FEATURES
■
Regulated Output with Input Above, Below or Equal
to the Output
■
Single Inductor
■
Up to 90% Effi ciency
■
VIN Range: 1.8V to 5.5V
■
200mA at 3.3V
■
125mA at 3V
■
Fixed V
■
Adjustable V
■
Burst Mode® Operation, No External Compensation
■
Ultra Low Quiescent Current: 16μA, Shutdown
Versions (TSOT, DFN): 3.3V, 3V
OUT
from 3.6V Input
OUT
from 2.5V Input
OUT
Version (DFN): 2V to 5V
OUT
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
U
APPLICATIO S
■
Handheld Instruments
■
MP3 Players
■
Handheld computers
■
PDA/GPS
LTC3531/
LTC3531-3.3/LTC3531-3
200mA Buck-Boost
Synchronous DC/DC
Converters
U
DESCRIPTIO
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, minimizing solution footprint and component count as well as
providing high conversion effi ciency 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 battery 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
3mm DFN package for fi xed 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.
TM
package for fi xed voltage versions or a 3mm ×
TYPICAL APPLICATIO
10μH
2.2μF
SW1 SW2
V
IN
LTC3531-3.3
SHDN GND
ON OFF
V
3.1V TO
4.2V
Li-Ion
IN
+
U
Effi ciency vs V
100
95
90
V
OUT
V
OUT
3.3V
160mA
10μF
3531 TA01a
85
80
75
EFFICIENCY (%)
70
65
60
1.5
BOOST
MODE
2
2.5
INPUT VOLTAGE (V)
3
4SW
MODE
3.5
3.3V
IN
4
BUCK
MODE
AT 100mA
OUT
4.5
5
3531 TA01b
5.5
3531fb
1
LTC3531/
LTC3531-3.3/LTC3531-3
WW
W
U
ABSOLUTE AXI U RATI GS
(Note 1)
VIN, VOUT, SW1, SW2,
SW1, SW2 Voltage, <100ns Pulse ..................–0.3 to 7V
SHDN
Voltage ...........–0.3 to 6V
Storage Temperature Range ................... –65°C to 125°C
Lead Temperature (TS6, Soldering, 10 sec) .......... 300°C
Operating Temperature Range (Notes 2, 3) –40°C to 85°C
UUW
FOR ATIOPACKAGE/ORDER I
TOP VIEW
SW2 1
GND, PGND 2
V
3
OUT
6-LEAD PLASTIC TSOT-23
T
= 125°C, θJA = 102°C/W
JMAX
TOP VIEW
S6 PACKAGE
6 SW1
5 V
IN
4 SHDN
EXPOSED PAD IS GND (PIN 9), MUST BE SOLDERED TO PCB
1SW1
V
2
IN
GND
3
SHDN
4
8-LEAD (3mm × 3mm) PLASTIC DFN
T
JMAX
*NC FOR LTC3531-3.3V, LTC3531-3.0V.
9
DD PACKAGE
= 125°C, θJA = 43°C/W
ORDER PART NUMBER S6 PART MARKING ORDER PART NUMBER DD PART MARKING
8
PGND
SW2
7
V
6
OUT
FB*
5
LTC3531ES6-3.3
LTC3531ES6-3
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 specifi ed with wider operating temperature ranges.
The ● denotes the specifi cations which apply over the full operating
ELECTRICAL CHARACTERISTICS
temperature range, otherwise specifi cations are at TA = 25°C. VIN = 3.6V V
PARAMETER CONDITIONS MIN TYP MAX UNITS
V
IN
Minimum Startup Voltage ● 1.65 1.8 V
V
Regulation
OUT
Output Voltage (3.3V Version) No Load ● 3.25 3.32 3.39 V
Output Voltage (3V Version) No Load ● 2.95 3.02 3.09 V
FB Voltage (Adj Version) No Load ● 1.20 1.225 1.25 V
FB Input Current (Adj Version) VFB = 1.225V 1 50 nA
Operating Current
Quiescent Current in Sleep: VIN VIN = 5V, V
V
Shutdown Current VIN
Switch Performance
NMOS Switch Leakage Switches B and C 0.2 2 μA
PMOS Switch Leakage Switches A and D 0.2 2 μA
NMOS B, C R
PMOS A R
VIN = 5V 0.5 Ω
DSON
VIN = 5V 0.5 Ω
DSON
LTBWM
LTCBK
OUT
V
OUT
SHDN
LTC3531EDD
LTC3531EDD-3.3
LTC3531EDD-3
= 3.3V unless otherwise noted.
