LTC3526-2/LTC3526B-2
500mA 2MHz Synchronous
Step-Up DC/DC Converters
in 2mm
×
2mm DFN
FEATURES
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DESCRIPTION
The LTC
®
3526-2/LTC3526B-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 an 850mV 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 LTC3526-2 features Burst Mode operation at light load
conditions, while the LTC3526B-2 features continuous
switching. Anti-ring circuitry eliminates EMI concerns by
damping the inductor in discontinuous mode. Additional
features include a low shutdown current of under 1μA and
thermal shutdown.
The LTC3526-2/LTC3526B-2 are housed in a 6-pin
2mm
×
2mm
×
0.75mm DFN package.
L,
LT, LTC and LTM are registered trademarks of Linear Technology Corporation. Burst Mode
is a trademark of Linear Technology Corporation. All other trademarks are the property of their
respective owners. Patents pending.
Delivers 3.3V at 100mA from a Single Alkaline/
NiMH Cell or 3.3V at 200mA from Two Cells
V
IN
Start-Up Voltage: 850mV
V
IN
Operating Range: 0.5V to 5V
1.6V 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 Quiescent Current
(LTC3526-2)
Low Noise PWM Operation (LTC3526B-2)
Internal Synchronous Rectifier
Logic Controlled Shutdown (I
Q
< 1μA)
Anti-Ringing Control
Low Profile (2mm
×
2mm
×
0.75mm) DFN-6 Package
APPLICATIONS
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Medical Instruments
Flash-Based MP3 Players
Noise Canceling Headphones
Wireless Mice
Bluetooth Headsets
TYPICAL APPLICATION
2.2μH
SW
V
IN
1.6V TO 3.2V
1μF
OFF ON
V
IN
V
OUT
1.78M
4.7μF
1M
35262b2fA01a
LTC3526-2 Efficiency and Power Loss vs Load Current
100
90
80
EFFICIENCY (%)
V
IN
= 2.4V
EFFICIENCY
100
POWER LOSS (mW)
1000
V
OUT
3.3V
200mA
70
60
50
40
30
20
10
0
0.01
0.1
1
10
100
0.01
1000
35262b2f TA01b
10
POWER LOSS
LTC3526-2
SHDN
GND
FB
1
0.1
LOAD CURRENT (mA)
35262b2fa
1
LTC3526-2/LTC3526B-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 (Note 2).... –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
LTC3526EDC-2#PBF
LTC3526BEDC-2#PBF
TAPE AND REEL
LTC3526EDC-2#TRPBF
LTC3526BEDC-2#TRPBF
PART MARKING
LCNM
LCNP
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
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
Output Voltage Adjust Range
0°C to 85°C
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
SHDN
Pin Input Current
V
SHDN
= 1.2V
V
SHDN
= 3.3V
0.3
1
(Note 3)
V
FB
= 1.15V, V
OUT
= 5V
V
FB
= 1.3V
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ELECTRICAL CHARACTERISTICS
I
LOAD
= 1mA
CONDITIONS
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MIN
1.7
1.6
1.165
TYP
0.85
MAX
1
5.25
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
SHDN
= 0V, Not Including Switch Leakage, V
OUT
= 0V
Measured on V
OUT
, Nonswitching
Measured on V
OUT
, FB > 1.230V (LTC3526-2 Only)
V
SW
= 5V
V
SW
= 5V, V
OUT
= 0V
V
OUT
= 3.3V
V
OUT
= 3.3V
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500
85
1.8
0.9
700
60
90
0
2
2.4
0.3
1
2
%
MHz
V
V
μA
μA
35262b2fa
2
LTC3526-2/LTC3526B-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 LTC3526E-2 is 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 (LTC3526-2)
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
0.1
PLOSS AT V
IN
= 2.4V
PLOSS AT V
IN
= 3.0V
1
10
100
LOAD CURRENT (mA)
0.01
1000
1
V
IN
= 1.2V
V
IN
= 2.4V
V
IN
