LTC3525DESC6-3.3#TRM [Linear]
LTC3525D-3.3 - 400mA Micropower Synchronous Step-Up DC/DC Converter with Pass Through Mode; Package: SC70; Pins: 6; Temperature Range: -40°C to 85°C;
| 型号： | LTC3525DESC6-3.3#TRM |
| 厂家： | 
Linear |
| 描述： | LTC3525D-3.3 - 400mA Micropower Synchronous Step-Up DC/DC Converter with Pass Through Mode; Package: SC70; Pins: 6; Temperature Range: -40°C to 85°C 开关 光电二极管 |
| 文件： | 总14页 (文件大小：528K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
LTC3525-3/
LTC3525-3.3/LTC3525-5
400mA Micropower
Synchronous Step-Up DC/DC
Converter with Output Disconnect
FEATURES
DESCRIPTION
The LTC®3525-3/LTC3525-3.3/LTC3525-5 are high ef-
n
Up to 95% Efficiency
n
Output Disconnect and Inrush Current Limit
Fixed Output Voltages of 3V, 3.3V or 5V
Delivers 65mA at 3V from a 1V Input
Delivers 60mA at 3.3V from a 1V Input,
or 140mA at 3.3V from a 1.8V Input
Delivers 175mA at 5V from a 3V Input
ficiency synchronous step-up DC/DC converters with
output disconnect that can start up with an input as low
as 1V. They offer a compact, high efficiency alternative to
charge pumps in single cell or dual cell alkaline or Li-Ion
applications. Only three small external components are
required. The LTC3525 is offered in fixed output voltages
of 3V, 3.3V or 5V.
n
n
n
n
n
n
n
n
n
n
n
n
Burst Mode® Operation: I = 7µA
Q
Only Three External Components
The device includes a 0.5Ω N-channel MOSFET switch
and a 0.8Ω P-channel synchronous rectifier. Peak switch
current ranges from 150mA to 400mA, depending on
load, providing enhanced efficiency. Quiescent current
is an ultralow 7µA, maximizing battery life in portable
applications.
V > V
Operation
IN
OUT
<1µA Shutdown Current
Antiringing Control
Short-Circuit and Overtemperature Protection
Very Low Profile of 1mm
Tiny 6-Pin SC70 Package
Other features include <1µA shutdown current, anti-
ringing control and thermal shutdown. The LTC3525 is
available in a tiny 6-pin SC70 package.
L, LT, LTC, LTM, Burst Mode, Linear Technology and the Linear logo are registered trademarks
and ThinSOT is a trademark of Linear Technology Corporation. All other trademarks are the
property of their respective owners. Patents pending.
APPLICATIONS
n
MP3 Players
Portable Instruments
Glucose Meters
Digital Cameras
n
n
n
TYPICAL APPLICATION
LTC3525-3.3 Efficiency and Power
Loss vs Load Current
L1*
100
90
80
70
60
50
40
30
20
100
10
10µH
LTC3525-3.3
EFFICIENCY
V
IN
V
IN
SW
OUT
1V TO 1.6V
V
OUT
3.3V
SHDN
V
OFF ON
1µF
1
POWER LOSS
60mA
GND
GND
10µF
0.1
V
V
V
= 3V
= 2.4V
= 1.2V
IN
IN
IN
3525 TA01
0.01
1000
0.01
0.1
1
10
100
*MURATA LQH32CN100K53
LOAD (mA)
LT3525 • TA02
3525fb
1
LTC3525-3/
LTC3525-3.3/LTC3525-5
ABSOLUTE MAXIMUM RATINGS
PIN CONFIGURATION
(Note 1)
TOP VIEW
V , V
Voltage........................................ –0.3V to 6V
IN OUT
SHDN 1
6 SW
5 GND
4 V
SW Voltage ................................................. –0.3V to 6V
SW Voltage < 100ns.................................... –0.3V to 7V
SHDN Voltage ............................................. –0.3V to 6V
Operating Temperature Range
GND 2
V
IN
3
OUT
SC6 PACKAGE
6-LEAD PLASTIC SC70
(Notes 2, 5)..............................................–40°C to 85°C
Storage Temperature Range .................. –65°C to 125°C
Lead Temperature (Soldering, 10 sec)...................300°C
T
JA
= 125°C
JMAX
θ
= 256°C/W IN FREE AIR, θ = 150°C/W ON BOARD OVER GROUND PLANE
JA
ORDER INFORMATION
LEAD FREE FINISH
TAPE AND REEL
PART MARKING
PACKAGE DESCRIPTION
6-Lead Plastic SC70
6-Lead Plastic SC70
6-Lead Plastic SC70
TEMPERATURE RANGE
–40°C to 85°C
LTC3525ESC6-3#PBF
LTC3525ESC6-3.3#PBF
LTC3525ESC6-5#PBF
LTC3525ESC6-3#TRPBF LCDR
LTC3525ESC6-3.3#TRPBF LBTG
LTC3525ESC6-5#TRPBF LBWT
–40°C to 85°C
–40°C to 85°C
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/
ELECTRICAL CHARACTERISTICS
VIN = 1.2V, VSHDN = 1.2V, VOUT = 3V unless otherwise noted.
