LTC3525D-3.3
400mA Micropower
Synchronous Step-Up DC/DC
Converter with Pass Through Mode
FeaTures
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DescripTion
The
LTC
®
3525D-3.3
is a high efficiency synchronous step-
up DC/DC converter that can start up with an input as low
as 0.85V. It offers 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 re-
quired. The LTC3525D features a fixed output voltage of 3.3V.
In shutdown, V
OUT
is connected to V
IN
through the inductor.
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.
Other features include anti-ringing control and thermal
shutdown. The LTC3525D is available in a tiny 6-Lead
SC70 package.
List of LTC3525 Options
PART
NAME
LTC3525-3
LTC3525-3.3
LTC3525-5
LTC3525D-3.3
LTC3525L-3
INPUT START-UP
VOLTAGE
0.85V
0.85V
0.85V
0.85V
0.7V
OUTPUT
VOLTAGE
3V
3.3V
5V
3.3V
3V
V
OUT
STATUS IN
SHUTDOWN MODE
Output Disconnect
Output Disconnect
Output Disconnect
Pass Through Mode
Output Disconnect
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V
OUT
Connected to V
IN
in Shutdown
Up to 95% Efficiency
0.85V Minimum Input Start-Up Voltage
Fixed Output Voltage of 3.3V
Delivers 60mA at 3.3V from a 1V Input,
or 140mA at 3.3V from a 1.8V Input
Burst Mode
®
Operation: I
Q
= 7µA
V
IN
Range: 0.5V to 4.5V
Only Three External Components
V
IN
> V
OUT
Operation
Anti-Ringing Control
Short-Circuit and Overtemperature Protection
Very Low Profile of 1mm
Tiny 6-Lead SC70 Package
applicaTions
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MP3 Players
Portable Instruments
Glucose Meters
Digital Cameras
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.
Typical applicaTion
L1*
10µH
100
90
LTC3525D-3.3
V
IN
PASS THROUGH ON
1µF
SHDN
GND
SW
V
OUT
GND
V
OUT
3.3V
140mA
10µF
EFFICIENCY (%)
80
70
60
50
40
30
20
0.01
LTC3525D-3.3 Efficiency and
Power Loss vs Load Current
100
10
EFFICIENCY
1
POWER LOSS (mW)
V
IN
1.8V TO 3.2V
POWER LOSS
0.1
V
IN
= 3V
V
IN
= 2.4V
V
IN
= 1.2V
0.1
1
10
LOAD (mA)
100
*MURATA LQH32CN100K53
3525 TA01
0.01
1000
LT3525 • TA02
3525d33fb
For more information
www.linear.com/LTC3525D3.3
1
LTC3525D-3.3
absoluTe MaxiMuM raTings
(Note 1)
pin conFiguraTion
TOP VIEW
SHDN
1
GND 2
V
IN
3
6 SW
5 GND
4 V
OUT
V
IN
, V
OUT
Voltage ........................................ –0.3V to 6V
SW Voltage ................................................. –0.3V to 6V
SW Voltage < 100ns.................................... –0.3V to 7V
SHDN
Voltage ............................................. –0.3V to 6V
Operating Junction Temperature Range
(Notes 2, 5) ............................................ –40°C to 125°C
Storage Temperature Range .................. –65°C to 125°C
Lead Temperature (Soldering, 10 sec)................... 300°C
SC6 PACKAGE
6-LEAD PLASTIC SC70
T
JMAX
= 125°C
θ
JA
= 256°C/W IN FREE AIR,
θ
JA
= 150°C/W ON BOARD OVER GROUND PLANE
orDer inForMaTion
LEAD FREE FINISH
LTC3525DESC6-3.3#PBF
LTC3525DISC6-3.3#PBF
TAPE AND REEL
LTC3525DESC6-3.3#TRPBF
LTC3525DISC6-3.3#TRPBF
PART MARKING
LCQZ
LCQZ
PACKAGE DESCRIPTION
6-Lead Plastic SC70
6-Lead Plastic SC70
TEMPERATURE RANGE
–40°C to 85°C
–40°C to 125°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/
2
3525d33fb
For more information
www.linear.com/LTC3525D3.3
LTC3525D-3.3
elecTrical characTerisTics
PARAMETER
Input Start-Up Voltage
Output Voltage
Quiescent Current, V
OUT
Quiescent Current, V
IN
Quiescent Current, V
IN
– Shutdown
NMOS Switch On-Resistance
PMOS Switch On-Resistance
Peak Current Limit
SHDN
Threshold Voltage
SHDN
Input Current
V
SHDN
= V
IN
or V
OUT
(Note 6)
SHDN
= V
IN
(Note 4)
SHDN
= V
IN
(Note 4)
SHDN
= 0V, V
OUT
= V
IN
= 3.3V
Including Switch Leakage
(Note 3)
(Note 3)
0.4
0.4
l
The
l
denotes the specifications which apply over the full operating junction temperature range, otherwise specifications are at
T
A
= 25°C. V
IN
= 1.2V, V
SHDN
= 1.2V, V
OUT
= 3.3V unless otherwise noted. (Note 2)
CONDITIONS
MIN
3.20
TYP
0.85
3.30
7
0.5
3
0.5
0.8
0.45
0.6
0.01
1
1
MAX
1
3.40
15
3
10
UNITS
V
V
µA
µA
µA
Ω
Ω
A
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 LTC3525D is tested under pulsed load conditions such that
T
J
≈ T
A
. The LTC3525DE is guaranteed to meet performance specifications
from 0°C to 85°C. Specifications over the –40°C to 85°C operating
junction temperature range are assured by design, characterization and
correlation with statistical process controls. The LTC3525DI is guaranteed
over the –40°C to 125°C operating junction temperature range. Note that
the maximum ambient temperature consistent with these specifications
is determined by specific operating conditions in conjunction with board
layout, the rated package thermal impedance and other environmental
factors. T
J
is calculated from the ambient temperature T
A
and power
dissipation PD according to the following formula:
T
J
= T
A
+ (P
D
• 150°C/W)
Note 3:
Specification is guaranteed by design and not 100% tested in
production.
