LTC3527/LTC3527-1
Dual 800mA/400mA,
1.2MHz/2.2MHz Synchronous
Step-Up DC/DC Converters
FEATURES
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DESCRIPTION
The LTC
®
3527/LTC3527-1 are dual high efficiency, step-up
DC/DC converters in a space saving 16-lead 3mm
×
3mm
QFN package. Battery life is maximized with a 700mV start-
up voltage and operation down to 500mV once started.
The
SHDN
and PGOOD pins enable the converters to be
sequenced or started together.
The LTC3527/LTC3527-1 limit inrush current during start-
up. Selectable 1.2MHz or 2.2MHz operation provides a
choice between the highest efficiency or smallest solu-
tion footprint. The current mode PWM design is internally
compensated reducing external parts count. Burst Mode
operation or fixed frequency operation is selectable via the
MODE pin. Anti-ring circuitry reduces EMI in discontinuous
mode. This device also features thermal shutdown.
True output disconnect allows the output to be completely
open in shutdown. The LTC3527-1 actively discharges
V
OUT1
or V
OUT2
when its respective
SHDN
goes low. Qui-
escent current in shutdown is less than 2μA.
L,
LT, LTC, LTM, 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.
Dual Synchronous Step-Up DC/DC Converters
Delivers 3.3V at 200mA/100mA from one Alkaline/
NiMH Cell, or 3.3V at 400mA/200mA from Two Cells
V
IN
Start-Up Voltage: 700mV
0.5V to 5V V
IN
Range After Start-Up
1.6V to 5.25V V
OUT
Range
Output Disconnect in Shutdown
V
IN
> V
OUT
Operation
1.2MHz or 2.2MHz Operation
Up to 94% Efficiency
12μA Quiescent Current in Burst Mode
®
Operation
Inrush Current Limiting and Soft-Start
Internal Synchronous Rectifiers
Logic-Controlled Shutdown (< 2μA)
Quick V
OUT
Discharge (LTC3527-1)
16-Lead, 0.75mm
×
3mm
×
3mm QFN Package
APPLICATIONS
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MP3/Personal Media Players
Noise Canceling/Bluetooth Headsets
Wireless Mice
Portable Medical Instruments
TYPICAL APPLICATION
Two-Cell Alkaline to 3.3V/1.8V Synchronous Boost Converters
+
1.6V to 3.2V
V
IN
4.7μF
4.7μH
V
OUT
3.3V
150mA
V
IN1
SW1
V
OUT1
4.7μF
1.78M
1M
15pF
FB1
ON
OFF
ON
OFF
35271 TA01
1.2MHz Efficiency and Power Loss
100
BURST
90 EFFICIENCY
1000
V
IN
V
IN2
SW2
V
OUT2
4.7μH
EFFICIENCY (%)
V
OUT
1.8V
150mA
80
70
60
50
40
30
POWER
20 LOSS
10
BURST
0
0.1
0.01
FIXED
FREQUENCY
100
POWER LOSS (mW)
10
LTC3527
FB2
PGOOD2
SHDN2
GND
F
SEL
PGOOD1
SHDN1
MODE
15pF
619k
1.21M
1
4.7μF
0.1
V
IN
= 2.4V
V
OUT1
= 3.3V
1
10
100
LOAD CURRENT (mA)
0.01
1000
35271 TA01b
35271fc
1
LTC3527/LTC3527-1
ABSOLUTE MAXIMUM RATINGS
(Note 1)
PIN CONFIGURATION
TOP VIEW
PGOOD1
PGOOD2
12
SHDN2
17