(LTC3525-3)
The l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C.
PARAMETER
CONDITIONS
MIN
TYP
0.85
3.00
7
MAX
1
UNITS
V
Input Start-Up Voltage
Output Voltage
l
(Note 6)
2.91
3.09
15
3
V
Quiescent Current, V
Quiescent Current, V
SHDN = V (Note 4)
µA
µA
µA
OUT
IN
IN
SHDN = V (Note 4)
0.5
0.1
IN
Quiescent Current, V – Shutdown
SHDN = 0V, V
Not Including Switch Leakage
= 0V
OUT
1
IN
NMOS Switch Leakage Current
PMOS Switch Leakage Current
NMOS Switch On-Resistance
PMOS Switch On-Resistance
Peak Current Limit
V
V
= V
= V = 5V, SHDN = 0V
0.1
0.1
1
3
µA
µA
Ω
Ω
A
IN
IN
OUT
SW
= V = 5V, V
= 0V, SHDN = 0V
OUT
SW
(Note 3)
(Note 3)
0.6
0.9
0.4
0.4
0.45
0.6
SHDN Threshold Voltage
SHDN Input Current
1
1
V
V
= V or V
OUT
0.01
µA
SHDN
IN
3525fb
2
LTC3525-3/
LTC3525-3.3/LTC3525-5
ELECTRICAL CHARACTERISTICS
VIN = 1.2V, VSHDN = 1.2V, VOUT = 3.3V unless otherwise noted.
(LTC3525-3.3)
The l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C.
PARAMETER
CONDITIONS
MIN
TYP
0.85
3.30
7
MAX
1
UNITS
V
Input Start-Up Voltage
Output Voltage
l
(Note 6)
3.20
3.40
15
3
V
Quiescent Current, V
Quiescent Current, V
SHDN = V (Note 4)
µA
µA
µA
OUT
IN
IN
SHDN = V (Note 4)
0.5
0.1
IN
Quiescent Current, V – Shutdown
SHDN = 0V, V
Not Including Switch Leakage
= 0V
OUT
1
IN
NMOS Switch Leakage Current
PMOS Switch Leakage Current
NMOS Switch On-Resistance
PMOS Switch On-Resistance
Peak Current Limit
V
V
= V
= V = 5V, SHDN = 0V
0.1
0.1
1
3
µA
µA
Ω
Ω
A
IN
IN
OUT
SW
= V = 5V, V
= 0V, SHDN = 0V
OUT
SW
(Note 3)
(Note 3)
0.5
0.8
0.4
0.4
0.45
0.6
SHDN Threshold Voltage
SHDN Input Current
1
1
V
V
= V or V
OUT
0.01
µA
SHDN
IN
(LTC3525-5)
The l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C.
VIN = 2.4V, VSHDN = 2.4V, VOUT = 5V unless otherwise noted.
PARAMETER
CONDITIONS
MIN
TYP
0.85
5.00
8
MAX
1
UNITS
V
Input Start-Up Voltage
Output Voltage
l
(Note 6)
4.85
5.15
18
5
V
Quiescent Current, V
Quiescent Current, V
SHDN = V (Note 4)
µA
µA
µA
OUT
IN
IN
SHDN = V (Note 4)
1.5
0.1
IN
Quiescent Current, V – Shutdown
SHDN = 0V, V
Not Including Switch Leakage
= 0V
OUT
1
IN
NMOS Switch Leakage Current
PMOS Switch Leakage Current
NMOS Switch On-Resistance
PMOS Switch On-Resistance
Peak Current Limit
V
V
= V
= V = 5V, SHDN = 0V
0.1
0.1
0.4
0.7
0.5
0.6
0.01
1
3
µA
µA
Ω
Ω
A
IN
IN
OUT
SW
= V = 5V, V
= 0V, SHDN = 0V
OUT
SW
(Note 3)
(Note 3)
0.4
0.4
SHDN Threshold Voltage
SHDN Input Current
1
1
V
V
= V or V
OUT
µA
SHDN
IN
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 LTC3525E is guaranteed to meet performance specifications
from 0°C to 85°C. Specifications over the –40°C to 85°C operating
Note 4: Current Measurements are performed when the LTC3525 is not
switching.
