FEATURES
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LTC3526L/LTC3526LB
550mA 1MHz Synchronous
Step-Up DC/DC Converters
in 2mm
×
2mm DFN
DESCRIPTION
The LTC
®
3526L/LTC3526LB 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 1MHz 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 features Burst Mode operation at light load
conditions allowing it to maintain high efficiency over a
wide range of load. The LTC3526LB features fixed frequency
operation for low noise applications. Anti-ring circuitry
reduces EMI by damping the inductor in discontinuous
mode. Additional features include a low shutdown current
of under 1μA and thermal shutdown.
The LTC3526L/LTC3526LB are housed in a 2mm
×
2mm
×
0.75mm DFN package.
, 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
1MHz 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)
Low Noise PWM Operation (LT3526LB)
Internal Synchronous Rectifier
Logic Controlled Shutdown (I
Q
< 1μA)
Anti-Ring Control
Low Profile (2mm
×
2mm
×
0.75mm)
DFN-6 Package
APPLICATIONS
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Medical Instruments
Noise Canceling Headphones
Wireless Mice
Bluetooth Headsets
TYPICAL APPLICATION
4.7μH
Efficiency and Power Loss vs Load Current
100
90
80
V
IN
= 2.4V
EFFICIENCY
100
POWER LOSS (mW)
1000
SW
V
IN
1.6V TO 3.2V
4.7μF
OFF ON
V
IN
V
OUT
1.78M
EFFICIENCY (%)
V
OUT
3.3V
200mA
4.7μF
1M
3526 TA01a
70
60
50
40
30
20
10
0
0.01
0.1
1
10
100
0.01
1000
3526 TA01b
10
POWER LOSS
LTC3526L
SHDN
GND
FB
1
0.1
LOAD CURRENT (mA)
3526lfb
1
LTC3526L/LTC3526LB
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
⎯
S
⎯
H
⎯
D
⎯
N, 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
= 60°C/W (NOTE 6)
EXPOSED PAD (PIN 7) IS GND, MUST BE SOLDERED TO PC BOARD
ORDER INFORMATION
LEAD FREE FINISH
LTC3526LEDC#PBF
LTC3526LBEDC#PBF
TAPE AND REEL
LTC3526LEDC#TRPBF
LTC3526LBEDC#TRPBF
PART MARKING
LCSS
LCST
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
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
●
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
⎯
S
⎯
H
⎯
D
⎯
N Pin Input Low Voltage
(Note 3)
V
FB
= 1.15V
V
FB
= 1.3V
●
●
●
ELECTRICAL CHARACTERISTICS
I
LOAD
= 1mA
CONDITIONS
After Start-Up. (Minimum Voltage is Load Dependent)
●
●
●
MIN
0.5
1.5
1.165
TYP
0.68
MAX
0.8
5
5.25
UNITS
V
V
V
V
nA
μA
μA
μA
μA
μA
Ω
Ω
mA
ns
%
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
⎯
S
⎯
H
⎯
D
⎯
N
= 0V, Not Including Switch Leakage, V
OUT
= 0V
Measured on V
OUT
, Nonswitching
Measured on V
OUT
, FB > 1.230V (LTC3526L Only)
V
SW
= 5V
V
SW
= 5V, V
OUT
= 0V
V
OUT
= 3.3V
V
OUT
= 3.3V
●
550
87
0.75
0.8
750
60
90
0
1
1.25
0.3
%
MHz
V
V
3526lfb
2
LTC3526L/LTC3526LB
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 reli-
ability and lifetime.