PGND
11 FB2
10 FSEL
9
5
V
OUT1
6
SW1
7
SW2
8
V
OUT2
V
IN2
GND
V
IN
V
IN
, V
IN1
, V
IN2
Voltage ................................. –0.3V to 6V
SW1, SW2 Voltage (DC) .............................. –0.3V to 6V
(Pulsed < 100ns) ..................................... –0.3V to 7V
SHDN1, SHDN2,
FB1, FB2 Voltage ............... –0.3V to 6V
V
OUT1
, V
OUT2
................................................ –0.3V to 6V
MODE, FSEL, PGOOD1, PGOOD2................. –0.3V to 6V
Operating Temperature (Notes 2, 5) .........–40°C to 85°C
Junction Temperature ........................................... 125°C
Storage Temperature Range...................–65°C to 125°C
16 15 14 13
SHDN1
1
FB1 2
MODE 3
V
IN1
4
UD PACKAGE
16-LEAD (3mm 3mm) PLASTIC QFN
T
JMAX
= 125°C,
θ
JA
= 68°C/W
EXPOSED PAD (PIN 17) IS PGND, MUST BE SOLDERED TO PCB
ORDER INFORMATION
LEAD FREE FINISH
LTC3527EUD#PBF
LTC3527EUD-1#PBF
LEAD BASED FINISH
LTC3527EUD
LTC3527EUD-1
TAPE AND REEL
LTC3527EUD#TRPBF
LTC3527EUD-1#TRPBF
TAPE AND REEL
LTC3527EUD#TR
LTC3527EUD-1#TR
PART MARKING
LDDK
LCXP
PART MARKING
LDDK
LCXP
PACKAGE DESCRIPTION
16-Lead (3mm
×
3mm) Plastic QFN
16-Lead (3mm
×
3mm) Plastic QFN
PACKAGE DESCRIPTION
16-Lead (3mm
×
3mm) Plastic QFN
16-Lead (3mm
×
3mm) Plastic QFN
TEMPERATURE RANGE
–40°C to 85°C
–40°C to 85°C
TEMPERATURE RANGE
–40°C to 85°C
–40°C to 85°C
Consult LTC Marketing for parts specified with wider operating temperature ranges.
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 Voltage
Output Voltage Adjust Range
The
l
denotes the specifications which apply over the full operating
temperature range, –40
°
C to 85
°
C. V
IN
= V
IN1
= V
IN2
= 1.2V, V
OUT1
= V
OUT2
= 3.3V, T
A
= 25°C, unless otherwise noted.
CONDITIONS
I
LOAD
= 1mA
V
OUT1
V
OUT1
V
OUT2
V
OUT2
V
IN
= 1V to 5V
l
l
l
MIN
1.7
1.6
1.7
1.6
TYP
0.7
MAX
0.88
5.25
5.25
5.25
5.25
UNITS
V
V
V
V
V
%/V
V
nA
μA
μA
Line Regulation
Feedback Voltage FB1, FB2
Feedback Input Current FB1, FB2
Quiescent Current: Shutdown
Quiescent Current: Burst Mode Operation
Quiescent Current: Active
NMOS Switch Leakage Current (LTC3527)
0.005
1.176
1.20
1
0.1
12
500
0.1
900
10
1.224
50
2
V
FB1,2
= 1.20V
V
SHDN1
= V
SHDN2
= 0V, Not Including Switch
Leakage, V
OUT1
= V
OUT2
= 0V
Measured on V
OUT
, V
FB1
= V
FB2
= 1.5V
V
FB1
= V
FB2
> 1.2V (Note 3)
V
SW1,2
= 5V,
SHDN1,2
= 0V
μA
μA
35271fc
2
LTC3527/LTC3527-1
ELECTRICAL CHARACTERISTICS
PARAMETER
PMOS Switch Leakage Current (LTC3527)
The
l
denotes the specifications which apply over the full operating
temperature range, –40
°
C to 85
°
C. V
IN
= V
IN1
= V
IN2
= 1.2V, V
OUT1
= V
OUT2
= 3.3V, T
A
= 25°C, unless otherwise noted.
