LTC3526L-2/LTC3526LB-2
550mA 2MHz Synchronous
Step-Up DC/DC Converters
in 2mm
×
2mm DFN
FEATURES
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DESCRIPTION
The LTC
®
3526L-2/LTC3526LB-2 are synchronous, fixed
frequency step-up DC/DC converters with output discon-
nect. Synchronous rectification enables high efficiency in
the low profile 2mm
×
2mm DFN package. Battery life in
single AA/AAA powered products is extended further with
a 680mV start-up voltage and operation down to 500mV
once started.
A switching frequency of 2MHz minimizes solution foot-
print by allowing the use of tiny, low profile inductors
and ceramic capacitors. The current mode PWM design
is internally compensated, reducing external parts count.
The LTC3526L-2 features Burst Mode operation at light
load conditions allowing it to maintain high efficiency over
a wide range of load. The LTC3526LB-2 features fixed
frequency operation for low noise applications. Anti-ring
circuitry reduces EMI by damping the inductor in discon-
tinuous mode. Additional features include a low shutdown
current of under 1μA and thermal shutdown.
The LTC3526L-2/LTC3526LB-2 are housed in a 2mm
×
2mm
×
0.75mm DFN package.
L,
LT, LTC, LTM and Burst Mode are registered trademarks of Linear Technology Corporation.
All other trademarks are the property of their respective owners.
Delivers 3.3V at 100mA from a Single Alkaline/
NiMH Cell or 3.3V at 200mA from Two Cells
V
IN
Start-Up Voltage: 680mV
1.5V to 5.25V V
OUT
Range
Up to 94% Efficiency
Output Disconnect
2MHz Fixed Frequency Operation
V
IN
> V
OUT
Operation
Integrated Soft-Start
Current Mode Control with Internal Compensation
Burst Mode
®
Operation with 9μA I
Q
(LTC3526L-2)
Low Noise PWM Operation (LTC3526LB-2)
Internal Synchronous Rectifier
Logic Controlled Shutdown (I
Q
< 1μA)
Anti-Ring Control
Low Profile (2mm
×
2mm
×
0.75mm) 6-Lead
DFN Package
APPLICATIONS
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Medical Instruments
Noise Canceling Headphones
Wireless Mice
Bluetooth Headsets
TYPICAL APPLICATION
Efficiency and Power Loss vs Load Current
100
2.2μH
90
80
SW
V
IN
1.6V TO 3.2V
4.7μF
OFF ON
V
IN
V
OUT
1.78M
33pF
4.7μF
1M
3526lb2 TA01a
V
IN
= 2.4V
EFFICIENCY
1000
100
POWER LOSS (mW)
EFFICIENCY (%)
V
OUT
3.3V
200mA
70
60
50
40
30
20
10
0
0.01
0.1
1
10
100
0.01
1000
0.1
POWER LOSS
1
10
LTC3526L-2
SHDN
GND
FB
LOAD CURRENT (mA)
3526lb2 TA01b
3526lb2f
1
LTC3526L-2/LTC3526LB-2
ABSOLUTE MAXIMUM RATINGS
(Note 1)
PIN CONFIGURATION
TOP VIEW
SW 1
GND 2
V
IN
3
7
6 V
OUT
5 FB
4
SHDN
V
IN
Voltage ................................................... –0.3V to 6V
SW Voltage
DC............................................................ –0.3V to 6V
Pulsed <100ns ......................................... –0.3V to 7V
SHDN,
FB Voltage ........................................ –0.3V to 6V
V
OUT
............................................................. –0.3V to 6V
Operating Temperature Range
(Notes 2, 5) .............................................. –40°C to 85°C
Storage Temperature Range................... –65°C to 150°C
DC PACKAGE
6-LEAD (2mm 2mm) PLASTIC DFN
T
JMAX
= 125°C,
θ
JA
= 102°C/W (NOTE 6)
EXPOSED PAD (PIN 7) IS GND, MUST BE SOLDERED TO PC BOARD
ORDER INFORMATION
LEAD FREE FINISH
LTC3526LEDC-2#PBF
LTC3526LBEDC-2#PBF
TAPE AND REEL
LTC3526LEDC-2#TRPBF
PART MARKING
LFFC
PACKAGE DESCRIPTION
6-Lead (2mm
×
2mm) Plastic DFN
6-Lead (2mm
×
2mm) Plastic DFN
TEMPERATURE RANGE
–40°C to 85°C
–40°C to 85°C
LTC3526LBEDC-2#TRPBF LFFD
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/
The
l
denotes the specifications which apply over the specified operating
temperature range of –40°C to 85°C, otherwise specifications are at T
A
= 25°C. V
IN
= 1.2V, V
OUT
= 3.3V unless otherwise noted.