OUT
= 3.6V, FB = 1.3V 16 30 μA
OUT
= 3.6V 6 10 μA
= 0V, V
= 0V 1 μA
OUT
LBVC
LBWH
LCBV
3531fb
2
LTC3531/
LTC3531-3.3/LTC3531-3
ELECTRICAL CHARACTERISTICS
The ● denotes the specifi cations which apply over the full operating
temperature range, otherwise specifi cations are at T
= 25°C. VIN = 3.6V V
A
= 3.3V unless otherwise noted.
OUT
PARAMETER CONDITIONS MIN TYP MAX UNITS
PMOS D R
PMOS D R
(3.3V Version or Adjustable Version set to 3.3V) V
DSON
(3V Version)
DSON
VOUT
= 3.1V 0.8 Ω
OUT
= 2.8V 0.9 Ω
Peak Current Limit L = 10μH, VIN = 5V 295 365 460 mA
SHDN
Input Threshold 0.4 1
SHDN
Hysteresis 60 mV
SHDN
Leakage Current 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
0.01 1 μA
SHDN
Continuous operation above the specifi ed maximum operating junction
temperature may result in device degradation or failure.
Note 3: The LTC3531 is guaranteed to meet performance specifi cations
from 0°C to 70°C. Specifi cations over the –40°C to 85°C operating
temperature range are assured by design, characterization and correlation
with statistical process controls.
1.4
V
temperature will exceed 125°C when overtemperature protection is active.
UW
3531 G01
CE CHARACTERISTICSA
I
PEAK
450
L = 10μH
400
350
300
250
200
CURRENT (mA)
150
100
50
0
1.5
, I
VALLEY
TA = 25°C unless otherwise specifi ed.
, I
vs V
ZERO
I
2.52
3.53
VIN (V)
ZERO
I
VALLEY
IN
I
PEAK
4.54
5.55
3531 G02
Sleep Currents
20
18
16
14
12
10
8
CURRENT (μA)
6
4
2
0
1.5
I
VIN
23
2.5
3.5
VIN (V)
I
VOUT
5
4.5
4
5.5
3531 G03
TYPICAL PERFOR
Maximum I
(3.3V Version)
350
L = 10μH
V
OUT
300
250
(mA)
200
OUT
150
MAXIMUM I
100
50
0
1.5
= 3.3V
vs V
OUT
2.52 3.5 5.5
IN
VIN (V)
4.5 543
IIN Short Circuit vs V
180
160
140
120
100
(mA)
IN
80
I
60
40
20
0
1.5 2
2.5 3
3.5 4
VIN (V)
V
Ripple vs C
OUT
IN
4.5 5
5.5
3531 G04
(3.3V Version)
100
90
80
70
(mV)
60
50
40
30
RIPPLE PEAK-PEAK
V
20
10
0
1.5
23
2.5
OUT
3.5
VIN (V)
10μF
22μF
4
50mA LOAD
5
4.5
3531 G05
5.5
Load Regulation vs C
(3.3V Version)
3.40
3.35
3.30
(V)
V
OUT
3.25
3.20
3.15
VIN = 3.6V
0.1
22μF
1
LOAD CURRENT (mA)
10μF
47μF
10
OUT
100
1000
3521 G06
3531fb
3
LTC3531/
LTC3531-3.3/LTC3531-3
UW
TYPICAL PERFOR A CE CHARACTERISTICS
TA = 25°C unless otherwise specifi ed.
Start-Up into Resistive Load
L = 10μH
30
28
26
24
22
(Ω)
20
MIN
R
18
16
14
12
10
1.5
23
2.5
3.5
4
V
(V)
IN
4.5
5
3531 G07
Switch On Resistances I
1000
V
= 5V
IN
= 3.3V
900
800
(mΩ)
700
DSON
R
600
500
400
–40
V
OUT
02040
–20
TEMPERATURE (°C)
D (PMOS)
A (PMOS)
B,C (NMOS)
60 80 100
3531 G10
5.5
Burst Frequency vs Load
(3.3V Version)
1000
L = 10μH
C
= 10μF
OUT
100
10mA
10
FREQUENCY (kHz)
1
0.1
1.5 3.53 4.54 5.55
400
350
300
250
200
150
CURRENT (mA)
100
50
0
–40
1mA
0.5mA
2.52
, I
PEAK
VALLEY
–20 0 40
5mA
V
(V)
IN
vs Temperature
I
PEAK
I
VALLEY
I
ZERO
20
TEMPERATURE (°C)
V
Regulation vs Temperature
OUT
(3.3V Version)
3.350
VIN = 3.6V
= 10mA
I
LOAD
(V)
OUT
V
3.325
3.300
3.275
3.250
–40
–20 0 20 40
TEMPERATURE (°C)
60 80 100
3531 G09
50mA
3531 G08
SHDN Pin Threshold and
Hysteresis
1
0.9
0.8
0.7
2.5V
IN
3.3V
OUT
10μH
80 100
60
3531 G11
VOLTAGE (V)
0.6
0.5
–40
SHUTDOWN
02040
–20
TEMPERATURE (°C)
OPERATING
60 80 100
3531 G12
4
3531fb
UW
TYPICAL PERFOR A CE CHARACTERISTICS
LTC3531/
LTC3531-3.3/LTC3531-3
TA = 25°C unless otherwise specifi ed.