Note 4:
Current Measurements are performed when the LTC3525D 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.
Note 6:
Consult LTC Marketing for other output voltage options.
3525d33fb
For more information
www.linear.com/LTC3525D3.3
3
LTC3525D-3.3
Typical perForMance characTerisTics
Maximum Output Current vs V
IN
(for V
OUT
to Drop 2.5%)
300
250
200
LOAD (mA)
I
OUT
(mA)
150
100
50
0
0.5
50
250
200
150
T
A
= 25°C unless otherwise noted.
Maximum Startup Load vs V
IN
(Resistive Load)
50
45
40
35
I
IN
(µA)
30
25
20
15
10
5
No-Load Input Current vs V
IN
100
1.0
1.5
2.0
2.5 3.0
V
IN
(V)
3.5
4.0
4.5
0
0.5
1.0
1.5
2.0
V
IN
(V)
2.5
3.0
3525d33 G02
0
1.0
1.5
2.0
2.5 3.0
V
IN
(V)
3.5
4.0
4.5
3525d33 G01
3525d33 G03
Efficiency and Power Loss
vs Load
100
90
EFFICIENCY
1
CHANGE IN V
OUT
(%)
80
EFFICIENCY (%)
70
60
50
40
30
20
0.01
0.1
1
10
LOAD (mA)
V
IN
= 3V
V
IN
= 2.4V
V
IN
= 1.2V
100
0.1
10
POWER LOSS (mW)
100
2.5
2.0
1.5
Load Regulation
V
IN
= 1.2V
2.5
2.0
1.5
CHANGE IN V
OUT
(%)
1.0
0.5
0
–0.5
–1.0
–1.5
–2.0
0
10
20
30 40 50
LOAD (mA)
60
70
80
–2.5
Load Regulation
V
IN
= 2.4V
1.0
0.5
0
–0.5
–1.0
–1.5
–2.0
–2.5
C
OUT
= 10µF
C
OUT
= 22µF
C
OUT
= 22µF
C
OUT
= 10µF
POWER LOSS
0.01
1000
0
20
40
60
80 100 120 140 160 180
LOAD (mA)
3525d33 G07
3525d33 G04
3525d33 G06
Light Load Burst Frequency
vs Load
40
35
BURST FREQUENCY (kHz)
CHANGE IN V
OUT
(%)
30
25
20
15
10
5
0
0.1
1
LOAD (mA)
C
OUT
= 10µF
V
OUT
Variation vs Temperature
(Normalized to 25°C)
0.40
0.30
SWITCHING DELAY (µs)
0.20
0.10
–0.00
–0.10
–0.20
–0.30
10
3525d33 G12
Start-Up Delay Coming Out of
Shutdown
120
100
80
60
40
20
0
C
OUT
= 22µF
–0.40
–50
–25
0
25
50
75
o
TEMPERATURE ( C)
100
125
1.0
1.5
2.0
3525d33 G13
2.5 3.0
V
IN
(V)
3.5
4.0
4.5
3525d33 G14
4
3525d33fb
For more information
www.linear.com/LTC3525D3.3
LTC3525D-3.3
Typical perForMance characTerisTics
Output Voltage Ripple
I
OUT
5mA
I
OUT
40mA
I
OUT
80mA
V
IN
= 1.2V
C
OUT
= 10µF
50µs/DIV
3525d33 G16
T
A
= 25°C unless otherwise noted.
Output Voltage Ripple
I
OUT
5mA
50mV/DIV
I
OUT
40mA
I
OUT
80mA
V
IN
= 1.2V
C
OUT
= 22µF
50µs/DIV
3525d33 G17
50mV/DIV
Output Voltage Ripple
I
OUT
5mA
I
OUT
100mA
I
OUT
190mA
50mV/DIV
50mA Load Step Response
OUTPUT
RIPPLE
50mV/DIV
LOAD
CURRENT
20mA/DIV
V
IN
= 2.4V
C
OUT
= 22µF
50µs/DIV
3525d33 G18
V
IN
= 1.2V
C
OUT
= 22µF
500µs/DIV
3525d33 G21
100mA Load Step Response
OUTPUT
RIPPLE
50mV/DIV
LOAD
CURRENT
50mA/DIV
V
IN
= 2.4V
C
OUT
= 22µF
500µs/DIV
3525d33 G22
3525d33fb
For more information
www.linear.com/LTC3525D3.3
5
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