LTC3527/LTC3527-1
Dual 800mA/400mA,
1.2MHz/2.2MHz Synchronous
Step-Up DC/DC Converters
FEATURES
DESCRIPTION
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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 startup voltage and operation down to 500mV once started.
The SHDN and PGOOD pins enable the converters to be
sequenced or started together.
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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
VIN Start-Up Voltage: 700mV
0.5V to 5V VIN Range After Start-Up
1.6V to 5.25V VOUT Range
Output Disconnect in Shutdown
VIN > VOUT 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 VOUT Discharge (LTC3527-1)
16-Lead, 0.75mm × 3mm × 3mm QFN Package
The LTC3527/LTC3527-1 limit inrush current during startup. Selectable 1.2MHz or 2.2MHz operation provides a
choice between the highest efficiency or smallest solution 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
VOUT1 or VOUT2 when its respective SHDN goes low. Quiescent current in shutdown is less than 2μA.
APPLICATIONS
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MP3/Personal Media Players
Noise Canceling/Bluetooth Headsets
Wireless Mice
Portable Medical Instruments
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.
TYPICAL APPLICATION
Two-Cell Alkaline to 3.3V/1.8V Synchronous Boost Converters
1.6V to 3.2V
VIN
4.7μF
4.7μH
VIN1
VIN
1.78M
LTC3527
15pF
15pF
FB1
ON
OFF
1M
PGOOD2
SHDN1
MODE
619k
1.21M
4.7μF
SHDN2
GND
FSEL
ON
OFF
VOUT
1.8V
150mA
FB2
PGOOD1
100
80
SW2
VOUT2
SW1
VOUT1
4.7μF
4.7μH
VIN2
35271 TA01
70
10
60
50
40
FIXED
FREQUENCY
1
30
POWER
20 LOSS
10
BURST
0
0.1
0.01
POWER LOSS (mW)
VOUT
3.3V
150mA
1000
BURST
90 EFFICIENCY
EFFICIENCY (%)
+
1.2MHz Efficiency and Power Loss
100
0.1
VIN = 2.4V
VOUT1 = 3.3V
1
10
100
LOAD CURRENT (mA)
0.01
1000
35271 TA01b
35271fc
1
LTC3527/LTC3527-1
ABSOLUTE MAXIMUM RATINGS
PIN CONFIGURATION
(Note 1)
PGOOD2
GND
PGOOD1
VIN
TOP VIEW
VIN, VIN1, VIN2 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
VOUT1, VOUT2 ................................................ –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
12 SHDN2
FB1 2
11 FB2
17
PGND
MODE 3
10 FSEL
VIN1 4
5
6
7
8
VOUT1
SW1
SW2
VOUT2
9
VIN2
UD PACKAGE
16-LEAD (3mm s 3mm) PLASTIC QFN
TJMAX = 125°C, θJA = 68°C/W
EXPOSED PAD (PIN 17) IS PGND, MUST BE SOLDERED TO PCB
ORDER INFORMATION
LEAD FREE FINISH
TAPE AND REEL
PART MARKING
PACKAGE DESCRIPTION
TEMPERATURE RANGE
LTC3527EUD#PBF
LTC3527EUD#TRPBF
LDDK
16-Lead (3mm × 3mm) Plastic QFN
–40°C to 85°C
LTC3527EUD-1#PBF
LTC3527EUD-1#TRPBF
LCXP
16-Lead (3mm × 3mm) Plastic QFN
–40°C to 85°C
LEAD BASED FINISH
TAPE AND REEL
PART MARKING
PACKAGE DESCRIPTION
TEMPERATURE RANGE
LTC3527EUD
LTC3527EUD#TR
LDDK
16-Lead (3mm × 3mm) Plastic QFN
–40°C to 85°C
LTC3527EUD-1
LTC3527EUD-1#TR
LCXP
16-Lead (3mm × 3mm) Plastic QFN
–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
The l denotes the specifications which apply over the full operating
temperature range, –40°C to 85°C. VIN = VIN1 = VIN2 = 1.2V, VOUT1 = VOUT2 = 3.3V, TA = 25°C, unless otherwise noted.
PARAMETER
CONDITIONS
Minimum Start-Up Voltage
ILOAD = 1mA
Output Voltage Adjust Range
VOUT1
VOUT1
VOUT2
VOUT2
Line Regulation
MIN
l
l
MAX
UNITS
0.7
0.88
V
5.25
5.25
5.25
5.25
V
V
V
V
1.7
1.6
1.7
1.6
VIN = 1V to 5V
0.005
l
Feedback Voltage FB1, FB2
TYP
1.176
%/V
1.20
1.224
V
1
50
nA
2
μA
Feedback Input Current FB1, FB2
VFB1,2 = 1.20V
Quiescent Current: Shutdown
VSHDN1 = VSHDN2 = 0V, Not Including Switch
Leakage, VOUT1 = VOUT2 = 0V
0.1
Quiescent Current: Burst Mode Operation
Measured on VOUT, VFB1 = VFB2 = 1.5V
12
Quiescent Current: Active
VFB1 = VFB2 > 1.2V (Note 3)
500
900
μA
NMOS Switch Leakage Current (LTC3527)
VSW1,2 = 5V, SHDN1,2 = 0V
0.1
10
μA
μA
35271fc
2
LTC3527/LTC3527-1
ELECTRICAL CHARACTERISTICS
The l denotes the specifications which apply over the full operating
temperature range, –40°C to 85°C. VIN = VIN1 = VIN2 = 1.2V, VOUT1 = VOUT2 = 3.3V, TA = 25°C, unless otherwise noted.
PARAMETER
CONDITIONS
MIN
PMOS Switch Leakage Current (LTC3527)
VSW1,2 = 5V, VOUT1,2 = 0V, SHDN1,2 = 0V
NMOS and PMOS Combined Switch Leakage Current VSW1,2 = 5V, VOUT1,2 = 0V, SHDN1,2 = 0V (Note 6)
(LTC3527-1)
TYP
MAX
UNITS
0.1
10
μA
0.2
20
μA
Ω
NMOS Switch On-Resistance, SW1
0.30
NMOS Switch On-Resistance, SW2
0.50
Ω
PMOS Switch On-Resistance, SW1
0.40
Ω
PMOS Switch On-Resistance, SW2
0.60
Ω
NMOS Current Limit, SW1
NMOS Current Limit, SW2
l
800
l
400
Current Limit Delay to Output Time
(Note 4)
Maximum Duty Cycle
VFB1,2 = 1V
l
Minimum Duty Cycle
VFB1,2 = 1.3V
l
Switching Frequency
VFSEL = 0V
l
Switching Frequency
VFSEL = 3.3V
l
SHDN1,2 Input High Voltage
85
mA
mA
60
ns
90
%
0
%
0.9
1.2
1.5
MHz
1.8
2.2
2.8
MHz
0.88
V
SHDN1,2 Input Low Voltage
0.35
V
1
2
μA
–9
–14
%
SHDN1,2 Input Current
VSHDN1,2 = 3.3V
PGOOD1, PGOOD2 Threshold
Referenced to the Feedback Voltage
PGOOD1, PGOOD2 Low Voltage
IPGOOD1,2 = 1mA
0.1
0.2
V
PGOOD1, PGOOD2 Leakage Current
VPGOOD1,2 = 5.25V
0.01
1
μA
MODE Input High Voltage
–6
1
V
MODE Input Low Voltage
MODE Input Current
VMODE = 3.3V
FSEL Input High Voltage
1
V
2
μA
0.88
V
FSEL Input Low Voltage
FSEL Input Current
0.35
VFSEL = 3.3V
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 VOUT pin since the supply current is
bootstrapped to the output. The current will reflect to the input supply by:
(VOUT /VIN) • (1/Efficiency). All switches are off.