SW1
5V/DIV
SW2
5V/DIV
(AC)
V
OUT
50mV/DIV
200mA/DIV
SW1
5V/DIV
SW2
5V/DIV
(AC)
V
OUT
50mV/DIV
200mA/DIV
Buck Mode at 5V
OUT
OUT
= 22μF
200mA
I
L
3.3V
L = 10μH
C
,
IN
5μs/DIV 5μs/DIV
Buck Mode Waveforms at 5VIN,
3.3V
I
L
OUT
20mA
Buck Mode at 5V
OUT
OUT
= 22μF
100mA
3.3V
SW1
5V/DIV
SW2
5V/DIV
(AC)
V
OUT
50mV/DIV
I
L
200mA/DIV
3531 G13 3531 G14
L = 10μH
C
,
IN
4 Switch Mode Waveforms at
SW1
5V/DIV
SW2
5V/DIV
(AC)
V
OUT
50mV/DIV
200mA/DIV
3.6VIN, 3.3V
I
L
OUT
200mA
SW1
5V/DIV
SW2
5V/DIV
(AC)
V
OUT
50mV/DIV
200mA/DIV
L = 10μH
= 22μF
C
OUT
5μs/DIV 5μs/DIV
4 Switch Mode Waveforms at
3.6V
I
L
L = 10μH
= 22μF
C
OUT
, 3.3V
IN
100mA
OUT
5μs/DIV 5μs/DIV
3531 G15
L = 10μH
= 22μF
C
OUT
3531 G16
4 Switch Mode Waveforms at
, 3.3V
3.6V
IN
SW1
5V/DIV
SW2
5V/DIV
(AC)
V
OUT
50mV/DIV
I
L
200mA/DIV
3531 G17 3531 G18
L = 10μH
C
= 22μF
OUT
OUT
20mA
SW1
SW2
V
OUT
I
L
(AC)
3531fb
5
LTC3531/
LTC3531-3.3/LTC3531-3
UW
TYPICAL PERFOR A CE CHARACTERISTICS
TA = 25°C unless otherwise specifi ed.
SW1
5V/DIV
SW2
5V/DIV
(AC)
V
OUT
50mV/DIV
200mA/DIV
SW1
5V/DIV
SW2
5V/DIV
(AC)
V
OUT
50mV/DIV
200mA/DIV
Boost Mode Waveforms at
2.5VIN, 3.3V
I
L
L = 10μH
= 22μF
C
OUT
100mA
OUT
5μs/DIV 5μs/DIV
Shorted Output
I
L
Boost Mode Waveforms at
2.5VIN, 3.3V
SW1
5V/DIV
SW2
5V/DIV
(AC)
V
OUT
50mV/DIV
I
L
200mA/DIV
3531 G19 3531 G20
L = 10μH
= 22μF
C
OUT
OUT
20mA
Start-Up into 50mA Load at
3.3 V
(Shows Start, Buck,
OUT
Then 4sw Modes)
V
200mA/DIV
OUT
1V/DIV
200mA/DIV
I
L
V
(AC)
OUT
20mV/DIV
L = 10μH
= 22μF
C
OUT
= 5
V
IN
3.6VIN, 3.3V
1μs/DIV 25μs/DIV
Load Step
OUT
3531 G21
200mA to 80mA
100mA LOAD
20mA LOAD
= 22μF VIN = 3.6V
C
OUT
25μs/DIV 200ns/DIV
20mA LOAD
3531 G23 3531 G24
SW1
2V/DIV
200mA/DIV
SW2
2V/DIV
I
L
3531 G22
SW1 and SW2 Close-Up in Four
Switch Mode
= 3.3V
V
OUT
3531fb
6
UUU
PI FU CTIO S
LTC3531/
LTC3531-3.3/LTC3531-3
ThinSOT/DFN Packages
SW2 (Pin 1/Pin 7): Buck-Boost Switch Pin Where Internal
Switches C and D are Connected. An optional Schottky
diode can be connected from SW2 to V
effi ciency improvement. Minimize trace length to keep
EMI down.