CONDITIONS
V
SW1,2
= 5V, V
OUT1,2
= 0V,
SHDN1,2
= 0V
MIN
TYP
0.1
0.2
0.30
0.50
0.40
0.60
l
l
MAX
10
20
UNITS
μA
μA
Ω
Ω
Ω
Ω
mA
mA
NMOS and PMOS Combined Switch Leakage Current V
SW1,2
= 5V, V
OUT1,2
= 0V,
SHDN1,2
= 0V (Note 6)
(LTC3527-1)
NMOS Switch On-Resistance, SW1
NMOS Switch On-Resistance, SW2
PMOS Switch On-Resistance, SW1
PMOS Switch On-Resistance, SW2
NMOS Current Limit, SW1
NMOS Current Limit, SW2
Current Limit Delay to Output Time
Maximum Duty Cycle
Minimum Duty Cycle
Switching Frequency
Switching Frequency
SHDN1,2
Input High Voltage
SHDN1,2
Input Low Voltage
SHDN1,2
Input Current
PGOOD1, PGOOD2 Threshold
PGOOD1, PGOOD2 Low Voltage
PGOOD1, PGOOD2 Leakage Current
MODE Input High Voltage
MODE Input Low Voltage
MODE Input Current
FSEL Input High Voltage
FSEL Input Low Voltage
FSEL Input Current
Soft-Start Time
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 LTC3527E/LTC3527E-1 are 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:
Current is measured into the V
OUT
pin since the supply current is
bootstrapped to the output. The current will reflect to the input supply by:
(V
OUT
/V
IN
) • (1/Efficiency). All switches are off.
V
FSEL
= 3.3V
V
MODE
= 3.3V
0.88
V
SHDN1,2
= 3.3V
Referenced to the Feedback Voltage
I
PGOOD1,2
= 1mA
V
PGOOD1,2
= 5.25V
1
–6
(Note 4)
V
FB1,2
= 1V
V
FB1,2
= 1.3V
V
FSEL
= 0V
V
FSEL
= 3.3V
l
l
l
l
800
400
60
85
0.9
1.8
0.88
0.35
1
–9
0.1
0.01
2
–14
0.2
1
0.35
1
2
0.35
1
0.5
2
90
0
1.2
2.2
1.5
2.8
ns
%
%
MHz
MHz
V
V
μA
%
V
μA
V
V
μA
V
V
μA
ms
Note 4:
Specification is guaranteed by design and not 100% tested in
production.
Note 5:
The LTC3527/LTC3527-1 includes an overtemperature shutdown
that is intended to protect the device during momentary overload
conditions. Junction temperature will exceed 125°C when the over-
temperature shutdown is active. Continuous operation above the specified
maximum junction temperature may impair device reliability.
Note 6:
The NMOS and PMOS switch leakage currents are tested in parallel
for the LTC3527-1 because V
OUT1,2
are actively pulled to ground when
SHDN1,2
= 0V
35271fc
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LTC3527/LTC3527-1
TYPICAL PERFORMANCE CHARACTERISTICS
Efficiency vs Load Current and V
IN
for V
OUT1
= 1.8V at 1.2MHz
100
90
80
EFFICIENCY (%)
70
60
50
40
30
20
0.01
0.1
1
10
100
LOAD CURRENT (mA)
1000
35271 G01
(T
A
= 25°C, unless otherwise noted)
Efficiency vs Load Current and V
IN
for V
OUT1
= 3.3V at 1.2MHz
100
2.4V
BURST
1.8V
2.4V
1.8V
FIXED
3V
3V
90
1.2V
80
EFFICIENCY (%)
1.5V
Efficiency vs Load Current and V
IN
for V
OUT2
= 1.8V at 1.2MHz
100
90
BURST
80
1V
FIXED
60
50
40
30
20
0.01
0.1
1
10
100
LOAD CURRENT (mA)
1000
35271 G02
1.2V
BURST
1V
1.5V
1.2V
1V
1.2V 1.5V
1.5V
EFFICIENCY (%)
70
1V
70
60
50
40
30
20
0.01
0.1
1
10
100
LOAD CURRENT (mA)
FIXED