Note 5: 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 impair device reliability.
temperature range are assured by design, characterization and correlation
with statistical process controls.
Note 6: Consult LTC Marketing for other output voltage options.
Note 3: Specification is guaranteed by design and not 100% tested in
production.
3525fb
3
LTC3525-3/
LTC3525-3.3/LTC3525-5
TYPICAL PERFORMANCE CHARACTERISTICS TA = 25°C unless otherwise noted.
Maximum Output Current vs VIN
(for VOUT to Drop 2.5%)
Maximum Startup Load vs VIN
(Resistive Load)
No-Load Input Current vs VIN
300
250
200
150
100
50
50
45
40
35
30
25
20
15
10
5
250
200
150
100
50
LTC3525-3.3
LTC3525-5
LTC3525-3
LTC3525-5
LTC3525-3.3
LTC3525-5
LTC3525-3
LTC3525-3.3
0
0
0
0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5
0.5
1.5
V
2.0
(V)
2.5
3.0
1.0
1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5
(V)
V
(V)
V
IN
IN
IN
3525 G03
3525 G01
3525 G02
LTC3525-3 Efficiency and Power
Loss vs Load
LTC3525-3.3 Efficiency and Power
Loss vs Load
LTC3525-5 Efficiency and Power
Loss vs Load
100
90
80
70
60
50
40
30
20
100
100
90
80
70
60
50
40
30
20
100
10
100
90
80
70
60
50
40
30
20
10
0
1000
100
10
10
EFFICIENCY
EFFICIENCY
EFFICIENCY
1
1
POWER LOSS
POWER LOSS
POWER LOSS
1
0.1
0.01
0.1
0.01
0.1
V
V
V
= 3V
= 2.4V
= 1.2V
V
V
V
= 3.6V
= 2.4V
= 1.2V
IN
IN
IN
IN
IN
IN
V
V
= 2.4V
= 1.2V
IN
IN
0.01
1000
0.01
0.1
1
10
100
1000
0.01
0.1
1
10
100
1000
0.01
0.1
1
10
100
LOAD (mA)
LOAD (mA)
LOAD (mA)
3525 G24
3525 G04
3525 G05
LTC3525-3.3 Load Regulation
LTC3525-3.3 Load Regulation
LTC3525-5 Load Regulation
2.5
2.0
2.5
2.0
2.5
V
= 1.2V
V
= 2.4V
V
= 1.2V
IN
IN
IN
2.0
1.5
1.5
1.5
1.0
1.0
1.0
0.5
0.5
0.5
C
= 22µF
C
= 22µF
OUT
OUT
C
= 22µF
OUT
0
0
0
C
= 10µF
C
= 10µF
OUT
–0.5
–1.0
–1.5
–2.0
–2.5
–0.5
–1.0
–1.5
–2.0
–2.5
–0.5
–1.0
–1.5
–2.0
–2.5
OUT
C
= 10µF
OUT
0
10 20 30 40 50 60 70 80
0
20 40 60 80 100 120 140 160 180
0
10
20
30
LOAD (mA)
40
50
60
LOAD (mA)
LOAD (mA)
3525 G06
3525 G07
3525 G08
3525fb
4
LTC3525-3/
LTC3525-3.3/LTC3525-5
TYPICAL PERFORMANCE CHARACTERISTICS TA = 25°C unless otherwise noted.