GND (Pin 2/Pin 3): Signal Ground for the IC.
PGND (Pin 2/Pin 8): Power Ground for the IC. (Shared
on ThinSOT version)
(Pin 3/Pin 6): Output of the Buck-Boost Synchronous
V
OUT
Rectifi er. A fi lter capacitor is placed from V
A ceramic bypass capacitor is recommended as close to
the V
SHDN
voltage of < 0.4V shuts down the converter. A voltage
above >1.4V will enable the converter.
and GND pins as possible.
OUT
(Pin 4/Pin 4): External Shutdown Pin. An applied
for a moderate
OUT
to GND.
OUT
(Pin 5/Pin 2): Input Supply Pin for the Buck-Boost
V
IN
Converter. A minimum 2.2μF Ceramic Capacitor should
be placed between V
FB (NA/Pin 5): Feedback Pin for the Adjustable Version.
Connect the resistor divider tap here. The output voltage
can be adjusted from 2V to 5V.
V
=+
12251
OUT
SW1 (Pin 6/Pin 1): Buck-Boost Switch Pin Where Internal
Switches A and B are Connected. Connect the inductor
from SW1 to SW2.
Exposed Pad (Pin 9, DFN): Solder to PCB ground for
optimal thermal performance.
.
IN
⎛
⎜
⎝
and GND.
R
2
⎞
⎟
⎠
R
1
3531fb
7
LTC3531/
LTC3531-3.3/LTC3531-3
W
BLOCK DIAGRA
SW1 SW2
V
SHDN
SHUTDOWN
SW A
GATE DRIVERS
AND
ANTICROSS
STATE
AND
LOGIC
CONDUCTION
BUCK, 4SW,
BOOST
COMPARATOR
SW B SW C
MACHINE
THERMAL
SHUTDOWN
V
BEST
V
OUT
PGND
COMBINED
FOR TSOT
V
MODE DETECT
GND
IN
PEAK
CURRENT
365mA
V
1.65V
LIMIT
IN
UVLO
I
ZERO/IVALLEY
BEST
AND
1.225V V
FOR ADJ VERSION
SW D
DETECT
R1
INTERNAL
R1 AND R2
DISABLED
V
V
REF
IN
OUT
R2
3531 BD
V
OUT
FB
NOT BONDED
FOR 3.3V AND
3V VERSIONS
8
3531fb
OPERATIO
LTC3531/
LTC3531-3.3/LTC3531-3
U
The LTC3531, LTC3531-3.3 and LTC3531-3 synchronous buck-boost converters utilize a Burst Mode control
technique to achieve high effi ciency over a wide dynamic
range of load currents. A 2% accurate comparator is
used to monitor the output voltage. If V
is above its
OUT
programmed reference threshold no switching occurs and
only quiescent current is drawn from the power source
(sleep mode). When V
drops below the reference
OUT
threshold the IC “wakes up”, switching commences, and
the output capacitor is charged. The value of the output
capacitor, the load current, and the comparator hysteresis
(~1%) determines the number of current pulses required
to pump-up the output capacitor before the part returns
to sleep.
In order to determine the best operating mode for the
converter, the LTC3531 contains a second comparator
that monitors the relative voltage difference between V
and V
. Input and output voltages in the various modes
OUT
IN
as well as typical inductor currents are shown in Figure 1.
Regions of the current waveforms where switches A and
D are on provide the highest effi ciency since energy is
transferred directly from the input source to the output.
Boost Mode
is ~400mV below V
If V
IN
, the LTC3531 operates in
OUT
boost or step-up mode. Referring to Figure 1 (left side)
when V
and C are turned on (V
and current is ramped until I
falls below its regulation voltage, switches A
OUT
is applied across the inductor)
IN
is detected. When this
PEAK
occurs, C is turned off, D is turned on and current is delivered to the output capacitor (V
IN
– V
is applied across
OUT
the inductor). Inductor current falls when D is on, until an
I
VALLEY
is detected. Terminating at I
VALLEY
, rather than I
ZERO
,
results in an increased load current capability for a given
peak current. This AC then AD switch sequence is repeated
until the output is pumped above its regulation voltage, a
fi nal I
(I
VALLEY
V
OUT
is detected, and the part returns to sleep mode
ZERO
is ignored and I
is used in all modes once
ZERO
is above its programmed value).