1
0.5
0.35
V
2
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 overtemperature 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 VOUT1,2 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 VIN
for VOUT1 = 1.8V at 1.2MHz
Efficiency vs Load Current and VIN
for VOUT1 = 3.3V at 1.2MHz
BURST
1.2V
EFFICIENCY (%)
1V
1.5V
FIXED
50
70
1V
FIXED
60
50
30
30
20
0.01
0.1
1
10
100
LOAD CURRENT (mA)
1.8V
50
30
1000
20
0.01
1000
2.4V
FIXED
60
40
1
10
100
LOAD CURRENT (mA)
3V
70
40
0.1
1.8V
80
1.5V
3V
BURST
1.2V
1V
40
20
0.01
2.4V
90
BURST
80
70
60
1.2V 1.5V
90
1V
80
100
1.5V
EFFICIENCY (%)
1.2V
90
0.1
1
10
100
LOAD CURRENT (mA)
1000
35271 G01
35271 G02
35271 G03
Efficiency vs Load Current and VIN
for VOUT1 = 3.3V at 2.2MHz
Efficiency vs Load Current and VIN
for VOUT2 = 3.3V at 1.2MHz
Efficiency vs Load Current and VIN
for VOUT2 = 3.3V at 2.2MHz
100
100
3V
90
BURST
1.8V
80
2.4V
3V
2.4V
70
1.8V
60
FIXED
50
100
3V
90
1.8V
2.4V
1.8V
70
60
FIXED
50
FIXED
50
30
30
20
0.01
0.1
1
10
100
LOAD CURRENT (mA)
35271 G04
100
3.6V
35271 G06
100
3.6V
3.6V
80
2.4V
2.4V
EFFICIENCY (%)
EFFICIENCY (%)
1000
4.2V
4.2V
90
70
60
50
40
3.6V
BURST
2.4V
2.4V
70
60
50
40
FIXED
30
20
0.01
1
10
100
LOAD CURRENT (mA)
Efficiency vs Load Current and VIN
for VOUT2 = 5V at 1.2MHz
4.2V
4.2V
BURST
80
0.1
35271 G05
Efficiency vs Load Current and VIN
for VOUT1 = 5V at 1.2MHz
90
20
0.01
1000
1.8V
60
30
1000
1.8V
2.4V
40
1
10
100
LOAD CURRENT (mA)
3V
70
40
0.1
3V
BURST
80
40
20
0.01
2.4V
3V
BURST
80
EFFICIENCY (%)
90
2.4V
EFFICIENCY (%)
EFFICIENCY (%)
Efficiency vs Load Current and VIN
for VOUT2 = 1.8V at 1.2MHz
100
100
EFFICIENCY (%)
(TA = 25°C, unless otherwise noted)
FIXED
30
0.1
1
10
100
LOAD CURRENT (mA)
1000
35271 G07
20
0.01
0.1
1
10
100
LOAD CURRENT (mA)
1000
35271 G08
35271fc
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LTC3527/LTC3527-1
TYPICAL PERFORMANCE CHARACTERISTICS
Maximum Output Current
vs VIN for Converter 1
800
1.2MHz
160
OUTPUT CURRENT (mA)
140
VOUT = 5V
IIN (μA)
120
100
80
60
40
VOUT =
1.8V
20
0
0.5
1
VOUT = 3.3V
VOUT =
2.4V
1.5
2.5
2
3
3.5
4
600
450
VOUT =
1.8V
500
400
300
VOUT = 5V
200
100
VOUT =
2.5V
350
VOUT =
1.8V
300
250
200
150
VOUT = 5V
50
0
0.5
4.5
VOUT = 3.3V
400
100
1
1.5
2
VIN (V)
2.5
3
3.5
4
0
0.5
4.5
1
1.5
3.5
4
LOAD CURRENT (mA)
12
25
2.2MHz OPERATION
CONVERTER 1
CONVERTER 2
8
LEAVE BURST
6
4
0
0.7
0.8
0.9
1.0
1.1
1.2
1.3
LEAVE
BURST
15
ENTER
BURST
10
5
ENTER BURST
2
2.2MHz OPERATION
CONVERTER 1
CONVERTER 2
20
10
CONVERTER 1
10
0.635 0.685 0.735 0.785 0.835 0.885 0.935
VIN (V)
Burst Mode Threshold Current
vs VIN for VOUT1 = VOUT2 = 3.3V
LOAD CURRENT (mA)
14
4.5
35271 G11
Burst Mode Threshold Current
vs VIN for VOUT1 = VOUT2 = 1.8V
1000
100
3
VIN (V)
35271 G10
Minimum Load Resistance During
Start-Up vs VIN
CONVERTER 2
2.5
2
VIN (V)
35271 G09
1.4
1.5
VIN (V)
0
0
1.2 1.4 1.6 1.8 2.0 2.2 2.4 2.6 2.8 3.0
VIN (V)
35271 G12
35271 G13
60
2.50
2.2MHz OPERATION
CONVERTER 1
CONVERTER 2
50
FSEL = 3.3V
LEAVE BURST
FREQUENCY (MHz)
70
ENTER BURST
40
30
20
2.00
VIN = 1.2V
VOUT = 3.3V
1.50
FSEL = 0V
10
0
1.0
35271 G14
Oscillator Frequency
vs Temperature
Burst Mode Threshold Current
vs VIN for VOUT1 = VOUT2 = 5V
LOAD CURRENT (mA)
LOAD RESISTANCE (Ω)
500
VOUT = 3.3V
VOUT =
2.5V
700
Maximum Output Current
vs VIN for Converter 2
OUTPUT CURRENT (mA)
No-Load Input Current vs VIN
180
(TA = 25°C, unless otherwise noted)
1.5
2.0
2.5 3.0
VIN (V)
3.5
4.0
4.5
1.00
–45 –30 –15
0 15 30 45 60
TEMPERATURE (°C)
75
90
35271 G16
35271 G15
35271fc
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LTC3527/LTC3527-1
TYPICAL PERFORMANCE CHARACTERISTICS
Current Limit vs Temperature
(TA = 25°C, unless otherwise noted)
Feedback Voltage vs Temperature
Start-Up Voltage vs Temperature
1.205
1.30
0.75
CONVERTER1
0.70
VIN = 1.2V
1.00 VOUT = 3.3V
0.90
0.80
VOLTAGE (V)
1.200
1.10
FB VOLTAGE (V)
CURRENT LIMIT (A)
1.20
1.195
0.60
0.55
1.190
0.70
CONVERTER2
0.50
0.60
0.50
–45 –30 –15
0 15 30 45 60
TEMPERATURE (°C)
75
90
1.185
–55 –35 –15
0.45
–50
5 25 45 65 85 105 125
TEMPERATURE (°C)
–30
30
50
–10 10
TEMPERATURE (°C)
35271 G18
35271 G17
70
90
35271 G19
RDS(ON) (NMOS and PMOS)
vs VOUT
Burst Mode Quiescent Current
vs VOUT
16
0.65
RDS(ON) (NMOS and PMOS)