LTC3525-5 Load Regulation
LTC3525-5 Load Regulation
Switching Frequency vs VIN
1200
1100
1000
900
800
700
600
500
400
300
2.5
2.0
2.5
2.0
L = 10µH
V
= 2.4V
V
= 3.6V
IN
IN
LTC3525-5
1.5
1.5
1.0
1.0
0.5
0.5
C
= 22µF
OUT
C
= 22µF
0
0
OUT
C
= 10µF
–0.5
–1.0
–1.5
–2.0
–2.5
–0.5
–1.0
–1.5
–2.0
–2.5
OUT
LTC3525-3.3
C
= 10µF
OUT
60
1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5
0
20
40
80 100 120 140
0
50
100
LOAD (mA)
150
200
V
(V)
LOAD (mA)
IN
3525 G11
3525 G09
3525 G10
V
OUT Variation vs Temperature
Startup Delay Coming Out of
Shutdown
Light Load Burst Frequency
vs Load
(Normalized to 25°C)
120
100
80
60
40
20
0
40
35
30
25
20
15
10
5
0.4
0.3
0.2
0.1
0
C
= 10µF
OUT
–0.1
–0.2
–0.3
–0.4
C
OUT
= 22µF
0
1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5
(V)
–40–30–20–10 0 10 20 30 40 50 60 70 80
TEMPERATURE (°C)
0.1
1
LOAD (mA)
10
V
IN
3525 G13
3525 G12
3525 G14
LTC3525-3.3 Input Current and
VOUT at Start-Up
LTC3525-3.3 Output Voltage
Ripple
V
= 1.2V
IN
I
OUT
5mA
I
OUT
V
OUT
40mA
50mV/DIV
1V/DIV
I
OUT
INPUT
CURRENT
100mA/DIV
80mA
3525 G15
3525 G16
V
C
= 1.2V
500µs/DIV
50µs/DIV
IN
OUT
= 10µF
3525fb
5
LTC3525-3/
LTC3525-3.3/LTC3525-5
TYPICAL PERFORMANCE CHARACTERISTICS TA = 25°C unless otherwise noted.
LTC3525-3.3 Output Voltage
Ripple
LTC3525-3.3 Output Voltage
Ripple
I
I
OUT
5mA
OUT
5mA
I
I
OUT
100mA
OUT
50mV/DIV
50mV/DIV
40mA
I
OUT
190mA
I
OUT
80mA
3525 G17
3525 G18
V
C
= 1.2V
50µs/DIV
V
C
= 2.4V
50µs/DIV
IN
OUT
IN
OUT
= 22µF
= 22µF
LTC3525-5 Output Voltage Ripple
LTC3525-5 Output Voltage Ripple
I
OUT
20mA
I
OUT
5mA
I
OUT
I
OUT
100mA
50mV/DIV
50mV/DIV
50mA
I
I
OUT
200mA
OUT
150mA
3525 G19
3525 G20
V
C
= 2.4V
50µs/DIV
50µs/DIV
V
C
= 3.6V
IN
OUT
IN
OUT
= 22µF
= 22µF
LTC3525-3.3 50mA Load Step
Response
LTC3525-3.3 100mA Load Step
Response
LTC3525-5 100mA Load Step
Response
OUTPUT
RIPPLE
50mV/DIV
OUTPUT
RIPPLE
50mV/DIV
OUTPUT
RIPPLE
50mV/DIV
LOAD
CURRENT
20mA/DIV
LOAD
CURRENT
50mA/DIV
LOAD
CURRENT
50mA/DIV
3525 G21
3525 G22
3525 G23
500µs/DIV
500µs/DIV
V
C
= 1.2V
V
C
= 2.4V
500µs/DIV
V
C
= 3.6V
IN
OUT
IN
OUT
IN
OUT
= 22µF
= 22µF
= 22µF
3525fb
6
LTC3525-3/
LTC3525-3.3/LTC3525-5
PIN FUNCTIONS
SHDN (Pin 1): Logic-Controlled Shutdown Input. Con-
nect to a voltage >1V to enable the LTC3525. Connect to
a voltage <0.4V to disable the LTC3525.
V
(Pin 4): Output Voltage Sense and the Output of the
OUT
Synchronous Rectifier. Connect the output filter capacitor
from V
to GND, close to the IC. A minimum value of
OUT
10µF ceramic is recommended. Use 22µF for reduced
GND (Pins 2, 5): Ground.
output ripple. The output disconnect feature disconnects
V (Pin 3): Input Voltage. The LTC3525 is powered from
V
from V when SHDN is <0.4V.