4-Switch Mode
If (V
– 400mV) < ~VIN < (V
OUT
+ 800mV), the LTC3531
OUT
operates in 4-switch step-up/down mode. Returning to
Figure 1 (center) when V
falls below its regulation volt-
OUT
age, switches A and C are turned on and current is ramped
until I
is detected. As with Boost Mode operation, C
PEAK
is then turned off, D is turned on and current is delivered
to the output. When A and D are on, the inductor current
, V
slope is dependant on the relationship between V
and the R
of the switches. In 4-switch mode, a t
DSON
IN
OUT
OFF
,
timer (approximately 3μs) is used to terminate the AD
pulse. Once the t
B is turned on and inductor current is ramped down (V
is applied across the inductor) until I
timer expires, switch A is turned off,
OFF
is detected.
VALLEY
OUT
This sequence is repeated until the output is regulated,
BD switches are turned on, and a fi nal I
is detected.
ZERO
Anticross conduction circuitry in all modes ensures the
P-channel MOSFET and N-channel MOSFET switch pairs (A
and B or D and C) are never turned on simultaneously.
V
IN
A
SW1 SW2
BC
D
L
V
OUT
V
OUT
V
IN
I
MAX
I
PEAK
t
OFF
I
VALLEY
I
ZERO
AC AC AC AD AD ADADAD AD AD ACAC BD BDBD BD BD
BOOST MODE 4SW MODE BUCK MODE
Figure 1. Voltage and Current Waveforms
t
OFF
t
OFF
V
IN
3531 F01
3531fb
9
LTC3531/
LTC3531-3.3/LTC3531-3
U
OPERATIO
Buck Mode
is ~800mV above V
If V
IN
buck or step-down mode. The higher offset between V
and V
(800mV) is required to ensure suffi cient mag-
OUT
netizing voltage across the inductor when the R
, the LTC3531 operates in
OUT
IN
DSONS
are taken into account. At the beginning of a buck mode
cycle (Figure 1 right side) switches A and D are turned
IN
– V
on (V
is delivered to the output and ramped up until I
is applied across the inductor), current
OUT
PEAK
is
detected. When this occurs, A is turned off, B is turned
on and inductor current falls (–V
tor) until an I
is detected. This AD then BD switch
VALLEY
across the induc-
OUT
sequence is repeated until the output is pumped above
its regulation voltage, a fi nal I
is detected, and the
ZERO
part returns to sleep mode.
Start-Up Mode
Before V
reaches approximately 1.6V, the D switch is
OUT
disabled and its body diode is used to transfer current to
the output capacitor. In start-up mode, the I
VALLEY/IZERO
sense circuit is disabled and an alternate algorithm is used
to control inductor current. When the LTC3531 is brought
out of shutdown (assuming V
is discharged) switches
OUT
A and C are turned on until the inductor current reaches
. The AC switches are then turned off and inductor
I
PEAK
current fl ows to the output through the B switch and D
body diode. The period for the B switch/D body diode is
controlled by the t
AC switch-on to I
~800ns is repeated until V
timer to ~800nS. This sequence of
OFF
then B switch and D body diode for
PEAK
reaches ~1.6V. Once this
OUT
threshold is reached, the LTC3531 will transfer through the
required modes until V
is brought into regulation.
OUT
Due to propagation delays in the sense circuitry, the
magnitudes of the I
PEAK
shift depending on V
IN
, I
, V
, and I
VALLEY
and operating mode.
OUT
ZERO
currents may
OTHER LTC3531 FEATURES
SHDN
or V
IN
, as long
OUT
below
OUT
.
Shutdown: The part is shut down by pulling
0.4V, and made active by pulling the pin up to V
SHDN
Note that
an be driven above VIN or V
as it is limited to less than 6V.
Output Disconnect and Inrush Limiting: The LTC3531
is designed to allow true output disconnect by opening
both P-channel MOSFET rectifi ers. This allows V
OUT
to go
to zero volts during shutdown, drawing no current from
the input source. It also provides inrush current limiting
at turn-on, minimizing surge currents seen by the input
supply.
Thermal Shutdown: If the die temperature reaches approximately 150°C, the part will go into thermal shutdown and all switches will be turned off. The part will be
enabled again when the die temperature has dropped by
10°C (nominal). To deliver the power that the LTC3531
is capable of, it is imperative that a good thermal path be
provided to dissipate the heat generated within the package. It is recommended that multiple vias in the printed
circuit board be used to conduct heat away from the IC
and into a copper plane with as much area as possible.
Soldering the Exposed Pad to the GND plane (DFN version)
is recommended to improve thermal performance.
