LINER LTC3539EDCB

LTC3539/LTC3539-2
2A, 1MHz/2MHz
Synchronous Step-Up
DC/DC Converters
FEATURES
DESCRIPTION
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The LTC®3539/LTC3539-2 are synchronous, 2A step-up
DC/DC converters with output disconnect. Synchronous
rectification enables high efficiency in the low profile
2mm × 3mm DFN package. Battery life is extended with
a 700mV start-up voltage and operation down to 500mV
once started.
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Delivers 3.3V at 900mA From 2 Alkaline/NiMH Cells
Delivers 5V at 900mA From a Lithium-Polymer
Battery
VIN Start-Up Voltage: 700mV
1.5V to 5.25V VOUT Range
Up to 94% Efficiency
VIN > VOUT Operation
1MHz (LTC3539) or 2MHz (LTC3539-2) Fixed
Frequency Operation
Output Disconnect
Selectable Burst Mode® or PWM Operation
10μA Quiescent Current
Logic Controlled Shutdown: <1μA
Requires Only 6 External Components
Low Profile (2mm × 3mm × 0.75mm) DFN Package
APPLICATIONS
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A switching frequency of 1MHz (LTC3539) or 2MHz
(LTC3539-2) minimizes solution footprint 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 LTC3539/LTC3539-2
feature a pin-enabled automatic Burst Mode operation at
light load conditions. Anti-ring circuitry reduces EMI by
damping the inductor in discontinuous mode. Additional
features include a low shutdown current of under 1μA and
thermal overload protection.
The LTC3539/LTC3539-2 are offered in a 2mm × 3mm ×
0.75mm DFN package.
Medical Instruments
Portable Bar Code Scanners
Noise Canceling Headphones
Portable GPS Navigation
Handheld PCs
L, LT, LTC, LTM and Burst Mode are registered trademarks of Linear Technology Corporation.
All other trademarks are the property of their respective owners.
TYPICAL APPLICATION
Wide VIN, High Power 3.3V Regulator
Efficiency and Power Loss vs
Load Current
4.7μH
100
2.2μF
VOUT
1M
OFF ON
SHDN
GND
22pF
FB
PGND
VOUT
3.3V
600mA
22μF
100
70
60
V = 2.4V
50 VIN = 3.3V
OUT
40
10
POWER LOSS
30
562k
POWER LOSS (mW)
LTC3539
MODE
EFFICIENCY
80
SW
VIN
PWM BURST
1000
90
EFFICIENCY (%)
VIN
1.8V TO 3.6V
1
20
3539 TA01a
FREQUENCY = 1MHz
FREQUENCY = 2MHz
10
0
0.1
1
10
100
ILOAD AVERAGE (mA)
0.1
1000
3539 TA01b
3539f
1
LTC3539/LTC3539-2
ABSOLUTE MAXIMUM RATINGS
PIN CONFIGURATION
(Note 1)
VIN Voltage ................................................... –0.3V to 6V
SW Voltage
DC............................................................ –0.3V to 6V
Pulsed <100ns ......................................... –0.3V to 7V
SHDN, FB, MODE Voltage ............................ –0.3V to 6V
VOUT ............................................................. –0.3V to 6V
Operating Temperature (Notes 2, 5) ......... –40°C to 85°C
Storage Temperature Range................... –65°C to 125°C
TOP VIEW
8 VOUT
SW 1
PGND 2
7 MODE
9
6 FB
GND 3
5 SHDN
VIN 4
DCB PACKAGE
8-LEAD (2mm s 3mm) PLASTIC DFN
TJMAX = 125°C, θJA = 60°C/W TO 85°C/W (NOTE 6)
EXPOSED PAD (PIN 9) IS GND, MUST BE SOLDERED TO PCB
ORDER INFORMATION
LEAD FREE FINISH
TAPE AND REEL
PART MARKING
PACKAGE DESCRIPTION
TEMPERATURE RANGE
LTC3539EDCB#PBF
LTC3539EDCB#TRPBF
LDCS
8-Lead (2mm × 3mm) Plastic DFN
–40°C to 85°C
LTC3539EDCB-2#PBF
LTC3539EDCB-2#TRPBF
LDPH
8-Lead (2mm × 3mm) Plastic DFN
–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
The l denotes the specifications which apply over the specified
temperature range of –40°C to 85°C, otherwise specifications are at TA = 25°C. VIN = 1.2V, VOUT = 3.3V, unless otherwise noted.