Note 2:
The LTC3526LE/LTC3526LBE 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)
100
90
80
EFFICIENCY (%)
70
60
50
40
30
20
10
0
0.01
0.1
PLOSS AT V
IN
= 1.0V
PLOSS AT V
IN
= 1.2V
PLOSS AT V
IN
= 1.5V
1
10
100
LOAD CURRENT (mA)
0.1
1
V
IN
= 1.0V
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
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
V
IN
= 1.2V
V
IN
= 1.8V
V
IN
= 2.4V
V
IN
= 3.0V
100
POWER LOSS (mW)
Efficiency vs Load Current and V
IN
for V
OUT
= 3.3V (LTC3526L)
1000
100
90
80
70
I
IN
(μA)
60
50
40
30
20
No-Load Input Current vs V
IN
(LTC3526L)
V
OUT
= 5V
V
OUT
= 3.3V
V
OUT
= 2.5V
V
OUT
= 1.8V
10
10
1
0.01
1000
0.01
1000
10
0.5
1.0
1.5
2.0
2.5
V
IN
(V)
3.0
3.5
4.0
4.5
3526 G01
3526 G02
3526 G04
Efficiency vs Load Current and V
IN
for V
OUT
= 5V (LTC3526L)
100
90
80
EFFICIENCY (%)
70
60
50
40
30
20
10
0
0.01
0.1
10
V
IN
= 1.2V
V
IN
= 2.4V
V
IN
= 3.6V 1
V
IN
= 4.2V
PLOSS AT V
IN
= 1.2V
PLOSS AT V
IN
= 2.4V
PLOSS AT V
IN
= 3.6V
PLOSS AT V
IN
= 4.2V
1
10
100
LOAD CURRENT (mA)
0.1
100
300
I
OUT
(mA)
250
200
POWER LOSS (mW)
1000
400
350
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 = 4.7μH
1.0
1.5
2.0
2.5
V
IN
(V)
3.0
3.5
4.0
4.5
100
0.01
1000
10
0.65
0.75
0.85
0.95
V
IN
(V)
1.05
1.15
3526 G06
3526 G03
3526 G05
3526lfb
3
LTC3526L/LTC3526LB
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
0
2.5 3.0
V
IN
(V)
3.5
4.0
4.5
1.0
1.25
V
IN
(V)
1.5
3526 G08a
Burst Mode Threshold Current
vs V
IN
(LTC3526L)
30
25
20
ENTER BURST
15
10
5
V
OUT
= 1.8V
C
OUT
= 10μF
L = 4.7μH
30
LEAVE BURST
Burst Mode Threshold Current
vs V
IN
(LTC3526L)
V
OUT
= 2.5V
C
OUT
= 10μF
25 L = 4.7μH
LEAVE BURST
LOAD CURRENT (mA)
20
ENTER BURST
15
10
5
0
1.0
1.25
1.5
V
IN
(V)
1.75
2.0
3526 G08b
3526 G07
Burst Mode Threshold Current
vs V
IN
(LTC3526L)
40
V
OUT
= 3.3V
35 C
OUT
= 10μF
L = 4.7μH
50
LEAVE BURST
40
LOAD CURRENT (mA)
Burst Mode Threshold Current
vs V
IN
(LTC3526L)
3
V
OUT
= 5V
C
OUT
= 10μF
L = 4.7μH
FREQUENCY CHANGE (%)
LEAVE BURST
30
2
1
0
–1
–2
Oscillator Frequency Change
vs V
OUT
NORMALIZED TO V
OUT
= 3.3V
LOAD CURRENT (mA)
30
25
20
15
10
5
0
1.0
1.5
2.0
V
IN
(V)
2.5
3.0
3526 G08c
ENTER BURST
20
ENTER BURST
10
0
1.0
1.5
2.0
2.5 3.0
V
IN
(V)
3.5
4.0
4.5
–3
1.5
2.0
2.5
3.0 3.5
V
OUT
(V)
4.0
4.5
5.0
3526 G08d
3526 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
NORMALIZED TO 25°C
1.3
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
3526 G10
3526 G11
3526 G12
3526lfb
4
LTC3526L/LTC3526LB
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)
0.80
NORMALIZED TO 25°C
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
9.5
Start-Up Voltage vs Temperature
10.0
Burst Mode Quiesent Current
vs V
OUT
(LTC3526L)
NO LOAD
80
100
25
0
25
50
TEMPERATURE (°C)
75
100
3526 G14
2.0
2.5
3.0 3.5
V
OUT
(V)
4.0
4.5
5.0
3526 G13
3526 G15
Fixed Frequency Switching
Waveform and V
OUT
Ripple
SW PIN
2V/DIV
V
OUT
10mV/DIV
AC COUPLED
V
IN
= 1.2V
500ns/DIV
V
OUT
= 3.3V AT 100mA
C
OUT
= 10μF
3526 G16
Burst Mode Waveforms
(LTC3526L)
SW PIN
2V/DIV
V
OUT
20mV/DIV
AC COUPLED
INDUCTOR
CURRENT
0.2A/DIV
V
IN
= 1.2V
V
OUT
= 3.3V
C
OUT
= 10μF
10μs/DIV
3526 G17
V
OUT
and I
IN
During Soft-Start
V
OUT
1V/DIV
INPUT
CURRENT
0.2A/DIV
SHDN
PIN
1V/DIV
V
OUT
= 3.3V
C
OUT
= 10μF
200μs/DIV
3526 G18
Load Step Response (from Burst
Mode Operation) (LTC3526L)
V
OUT
100mV/DIV
AC COUPLED
LOAD
CURRENT
50mA/DIV
V
IN
= 3.6V
100μs/DIV
V
OUT
= 5V
20mA TO 170mA STEP
C
OUT
= 10μF
3526 G19
Load Step Response
(Fixed Frequency)
V
OUT
100mV/DIV
AC COUPLED
LOAD
CURRENT
50mA/DIV
V
IN
= 3.6V
100μs/DIV
V
OUT
= 5V
50mA TO 150mA STEP
C
OUT
= 10μF
3526 G20
3526lfb
5
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