10
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LTC3531/
LTC3531-3.3/LTC3531-3
U
WUU
S I FOR ATIOAPPLICATIO
Component Selection
Only three power components are required to
complete the design of the buck-boost converter, V
programming resistors are needed for the adjustable
version. The high operating frequency and low peak
currents of the LTC3531 allow the use of low value, low
profi le inductors and tiny external ceramic capacitors.
Inductor Selection
For best effi ciency, choose an inductor with high frequency
core material, such as ferrite, to reduce core loses. The
inductor should have low DCR (DC resistance) to reduce
2
R losses, and must be able to handle the peak
the I
inductor current without saturating. A 10μH to 22μH in-
Table 2. Inductor Vendor Information
Supplier Series Phone Website
COEV DN4835 (800) 227-7040 www.coev.net
Coilcraft MSS4020 (847) 639-6400 www.coilcraft.com
LPO3310
DS1608
Murata LQH43CN USA: (814) 237-1431 www.murata.com
LQH32CN (800) 831-9172
Sumida CDRH4D18 USA: (847) 956-0666 www.sumida.com
CDRH3D16/HP Japan: 81-3-3607-5111
Toko D312C (847) 297-0070 www.tokoam.com
D412C
DB320C
OUT
ductor value with a >500mA current rating and <400mΩ
DCR is recommended. For applications where radiated
noise is a concern, a toroidal or shielded inductor can be
used. Table 2 contains a list of inductor manufacturers.
Capacitor Selection
The buck-boost convertor requires two capacitors. Ceramic
X5R types will minimize ESL and ESR while maintaining
capacitance at rated voltage over temperature. The V
capacitor should be at least 2.2μF. The V
capacitor
OUT
IN
should be between 4.7μF and 22μF. A larger output capacitor should be used if lower peak to peak output voltage
ripple is desired. A larger output capacitor will also improve
load regulation on V
. See Table 3 for a list of capacitor
OUT
manufacturers for input and output capacitor selection.
Table 3. Capacitor Vendor Information
Supplier Series Phone Website
AVX X5R (803) 448-9411 www.avxcorp.com
Murata X5R USA: (814) 237-1431 www.murata.com
(800) 831-9172
Sanyo POSCAP (619) 661-6322 www.sanyovideo.com
Taiyo Yuden X5R (408) 573-4150 www.taiyo-yuden.com
TDK X5R (847) 803-6100 www.component.tdk.com
3531fb
11
LTC3531/
LTC3531-3.3/LTC3531-3
U
WUU
S I FOR ATIOAPPLICATIO
SHUTDOWN
C
C
V
IN
GND GND
IN
4 – SHDN
5 – V
IN
6 – SW1 SW2 – 1
SOT PIN-OUT
OUT
V
OUT
L
V
– 3
OUT
GND – 2
Recommended Layout (SOT Versions)
12
3531fb
TYPICAL APPLICATIO
LTC3531/
LTC3531-3.3/LTC3531-3
U
5V/Li-Ion to 3.3V with ThinSOT (3.3V Version)
V
IN
3.1V TO
5V
5V/Li-Ion
V
IN
1.8V TO
3.2V
2 x AA
ALKALINE
10μH
SW1 SW2
V
V
IN
OUT
+
–
LTC3531-3.3
2.2μF10μF
SHDN GND
ON OFF
V
OUT
3.3V
160mA