Change vs Temperature
0.90
VIN = 1.2V
15
0.80
14
0.70
0.70
PMOS2
13
12
RDS(ON) (Ω)
RDS(ON) (Ω)
IQ (μA)
PMOS2
NMOS2
0.60
0.60
NMOS2
0.50
0.50
PMOS1
PMOS1
NMOS1
11
0.40
NMOS1
0.40
10
1.5
2
2.5
3.5
3
VOUT (V)
4
4.5
5
0.30
1.5
2
2.5
35271 G20
3.5
3
VOUT (V)
4
4.5
5
0.30
–45 –30 –15
0 15 30 45 60
TEMPERATURE (°C)
90
35271 G22
35271 G21
Fixed Frequency Switching
Waveform and VOUT Ripple
75
Burst Mode Waveforms
SW1 PIN
2V/DIV
SW1 PIN
2V/DIV
VOUT1
50mV/DIV
AC-COUPLED
VOUT1
10mV/DIV
AC-COUPLED
INDUCTOR
CURRENT
200mA/DIV
500μs/DIV
VIN1 = 1.2V
VOUT1 = 3.3V AT 100mA
COUT1 = 10μF
35271 G23
10μs/DIV
35271 G24
VIN1 = 1.2V
VOUT1 = 3.3V
COUT1 = 10μF
35271fc
6
LTC3527/LTC3527-1
TYPICAL PERFORMANCE CHARACTERISTICS
(TA = 25°C, unless otherwise noted)
VOUT1 Load Step Response
Fixed Frequency at 1.2MHz
VOUT and IIN During Start-Up
VOUT1
100mV/DIV
AC-COUPLED
VOUT1
1V/DIV
INPUT
CURRENT
200mA/DIV
LOAD
CURRENT
50mA/DIV
SHDN1 PIN
1V/DIV
100μs/DIV
35271 G25
100μs/DIV
VOUT1 = 3.3V
COUT1 = 10μF
VIN = 3.6V
VOUT1 = 5V
VOUT1 Load Step Response
Burst Mode Operation at 1.2MHz
VOUT2 Load Step Response
Fixed Frequency at 2.2MHz
VOUT1
100mV/DIV
AC-COUPLED
VOUT2
100mV/DIV
AC-COUPLED
LOAD
CURRENT
50mA/DIV
LOAD
CURRENT
50mA/DIV
100μs/DIV
VIN = 3.6V
VOUT1 = 5V
100μs/DIV
VIN = 3.6V
VOUT2 = 5V
VOUT1 = 5V Load Regulation
0.3
50mA TO 100mA STEP
COUT2 = 10μF
VIN = 2.4V
L = 3.3µH
MODE = HIGH
0.2
VOUT2 CHANGE (%)
VOUT1 CHANGE (%)
35271 G28
VOUT2 = 3.3V Load Regulation
0.3
VIN = 2.4V
L = 3.3µH
MODE = HIGH
0.2
50mA TO 150mA STEP
COUT1 = 10μF
35271 G27
20mA TO 170mA STEP
COUT1 = 10μF
35271 G26
0.1
0
–0.1
–0.2
0.1
0
–0.1
–0.2
–0.3.
0
50
100 150 200 250 300 350 400
ILOAD1 (mA)
35271 G29
–0.3.
0
100
200
ILOAD2 (mA)
300
35271 G30
35271fc
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LTC3527/LTC3527-1
PIN FUNCTIONS
SHDN1 (Pin 1): Boost Converter 1 Logic-Controlled
Shutdown Input. There is an internal 4MΩ pull-down on
this pin.
MOSFET. Driver bias is derived from VOUT2. PCB trace
length from VOUT2 to the output filter capacitor(s) should
be as short and wide as possible.
• SHDN1 = High: Normal free running operation, 1.2MHz/
2.2MHz typical operating frequency.
FSEL (Pin 10): Logic-Controlled Frequency Select
Input.
• SHDN1 = Low: Shutdown, quiescent current < 2μA.
• FSEL = High: 2.2MHz operation
Note: Both converters must be shut down together to
achieve < 2μA quiescent current.
• FSEL = Low: 1.2MHz operation
FB1 (Pin 2): Boost Converter 1 Feedback Input to the gm
Error Amplifier. Connect resistor divider tap to this pin. The
output voltage can be adjusted from 1.6V to 5.25V by:
FB2 (Pin 11): Boost Converter 2 Feedback Input to the
gm Error Amplifier. Connect resistor divider tap to this
pin. The output voltage can be adjusted from 1.6V to
5.25V by:
⎡ R1 ⎤
VOUT1 = 1 . 20 V • ⎢1 + ⎥ (See Block Diagram)
⎣ R2 ⎦
⎡ R3 ⎤
VOUT2 = 1 . 20 V • ⎢1 + ⎥ (See Block Diagram)
⎣ R4 ⎦
MODE (Pin 3): Logic-Controlled Mode Input for Both
Boost Converters.
SHDN2 (Pin 12): Boost Converter 2 Logic-Controlled
Shutdown Input. There is an internal 4MΩ pull-down on
this pin.
• MODE = High: Fixed frequency operation
• MODE = Low: Automatic Burst Mode operation
MODE pin must be 1V or greater to ensure fixed frequency
over all operating conditions.
VOUT1 (Pin 5): Boost Converter 1 Output Voltage Sense
Input and Drain of the Internal Synchronous Rectifier
MOSFET. Driver bias is derived from VOUT1. PCB trace
length from VOUT1 to the output filter capacitor(s) should
be as short and wide as possible.
• SHDN2 = High: Normal free-running operation,
1.2MHz/2.2MHz typical operating frequency.
• SHDN2 = Low: Shutdown, quiescent current < 2μA.
Note: Both converters must be shut down together to
achieve < 2μA quiescent current.
PGOOD2 (Pin 13): Boost Converter 2 Power Good Comparator Output. This open-drain output is low when VFB
is 9% below its regulation voltage.
SW1 (Pin 6): Boost Converter 1 Switch Pin. Connect the
inductor between SW1 and VIN1. Keep these PCB trace
lengths as short and wide as possible to reduce EMI and
voltage overshoot. If the inductor current falls to zero or
SHDN1 is low, an internal 100Ω anti-ringing switch is
connected from SW1 to VIN1 to minimize EMI.
