
VIN, VOUT, SW1, SW2, SHDN Voltage ...........–0.3 to 6V
SW1, SW2 Voltage, <100ns Pulse ..................–0.3 to 7V
Operating Temperature Range (Notes 2, 3) –40°C to 85°C
PACKAGE/ORDER I FOR ATIO
TOP VIEW
SW2 1
GND, PGND 2
V
OUT
3
6 SW1
5 V
IN
4 SHDN
S6 PACKAGE
6-LEAD PLASTIC TSOT-23
T
JMAX
= 125°C,
θ
JA
= 102°C/W
ORDER PART NUMBER
LTC3531ES6-3.3
LTC3531ES6-3
S6 PART MARKING
LTBWM
LTCBK
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.
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.
PARAMETER
V
IN
Minimum Startup Voltage
V
OUT
Regulation
Output Voltage (3.3V Version)
Output Voltage (3V Version)
FB Voltage (Adj Version)
FB Input Current (Adj Version)
Operating Current
Quiescent Current in Sleep:
Shutdown Current
Switch Performance
NMOS Switch Leakage
PMOS Switch Leakage
NMOS B, C R
DSON
PMOS A R
DSON
CONDITIONS
●
ELECTRICAL CHARACTERISTICS
No Load
No Load
No Load
V
FB
= 1.225V
V
IN
V
OUT
V
IN
V
IN
= 5V, V
OUT
= 3.6V, FB = 1.3V
V
OUT
= 3.6V
SHDN = 0V, V
OUT
= 0V
Switches B and C
Switches A and D
V
IN
= 5V
V
IN
= 5V
2
U
U
W
W W
U
W
TOP VIEW
SW1 1
V
IN
2
GND
3
SHDN 4
9
8
7
6
5
PGND
SW2
V
OUT
FB*
DD PACKAGE
8-LEAD (3mm
×
3mm) PLASTIC DFN
T
JMAX
= 125°C,
θ
JA
= 43°C/W
EXPOSED PAD IS GND (PIN 9), MUST BE SOLDERED TO PCB
*NC FOR LTC3531-3.3V, LTC3531-3.0V.
ORDER PART NUMBER
LTC3531EDD
LTC3531EDD-3.3
LTC3531EDD-3
DD PART MARKING
LBVC
LBWH
LCBV
MIN
TYP
1.65
MAX
1.8
3.39
3.09
1.25
50
30
10
1
2
2
UNITS
V
V
V
V
nA
μA
μA
μA
μA
μA
Ω
Ω
3531fb
●
●
●
3.25
2.95
1.20
3.32
3.02
1.225
1
16
6
0.2
0.2
0.5
0.5
LTC3531/
LTC3531-3.3/LTC3531-3
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.
PARAMETER
PMOS D R
DSON
(3.3V Version or Adjustable Version set to 3.3V)
PMOS D R
DSON
(3V Version)
Peak Current Limit
SHDN
SHDN Input Threshold
SHDN Hysteresis
SHDN Leakage Current
CONDITIONS
V
OUT
= 3.1V
V
OUT
= 2.8V
L = 10μH, V
IN
= 5V
MIN
TYP
0.8
0.9
365
1
60
0.01
MAX
UNITS
Ω
Ω
mA
V
mV
μA
ELECTRICAL CHARACTERISTICS
295
0.4
460
1.4
1
V
SHDN
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:
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.
Note 3:
The LTC3531 is guaranteed to meet performance specifications
from 0°C to 70°C. Specifications over the –40°C to 85°C operating
temperature range are assured by design, characterization and correlation
with statistical process controls.
TYPICAL PERFOR A CE CHARACTERISTICS
Maximum I
OUT
vs V
IN
(3.3V Version)
350
300
MAXIMUM I
OUT
(mA)
250
CURRENT (mA)
200
150
100
50
0
1.5
L = 10μH
V
OUT
= 3.3V
450
400
350
300
250
200
150
100
50
2
2.5
3
3.5
V
IN
(V)
3531 G01
CURRENT (μA)
4
180
160
I
IN
Short Circuit vs V
IN
V
RIPPLE PEAK-PEAK
(mV)
140
120
I
IN
(mA)
100
80
60
40
20
0
1.5
2
2.5
3
3.5
V
IN
(V)
3531 G04
50
40
30
20
10
0
50mA LOAD
1.5
2
2.5
3
3.5
4
V
IN
(V)
4.5
5
5.5
22μF
V
OUT
(V)
4
U W
4.5
5
4.5
5
T
A
= 25°C unless otherwise specified.