3531 TA02a
95
90
85
80
EFFICIENCY (%)
75
70
65
0.1 10 100 1000
4.4V
IN
5V
IN
3.6V
IN
3.1V
IN
POWER LOSS AT 3.6V
1
LOAD CURRENT (mA)
IN
100
POWER LOSS (mW)
10
1
0.1
3531 TA02b
2 AA Alkaline to 3V with ThinSOT (3V Version)
90
10μH
SW1 SW2
V
V
IN
+
–
2.2μF10μF
+
–
ON OFF
OUT
LTC3531-3
SHDN GND
V
OUT
3V
80mA
3531 TA03a
85
80
2.5V
IN
3.2V
75
EFFICIENCY (%)
70
65
60
0.1 10 100 1000
IN
1.8V
POWER LOSS AT 3.2V
1
LOAD CURRENT (mA)
IN
IN
100
POWER LOSS (mW)
10
1
0.1
3531 TA03b
USB
4.35V TO
5.25V
1Ω
4.7μF
2.2μF
10μH
SW1 SW2
V
IN
LTC3531
SHDN GND
ON OFF
USB to 5V with 3 × 3 DFN (Adjustable Version)
V
V
OUT
R2
1M
FB
R1
324k
OUT
5V
200mA
10μF
3531 TA04a
95
90
85
80
EFFICIENCY (%)
75
70
65 0.1
0.1 10 100 1000
EFFICIENCY
POWER LOSS
1
LOAD CURRENT (mA)
3531 TA04b
100
POWER LOSS (mW)
10
1
3531fb
13
LTC3531/
LTC3531-3.3/LTC3531-3
U
PACKAGE DESCRIPTIO
S6 Package
6-Lead Plastic TSOT-23
(Reference LTC DWG # 05-08-1636)
3.85 MAX
0.20 BSC
0.62
MAX
2.62 REF
RECOMMENDED SOLDER PAD LAYOUT
PER IPC CALCULATOR
DATUM ‘A’
NOTE:
1. DIMENSIONS ARE IN MILLIMETERS
2. DRAWING NOT TO SCALE
3. DIMENSIONS ARE INCLUSIVE OF PLATING
0.95
REF
0.30 – 0.50 REF
1.22 REF
1.4 MIN
2.90 BSC
(NOTE 4)
2.80 BSC
0.09 – 0.20
(NOTE 3)
4. DIMENSIONS ARE EXCLUSIVE OF MOLD FLASH AND METAL BURR
5. MOLD FLASH SHALL NOT EXCEED 0.254mm
6. JEDEC PACKAGE REFERENCE IS MO-193
1.50 – 1.75
(NOTE 4)
PIN ONE ID
0.95 BSC
0.80 – 0.90
1.00 MAX
1.90 BSC
0.30 – 0.45
6 PLCS (NOTE 3)
0.01 – 0.10
S6 TSOT-23 0302
14
3531fb
PACKAGE DESCRIPTIO
LTC3531/
LTC3531-3.3/LTC3531-3
U
DD Package
8-Lead Plastic DFN (3mm × 3mm)
(Reference LTC DWG # 05-08-1698)
0.675 ±0.05
3.5 ±0.05
1.65 ±0.05
(2 SIDES)2.15 ±0.05
PACKAGE
OUTLINE
0.25 ± 0.05
RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS
PIN 1
TOP MARK
(NOTE 6)
0.200 REF
NOTE:
1. DRAWING TO BE MADE A JEDEC PACKAGE OUTLINE M0-229 VARIATION OF (WEED-1)
2. DRAWING NOT TO SCALE
3. ALL DIMENSIONS ARE IN MILLIMETERS
4. DIMENSIONS OF EXPOSED PAD ON BOTTOM OF PACKAGE DO NOT INCLUDE
MOLD FLASH. MOLD FLASH, IF PRESENT, SHALL NOT EXCEED 0.15mm ON ANY SIDE
5. EXPOSED PAD SHALL BE SOLDER PLATED
6. SHADED AREA IS ONLY A REFERENCE FOR PIN 1 LOCATION
ON TOP AND BOTTOM OF PACKAGE
0.50
BSC
2.38 ±0.05
(2 SIDES)
3.00 ±0.10
(4 SIDES)
0.75 ±0.05
0.00 – 0.05
1.65 ± 0.10
(2 SIDES)
R = 0.115
TYP
0.25 ± 0.05
2.38 ±0.10
(2 SIDES)
BOTTOM VIEW—EXPOSED PAD
0.38 ± 0.10
85
14
0.50 BSC
(DD) DFN 1203
Information furnished by Linear Technology Corporation is believed to be accurate and reliable.
no responsibility is assumed for its use. Linear Technology Corporation makes no representation that
the interconnection of its circuits as described herein will not infringe on existing patent rights.