PARAMETER
Minimum Start-Up Input Voltage
Input Voltage Range
Output Voltage Adjust Range
Feedback Pin Voltage
Feedback Pin Input Current
Quiescent Current—Shutdown
Quiescent Current—Active
Quiescent Current—Burst
N-Channel MOSFET Switch Leakage Current
P-Channel MOSFET Switch Leakage Current
N-Channel MOSFET Switch On Resistance
P-Channel MOSFET Switch On Resistance
N-Channel MOSFET Current Limit
Current Limit Delay to Output
Maximum Duty Cycle
Minimum Duty Cycle
Switching Frequency
SHDN
Pin Input High Voltage
SHDN
Pin Input Low Voltage
(Note 3)
V
FB
= 1.15V, V
OUT
= 5V
V
FB
= 1.3V
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ELECTRICAL CHARACTERISTICS
CONDITIONS
I
LOAD
= 1mA
MIN
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TYP
0.68
MAX
0.8
5
5.25
UNITS
V
V
V
V
nA
μA
μA
μA
μA
μA
Ω
Ω
mA
ns
%
After Start-Up. (Minimum Voltage is Load Dependent)
0.5
1.5
1.165
1.195
1
0.01
250
9
0.1
0.1
0.4
0.6
1.225
50
1
500
18
5
10
V
FB
= 1.30V
V
SHDN
= 0V, Not Including Switch Leakage, V
OUT
= 0V
Measured on V
OUT
, Nonswitching
Measured on V
OUT
, FB > 1.230V (LTC3526L-2 Only)
V
SW
= 5V
V
SW
= 5V, V
OUT
= 0V
V
OUT
= 3.3V
V
OUT
= 3.3V
l
550
87
1.8
0.8
750
60
90
0
2
2.4
0.3
%
MHz
V
V
3526lb2f
2
LTC3526L-2/LTC3526LB-2
ELECTRICAL CHARACTERISTICS
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 LTC3526LE-2/LTC3526LBE-2 are guaranteed to meet
performance specifications from 0°C to 85°C. Specifications over –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.
Note 4:
Current measurements are made when the output 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 result in device degradation or failure.
Note 6:
Failure to solder the exposed backside of the package to the PC
board ground plane will result in a thermal resistance much higher than
60°C/W.
TYPICAL PERFORMANCE CHARACTERISTICS
Efficiency vs Load Current and V
IN
for V
OUT
= 1.8V (LTC3526L-2)
100
90
80
EFFICIENCY (%)
70
60
50
40
30
20
10
0
0.01
0.1
PLOSS AT V
IN
= 0.9V
PLOSS AT V
IN
= 1.2V
PLOSS AT V
IN
= 1.5V
1
10
100
LOAD CURRENT (mA)
0.1
V
IN
= 0.9V
V
IN
= 1.2V
V
IN
= 1.5V
100
POWER LOSS (mW)
EFFICIENCY (%)
1000
100
90
80
70
60
50
40
30
20
10
0
0.01
0.1
T
A
= 25°C, unless otherwise noted.
