NOT RECOMMENDED FOR NEW DESIGNS
Contact Linear Technology for Potential Replacement
LTC3526/LTC3526B
500mA 1MHz Synchronous
Step-Up DC/DC Converters
in 2mm
×
2mm DFN
DESCRIPTION
The LTC
®
3526/LTC3526B are synchronous, fixed frequency
step-up DC/DC converters with output disconnect. Syn-
chronous 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 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
LTC3526 features automatic Burst Mode operation at light
load conditions, while the LTC3526B features continuous
switching at light loads. Anti-ringing control circuitry also
reduces EMI concerns by damping the inductor in discon-
tinuous mode. Additional features include a low shutdown
current of under 1μA and thermal shutdown.
The LTC3526/LTC3526B are housed in a 2mm
×
2mm
×
0.75mm DFN package.
For new designs, we recommend the LTC3526L/LTC3526LB.
L,
LT, LTC, LTM and Burst Mode are registered trademarks of Linear Technology Corporation.
All other trademarks are the property of their respective owners.
FEATURES
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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
1.6V 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
Automatic Burst Mode
®
Operation with 9μA
Quiescent Current (LTC3526)
Low Noise PWM Operation (LTC3526B)
Internal Synchronous Rectifier
Logic Controlled Shutdown (I
Q
< 1μA)
Anti-Ringing Control
Low Profile (2mm
×
2mm
×
0.75mm) DFN Package
APPLICATIONS
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Medical Instruments
Flash-Based MP3 Players
Noise Canceling Headphones
Wireless Mice
Bluetooth Headsets
TYPICAL APPLICATION
4.7μH
LTC3526 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
1μF
OFF ON
V
IN
V
OUT
1.78M
FB
1M
V
OUT
3.3V
200mA
4.7μF
EFFICIENCY (%)
70
60
50
40
30
20
0.1
POWER LOSS
1
10
LTC3526
SHDN
GND
3526 TA01a
10
0
0.01
0.1
1
10
100
0.01
1000
3526 TA01b
LOAD CURRENT (mA)
3526bfc
1
LTC3526/LTC3526B
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#PBF
LTC3526BEDC#PBF
TAPE AND REEL
LTC3526EDC#TRPBF
LTC3526BEDC#TRPBF
PART MARKING
LCHW
LCNN
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/
ELECTRICAL CHARACTERISTICS
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
(Note 3)
V
FB
= 1.15V
V
FB
= 1.3V
V
FB
= 1.30V
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.
CONDITIONS
I
LOAD
= 1mA
l
l
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
SHDN
= 0V, Not Including Switch Leakage, V
OUT
= 0V
Measured on V
OUT
, Nonswitching, LTC3526 Only
Measured on V
OUT
, FB > 1.230V
V
SW
= 5V
V
SW
= 5V, V
OUT
= 0V
V
OUT
= 3.3V
V
OUT
= 3.3V
l
l
l
l
500
85
0.7
0.9
700
60
90
0
1
1.3
0.3
%
MHz
V
V
μA
μA
3526bfc
V
SHDN
= 1.2V
V
SHDN
= 3.3V
0.3
1
1
2
2
LTC3526/LTC3526B
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 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)
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
V
IN
= 1.2V
V
IN
= 1.8V
V
IN
= 2.4V
V
IN
= 3.0V
100
POWER LOSS (mW)
I
IN
(μA)
Efficiency vs Load Current and V
IN
for V
OUT
= 3.3V (LTC3526)
1000
100
90
80
70
60
50
40
30
20
10
0.5
No-Load Input Current vs V
IN
V
OUT
= 5V
V
OUT
= 3.3V
V
OUT
= 2.5V
V
OUT
= 1.8V
10
10
1
0.01
1000
PLOSS AT V
IN
= 1.2V
0.1
PLOSS AT V
IN
= 1.8V
PLOSS AT V
IN
= 2.4V
PLOSS AT V
IN
= 3.0V
0.01
0.1
1
10
100
1000
LOAD CURRENT (mA)
3526 G02
1.0
1.5
2.0
2.5
V
IN
(V)
3.0
3.5
4.0
4.5
3526 G04
3526 G01
Efficiency vs Load Current and V
IN
for V
OUT
= 5V (LTC3526)
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
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
Minimum Load Resistance
During Start-Up vs V
IN
LOAD (Ω)
4.0
4.5
100
V
OUT
= 5V
150
100
50
0
0.5
L = 4.7μH
1.0
1.5
2.0
2.5
V
IN
(V)
3526 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)
3526 G03
3.0
3.5
10
0.85
0.95
1.05
V
IN
(V)
1.15
1.25
3526 G06
3526bfc
3
LTC3526/LTC3526B
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
1.25
V
IN
(V)
1.5
3526 G08a
Burst Mode Threshold Current
vs V
IN
30
25
20
LEAVE BURST
15
ENTER BURST
10
5
V
OUT
= 1.8V
C
OUT
= 10μF
L = 4.7μH
LOAD CURRENT (mA)
40
Burst Mode Threshold Current
vs V
IN
V
OUT
= 2.5V
35 C
OUT
= 10μF
L = 4.7μH
30
25
LEAVE BURST
20
15
ENTER BURST
10
5
0
1
1.25
V
IN
(V)
3526 G08b
1.5
1.75
3526 G07
Burst Mode Threshold Current
vs V
IN
50
V
OUT
= 3.3V
45 C
OUT
= 10μF
L = 4.7μH
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
3526 G08c
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 = 4.7μH
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 3.3
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
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
3526 G10
3526 G11
3526 G12
3526bfc
4
LTC3526/LTC3526B
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 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
3526 G13
3526 G14
3526 G15
Fixed Frequency Switching
Waveform and V
OUT
Ripple
SW PIN
2V/DIV
V
OUT
10mV/DIV
AC COUPLED
500ns/DIV
V
IN
= 1.2V
V
OUT
= 3.3V AT 100mA
C
OUT
= 10μF
3526 G16
Burst Mode Waveforms
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)
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
3526bfc
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