Sleep Currents
20
18
I
VIN
I
PEAK
, I
VALLEY
, I
ZERO
vs V
IN
L = 10μH
I
PEAK
16
14
12
10
8
6
4
I
VALLEY
I
VOUT
I
ZERO
2
2.5
3
3.5
V
IN
(V)
3531 G02
2
0
4
4.5
5
5.5
1.5
2
2.5
3
3.5
4
V
IN
(V)
4.5
5
5.5
5.5
0
1.5
3531 G03
V
OUT
Ripple vs C
OUT
(3.3V Version)
100
90
80
70
60
3.30
10μF
3.35
3.40
Load Regulation vs C
OUT
(3.3V Version)
10μF
22μF
3.25
47μF
3.20
V
IN
= 3.6V
3.15
1
0.1
5.5
100
LOAD CURRENT (mA)
10
1000
3521 G06
3531 G05
3531fb
3
LTC3531/
LTC3531-3.3/LTC3531-3
TYPICAL PERFOR A CE CHARACTERISTICS
Start-Up into Resistive Load
L = 10μH
30
28
26
FREQUENCY (kHz)
24
R
MIN
(Ω)
22
20
18
16
14
12
10
1.5
2
2.5
3
3.5
4
V
IN
(V)
4.5
5
5.5
0.1
1.5
2
2.5
3
3.5 4
V
IN
(V)
4.5
5
5.5
3.250
–40
–20
60
0
20
40
TEMPERATURE (°C)
80
100
3531 G09
V
OUT
(V)
Switch On Resistances
1000
900
800
700
600
500
400
–40
A (PMOS)
V
IN
= 5V
V
OUT
= 3.3V
400
D (PMOS)
350
CURRENT (mA)
VOLTAGE (V)
R
DSON
(mΩ)
B,C (NMOS)
60
0
20
40
TEMPERATURE (°C)
80
100
–20
4
U W
3531 G07
3531 G10
T
A
= 25°C unless otherwise specified.
V
OUT
Regulation vs Temperature
(3.3V Version)
3.350
V
IN
= 3.6V
I
LOAD
= 10mA
Burst Frequency vs Load
(3.3V Version)
1000
L = 10μH
C
OUT
= 10μF
50mA
10mA
10
1mA
1
0.5mA
3.275
3.300
5mA
100
3.325
3531 G08
I
PEAK
, I
VALLEY
vs Temperature
1
I
PEAK
0.9
300
250
200
150
100
50
0
–40
–20
0
I
ZERO
40
60
20
TEMPERATURE (°C)
80
100
2.5V
IN
3.3V
OUT
10μH
I
VALLEY
0.8
SHDN Pin Threshold and
Hysteresis
OPERATING
0.7
SHUTDOWN
0.6
0.5
– 40
– 20
60
0
20
40
TEMPERATURE (°C)
80
100
3531 G12
3531 G11
3531fb
LTC3531/
LTC3531-3.3/LTC3531-3
TYPICAL PERFOR A CE CHARACTERISTICS
Buck Mode at 5V
IN
,
3.3V
OUT
200mA
SW1
5V/DIV
SW2
5V/DIV
V
OUT
(AC)
50mV/DIV
I
L
200mA/DIV
L = 10μH
C
OUT
= 22μF
5μs/DIV
3531 G13
Buck Mode Waveforms at 5V
IN
,
3.3V
OUT
20mA
SW1
5V/DIV
SW2
5V/DIV
V
OUT
(AC)
50mV/DIV
I
L
200mA/DIV
SW1
5V/DIV
SW2
5V/DIV
V
OUT
(AC)
50mV/DIV
I
L
200mA/DIV
L = 10μH
C
OUT
= 22μF
4 Switch Mode Waveforms at
3.6V
IN
, 3.3V
OUT
100mA
SW1
5V/DIV
SW2
5V/DIV
V
OUT
(AC)
50mV/DIV
I
L
200mA/DIV
SW1
5V/DIV
SW2
5V/DIV
V
OUT
(AC)
50mV/DIV
I
L
200mA/DIV
L = 10μH
C
OUT
= 22μF
U W
T
A
= 25°C unless otherwise specified.
Buck Mode at 5V
IN
,
3.3V
OUT
100mA
SW1
5V/DIV
SW2
5V/DIV
V
OUT
(AC)
50mV/DIV
I
L
200mA/DIV
L = 10μH
C
OUT
= 22μF
5μs/DIV
3531 G14
4 Switch Mode Waveforms at
3.6V
IN
, 3.3V
OUT
200mA
5μs/DIV
3531 G15
L = 10μH
C
OUT
= 22μF
5μs/DIV
3531 G16
4 Switch Mode Waveforms at
3.6V
IN
, 3.3V
OUT
20mA
SW1
SW2
V
OUT
(AC)
I
L
5μs/DIV
3531 G17
L = 10μH
C
OUT
= 22μF
5μs/DIV
3531 G18
3531fb
5
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