PARAMETER
CONDITIONS
MIN
Input Voltage Range
After Start-Up
0.5
Minimum Start-Up Voltage
ILOAD = 1mA, VOUT = 0V
Output Voltage Adjust Range
TYP
0.7
l
1.5
l
1.170
MAX
UNITS
5
V
0.88
V
5.25
V
1.200
1.230
V
1
50
nA
VSHDN = 0V, Not Including Switch Leakage, VOUT = 0V
0.01
1
μA
Quiescent Current - Active
Measured on VOUT, Non-Switching
300
500
μA
Quiescent Current - Burst
Measured on VOUT, FB >1.230V
10
18
μA
Feedback Voltage
Feedback Input Current
VFB = 1.2V
Quiescent Current - Shutdown
N-Channel MOSFET Switch Leakage Current
VSW = 5V
0.1
10
μA
P-Channel MOSFET Switch Leakage Current
VSW = 5V, VOUT = 0V
0.1
20
μA
N-Channel MOSFET Switch On Resistance
VOUT = 3.3V
0.09
Ω
P-Channel MOSFET Switch On Resistance
VOUT = 3.3V
0.125
Ω
2.6
A
N-Channel MOSFET Current Limit
l
2
3539f
2
LTC3539/LTC3539-2
ELECTRICAL CHARACTERISTICS
The l denotes the specifications which apply over the specified
temperature range of –40°C to 85°C, otherwise specifications are at TA = 25°C. VIN = 1.2V, VOUT = 3.3V, unless otherwise noted.
PARAMETER
CONDITIONS
Maximum Duty Cycle
VFB = 1.15V
l
Minimum Duty Cycle
VFB = 1.3V
l
Switching Frequency
LTC3539
LTC3539-2
l
l
MODE Input High Voltage
MIN
TYP
87
90
0.7
1.8
1
2
SHDN Input High Voltage
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 LTC3539E/LTC3539E-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.
MHz
MHz
0.3
0.3
V
1
μA
0.88
VSHDN = 1.2V
VSHDN = 3.3V
%
V
V
SHDN Input Low Voltage
SHDN Input Current
1.3
2.4
0.88
VMODE = 1.2V
UNITS
%
0
MODE Input Low Voltage
MODE Input Current
MAX
0.3
1
0.3
V
1
2
μA
μA
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.