IN
IN
OUT
V until V
IN
exceeds V . Once V
is greater than (V
OUT
OUT
IN
OUT IN
SW (Pin 6): Switch Pin. Connect an inductor from this
+ 0.2V typical), it is powered from V . Place a ceramic
pin to V . An internal antiringing resistor is connected
IN
bypass capacitor from V to GND. A minimum value of
IN
across SW and V after the inductor current has dropped
IN
1µF is recommended.
to zero to minimize EMI.
BLOCK DIAGRAM
SW
6
V
IN
3
V
OUT
V
SEL
WELL
SWITCH
V
BEST
VB
4
V
OUT
GATE DRIVERS
AND
ANTI-CROSS
CONDUCTION
SHUTDOWN
SHDN
1
SHUTDOWN
+
OFFSET –
ADJUST
V
REF
V
REF
–
+
I
UVLO
PK
UVLO
+
I
OFFSET –
PK
COMPARATOR
ADJUST
START-UP
LOGIC
–
+
I
VAL
SHUTDOWN
TSD
I
VALLEY
COMPARATOR
–
+
FB
WAKE
THERMAL
SHUTDOWN
V
REF
INTEGRATOR
SLEEP
COMPARATOR
ADJUST
5
2
3525 BD
GND
GND
3525fb
7
LTC3525-3/
LTC3525-3.3/LTC3525-5
OPERATION
The LTC3525 is a high performance Burst Mode operation
only, synchronous boost converter requiring only three
small external components. Its simplicity and small size
makeitahighefficiencyalternativetochargepumpdesigns.
It is designed to start up from a single alkaline or nickel
cell, with input voltages as low as 1V, or from two or three
cells (or a Li-Ion battery), with voltages as high as 4.5V.
LTC3525
V
LTC3525
IN
SHDN
SHDN
3525 F01
R
V
CNTRL
R > (V
ZETEX ZC2811E
1M
1M
V
CNTRL
/(V + 0.4) – 1) MΩ
CNTRL IN
Once started, V can be as low as 0.5V (depending on
IN
load current) and maintain regulation. The output voltage
is preset internally to either 3V, 3.3V or 5V. Peak switch
currentis400mAminimum,providingregulationwithload
currents up to 150mA, depending on input voltage.
Figure 1
After the SHDN pin rises, there is a short delay before
switching starts. The delay is 20µs to 120µs, depending
on input voltage (see Typical Performance Characteristics
curve).
Synchronous rectification provides high efficiency opera-
tion while eliminating the need for an external Schottky
diode. True output disconnect eliminates inrush current
Start-Up
at start-up, and allows V
to be disconnected from V ,
OUT
IN
for zero shutdown current.
A start-up oscillator allows the LTC3525 to start with input
voltages as low as 1V. It remains in start-up mode until
The output disconnect feature also allows the LTC3525 to
maintainregulationwithaninputvoltageequaltoorgreater
two conditions are met. V
must exceed V by at least
OUT
IN
0.2V typical and either V or V
must be greater than
OUT
than V . Note, however, that the synchronous rectifier
IN
OUT
1.8V typical.
is not enabled in this mode resulting in lower efficiency
and reduced output current capability.
During start-up, the synchronous rectifier is not enabled,
and the internal P-channel synchronous rectifier acts as
The operating quiescent current is only 7µA typical, allow-
ing the converter to maintain high efficiency at extremely
light loads.
a follower, causing the peak voltage on SW to reach (V
IN
+ 1V) typical. This limits inrush current by maintaining
control of the inductor current when V
is less than V .
OUT
IN
Shutdown
ToreducepowerdissipationintheP-channelsynchronous
rectifier when the output is shorted, a foldback feature is
incorporated that reduces the peak inductor current when
The LTC3525 is shut down by pulling SHDN below 0.4V,
andmadeactivebyraisingitabove1V.AlthoughSHDNcan
V is more than 1.7V greater than V
.
IN
OUT
be driven above V or V
(up to the absolute maximum
IN
OUT
rating)withoutdamage,theLTC3525hasaproprietarytest
mode that may be engaged if SHDN is held in the range
of 0.5V to 1V higher than the greater of V or V . If
Normal Operation
Once V
IN
has increased more than 0.2V typical above
OUT
IN
OUT
V , and either voltage is above 1.8V, normal operation
the test mode is engaged, normal PWM switching action
is interrupted, which can cause undesirable operation
in some applications. Therefore, in applications where
begins, with synchronous rectification enabled. In this
mode, the internal N-channel MOSFET connected be-
tween SW and GND stays on until the inductor current
reaches a maximum peak value, after which it is turned
off and the P-channel synchronous rectifier is turned
on. It stays on, delivering current to the output, until the
inductor current has dropped below a minimum value at
SHDN may be driven above V , a resistor divider or other
IN
meansmustbeemployedtokeeptheSHDNvoltagebelow
(V + 0.4V) to prevent the possibility of the test mode
IN
being engaged. Please refer to Figure 1 for two possible
implementations.