GND (Pin 14): Signal Ground. This pin is used as a
ground reference for the internal circuitry of the LTC3527/
LTC3527-1.
SW2 (Pin 7): Boost Converter 2 Switch Pin. Connect the
inductor between SW2 and VIN2. Keep these PCB trace
lengths as short and wide as possible to reduce EMI and
voltage overshoot. If the inductor current falls to zero or
SHDN2 is low, an internal 100Ω anti-ringing switch is
connected from SW2 to VIN2 to minimize EMI.
PGOOD1 (Pin 16) Boost Converter 1 Power Good Comparator Output. This open-drain output is low when VFB
is 9% below its regulation voltage.
VOUT2 (Pin 8): Boost Converter 2 Output Voltage Sense
Input and Drain of the Internal Synchronous Rectifier
VIN, VIN1, VIN2 (Pins 15, 4, 9): Battery Input Voltage. See
Operation section for more information.
PGND (Exposed Pad Pin 17): Backplane. The exposed pad
is PGND and must be soldered to the PCB ground plane.
It serves as the power ground connection for VOUT1 and
VOUT2, and as a means of conducting heat away from the
package.
35271fc
8
LTC3527/LTC3527-1
BLOCK DIAGRAM
BULK CONTROL SIGNALS
SW1
6
VIN
0.88V
TO 5V
VIN
ANTI-RING
VOUT
L1
4.7μH
VOUT1
VOUT1
1.6V TO 5.25V
5
VIN1
4
CIN
4.7μF
SHUTDOWN
AND VBIAS
– ++
0.30Ω
+
1
0.40Ω
PWM
LOGIC
AND
DRIVERS
OSC1
START1
SD1
SHDN1 VREF_GD
CURRENT
SENSE
SD1
R1
FB1
–
+
VC1
+
ILIM
REF
IZERO
COMP
MODE
WAKE1
MODE
CONTROL
PWM
COMP
–
COUT1
4.7μF
2
1.20V
R2
ERROR
AMPLIFIER
+
SLOPE COMPENSATION
16
BURST 1
SLP1
PGOOD1
–
+
SOFT-START
VC CLAMP
SD1
TSD
FB1
1.20V - 9%
CONVERTER 1
15 VIN
FSEL
10
OSC1
SLP1
OSC2
SLP2
OSCILLATOR
3 MODE
START-UP
OSCILLATOR
VREF_GD
7
START1
START2
VREF_GD
1.20V
GND
1.20V - 9%
14
TSD EXPOSED
REFERENCE
UVLO
THERMAL SD
PAD/
PGND
17
SHARED
BULK CONTROL SIGNALS
SW2
VIN
ANTI-RING
VOUT
VOUT2
L2
4.7μH
9
PWM
LOGIC
AND
DRIVERS
OSC2
START2
SD2
SHDN2 VREF_GD
SHUTDOWN
AND VBIAS
– ++
SD2
0.60Ω
0.50Ω
CURRENT
SENSE
MODE
CONTROL
PWM
COMP
+
12
VOUT2
1.6V TO 5.25V
8
VIN2
ILIM
REF
IZERO
COMP
MODE
WAKE2
VC2
+
–
R3
–
+
FB2
11
1.20V
COUT2
4.7μF
R4
ERROR
AMPLIFIER
+
SLOPE COMPENSATION
13
SLP2
PGOOD2
–
+
BURST2
SD2
TSD
FB2
SOFT-START
VC CLAMP
1.20V - 9%
CONVERTER 2
35271fc
9
LTC3527/LTC3527-1
OPERATION
(Refer to Block Diagram)
The LTC3527/LTC3527-1 are dual 1.2MHz/2.2MHz synchronous boost converters housed in a 16-lead 3mm ×
3mm QFN package. With the ability to start up and operate
from inputs less than 880mV, these devices feature fixed
frequency, current mode PWM control for exceptional line
and load regulation. The current mode architecture with
adaptive slope compensation provides excellent transient
load response, requiring minimal output filtering. Internal
soft-start and loop compensation simplifies the design
process while minimizing the number of external components. Each converter has a separate input supply pin
and is operated independently of the other, but they share
the same oscillator thus providing in-phase switching.
If different input supply voltages are used, the third VIN
pin must be wired to the higher of the two supplies and
each VOUT must be higher than the highest VIN. Bypass
capacitors are recommended on all VIN pins.
With low RDS(ON) and low gate charge internal N-channel
MOSFET switches and P-channel MOSFET synchronous
rectifiers, the LTC3527/LTC3527-1 achieve high efficiency
over a wide range of load current. With the MODE pin low,
automatic Burst Mode operation maintains high efficiency
at very light loads, reducing the quiescent current to just
12μA. If MODE is high, fixed frequency PWM switching
provides low voltage ripple on the outputs. Operation can
be best understood by referring to the Block Diagram.
current limiting are provided to each converter independently during start-up, as well as during normal mode.
When VIN, VOUT1, or VOUT2 exceeds 1.4V (typical), the IC
enters normal operating mode. Once the higher of VOUT1
or VOUT2 exceeds VIN by 0.24V, the IC powers itself from
the higher VOUT instead of VIN. At this point the internal
circuitry has no dependency on the VIN input voltage,
eliminating the requirement for a large input capacitor.
The input voltage can drop as low as 0.5V.
With single-cell operation, the limiting factor for the application becomes the availability of the power source to
supply sufficient energy to the outputs at low voltages, and
maximum duty cycle, which is clamped at 90% (typical).
Note that at low input voltages, small voltage drops due
to the higher series resistance of a depleted cell become
critical and greatly limit the power delivery capability of
the converter. A higher value, low ESR input capacitor can
help to improve this to a small degree.
Low Noise Fixed Frequency Operation
A PGOOD signal is provided independently for each converter which can be used with the SHDN pins to provide
sequencing of the outputs.
Soft-Start: The LTC3527/LTC3527-1 contain internal circuitry to provide independent soft-start operation to each
converter. The soft-start circuitry ramps the peak inductor
current from zero to its peak value of 900mA (typical)
for converter 1 or 500mA (typical) for converter 2 in approximately 0.5ms, allowing start-up into heavy loads. The
soft-start circuitry for both converters is reset in the event
of a thermal shutdown or shutdown command.
The LTC3527-1 provides an instant off feature which
discharges VOUT1 or VOUT2 when their respective SHDN
pins go low.
Oscillator: An internal oscillator sets the switching frequency to 1.2MHz if the FSEL pin is below 0.35V, or 2.2MHz
if the FSEL pin is above 0.88V.
A frequency select function allows for 1.2MHz switching
(FSEL = Low) or 2.2MHz switching (FSEL = High).
Shutdown: Shutdown is accomplished independently for
each converter by pulling its respective SHDN pin below
0.35V, and enabled by pulling each SHDN pin above
0.88V. Note that the SHDN pins can be driven above VIN
or VOUT, as long as it is limited to less than the absolute
maximum rating.