3539f
3
LTC3539/LTC3539-2
TYPICAL PERFORMANCE CHARACTERISTICS
Efficiency vs Load Current and
VIN, VOUT = 1.8V
Efficiency vs Load Current and
VIN, VOUT = 3.3V
100
1000
100
90
1000
90
100
50
POWER LOSS
1
40
30
20
VIN = 1V
VIN = 1.2V
VIN = 1.5V
10
0
0.1
1
EFFICIENCY
60
10
50
40
POWER LOSS
30
0.1
1
20
VIN = 1.2V
VIN = 1.8V
VIN = 3V
10
0.01
1000
10
100
LOAD CURRENT (mA)
100
70
0
0.1
1
10
100
LOAD CURRENT (mA)
3539 G01
Efficiency vs Load Current and
VIN, VOUT = 5V
90
90
80
80
40
POWER LOSS
30
VIN = 2.4V
VIN = 3.6V
VIN = 4.2V
10
0
0.1
1
10
100
LOAD CURRENT (mA)
60
1200
50
20
400
10
200
0
0.5
1.0
1.5
2.0
2.5 3.0
VIN (V)
3.5
0
0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0
VIN (V)
3539 G04
3539 G05
OUTPUT CURRENT (mA)
LOAD RESISTANCE (Ω)
40
30
20
VOUT = 1.8V
VOUT = 2.5V
VOUT = 3.3V
VOUT = 5V
10
0
0.75
0.85
0.95
VIN (V)
1.05
1.15
3539 G06
Normalized Current Limit vs VOUT
1.10
60
50
0.1
0.65
VOUT = 1.8V
VOUT = 2.5V
VOUT = 3.3V
VOUT = 5V
4.5
4.0
Burst Mode Threshold Current vs
VIN and VOUT
VOUT = 3.3V
10
800
600
Minimum Load Resistance During
Start-Up vs VIN
100
1000
30
0.1
1000
1000
1600
1400
3539 G03
10000
1800
70
40
1
20
VOUT = 1.8V
VOUT = 2.5V
VOUT = 3.3V
VOUT = 5V
IOUT (mA)
10
50
Maximum Output Current vs VIN
2000
0
0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5
INPUT VOLTAGE (V)
3539 G11
NORMALIZED CURRENT LIMIT (A)
60
IIN (μA)
100
EFFICIENCY
70
POWER LOSS (mW)
EFFICIENCY (%)
100
1000
0.1
1000
3539 G02
No Load Input Current vs VIN
100
POWER LOSS (mW)
10
60
80
POWER LOSS (mW)
EFFICIENCY
70
EFFICIENCY (%)
80
EFFICIENCY (%)
(TA = 25°C unless otherwise noted)
1.05
1.00
0.95
0.90
0.85
0.80
1.0
1.5
2.0
2.5 3.0 3.5
VOUT (V)
4.0
4.5
5.0
3539 G16
3539f
4
LTC3539/LTC3539-2
TYPICAL PERFORMANCE CHARACTERISTICS
RDS(ON) vs VOUT
VFB vs Temperature
0.25
1.2
0.25
PMOS
0.15
0.10
NMOS
0.05
CHANGE IN VFB (%)
0.50
NORMALIZED RDS(ON) (Ω)
1.3
0.20
RDS(ON) (Ω)
RDS(ON) Change vs Temperature
0.30
1.1
1.0
0.9
0.8
0
1.5
2.0
2.5
3.0 3.5 4.0
VOUT (V)
4.5
5.0
–0.25
–0.50
–0.75
0.7
–50
5.5
0
–30
–10 10
30
50
TEMPERATURE (°C)
70
90
3539 G07
–1.00
–60 –40 –20 0
20 40 60
TEMPERATURE (°C)
3539 G08
Start-Up Voltage vs Temperature
80
100
3539 G09
Burst Mode SW and IL(AC)
Fixed Frequency SW and IL(AC)
0.80
0.75
1mA LOAD
VIN (V)
0.70
0.65
NO LOAD
SW PIN
2V/DIV
SW PIN
5V/DIV
VOUT
20mV/DIV
AC-COUPLED
VOUT
20mV/DIV
AC-COUPLED
INDUCTOR
CURRENT
500mA/DIV
INDUCTOR
CURRENT
200mA/DIV
0.60
0.55
0.50
–50
–25
0
25
50
TEMPERATURE (°C)
75
500ns/DIV
VIN = 2.4V
VOUT = 3.3V AT 400mA
COUT = 22μF
3539 G12
5μs/DIV
3539 G13
VIN = 3.3V
VOUT = 5V
COUT = 22μF
100
3539 G10
Load Step, Fixed Frequency
Load Step, Burst Mode Operation
VOUT
50mV/DIV
AC-COUPLED
VOUT
50mV/DIV
AC-COUPLED
LOAD
CURRENT
200mA/DIV
LOAD
CURRENT
200mA/DIV
500μs/DIV
VIN = 2.4V
VOUT = 3.3V
COUT = 22μF
ILOAD = 100mA TO 250mA STEP
3539 G14
500μs/DIV
VIN = 2.4V
VOUT = 3.3V
COUT = 22μF
ILOAD = 20mA TO 170mA
3539 G15
3539f
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LTC3539/LTC3539-2
PIN FUNCTIONS
SW (Pin 1): Switch Pin. Connect inductor between SW
and VIN. Keep PCB trace lengths as short and wide as possible to reduce EMI. If the inductor current falls to zero,
or SHDN is low, an internal anti-ring resistor is connected
from SW to VIN to minimize EMI.