No-Load Input Current vs V
IN
(LTC3526L-2)
1000
100
90
100
POWER LOSS (mW)
80
70
I
IN
(μA)
60
50
40
30
20
10
0.5
1.0
1.5
2.0
2.5
V
IN
(V)
3.0
3.5
4.0
4.5
V
OUT
= 3.3V
V
OUT
= 2.5V
V
OUT
= 1.8V
V
OUT
= 5V
Efficiency vs Load Current and V
IN
for V
OUT
= 3.3V (LTC3526L-2)
10
10
V
IN
= 1.2V
V
IN
= 1.8V
1
V
IN
= 2.4V
V
IN
= 3.0V
PLOSS AT V
IN
= 1.2V
PLOSS AT V
IN
= 1.8V
PLOSS AT V
IN
= 2.4V
PLOSS AT V
IN
= 3.0V
1
10
100
LOAD CURRENT (mA)
0.1
1
0.01
1000
0.01
1000
3526lb2 G01
3526lb2 G02
3526lb2 G03
Efficiency vs Load Current and V
IN
for V
OUT
= 5V (LTC3526L-2)
100
90
80
EFFICIENCY (%)
70
60
50
40
30
20
10
0
0.01
0.1
1
10
100
LOAD CURRENT (mA)
0.1
1000
1
10
100
POWER LOSS (mW)
I
OUT
(mA)
1000
400
350
300
250
200
Maximum Output Current vs V
IN
V
OUT
= 3.3V
V
OUT
= 2.5V
V
OUT
= 1.8V
1000
LOAD (Ω)
10000
Minimum Load Resistance
During Start-Up vs V
IN
V
OUT
= 3.3V
V
OUT
= 5V
150
100
50
0
0.5
L = 2.2μH
1.0
1.5
2.0
2.5
V
IN
(V)
3526lb2 G05
100
3.0
3.5
4.0
4.5
10
0.65
0.75
0.85
0.95
V
IN
(V)
1.05
1.15
3526lb2 G06
PLOSS AT V
IN
= 1.2V
PLOSS AT V
IN
= 2.4V
PLOSS AT V
IN
= 3.6V
PLOSS AT V
IN
= 4.2V
V
IN
= 1.2V
V
IN
= 2.4V
V
IN
= 3.6V
V
IN
= 4.2V
3526lb2 G04
3526lb2f
3
LTC3526L-2/LTC3526LB-2
TYPICAL PERFORMANCE CHARACTERISTICS
Start-Up Delay Time vs V
IN
100
90
80
LOAD CURRENT (mA)
70
DELAY (μs)
60
50
40
30
20
10
0
1.0
1.5
2.0
2.5 3.0
V
IN
(V)
3.5
4.0
4.5
5
0
1.0
1.1
1.2
1.3
V
IN
(V)
1.4
1.5
1.6
25
ENTER BURST
20
15
10
35
30
T
A
= 25°C, unless otherwise noted.
Burst Mode Threshold Current
vs V
IN
(LTC3526L-2)
V
OUT
= 2.5V
C
OUT
= 10μF
35
L = 2.2μH
LOAD CURRENT (mA)
30
25
ENTER BURST
20
15
10
5
0
1.0
1.2
1.4
1.6
V
IN
(V)
1.8
2.0
2.2
40
LEAVE BURST
Burst Mode Threshold Current
vs V
IN
(LTC3526L-2)
V
OUT
= 1.8V
C
OUT
= 10μF
L = 2.2μH
LEAVE BURST
3526lb2 G07
3526lb2 G08a
3526lb2 G08b
Burst Mode Threshold Current
vs V
IN
(LTC3526L-2)
60
V
OUT
= 3.3V
C
OUT
= 10μF
50 L = 2.2μH
LOAD CURRENT (mA)
LOAD CURRENT (mA)
40
30
20
10
0
ENTER BURST
LEAVE BURST
70
60
50
Burst Mode Threshold Current
vs V
IN
(LTC3526L-2)
V
OUT
= 5V
C
OUT
= 10μF
L = 2.2μH
FREQUENCY CHANGE (%)
4.5
4
3
2
1
0
–1
–2
–3
1.5
2.0
2.5 3.0
V
IN
(V)
3.5
4.0
Oscillator Frequency Change
vs V
OUT
NORMALIZED TO V
OUT
= 3.3V
LEAVE BURST
40
30
20
10
0