3525fb
8
LTC3525-3/
LTC3525-3.3/LTC3525-5
OPERATION
which point it turns off and the cycle repeats. When the
output voltage reaches its regulated value both switches
are turned off and the LTC3525 goes to sleep, during
which time the output capacitor supplies current to the
load. Once the output voltage drops approximately 9mV
below the regulation value the IC leaves sleep mode and
switching is resumed.
from 150mA to 400mA. Figure 2 shows an example of
how the inductor current changes as the load increases.
Please note that output capacitor values greater than 47µF
will result in higher peak currents than necessary at light
load. This will lower the light load efficiency.
Thevalleyoftheinductorcurrentisautomaticallyadjusted
as well, to maintain a relatively constant inductor ripple
current. This keeps the switching frequency relatively
constant.
The LTC3525 has been designed for low output voltage
ripple. The output voltage ripple is typically only 20mV
peak-to-peak at light load and 60mV peak-to-peak at
full load using the minimum recommended 10µF output
capacitor for the LTC3525-3.3 and a 22µF capacitor for
the LTC3525-5 (due to the capacitor’s DC bias effect). An
antiring circuit damps any oscillation at the switch node
when the inductor current falls to zero.
The maximum average load current that can be supported
is given by:
0.3• V • η
IN
IO(MAX
=
Amps
)
VO
where η is the efficiency (see Typical Performance Char-
acteristics).
Power Adjust Feature
The “burst” frequency (how often the LTC3525 delivers
a burst of current pulses to the load) is determined by
the internal hysteresis (output voltage ripple), the load
current and the amount of output capacitance. All Burst
Mode operation or hysteretic converters will enter the
audible frequency range when the load is light enough.
However, due to the low peak inductor current at light
load, circuits using the LTC3525 do not typically generate
any audible noise.
The LTC3525 incorporates a feature that maximizes
efficiency at light load while providing increased power
capability at heavy load by adjusting the peak and valley
of the inductor current as a function of load. Lowering the
peak inductor current to 150mA at light load optimizes
efficiency by reducing conduction losses in the internal
MOSFETswitches.Astheloadincreases,thepeakinductor
currentisautomaticallyincreasedtoamaximumof400mA.
At intermediate loads, the peak inductor current may vary
INDUCTOR
CURRENT
100mA/DIV
LOAD
CURRENT
50mA/DIV
3525 F02
10µs/DIV
Figure 2. Inductor Current Changing as a Function of Load
3525fb
9
LTC3525-3/
LTC3525-3.3/LTC3525-5
OPERATION
Component Selection
A ceramic input bypass capacitor should be located as
close as possible to the V and GND pins of the IC. A
IN
Inductor values between 4.7µH and 15µH are recom-
mended. In most applications 10µH will yield the best
compromise between size and efficiency. The inductor
should be a low loss ferrite design and must be rated for
peakcurrentsofatleast400mAwithoutsaturating. Induc-
tors with lower DC resistance will improve efficiency. Note
that the inductor value does not have a significant effect
on ripple current, so while lower values will increase the
operating frequency, they do not reduce output voltage
ripple.
minimum value of 1µF is recommended. If the battery is
more than a few inches away, a bulk tantalum decoupling
cap of at least 10µF is recommended on V .
IN
Theoutputcapacitorshouldalsobeaceramic,locatedclose
to the V
and GND pins. A minimum value of 10µF is
OUT
recommended.Increasingthevalueoftheoutputcapacitor
to 22µF will result in lower output ripple. Higher capacitor
values will only offer a small reduction in output ripple,
while reducing light load efficiency by causing the peak
inductor current to increase above its minimum value of
150mA. The input and output capacitors should be X5R
or X7R types, not Y5V.
Some recommended inductor examples are Murata
LQH32C and Coilcraft LPO4812, LPO3310, DO3314,
DS1608 and MSS4020.