FB (Pin 6): Feedback Input to the gm Error Amplifier. Connect resistor divider tap to this pin. The output voltage
can be adjusted from 1.5V to 5.25V by: VOUT = 1.20V •
[1 + (R2/R1)]
MODE (Pin 7): Burst Mode Pin. A logic controlled input
to select either automatic Burst Mode operation or forced
fixed frequency operation.
PGND (Pin 2), GND (Pin 3): Signal and Power Ground.
Provide a short direct PCB path between PGND, GND and
the (–) side of the input and output capacitors.
MODE = High: Burst Mode operation at light loads
VIN (Pin 4): Battery Input Voltage. Connect a minimum
of 2.2μF ceramic decoupling capacitor from this pin to
ground.
MODE = Low: Fixed frequency PWM Mode
VOUT (Pin 8): Output Voltage Sense and Drain of the
Internal Synchronous Rectifier. PCB trace length from
VOUT to the output filter capacitor should be as short and
wide as possible.
SHDN (Pin 5): Logic Controlled Shutdown Input. There
is an internal 4MΩ pull-down on this pin.
SHDN = High: Normal operation.
Exposed Pad (Pin 9): The exposed pad must be soldered
to the PCB ground plane. It serves as another ground
connection, and as a means of conducting heat away
from the die.
SHDN = Low: Shutdown, quiescent current <1μA.
BLOCK DIAGRAM
VIN
1
VOUT
4
SW
VIN
VSEL
VBEST
WELL
SWITCH
VB
VOUT
8
VOUT
SHDN
–
VREF
IPK
UVLO
UVLO
3
SLOPE
COMPARATOR
+
1MHz/2MHz
OSC
CLK
THERMAL
SHUTDOWN
TSD
BURST
9
VREF
FB
ERROR
AMPLIFIER/SLEEP
COMPARATOR
LOGIC AND
BURST MODE
CONTROL
7
MODE
R1
IZERO
START-UP
PWM BURST
FB
–
IPK
COMPARATOR
VREF
6
IZERO
COMPARATOR
+
SHUTDOWN
+
SHUTDOWN
5
–
OFF ON
R2
GATE DRIVERS
AND
ANTI-CROSS
CONDUCTION
EXPOSED PAD
CLAMP
WAKE
SOFT-START
2
PGND
3
GND
3539 BD
3539f
6
LTC3539/LTC3539-2
OPERATION
DETAILED DESCRIPTION
The LTC3539 is a high power synchronous boost converter
in an 8-lead 2mm × 3mm DFN package. With the ability
to start up and operate from inputs of 700mV, the device
features 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 internal loop compensation simplifies the design process while minimizing the
number of external components. The switching frequency
of the LTC3539 is nominally 1MHz, while the LTC3539-2
switches at 2MHz. Operation of the LTC3539 and LTC3539-2
is identical in all other respects.
With its low RDS(ON) and low gate charge internal N-channel MOSFET switch and P-channel MOSFET synchronous
rectifier, the LTC3539 achieves high efficiency over a wide
range of load current. Burst Mode operation maintains
high efficiency at very light loads, reducing the quiescent
current to just 10μA.
Converter operation can be best understood by referring
to the Block Diagram.
Low Voltage Start-Up
The LTC3539 includes an independent start-up oscillator
designed to start up at an input voltage of 0.7V (typical).
Soft-start and inrush current limiting are provided during
start-up, as well as normal mode.