Low Voltage Start-Up
The LTC3527/LTC3527-1 include an independent start-up
oscillator designed to start up at an input voltage of 0.7V
(typical). The two converters can be started together or
in either sequence of boost 1 and boost 2 with appropriate control of SHDN1 and SHDN2. Soft-start and inrush
Error Amplifier: The noninverting input of each
transconductance error amplifier is internally connected
to the 1.20V reference. The inverting inputs are connected
35271fc
10
LTC3527/LTC3527-1
OPERATION
to FB1 for converter 1 and FB2 for converter 2. Clamps
limit the minimum and maximum error amp output voltages for improved large-signal transient response. Power
converter control loop compensation is provided internally.
An external resistive voltage divider from VOUT1 (VOUT2)
to ground programs the respective output voltage via FB1
(FB2) from 1.6V to 5.25V.
⎡ R1 ⎤
VOUT1 = 1 . 20 V • ⎢1 + ⎥
⎣ R2 ⎦
⎡ R3 ⎤
VOUT2 = 1 . 20 V • ⎢1 + ⎥ (See Block Diagram)
⎣ R4 ⎦
Current Sensing: Lossless current sensing converts the
peak current signal of each N-channel MOSFET switch
into a voltage which is summed with its corresponding
internal slope compensation. The summed signals are
compared to their respective error amplifier outputs to
provide individual peak current control commands for the
PWM of each converter.
Current Limit: The current limit comparators shut off
the N-channel MOSFET switches once their threshold
is reached. Each current limit comparator delay time to
output is typically 60ns. Peak switch current is limited
to approximately 900mA for converter 1 and 500mA for
converter 2, independent of input or output voltage. If
VOUT1 or VOUT2 falls below 1V, its respective current limit
is cut in half.
Zero Current Comparator: The zero current comparators
monitor the inductor current to the outputs and shut off
the synchronous rectifiers when the current reduces to approximately 30mA. This prevents the inductor current from
reversing in polarity, improving efficiency at light loads.
Synchronous Rectifier: To control inrush current and to
prevent the inductor currents from running away when
VOUT1 or VOUT2 is close to VIN, the P-channel MOSFET
synchronous rectifiers are only enabled when their respective VOUT > (VIN + 0.24V).
Anti-Ringing Control: The anti-ringing control connects a
resistor across the inductor to prevent high frequency ringing on the SW1 (SW2) pins during discontinuous current
mode operation. Although the ringing of the resonant circuit
formed by the inductors and CSW (capacitance on SW1 or
SW2 pins) is low energy, it can cause EMI radiation.
Output Disconnect: The LTC3527/LTC3527-1 are designed
to allow true output disconnect by eliminating body diode
conduction of the internal P-channel MOSFET rectifiers.
This allows VOUT1 and VOUT2 to go to zero volts during
shutdown, drawing no current from the input source. It
also allows for inrush current limiting at turn-on, minimizing surge currents seen by the input supply. Note that to
obtain the advantages of output disconnect, there must
not be external Schottky diodes connected between the
SW1 (SW2) pins and VOUT1 (VOUT2). The output disconnect feature also allows VOUT1 or VOUT2 to be pulled high,
without any reverse current into a battery on VIN.
Thermal Shutdown: If the die temperature exceeds 160°C,
the device will go into thermal shutdown. All switches
will be turned off and the soft-start capacitors will be
discharged. The device will be enabled again when the
die temperature drops by about 15°C.
Burst Mode Operation
To realize the efficiency benefits of Burst Mode operation,
both VOUT1 and VOUT2 must be under a light load current
condition, if they are both enabled. If one converter is shut
down, then Burst Mode operation is enabled on the other
converter. With the MODE pin low, the LTC3527/LTC3527-1
will automatically enter Burst Mode operation at light load
and return to fixed frequency PWM mode when the load
increases. Refer to the Typical Performance Characteristics
to see the Output Load Burst Mode Threshold Current vs
VIN. The load current at which Burst Mode operation is
entered can be changed by adjusting the inductor value.
Raising the inductor value will lower the load current at
which Burst Mode is operation entered.
In Burst Mode operation, the LTC3527/LTC3527-1 still
switch at a fixed frequency of 1.2MHz (FSEL = 0) or 2.2MHz
(FSEL = 1), using the same error amplifier and loop compensation for peak current mode control. This control method
eliminates the output transient when switching between
modes. In Burst Mode operation, energy is delivered to the
35271fc
11
LTC3527/LTC3527-1
OPERATION
output until it reaches the nominal regulation value, then
the LTC3527/LTC3527-1 transition to sleep mode where
the outputs are off and the LTC3527/LTC3527-1 consume
only 12μA of quiescent current from the higher of VOUT1 or
VOUT2. When the output voltage droops slightly, switching
resumes. This maximizes efficiency at very light loads by
minimizing switching and quiescent current losses. Burst
Mode output voltage ripple, which is typically 1% peak-topeak, can be reduced by using more output capacitance
(10μF or greater), or with a small capacitor (15pF) connected between VOUT1 (VOUT2) and FB1 (FB2).
If either load current increases, the LTC3527/LTC3527-1
will automatically leave Burst Mode operation. Note that
larger output capacitor values may cause this transition
to occur at lighter loads. Once the LTC3527/LTC3527-1
have left Burst Mode operation and returned to normal
operation, they will remain there until both output loads
are reduced below the burst threshold current.
Burst Mode operation is inhibited during start-up and softstart and until both VOUT1 and VOUT2 are at least 0.24V
greater than VIN if neither channel is in shutdown.
When the MODE pin is high, LTC3527/LTC3527-1 feature
continuous PWM fixed frequency operation at 1.2MHz
(FSEL = Low) or 2.2MHz (FSEL = High). At very light
loads, the LTC3527/LTC3527-1 will exhibit pulse-skipping
operation.
Single Cell to 5V Step-Up Applications
Due to the high inductor current slew rate in applications boosting to 5V from a single-cell (alkaline, NiCd
or NiMH), the LTC3527/LTC3527-1 may not enter Burst
Mode operation at input voltages below 1.5V in a 2.2MHz
application (FSEL = high). For a single-cell to 5V application requiring Burst Mode 1.2MHz operation, (FSEL =
low) is recommended. Refer to the Typical Performance
Characteristics for the Burst Mode thresholds for different
input and output voltages.
APPLICATIONS INFORMATION
VIN > VOUT Operation
Short-Circuit Protection
The LTC3527/LTC3527-1 will maintain output voltage
regulation even when the input voltage is above one or
both of the desired output voltages. Note, all VINS must
be common to support this mode of operation. Since
this mode is less efficient and will dissipate more power
in the LTC3527/LTC3527-1, the maximum output current
capability is limited in order to maintain an acceptable
junction temperature. When operating with VIN > VOUT
the power is defined by:
The LTC3527/LTC3527-1 output disconnect feature allows
an output short-circuit while maintaining a maximum internally set current limit. The converters also incorporate
internal features such as current limit foldback and thermal
shutdown for protection from an excessive overload or
short circuit. To reduce power dissipation under shortcircuit conditions, the peak switch current limit is reduced
to 500mA (typical) for converter 1 and 350mA (typical)
for converter 2 when VOUT is less than 1V.