1.0
ENTER BURST
1.0 1.2 1.4 1.6 1.8 2.0 2.2 2.4 2.6 2.8 3.0
V
IN
(V)
3526lb2 G08c
–4
1.5
2.0
2.5
3.0 3.5
V
OUT
(V)
4.0
4.5
5.0
3526lb2 G08d
3526lb2 G09
R
DS(ON)
vs V
OUT
0.90
0.85
0.80
0.75
0.70
R
DS(ON)
(Ω)
0.65
0.60
0.55
0.50
0.45
0.40
0.35
0.30
1.5
2.0
2.5
3.0 3.5
V
OUT
(V)
4.0
4.5
5.0
NMOS
PMOS
FREQUECNY CHANGE (%)
10
8
6
4
2
0
–2
–4
–6
–8
Oscillator Frequency Change
vs Temperature
1.3
NORMALIZED TO 25°C
1.2
NORMALIZED R
DS(ON)
1.1
1.0
0.9
0.8
R
DS(ON)
Change vs Temperature
NORMALIZED TO 25°C
–10
–50
–30
–10 10
30
50
TEMPERATURE (°C)
70
90
0.7
–50
–30
–10 10
30
50
TEMPERATURE (°C)
70
90
3526lb2 G10
3526lb2 G11
3526lb2 G12
3526lb2f
4
LTC3526L-2/LTC3526LB-2
TYPICAL PERFORMANCE CHARACTERISTICS
V
FB
vs Temperature
0.50
0.25
CHANGE IN V
FB
(%)
0
–0.25
–0.50
–0.75
–1.00
20 40 60
–60 –40 –20 0
TEMPERATURE (°C)
NORMALIZED TO 25°C
0.80
0.75
1mA LOAD
0.70
V
IN
(V)
I
Q
(μA)
0.65
0.60
0.55
0.50
–50
9.0
8.5
8.0
7.5
7.0
1.5
T
A
= 25°C, unless otherwise noted.
Burst Mode Quiesent Current
vs V
OUT
(LTC3526L-2)
10.0
9.5
Start-Up Voltage vs Temperature
NO LOAD
80
100
25
0
25
50
TEMPERATURE (°C)
75
100
2.0
2.5
3526lb2 G13
3526lb2 G14
3.0 3.5
V
OUT
(V)
4.0
4.5
5.0
3526lb2 G15
Load Regulation
0.5
0.4
0.3
CHANGE IN V
OUT
(%)
CHANGE IN V
OUT
(%)
0.2
0.1
0
–0.1
–0.2
–0.3
–0.4
–0.5
0.01
0.1
1
10
LOAD (mA)
V
IN
= 0.9V
V
IN
= 1.2V
V
IN
= 1.5V
100
1000
3526lb2 G23
Load Regulation
0.5
0.4
0.3
CHANGE IN V
OUT
(%)
0.2
0.1
0
–0.1
–0.2
–0.3
–0.4
–0.5
0.01
0.1
1
10
LOAD (mA)
V
IN
= 1.2V
V
IN
= 1.8V
V
IN
= 2.4V
100
1000
3526lb2 G24
Load Regulation
0.5
0.4
0.3
0.2
0.1
0
–0.1
–0.2
–0.3
–0.4
–0.5
0.01
0.1
1
10
LOAD (mA)
V
IN
= 1.2V
V
IN
= 2.4V
V
IN
= 3.6V
V
IN
= 4.2V
100
1000
3526lb2 G25
V
OUT
= 1.8V
V
OUT
= 3.3V
V
OUT
= 5V
Fixed Frequency Switching
Waveform and V
OUT
Ripple
SW PIN
2V/DIV
V
OUT
20mV/DIV
AC-COUPLED
V
IN
= 1.2V
200ns/DIV
V
OUT
= 3.3V AT 100mA
C
OUT
= 4.7μF
3526lb2 G16
Burst Mode Waveforms
(LTC3526L-2)
V
OUT
1V/DIV
INPUT
CURRENT
0.2A/DIV
SHDN
PIN
1V/DIV
V
IN
= 1.2V
20μs/DIV
V
OUT
= 3.3V AT 5mA
C
OUT
= 10μF
3526lb2 G17
V
OUT
and I
IN
During Soft-Start
SW PIN
2V/DIV
V
OUT
20mV/DIV
AC-COUPLED
V
OUT
= 3.3V
C
OUT
= 4.7μF
200μs/DIV
3526lb2 G18
3526lb2f
5
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