Table 1. Inductor Vendor Information
SUPPLIER
Murata
PHONE
FAX
WEBSITE
USA: (814) 237-1431
(847) 639-6400
USA: (847) 956-0666
USA: (814) 238-0490
(847) 639-1469
www.murata.com
www.coilcraft.com
www.sumida.com
Coilcraft
Sumida
USA: (847) 956-0702
Table 2. Capacitor Vendor Information
SUPPLIER
Murata
Taiyo Yuden
TDK
PHONE
FAX
WEBSITE
USA: (814) 237-1431
(408) 573-4150
(847) 803-6100
(803) 448-9411
USA: (814) 238-0490
(408) 573-4159
(847) 803-6296
(803) 448-1943
www.murata.com
www.t-yuden.com
www.component.tdk.com
www.avxcorp.com
AVX
SHDN
SW
SHDN
LTC3525
GND
GND
V
IN
V
V
V
OUT
OUT
IN
3525 F03
Figure 3. Recommended Component Placement
3525fb
10
LTC3525-3/
LTC3525-3.3/LTC3525-5
TYPICAL APPLICATIONS
Single Cell to 3V Converter Using 1mm High Monolithic Inductor
Single Alkaline or NiMH to 3.3V Converter with 1mm Profile
6.8µH*
6.8µH*
LTC3525-3
LTC3525-3.3
1V TO 1.6V
1V TO 1.6V
3
1
2
6
4
5
3
1
2
6
4
5
V
SW
OUT
V
SW
OUT
IN
IN
V
V
OUT
OUT
3V
3.3V
60mA
SHDN
V
SHDN
V
+
+
65mA
GND
GND
GND
GND
10µF
4V
10µF**
6.3V
1µF
1µF
3525 TA03
3525 TA04
*COILCRAFT LPO3310-682MXD
**MURATA GRM219R60J106KE191D
*FDK MIP3226D6R8M
2-Alkaline or NiMH to 3.3V
Li-Ion to 5V
10µH*
10µH*
LTC3525-3.3
3
LTC3525-5
3V TO 4.2V
Li-Ion
1.8V TO 3.2V
6
4
5
3
1
2
6
V
IN
SW
OUT
V
SW
IN
V
V
OUT
OUT
1
2
4
5
+
+
3.3V
5V
SHDN
V
SHDN
V
OUT
OFF ON
1µF
+
140mA
175mA
GND
GND
GND
GND
1µF
10µF
10µF
3525 TA05
3525 TA06
*COILCRAFT MSS4020-103MXD
*MURATA LQH32CN1002K53
3525fb
11
LTC3525-3/
LTC3525-3.3/LTC3525-5
PACKAGE DESCRIPTION
SC6 Package
6-Lead Plastic SC70
(Reference LTC DWG # 05-08-1638 Rev B)
0.47
MAX
0.65
REF
1.80 – 2.20
(NOTE 4)
1.00 REF
INDEX AREA
(NOTE 6)
1.15 – 1.35
(NOTE 4)
1.80 – 2.40
2.8 BSC 1.8 REF
PIN 1
RECOMMENDED SOLDER PAD LAYOUT
PER IPC CALCULATOR
0.15 – 0.30
6 PLCS (NOTE 3)
0.65 BSC
0.10 – 0.40
0.80 – 1.00
0.00 – 0.10
REF
1.00 MAX
GAUGE PLANE
0.15 BSC
0.26 – 0.46
SC6 SC70 1205 REV B
0.10 – 0.18
(NOTE 3)
NOTE:
5. MOLD FLASH SHALL NOT EXCEED 0.254mm
6. DETAILS OF THE PIN 1 IDENTIFIER ARE OPTIONAL,
BUT MUST BE LOCATED WITHIN THE INDEX AREA
7. EIAJ PACKAGE REFERENCE IS EIAJ SC-70
1. DIMENSIONS ARE IN MILLIMETERS
2. DRAWING NOT TO SCALE
3. DIMENSIONS ARE INCLUSIVE OF PLATING
4. DIMENSIONS ARE EXCLUSIVE OF MOLD FLASH AND METAL BURR
8. JEDEC PACKAGE REFERENCE IS MO-203 VARIATION AB
3525fb
12
LTC3525-3/
LTC3525-3.3/LTC3525-5
REVISION HISTORY (Revision history begins at Rev B)
REV
DATE
DESCRIPTION
PAGE NUMBER
B
09/10 Updated “Shutdown” section
8
3525fb
Information furnished by Linear Technology Corporation is believed to be accurate and reliable.