POUT = IOUT ⎡⎣( VIN + 1 . 5) − VOUT ⎤⎦
To maintain a junction temperature below 125°C, the following formula must be adhered to:
(POUT1 + POUT 2 ) 68 °C / W = 125 − TA
Schottky Diode
Although it is not required, adding a Schottky diode from
SW1 (SW2) to VOUT1 (VOUT2) will improve efficiency by
about 2%. Note that this defeats the output disconnect
and short-circuit protection features.
where TA is the ambient temperature.
35271fc
12
LTC3527/LTC3527-1
APPLICATIONS INFORMATION
PCB Layout Guidelines
The minimum inductance value is given by:
The high speed operation of the LTC3527/LTC3527-1
demands careful attention to board layout. A careless
layout will result in reduced performance. Figure 1 shows
the recommended component placement. A large ground
pin copper area will help to lower the die temperature. A
multilayer board with a separate ground plane is ideal, but
not absolutely necessary.
L>
f • Ripple • VOUT(MAX )
where:
Ripple = Allowable inductor current ripple (amps
peak-to-peak)
VIN(MIN) = Minimum input voltage
VOUT(MAX) = Maximum output voltage
f = Oscillator frequency (MHz)
COMPONENT SELECTION
The inductor current ripple is typically set for 20% to
40% of the maximum inductor current. High frequency
ferrite core inductor materials reduce frequency dependent
power losses compared to cheaper powdered iron types,
improving efficiency. The inductor should have low ESR
(series resistance of the windings) to reduce the I2R power
losses, and must be able to support the peak inductor
current without saturating. Molded chokes and some
chip inductors usually do not have enough core area to
support the peak inductor currents of 900mA (500mA)
seen on the LTC3527/LTC3527-1. To minimize radiated
noise, use shielded inductors. See Table 1 for suggested
components and suppliers.
Inductor Selection
The LTC3527/LTC3527-1 can utilize small surface mount
inductors due to their fast 1.2MHz/2.2MHz switching
frequencies. Inductor values between 3.3μH and 4.7μH
are suitable for most 1.2MHz applications. Inductor values
between 1.5μH and 2.2μH are suitable for most 2.2MHz
applications. Larger values of inductance will allow slightly
greater output current capability (and lower the Burst
Mode threshold) by reducing the inductor ripple current. Increasing the inductance above 10μH will increase
size while providing little improvement in output current
capability.
MODE SHDN1
VIN(MIN) • ( VOUT(MAX ) – VIN(MIN) )
SHDN2 FSEL
GND
VIN
GND
GND
VIN1
VIN2
VOUT1
GND
VOUT2
35271 F01
Figure 1. Recommended Component Placement for a Dual-Layer Board
35271fc
13
LTC3527/LTC3527-1
APPLICATIONS INFORMATION
Table 1. Recommended Inductors
PART/STYLE
L
(μH)
MAXIMUM
CURRENT
(mA)
DCR
(Ω)
DIMENSIONS
L×W×H
(mm)
Coilcraft
www.coilcraft.com
MSS5131
MSS4020
ME3220
2.2-10
3.3-10
1-10
1900-870
1100-540
3000-780
0.023-0.083
0.085-0.210
0.05-0.90
5.1 × 5.1 × 1
4×4×2
3.2 × 2.5 × 2
Coiltronics
www.cooperet.com
SD10
SD12
1-10
1.2-10
1930-760
2450-818
0.045-0.289
0.037-0.284
5.2 × 5.2 × 1
5.2 × 5.2 × 1.2
MIP3226D
MIPF2520D
1.5-6.8
1.5-4.7
1400-1000
1500-1000
0.07-0.12
0.07-0.11
3.2 × 2.6 × 1
2.5 × 2 × 1
Murata
www.murata.com
LQH43C
LQH32C
1-10
1-4.7
1080-650
800-650
0.08-0.24
0.09-0.15
4.5 × 3.2 × 2.6
3.2 × 2.5 × 2
Sumida
www.sumida.com
CDRH3D16
CDRH2D14
4.7-15
4.7-12
900-450
680-420
0.11-0.29
0.12-0.32
3.8 × 3.8 × 1.8
3.2 × 3.2 × 1.5
TDK
www.global.tdk.co.jp
VLF3010A
VLF5012A
1.5-10
2.2-10
1200-490
1500-800
0.068-0.58
0.090-0.30
2.6 × 2.8 × 1
4.5 × 4.7 × 1.2
NR3010
NR3015
4.7-15
4.7-15
750-400
1000-560
0.19-0.74
0.12-0.36
3×3×1
3 × 3 × 1.5
VENDOR
FDK
www.fdk.com
Taiyo Yuden
www.t-yuden.com
Output and Input Capacitor Selection
Low ESR (equivalent series resistance) capacitors should
be used to minimize output voltage ripple. Multilayer
ceramic capacitors are an excellent choice as they have
extremely low ESR and are available in small footprints.
A 4.7μF to 10μF output capacitor is sufficient for most
applications. Larger values up to 22μF may be used to
obtain lower output voltage ripple and improve transient
response. X5R and X7R dielectric materials are preferred
for their ability to maintain capacitance over wide voltage
and temperature ranges. Y5V types should not be used.
The internal loop compensation of the LTC3527/
LTC3527-1 is designed to be stable with output capacitor
values of 4.7μF or greater. Although ceramic capacitors
are recommended, low ESR tantalum capacitors may be
used as well.
A small ceramic capacitor in parallel with a larger tantalum
capacitor may be used in demanding applications which
have large load transients. Another method of improv-
ing the transient response is to add a small feedforward
capacitor across the top resistor of the feedback divider
[from VOUT1 (VOUT2) to FB1 (FB2)]. A typical value of 15pF
will generally suffice.
Low ESR input capacitors reduce input switching noise and
reduce the peak current drawn from the battery. It follows
that ceramic capacitors are also a good choice for input
decoupling and should be located as close as possible to
the device. A 2.2μF input capacitor is sufficient for most
applications, although larger values may be used without
limitations. Table 2 shows a list of several ceramic capacitor manufacturers. Consult the manufacturers directly for
detailed information on their selection of ceramic parts.