When either VIN or VOUT exceeds 1.4V typical, the IC
enters normal operating mode. Once the output voltage
exceeds the input by 0.24V, the IC powers itself from
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. The limiting factor for the application becomes the ability of the power source to supply
sufficient energy to the output at the low voltages, and the
maximum duty cycle, which is clamped at 90% typical.
Note that at low input voltages, small voltage drops due
to series resistance become critical, and greatly limit the
power delivery capability of the converter.
Low Noise Fixed Frequency Operation
Soft-Start: The LTC3539/LTC3539-2 contains internal
circuitry to provide soft-start operation. The internal
soft-start circuitry ramps the peak inductor current from
zero to its peak value of 2.6A (typical) in approximately
0.5ms, allowing start-up into heavy loads. The soft-start
circuitry is reset in the event of a thermal shutdown or
shutdown command.
Oscillator: An internal oscillator sets the switching
frequency to 1MHz for the LTC3539, and 2MHz for the
LTC3539-2.
Shutdown: The part is shutdown by pulling the SHDN
pin below 0.3V, and activated by pulling the SHDN pin
above 0.88V. Note that SHDN can be driven above VIN
or VOUT, as long as it is limited to less than the absolute
maximum rating.
Error Amplifier: The error amplifier is a transconductance
type. The non-inverting input is internally connected to
the 1.2V reference and the inverting input is connected
to FB. Clamps limit the minimum and maximum error
amp output voltage for improved large signal transient
response. Power converter control loop compensation is
provided internally. A voltage divider from VOUT to ground
programs the output voltage via FB from 1.5V to 5.25V.
VOUT = 1.2V • [1 + (R2/R1)].
Current Sensing: Lossless current sensing converts the
peak current signal of the N-channel MOSFET switch
into a voltage which is summed with the internal slope
compensation. The summed signal is compared to the
error amplifier output to provide a peak current control
command for the PWM.
Current Limit: The current limit comparator shuts off the
N-channel MOSFET switch once its threshold is reached.
Peak switch current is limited to approximately 2.6A,
independent of input or output voltage, unless VOUT falls
below 0.7V, in which case the current limit is cut in half.
3539f
7
LTC3539/LTC3539-2
OPERATION
Zero Current Comparator: The zero current comparator
monitors the inductor current to the output and shuts off
the synchronous rectifier once this current reduces to approximately 40mA. This prevents the inductor current from
reversing in polarity, improving efficiency at light loads.
Synchronous Rectifier: The P-channel MOSFET synchronous rectifier is disabled when VOUT is much less than VIN.
This is to control inrush current and to prevent inductor
current from running away
Anti-ringing Control: The anti-ringing control connects
a resistor across the inductor to prevent high frequency
ringing on the SW pin during discontinuous current mode
operation. The ringing of the resonant circuit formed by L
and CSW (capacitance on SW pin) is low energy, but can
cause EMI radiation.
Output Disconnect: The LTC3539 is designed to allow true
output disconnect by eliminating body diode conduction of
the internal P-channel MOSFET rectifier. This allows VOUT
to go to zero volts during shutdown, drawing no current
from the input source. It also provides 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 an external Schottky
diode connected between the SW pin and VOUT. The output
disconnect feature also allows VOUT 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 internal soft-start capacitor will be
discharged. The device will be enabled again when the die
temperature drops by about 15°C.
Burst Mode Operation
When Burst Mode operation is enabled by bringing the
MODE pin above 0.88V, the LTC3539 will automatically
enter Burst Mode operation at light load current, then
return to fixed frequency PWM mode when the load increases. Refer to the typical performance characteristics
to see the output load Burst Mode threshold 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 operation is entered.
In Burst Mode operation, the LTC3539 still switches at a
fixed frequency, using the same error amplifier and loop
compensation for peak current mode control. This control
method eliminates any output transient when switching
between modes. In Burst Mode operation, energy is delivered to the output until it reaches the nominal regulation
value, then the LTC3539 transitions to Sleep mode where
the outputs are off and the LTC3539 consumes only 10μA
of quiescent current from VOUT. 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 to peak, can be reduced by
using more output capacitance (47μF or greater).
