LTC3525L-3
400mA Micropower
Synchronous Step-Up DC/DC
Converter with Output Disconnect
FEATURES
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DESCRIPTION
The LTC
®
3525L-3 is a high efficiency synchronous step-
up DC/DC converter with output disconnect that can
start up with an input as low as 0.7V. It offers a compact,
high efficiency alternative to charge pumps in single
cell or dual cell alkaline applications. Only three small
external components are required. The LTC3525L-3
generates a fixed 3V output voltage.
The device includes a 0.5 N-channel MOSFET switch
and a 0.85 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 <1µA shutdown current, anti-
ringing control and thermal shutdown. The LTC3525L-3
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.
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Start-Up at 0.7V Typical, 0.88V Guaranteed
Up to 95% Efficiency
Output Disconnect and Inrush Current Limit
3V Fixed Output Voltage
Delivers 65mA at 3V from a 1V Input or 160mA
from a 1.8V Input
Burst Mode
®
Operation: I
Q
= 7µA
V
IN
: 0.5V to 4.5V
Only Three External Components
V
IN
> V
OUT
Operation
<1µA Shutdown Current
Anti-Ringing Control
Short-Circuit and Overtemperature Protection
Tiny 6-Pin SC70 Package
APPLICATIONS
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MP3 Players
Portable Instruments
Glucose Meters
Digital Cameras
TYPICAL APPLICATION
LTC3525L-3 Efficiency and Power
Loss vs Load Current
L1*
10µH
100
90
80
EFFICIENCY (%)
SW
V
OUT
GND
V
OUT
3V
65mA
10µF
70
60
50
40
30
20
0.01
0.1
1
10
LOAD (mA)
V
IN
= 2.4V
V
IN
= 1.2V
100
0.1
EFFICIENCY
1
10
POWER LOSS (mW)
100
V
IN
0.9V TO 1.6V
OFF ON
1µF
LTC3525L-3
V
IN
SHDN
GND
POWER LOSS
*MURATA LQH32CN100K53
3525 TA01
0.01
1000
LT3525 • TA02
3525lfa
1
LTC3525L-3
(Note 1)
ABSOLUTE MAXIMUM RATINGS
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 Temperature Range
(Notes 2, 5) ..............................................–40°C to 85°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
= 120°C/W ON BOARD OVER GROUND PLANE
ORDER INFORMATION
LEAD FREE FINISH
LTC3525LESC6-3#PBF
TAPE AND REEL
PART MARKING
PACKAGE DESCRIPTION
6-Lead Plastic SC70
TEMPERATURE RANGE
–40°C to 85°C
LTC3525LESC6-3#TRPBF LCPY
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
The
l
denotes the specifications which apply over the full operating temperature range, otherwise specifications are at T
A
= 25°C.
V
IN
= 1.2V, V
SHDN
= 1.2V, V
OUT
= 3V unless otherwise noted.
PARAMETER
Minimum Input Start-Up Voltage
Output Voltage
Quiescent Current, V
OUT
Quiescent Current, V
IN
Quiescent Current, V
IN
– Shutdown
NMOS Switch Leakage Current
PMOS Switch Leakage Current
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 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 LTC3525LE-3 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
correlation with statistical process controls.
Note 3:
Specification is guaranteed by design and not 100% tested in
production.
CONDITIONS
(Note 6)
SHDN
= V
IN
(Note 4)
SHDN
= V
IN
(Note 4)
SHDN
= 0V, V
OUT
= 0V
Not Including Switch Leakage
V
IN
= V
OUT
= V
SW
= 5V,
SHDN
= 0V
V
IN
= V
SW
= 5V, V
OUT
= 0V,
SHDN
= 0V
(Note 3)
(Note 3)
0.4
0.3
l
MIN
2.91
TYP
0.7
3.00
7
0.5
0.1
0.1
0.1
0.5
0.85
0.45
0.5
0.01
MAX
0.88
3.09
15
3
1
3
6
UNITS
V
V
µA
µA
µA
µA
µA
A
0.88
1
V
µA
Note 4:
Current Measurements are performed when the LTC3525L-3 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.
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LTC3525L-3
TYPICAL PERFORMANCE CHARACTERISTICS
T
A
= 25°C unless otherwise noted.