Table 2. Capacitor Vendor Information
SUPPLIER
PHONE
WEBSITE
AVX
(803) 448-9411
www.avxcorp.com
Murata
(714) 852-2001
www.murata.com
Taiyo-Yuden
(408) 573-4150
www.t-yuden.com
TDK
(847) 803-6100
www.component.tdk.com
35271fc
14
LTC3527/LTC3527-1
TYPICAL APPLICATIONS
1.2MHz, 1-Cell to VOUT1 = 3V, VOUT2 = 1.8V
+
0.85V TO 1.60V
SINGLE
ALKALINE
CELL
VOUT
3V
150mA
CIN
4.7μF
COUT1
4.7μF
1.84M
4.7μH
VIN1
VIN
SW1
SW2
VOUT1
VOUT2
15pF
15pF
LTC3527
FB1
1.21M
ON
PGOOD1
MODE
VOUT
1.8V
150mA
612k
FB2
1.21M
PGOOD2
SHDN1
OFF
4.7μH
VIN2
SHDN2
GND
COUT2
4.7μF
FSEL
ON
OFF
35271 TA02
L: SUMIDA CDRH3D164R7
CIN, COUT: TAIYO YUDEN X5R JMK212BJ475MD
Boost 1 Efficiency
Boost 2 Efficiency
100
100
1.2V
90
BURST
BURST
80
1.2V
1V
70
1V
60
50
FIXED
50
30
1000
35271 TA02b
1V
60
30
1
10
100
LOAD CURRENT (mA)
1.5V
FIXED
40
0.1
1.2V
1V
70
40
20
0.01
1.2V 1.5V
90
1.5V
EFFICIENCY (%)
EFFICIENCY (%)
80
1.5V
20
0.01
0.1
1
10
100
LOAD CURRENT (mA)
1000
35271 TA02c
35271fc
15
LTC3527/LTC3527-1
TYPICAL APPLICATIONS
1.2MHz, 1-Cell to VOUT1 = 1.8V, VOUT2 = 5V
0.85V TO 1.60V
+
SINGLE
ALKALINE
CELL
VOUT
1.8V
200mA
CIN
4.7μF
COUT1
4.7μF
612M
4.7μH
VIN1
VIN
SW1
SW2
VOUT1
VOUT2
15pF
1.21M
FB2
PGOOD1
MODE
1.02M
PGOOD2
SHDN1
OFF
VOUT
5V
50mA
3.24M
15pF
LTC3527
FB1
ON
10μH
VIN2
COUT2
4.7μF
SHDN2
GND
FSEL
ON
OFF
35271 TA03
L: SUMIDA CDRH3D164R7
CIN, COUT: TAIYO YUDEN X5R JMK212BJ475MD
Boost 1 Efficiency
100
1.2V
90
1.2V
1.2V
1V
80
EFFICIENCY (%)
1.5V
BURST
1V
70
1.5V
FIXED
60
1.5V
1.5V
80
50
EFFICIENCY (%)
90
Boost 2 Efficiency
100
70
1.2V
BURST
1V
1V
60
50
40
40
30
30
FIXED
20
0.01
0.1
1
10
100
LOAD CURRENT (mA)
1000
35271 TA03b
20
0.01
0.1
1
10
100
LOAD CURRENT (mA)
1000
35271 TA03c
35271fc
16
LTC3527/LTC3527-1
TYPICAL APPLICATIONS
2.2MHz, 1-Cell to VOUT1 = 3.3V, VOUT2 = 1.8V
0.85V TO 1.60V
+
SINGLE
ALKALINE
CELL
VOUT
3.3V
150mA
CIN
4.7μF
COUT1
4.7μF
1.78M
2.2μH
VIN1
VIN
SW1
SW2
VOUT1
VOUT2
15pF
FB2
PGOOD1
1M
MODE
1.21M
PGOOD2
SHDN1
OFF
VOUT
1.8V
150mA
612k
15pF
LTC3527
FB1
ON
2.2μH
VIN2
COUT2
4.7μF
SHDN2
GND
FSEL
ON
OFF
35271 TA04
L: SUMIDA CDRH3D162R2
CIN, COUT: TAIYO YUDEN X5R JMK212BJ475MD
Boost 1 Efficiency
Boost 2 Efficiency
100
100
1.2V
90
1.5V
1.5V
1V
80
1.2V
70
1V
60
FIXED
50
EFFICIENCY (%)
EFFICIENCY (%)
80
35271 TA04b
1V
FIXED
30
1000
1.2V
1V
50
30
1
10
100
LOAD CURRENT (mA)
1.5V
60
40
0.1
1.5V
BURST
70
40
20
0.01
1.2V
90
BURST
20
0.01
0.1
1
10
100
LOAD CURRENT (mA)
1000
35271 TA04c
35271fc
17
LTC3527/LTC3527-1
TYPICAL APPLICATIONS
1.2MHz, 2-Cell to VOUT1 = 5V, VOUT2 = 3.3V
+
+
1.8V TO 3.2V
CIN
4.7μF
ALKALINE
CELLS
VOUT
5V
300mA
COUT1
4.7μF
3.24M
10μH
VIN1
VIN
SW1
SW2
VOUT1
VOUT2
15pF
1.02M
FB2
PGOOD1
MODE
1M
PGOOD2
SHDN1
OFF
VOUT
3.3V
200mA
1.78M
15pF
LTC3527
FB1
ON
4.7μH
VIN2
COUT2
4.7μF
SHDN2
GND
FSEL
ON
OFF
35271 TA05
L: SUMIDA CDRH3D164R7
CIN, COUT: TAIYO YUDEN X5R JMK212BJ475MD
Boost 1 Efficiency
Boost 2 Efficiency
100
100
2.4V
90
90
BURST
2.4V
1.8V
1.8V
60
50
40
3V
1.8V
2.4V
1.8V
70
60
FIXED
50
40
FIXED
30
20
0.01
3V
BURST
80
EFFICIENCY (%)
EFFICIENCY (%)
80
70
2.4V
3V
3V
0.1
30
1
10
100
LOAD CURRENT (mA)
1000
35271 TA05b
20
0.01
0.1
1
10
100
LOAD CURRENT (mA)
1000
35271 G05
35271fc
18
LTC3527/LTC3527-1
TYPICAL APPLICATIONS
Sequenced Start-Up VOUT1 to VOUT2
1.2MHz, 1-Cell to VOUT1 = 1.8V, VOUT2 = 3.3V
0.85V TO 1.60V
+
SINGLE
ALKALINE
CELL
VOUT
1.8V
200mA
CIN
4.7μF
COUT1
4.7μF
612k
VIN1
VIN
SW1
SW2
VOUT1
VOUT2
15pF
1M
PGOOD2
COUT2
4.7μF
SHDN2
GND
FSEL
L: SUMIDA CDRH3D164R7
CIN, COUT: TAIYO YUDEN X5R JMK212BJ475MD
35271 TA06
Boost 2 Efficiency
Boost 1 Efficiency
100
BURST
80
1.2V
70
1.5V
FIXED
60
50
30
1000
35271 TA06b
1V
50
30
1
10
100
LOAD CURRENT (mA)
1.5V
1.2V
1V
60
40
0.1
1.5V
BURST
70
40
20
0.01
1.2V
90
1V
1V
80
EFFICIENCY (%)
100
1.5V
EFFICIENCY (%)
90
1.2V
VOUT
3.3V
150mA
FB2
PGOOD1
MODE
1.78M
15pF
LTC3527
SHDN1
OFF
4.7μH
VIN2
FB1
1.21M
ON
4.7μH
20
0.01
FIXED
0.1
1
10
100
LOAD CURRENT (mA)
1000
35271 TA06c
35271fc
19
LTC3527/LTC3527-1
PACKAGE DESCRIPTION
UD Package
16-Lead Plastic QFN (3mm × 3mm)
(Reference LTC DWG # 05-08-1691)
0.70 ±0.05
3.50 ± 0.05
1.45 ± 0.05
2.10 ± 0.05 (4 SIDES)
PACKAGE OUTLINE
0.25 ±0.05
0.50 BSC
RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS
3.00 ± 0.10