= 3.0V
100
POWER LOSS (mW)
Efficiency vs Load Current and V
IN
for V
OUT
= 3.3V (LTC3526-2)
1000
100
90
80
70
I
IN
(μA)
60
50
40
30
20
No-Load Input Current vs V
IN
V
OUT
= 5V
V
OUT
= 3.3V
V
OUT
= 2.5V
V
OUT
= 1.8V
10
10
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
35262b2f G01
35262b2f G02
35262b2f G04
Efficiency vs Load Current and V
IN
for V
OUT
= 5V (LTC3526-2)
100
90
80
EFFICIENCY (%)
70
60
50
40
30
20
10
0
0.01
10
V
IN
= 1.2V
V
IN
= 2.4V
V
IN
= 3.6V 1
V
IN
= 4.2V
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
LOAD (Ω)
1000
Minimum Load Resistance
During Start-Up vs V
IN
100
V
OUT
= 5V
150
100
50
0
0.5
L = 2.2μH
1.0
1.5
2.0
2.5
V
IN
(V)
35262b2f G05
PLOSS AT V
IN
= 1.2V
0.1
PLOSS AT V
IN
= 2.4V
PLOSS AT V
IN
= 3.6V
PLOSS AT V
IN
= 4.2V
0.01
0.1
1
10
100
1000
LOAD CURRENT (mA)
35262b2f
3.0
3.5
4.0
4.5
10
0.85
0.95
1.05
V
IN
(V)
1.15
1.25
35262b2f
35262b2fa
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LTC3526-2/LTC3526B-2
TYPICAL PERFORMANCE CHARACTERISTICS
Start-Up Delay Time vs V
IN
100
90
80
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
1.25
V
IN
(V)
1.5
35262b2f G08a
Burst Mode Threshold Current
vs V
IN
30
25
LOAD CURRENT (mA)
20
LEAVE BURST
15
ENTER BURST
10
5
V
OUT
= 1.8V
C
OUT
= 10μF
L = 2.2μH
LOAD CURRENT (mA)
40
Burst Mode Threshold Current
vs V
IN
V
OUT
= 2.5V
35 C
OUT
= 10μF
L = 2.2μH
30
25
LEAVE BURST
20
15
ENTER BURST
10
5
0
1
1.25
V
IN
(V)
35262b2f
1.5
1.75
35262b2f
Burst Mode Threshold Current
vs V
IN
50
V
OUT
= 3.3V
45 C
OUT
= 10μF
L = 2.2μH
40
LOAD CURRENT (mA)
35
30
25
20
15
10
5
0
1.0
1.5
2.0
V
IN
(V)
2.5
3.0
35262b2f
Burst Mode Threshold Current
vs V
IN
60
50
LOAD CURRENT (mA)
40
LEAVE BURST
30
20
ENTER BURST
10
0
1.0
V
OUT
= 5V
C
OUT
= 10μF
L = 2.2μH
FREQUENCY CHANGE (%)
2
1
0
–1
–2
–3
–4
–5
1.5
2.0
2.5 3.0
V
IN
(V)
3.5
4.0
4.5
Oscillator Frequency Change
vs V
OUT
NORMALIZED TO 3.3V
LEAVE BURST
ENTER BURST
–6
1.5
2.0
2.5
3.0 3.5
V
OUT
(V)
4.0
4.5
5.0
35262b2f G08d
35262b2f
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
FREQUENCY 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
35262b2f
35262b2f G11
35262b2f G12
35262b2fa
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LTC3526-2/LTC3526B-2
TYPICAL PERFORMANCE CHARACTERISTICS
V
FB
vs Temperature
0.50
0.25
CHANGE IN V
FB
(%)
0
V
IN
(V)
–0.25
–0.50
–0.75
–1.00
20 40 60
–60 –40 –20 0
TEMPERATURE (˚C)
1.00
NORMALIZED TO 25˚C
0.95
0.90
I
Q
(μA)
0.85
0.80
0.75
0.70
–50
Start-Up Voltage vs Temperature
LOAD = 1mA
10.0
9.5
9.0
8.5
8.0
7.5
7.0
1.5
Burst Mode Quiescent Current
vs V
OUT
80
100
–30
–10 10
30 –50
TEMPERATURE (°C)
70
90
2.0
2.5
3.0 3.5
V
OUT
(V)
4.0
4.5
5.0
35262b2f
35262b2f G14
35262b2f
Fixed Frequency Switching
Waveform and V
OUT
Ripple
Burst Mode Waveforms
V
OUT
1V/DIV
INPUT
CURRENT
0.2A/DIV
SHDN PIN
1V/DIV
20μs/DIV
V
IN
= 1.2V
V
OUT
= 3.3V AT 5mA
C
OUT
= 10μF
35262b2
V
OUT
and I
IN
During Soft-Start
SW PIN
2V/DIV
V
OUT
10mV/DIV
AC COUPLED
200ns/DIV
35262b2f
SW PIN
2V/DIV
V
OUT
50mV/DIV
AC COUPLED
V
IN
= 1.2V
V
OUT
= 3.3V AT 50mA
C
OUT
= 4.7μF
V
OUT
= 3.3V
C
OUT
= 10μF
200μs/DIV
35262b2f
Load Step Response (from Burst
Mode Operation)
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
35262b2f
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
35262b2f
35262b2fa
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