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
30
25
20
15
10
5
0
0.60 0.65 0.70 0.75 0.80 0.85 0.90 0.95 1.00
V
IN
(V)
3525L G02
Maximum Startup Load vs V
IN
(Resistive Load)
30
25
20
I
IN
(µA)
15
10
5
0
No-Load Input Current vs V
IN
1.0
1.5
V
IN
(V)
2.0
2.5
3525L G01
1.0
1.5
2.0
V
IN
(V)
2.5
3.0
3525L 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
= 2.4V
V
IN
= 1.2V
100
0.1
10
POWER LOSS (mW)
100
2.5
2.0
1.5
1.0
0.5
0
–0.5
–1.0
–1.5
–2.0
–2.5
Load Regulation
V
IN
= 1.2V
40
35
BURST FREQUENCY (kHz)
30
25
20
15
10
5
0
10
20
30 40 50
LOAD (mA)
60
70
80
0
Light Load Burst Frequency
vs Load
C
OUT
= 22µF
C
OUT
= 10µF
POWER LOSS
C
OUT
= 10µF
C
OUT
= 22µF
0.01
1000
0.1
1
LOAD (mA)
10
3525L G12
3525L G24
3525L G06
V
OUT
Variation vs Temperature
(Normalized to 25°C)
0.4
0.3
SWITCHING DELAY (µs)
CHANGE IN V
OUT
(%)
0.2
0.1
0
–0.1
–0.2
–0.3
–0.4
–40–30–20–10 0 10 20 30 40 50 60 70 80
TEMPERATURE (°C)
3525L G13
Startup Delay Coming Out of
Shutdown
120
100
80
60
40
20
0
1.0
1.5
2.0
2.5 3.0
V
IN
(V)
3.5
4.0
4.5
3525L G14
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LTC3525L-3
TYPICAL PERFORMANCE CHARACTERISTICS
T
A
= 25°C unless otherwise noted.
Input Current and V
OUT
at Start-Up
V
IN
= 1.2V
I
OUT
5mA
I
OUT
40mA
I
OUT
80mA
100µs/DIV
3525L G15
Output Voltage Ripple
V
OUT
1V/DIV
INPUT
CURRENT
100mA/DIV
50mV/DIV
V
IN
= 1.2V
C
OUT
= 10µF
50µs/DIV
3525L G16
Output Voltage Ripple
I
OUT
5mA
I
OUT
40mA
I
OUT
80mA
V
IN
= 1.2V
C
OUT
= 22µF
50µs/DIV
3525L G17
Output Voltage Ripple
I
OUT
5mA
50mV/DIV
I
OUT
100mA
I
OUT
190mA
50mV/DIV
V
IN
= 2.4V
C
OUT
= 22µF
50µs/DIV
3525L G18
50mA Load Step Response
100mA Load Step Response
OUTPUT
RIPPLE
50mV/DIV
LOAD
CURRENT
20mA/DIV
V
IN
= 1.2V
C
OUT
= 22µF
500µs/DIV
3525L G21
OUTPUT
RIPPLE
50mV/DIV
LOAD
CURRENT
50mA/DIV
V
IN
= 2.4V
C
OUT
= 22µF
500µs/DIV
3525L G22
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LTC3525L-3
PIN FUNCTIONS
SHDN
(Pin 1):
Logic-Controlled Shutdown Input. Connect
to a voltage >0.88V to enable the LTC3525L-3. Connect to
a voltage <0.3V to disable the LTC3525L-3.
GND (Pins 2, 5):
Ground.
V
IN
(Pin 3):
Input Voltage. The LTC3525L-3 is powered
from V
IN
until V
OUT
exceeds V
IN
. Once V
OUT
is greater
than (V
IN
+ 0.2V typical), it is powered from V
OUT
. Place a
ceramic bypass capacitor from V
IN
to GND. A minimum
value of 1µF is recommended.
V
OUT
(Pin 4):
Output Voltage Sense and the Output of the
Synchronous Rectifier. Connect the output filter capacitor
from V
OUT
to GND, close to the IC. A minimum value of
10µF ceramic is recommended. Use 22µF for reduced
output ripple. The output disconnect feature disconnects
V
OUT
from V
IN
when
SHDN
is <0.3V.
SW (Pin 6):
Switch Pin. Connect an inductor from this
pin to V
IN
. An internal antiringing resistor is connected
across SW and V
IN
after the inductor current has dropped
to zero to minimize EMI.
BLOCK DIAGRAM
V
IN
10µH
6
V
OUT
V
SEL
V
BEST
VB
WELL
SWITCH
4
SHDN
1
SHUTDOWN
SHUTDOWN GATE DRIVERS
AND
ANTI-CROSS
CONDUCTION
OFFSET
V
REF
UVLO
V
REF
UVLO
I
PK
SW
V
IN
3
1µF
V
OUT
V
OUT
10µF
+
–
ADJUST
I
PK
COMPARATOR
START-UP
LOGIC
I
VAL
SHUTDOWN
THERMAL
SHUTDOWN
TSD
WAKE
I
VALLEY
COMPARATOR
INTEGRATOR
ADJUST
5
GND
2
GND
SLEEP
COMPARATOR
+
–
+
–
+
–
OFFSET
+
–
ADJUST
FB
V
REF
3525L BD
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