However, no responsibility is assumed for its use. Linear Technology Corporation makes no representa-
tion that the interconnection of its circuits as described herein will not infringe on existing patent rights.
13
LTC3525-3/
LTC3525-3.3/LTC3525-5
TYPICAL APPLICATION
3.3V TO 5V Converter with 1.4mm Profile
10µH*
LTC3525-5
3
1
2
6
4
5
3.3V
V
SW
OUT
IN
V
OUT
5V
SHDN
V
200mA
GND
GND
22µF**
6.3V
1µF
3525 TA07
*COILCRAFT DO3314-103MXD
**MURATA GRM21BR60J226ME39L
RELATED PARTS
PART NUMBER
DESCRIPTION
COMMENTS
LT®1615/LT1615-1
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I
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I
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LT1930/LTC1930A
LTC3200-5
LTC3400/LTC3400B
LTC3401
1A (I ), 1.2MHz/2MHz, High Efficiency Step-Up DC/DC Converter
High Efficiency, V : 2.6V to 16V, V
= 34V,
SW
IN
OUT(MAX)
I = 4.2mA/5.5mA, I < 1µA, ThinSOT Package
Q
SD
100mA, 2MHz, Regulated 5V Charge Pump
V : 2.7V to 4.5V, V
SD
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IN
I
< 1µA, ThinSOT Package
600mA (I ), 1.2MHz, Synchronous Step-Up DC/DC Converter
92% Efficiency, V : 0.5V to 5V, V
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SW
IN
I = 19µA/300µA, I < 1µA, ThinSOT Package
Q
SD
1A (I ), 3MHz, Synchronous Step-Up DC/DC Converter
97% Efficiency, V : 0.5V to 5V, V
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IN
I = 38µA, I < 1µA, MS Package
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SD
LTC3402
2A (I ), 3MHz, Synchronous Step-Up DC/DC Converter
97% Efficiency, V : 0.5V to 5V, V
IN OUT(MAX)
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SW
I = 38µA, I < 1µA, MS Package
Q
SD
LTC3421
3A (I ), 3MHz, Synchronous Step-Up DC/DC Converter
95% Efficiency, V : 0.5V to 4.5V, V
= 5.25V,
OUT(MAX)
SW
IN
with Output Disconnect
I = 12µA, I < 1µA, QFN-24 Package
Q SD
LTC3425
5A (I ), 8MHz, 4-Phase Synchronous Step-Up DC/DC Converter
95% Efficiency, V : 0.5V to 4.5V, V
= 5.25V,
OUT(MAX)
SW
IN
with Output Disconnect
I = 12µA, I < 1µA, QFN-32 Package
Q SD
LTC3429/LTC3429B
LTC3458
600mA, 500kHz Single/Dual Cell Micropower Synchronous
Boost Converter with Output Disconnect
95% Efficiency, V : 1V to 4.5V, V
= 5V,
OUT(MAX)
IN
I = 20µA, I < 1µA, SC70 Package
Q
SD
1.4A (I ), 1.5MHz, Synchronous Step-Up DC/DC Converter
V : 1.5V to 6V, V
= 7.5V, I < 1µA,
OUT(MAX) SD
SW
IN
with Output Disconnect
3mm × 4mm DFN Package
LTC3458L
1.7A (I ), 1.5MHz, Synchronous Step-Up DC/DC Converter
V : 1.5V to 6V, V = 6V, I < 1µA,
SW
IN
OUT(MAX)
SD
with Output Disconnect
3mm × 4mm DFN Package
LTC3459
60mA, 10V Micropower Synchronous Boost Converter
95% Efficiency, V : 1.5V to 6V, V
SD
= 10V, I = 10µA,
OUT(MAX) Q
IN
I
< 1µA, ThinSOT Package
LT3464
85mA (I ), High Efficiency Step-Up DC/DC Converter
V : 2.3V to 10V, V
SD
= 34V, I = 25µA,
SW
IN
OUT(MAX) Q
with Integrated Schottky and PNP Disconnect
I
< 1µA, ThinSOT Package
3525fb
LT 0910 REV B • PRINTED IN USA
14 LinearTechnology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
●
●
LINEAR TECHNOLOGY CORPORATION 2005
(408)432-1900 FAX: (408) 434-0507 www.linear.com
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