(4 SIDES)
BOTTOM VIEW—EXPOSED PAD
PIN 1 NOTCH R = 0.20 TYP
OR 0.25 × 45° CHAMFER
R = 0.115
TYP
0.75 ± 0.05
15
PIN 1
TOP MARK
(NOTE 6)
16
0.40 ± 0.10
1
1.45 ± 0.10
(4-SIDES)
2
(UD16) QFN 0904
0.200 REF
0.00 – 0.05
NOTE:
1. DRAWING CONFORMS TO JEDEC PACKAGE OUTLINE MO-220 VARIATION (WEED-2)
2. DRAWING NOT TO SCALE
3. ALL DIMENSIONS ARE IN MILLIMETERS
4. DIMENSIONS OF EXPOSED PAD ON BOTTOM OF PACKAGE DO NOT INCLUDE
MOLD FLASH. MOLD FLASH, IF PRESENT, SHALL NOT EXCEED 0.15mm ON ANY SIDE
5. EXPOSED PAD SHALL BE SOLDER PLATED
6. SHADED AREA IS ONLY A REFERENCE FOR PIN 1 LOCATION
ON THE TOP AND BOTTOM OF PACKAGE
0.25 ± 0.05
0.50 BSC
35271fc
20
LTC3527/LTC3527-1
REVISION HISTORY
(Revision history begins at Rev C)
REV
DATE
DESCRIPTION
C
11/09
Changes to Typical Applications
PAGE NUMBER
1, 15, 16, 17, 18, 19
Change to Operation Section
12
Changes to Applications Information Section
14
35271fc
Information furnished by Linear Technology Corporation is believed to be accurate and reliable.
However, no responsibility is assumed for its use. Linear Technology Corporation makes no representation that the interconnection of its circuits as described herein will not infringe on existing patent rights.
21
LTC3527/LTC3527-1
RELATED PARTS
PART NUMBER DESCRIPTION
COMMENTS
LTC3400/
LTC3400B
600mA ISW, 1.2MHz Synchronous Step-Up DC/DC Converters
92% Efficiency, VIN : 0.85V to 5V, VOUT(MAX) = 5V, IQ = 19μA/300μA,
ISD < 1μA, ThinSOT™ Package
LTC3401
1A ISW, 3MHz Synchronous Step-Up DC/DC Converter
97% Efficiency, VIN : 0.5V to 5V, VOUT(MAX) = 6V, IQ = 38μA, ISD < 1μA,
10-Lead MS Package
LTC3421
3A ISW, 3MHz Synchronous Step-Up DC/DC Converter with
Output Disconnect
95% Efficiency, VIN : 0.5V to 4.5V, VOUT(MAX) = 5.25V, IQ = 12μA,
ISD < 1μA, QFN-24 Package
LTC3422
1.5A ISW, 3MHz Synchronous Step-Up DC/DC Converter with
Output Disconnect
95% Efficiency, VIN : 0.5V to 4.5V, VOUT(MAX) = 5.25V, IQ = 25μA,
ISD < 1μA, 3mm × 3mm DFN Package
LTC3423/
LTC3424
2A ISW, 3MHz Synchronous Step-Up DC/DC Converter
97% Efficiency, VIN : 0.5V to 5V, VOUT(MAX) = 6V, IQ = 38μA, ISD < 1μA,
10-Lead MS Package
LTC3426
2A ISW, 1.2MHz Synchronous Step-Up DC/DC Converter
92% Efficiency, VIN : 1.6V to 4.3V, VOUT(MAX) = 5V, ISD < 1μA,
SOT-23 Package
LTC3428
500mA ISW, 1.25MHz/2.5MHz Synchronous Step-Up DC/DC
Converter with Output Disconnect
92% Efficiency, VIN : 1.8V to 5V, VOUT(MAX) = 5.25V, ISD < 1μA,
2mm × 2mm DFN Package
LTC3429
600mA ISW, 500kHz Synchronous Step-Up DC/DC Converter
with Output Disconnect and Soft-Start
96% Efficiency, VIN : 0.5V to 4.4V, VOUT(MAX) = 5V, IQ = 20μA/300μA,
ISD < 1μA, ThinSOT Package
LTC3458
1.4A ISW, 1.5MHz Synchronous Step-Up DC/DC Converter/
Output Disconnect/Burst Mode Operation
93% Efficiency, VIN : 1.5V to 6V, VOUT(MAX) = 7.5V, IQ = 15μA, ISD < 1μA,
DFN-12 Package
LTC3458L
1.7A ISW, 1.5MHz Synchronous Step-Up DC/DC Converter with 94% Efficiency, VOUT(MAX ) = 6V, IQ = 12μA, DFN-12 Package
Output Disconnect, Automatic Burst Mode Operation
LTC3459
70mA ISW, 10V Micropower Synchronous Boost Converter/
Output Disconnect/Burst Mode Operation
VIN : 1.5V to 5.5V, VOUT(MAX) = 10V, IQ = 10μA, ISD < 1μA,
ThinSOT Package
LTC3525L-3
500mA ISW, 1.2MHz Synchronous Step-Up DC/DC Converters
with Output Disconnect, Automatic Burst Mode Operation
94% Efficiency, VIN : 0.85V to 5V, VOUT(MAX) = 5.25V, IQ = 7μA,
ISD < 1μA, SC70 Package
LTC3526/
LTC3526B
500mA ISW, 1.2MHz Synchronous Step-Up DC/DC Converters
with Output Disconnect, Automatic Burst Mode Operation
(LTC3526), PWM Only (LTC3526B)
94% Efficiency, VIN : 0.85V to 5V, VOUT(MAX) = 5.25V, IQ = 10μA/300μA,
ISD < 1μA, 2mm × 2mm DFN Package
LTC3528/
LTC3528B
1A, 1MHz Synchronous Step-Up DC/DC Converter with Output 94% Efficiency, VIN : 0.85V to 5V, VOUT(MAX) = 5.25V, IQ = 10μA/300μA,
Disconnect, Automatic Burst Mode Operation, PWM Only
ISD < 1μA, 2mm × 3mm DFN Package
(LTC3528B)
35271fc
22
Linear Technology Corporation
LT 1109 REV C • PRINTED IN USA
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408) 432-1900 ● FAX: (408) 434-0507
●
www.linear.com
© LINEAR TECHNOLOGY CORPORATION 2007
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