However,
3531fb
15
LTC3531/
LTC3531-3.3/LTC3531-3
U
TYPICAL APPLICATIO
Complete USB/Li-Ion Powered System
with 3.3V
and Linear Charger
OUT
5V (NOM)
FROM USB
CABLE
SUSPEND
USB POWER
+
Li-Ion
–
C1, C2: TAIYO YUDEN JMK316BJ106ML
L1: MURATA LQH43CN100K03 (650mA 0.24Ω)
IN1
IN2
HPWR
SUSP
BAT
GND
SHDN
LTC4055
CLPROG
WALL NTC
OUT
CHRG
ACPR
VNTC
TIMER
PROG
V
: USB OR BATTERY
OUT
100k
100k
0.1μF
OTHER
DC/DC
3.1V TO 5.25V
C1
22μF
L1
10μH
SW1 SW2
V
V
IN
OUT
LTC3531-3.3
SHDN
GND
V
OUT
3.3V
160mA
C2
10μF
3531 TA05
RELATED PARTS
PART NUMBER DESCRIPTION COMMENTS
LT1930/LT1930A 1A (I
I
LTC3400/LTC3400B 600mA (ISW), 1.2MHz Synchronous Step-Up DC/DC Converter VIN: 0.85V to 5V, V
I
LTC3401/LTC3402 1A/2A (ISW), 3MHz Synchronous Step-Up DC/DC Converter VIN: 0.5V to 5V, V
I
LTC3405/LTC3405A 300mA (I
I
LTC3406/LTC3406B 600mA (I
I
LTC3421 3A (ISW), 3MHz Synchronous Step-Up DC/DC Converter VIN: 0.5V to 4.5V, V
I
LTC3422 1.5A (ISW), 3MHz Synchronous Step-Up DC/DC Converter VIN: 0.5V to 4.5V, V
I
LTC3426 2A (I
LTC3428 4A (ISW), 1.2MHz Step-Up DC/DC Converter VIN: 1.6V to 5V, V
LTC3429 600mA (ISW), 500kHz Synchronous Step-Up DC/DC Converter VIN: 0.5V to 4.4V, V
I
LTC3440 600mA (I
I
LTC3441 600mA (I
I
LTC3442 2MHz Synchronous Buck-Boost with Auto-Burst VIN: 2.4V to 5.5V, V
LTC3443 1.2A (I
I
LTC3458 1.4A, 1.5MHz Synchronous Step-Up DC/DC Converter VIN: 1.5V to 6V, V
LTC3458L 1.7A, 1.5MHz Synchronous Step-Up DC/DC Converter VIN: 1.5V to 6V, V
LTC3459 10V Micropower Synchronous Step-Up DC/DC Converter VIN: 1.5V to 5.5V, V
LTC3525/LTC3525-3.3/ 400mA (ISW), Synchronous Step-Up DC/DC Converter VIN: 0.5V to 4.5V, IQ = 7μA, ISD < 1μA,
LTC3525-5 with Output Disconnect 2mm × 2mm SC70 Package
Linear Technology Corporation
16
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408) 432-1900
), 1.2MHz/2.2MHz, High Effi ciency Step-Up DC/DC Converter VIN: 2.6V to 16V, V
SW
), 1.5MHz Synchronous Step-Down DC/DC Converter VIN: 2.7V to 6V, V
OUT
), 1.5MHz Synchronous Step-Down DC/DC Converter VIN: 2.5V to 5.5V, V
OUT
), 1.2MHz Step-Up DC/DC Converter in SOT-23 VIN: 1.6V to 5V, V
SW
), 2MHz Synchronous Buck-Boost DC/DC Converter VIN: 2.5V to 5.5V, V
OUT
), 2MHz Synchronous Buck-Boost DC/DC Converter VIN: 2.5V to 5.5V, V
OUT
), 600kHz Synchronous Buck-Boost DC/DC Converter VIN: 2.4V to 5.5V, V
OUT
●
FAX: (408) 434-0507 ● www.linear.com
= 4.2mA/5.5mA, ISD < 1μA, ThinSOT Package
Q
= 19μA/300μA, ISD < 1μA, ThinSOT Package
Q
SD
SD
SD
SD
SD
SD
SD
SD
SD
= 34V,
OUT(MAX)
= 5V,
OUT(MAX)
= 6V, IQ = 38μA,
OUT(MAX)
< 1μA, MS Package
= 0.8V, IQ = 20μA,
OUT(MIN)
≤ 1μA, MS10 Package
= 0.6V, IQ = 20μA,
OUT(MIN)
≤ 1μA, ThinSOT Package
= 5.25V, IQ = 12μA,
OUT(MAX)
< 1μA, QFN Package
= 5.25V, IQ = 25μA,
OUT(MAX)
< 1μA, 3mm × 3mm DFN Package
up to 5.5V
OUT
up to 5.5V
OUT
= 5V, IQ = 20μA,
OUT(MIN)
< 1μA, QFN Package
= 5.5V, IQ = 25μA,
OUT(MIN)
< 1μA, MS, DFN Packages
= 5.5V, IQ = 25μA,
OUT(MIN)
< 1μA, DFN Package
up to 5.25V
OUT
= 5.25V, IQ = 28μA,
OUT(MIN)
< 1μA, MS Package
up to 7.5V
OUT
up to 6V
OUT
up to 10V
OUT
LT 0807 REV B • PRINTED IN USA
© LINEAR TECHNOLOGY CORPORATION 2006
3531fb
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