1000
35271 G03
Efficiency vs Load Current and V
IN
for V
OUT1
= 3.3V at 2.2MHz
100
90
80
EFFICIENCY (%)
70
60
FIXED
50
40
30
20
0.01
0.1
1
10
100
LOAD CURRENT (mA)
1000
35271 G04
Efficiency vs Load Current and V
IN
for V
OUT2
= 3.3V at 1.2MHz
100
2.4V
BURST
1.8V
2.4V
1.8V
3V
100
3V
90
80
EFFICIENCY (%)
70
60
90
Efficiency vs Load Current and V
IN
for V
OUT2
= 3.3V at 2.2MHz
2.4V
BURST
1.8V
1.8V
2.4V
3V
3V
2.4V
BURST
1.8V
3V
2.4V
3V
80
EFFICIENCY (%)
1.8V
70
60
FIXED
50
40
30
20
0.01
0.1
1
10
100
LOAD CURRENT (mA)
1000
35271 G05
FIXED
50
40
30
20
0.01
0.1
1
10
100
LOAD CURRENT (mA)
1000
35271 G06
Efficiency vs Load Current and V
IN
for V
OUT1
= 5V at 1.2MHz
100
3.6V
90
80
EFFICIENCY (%)
70
60
50
40
FIXED
30
20
0.01
0.1
1
10
100
LOAD CURRENT (mA)
1000
35271 G07
Efficiency vs Load Current and V
IN
for V
OUT2
= 5V at 1.2MHz
100
3.6V
90
BURST
2.4V
2.4V
4.2V
4.2V
3.6V
4.2V
4.2V
3.6V
BURST
2.4V
2.4V
80
EFFICIENCY (%)
70
60
50
40
30
20
0.01
FIXED
0.1
1
10
100
LOAD CURRENT (mA)
1000
35271 G08
35271fc
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LTC3527/LTC3527-1
TYPICAL PERFORMANCE CHARACTERISTICS
No-Load Input Current vs V
IN
180
160
OUTPUT CURRENT (mA)
140
120
I
IN
(μA)
100
80
60
40
20
0
0.5
V
OUT
=
1.8V
1
1.5
2
V
OUT
=
2.4V
2.5
V
IN
(V)
35271 G09
(T
A
= 25°C, unless otherwise noted)
Maximum Output Current
vs V
IN
for Converter 2
500
450
OUTPUT CURRENT (mA)
400
350
300
250
200
150
100
50
V
OUT
= 5V
V
OUT
=
1.8V
V
OUT
= 3.3V
V
OUT
=
2.5V
Maximum Output Current
vs V
IN
for Converter 1
800
700
V
OUT
=
2.5V
V
OUT
=
1.8V
V
OUT
= 3.3V
1.2MHz
V
OUT
= 5V
600
500
400
300
200
100
V
OUT
= 5V
V
OUT
= 3.3V
3
3.5
4
4.5
0
0.5
1
1.5
2
2.5
V
IN
(V)
3
3.5
4
4.5
0
0.5
1
1.5
2
2.5
V
IN
(V)
3
3.5
4
4.5
35271 G10
35271 G11
Minimum Load Resistance During
Start-Up vs V
IN
1000
14
12
LOAD RESISTANCE (Ω)
LOAD CURRENT (mA)
10
8
Burst Mode Threshold Current
vs V
IN
for V
OUT1
= V
OUT2
= 1.8V
2.2MHz OPERATION
CONVERTER 1
CONVERTER 2
LOAD CURRENT (mA)
25
Burst Mode Threshold Current
vs V
IN
for V
OUT1
= V
OUT2
= 3.3V
2.2MHz OPERATION
CONVERTER 1
CONVERTER 2
LEAVE
BURST
20
CONVERTER 2
100
15
ENTER
BURST
10
LEAVE BURST
6
4
2
ENTER BURST
CONVERTER 1
5
10
0.635 0.685 0.735 0.785 0.835 0.885 0.935
V
IN
(V)
35271 G12
0
0.7
0.8
0.9
1.0
1.1
V
IN
(V)
1.2
1.3
1.4
1.5
0
0
1.2 1.4 1.6 1.8 2.0 2.2 2.4 2.6 2.8 3.0
V
IN
(V)
35271 G14
35271 G13
Burst Mode Threshold Current
vs V
IN
for V
OUT1
= V
OUT2
= 5V
70
60
LOAD CURRENT (mA)
50
40
30
20
10
0
1.0
2.2MHz OPERATION
CONVERTER 1
CONVERTER 2
FREQUENCY (MHz)
LEAVE BURST
ENTER BURST
2.50
Oscillator Frequency
vs Temperature
FSEL = 3.3V
2.00
V
IN
= 1.2V
V
OUT
= 3.3V
1.50
FSEL = 0V
1.00
–45 –30 –15
1.5
2.0
2.5 3.0
V
IN
(V)
3.5
4.0
4.5
0 15 30 45 60
TEMPERATURE (°C)
75
90
35271 G16
35271 G15
35271fc
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