As the load increases, the LTC3539 will automatically leave
Burst Mode operation. Once the LTC3539 has left Burst
Mode operation and returned to normal operation, it will
remain there until the output load is reduced below the
burst threshold.
Burst Mode operation is inhibited during start-up until
soft-start is complete and VOUT is at least 0.24V greater
than VIN.
When the MODE pin is below 0.3V, the LTC3539 features
continuous PWM operation. In this mode, at very light
loads, the LTC3539 will exhibit pulse-skip operation. If the
MODE pin voltage exceeds the greater of VIN or VOUT by
0.5V, the MODE pin will sink additional current.
3539f
8
LTC3539/LTC3539-2
APPLICATIONS INFORMATION
VIN > VOUT Operation
COMPONENT SELECTION
The LTC3539 will maintain output voltage regulation
even when the input voltage is above the desired output.
Note that the efficiency and the maximum output current
capability are reduced. Refer to Typical Performance
Characteristics.
Inductor Selection
Short-Circuit Protection
The LTC3539 output disconnect feature allows an output
short circuit while maintaining a maximum internally set
current limit. To reduce power dissipation under shortcircuit conditions, the peak switch current limit is reduced
to 1.4A (typical).
The LTC3539 can utilize small surface mount and chip
inductors due to the high switching frequency. Inductor
values between 3.3μH and 4.7μH for the LTC3539 and
between 1.5μH and 2.5μH for the LTC3539-2 are suitable
for most applications*. Larger values of inductance will
allow slightly greater output current capability (and lower
the Burst Mode threshold) by reducing the inductor ripple
current. However, increasing the inductance above 10μH
will increase size while providing little improvement in
output current capability.
The minimum inductance value is given by:
Schottky Diode
Although it is not required, adding a Schottky diode from
SW to VOUT will improve efficiency by about 2%. Note that
this defeats the output disconnect, VIN > VOUT operation
and short circuit protection features.
PCB LAYOUT GUIDELINES
The high speed operation of the LTC3539 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.
LTC3539
SW 1
PGND 2
GND 3
+
VIN 4
8 VOUT
7 MODE
6 FB
MINIMIZE
TRACE ON FB
AND SW
5 SHDN
L>
VIN(MIN) • ( VOUT(MAX ) − VIN(MIN) )
Ripple • VOUT(MAX ) • f
Where:
f = 1 for the LTC3539 or 2.2 for the LTC3539-2
Ripple = allowable inductor current ripple (Amps
peak-to-peak)
VIN(MIN) = minimum input voltage
VOUT(MAX) = maximum output voltage
The inductor current ripple is typically set for 20% to 40%
of the maximum inductor current. High frequency ferrite
core inductor materials improve efficiency by reducing
frequency dependent power losses compared to cheaper
powdered iron types. The inductor should have low ESR
(series resistance of the windings) to reduce the I2R power
losses, and must accomodate the peak inductor current
without saturating. Molded chokes and some chip inductors
usually do not have enough core area to support the peak
inductor current of 2.6A seen on the LTC3539. To minimize
radiated noise, use a shielded inductor. See Table 1 for
suggested suppliers and representative components.
*Single cell applications (VIN < 1.6V) should use a 2.2μH inductor for the LTC3539
VIN
MULTIPLE VIAS
TO GROUND PLANE
3539 F01
Figure 1. Recommended Component Placement for
Single Layer Board
3539f
9
LTC3539/LTC3539-2
APPLICATIONS INFORMATION
An output capacitor of up to 100μF is required at lower
output voltages. Even with VOUT greater than 3V, larger
values up to 100μF may be used to obtain extremely low
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.
Table 1. Representative Inductors
VENDOR
PART/STYLE
Coilcraft
(847) 639-6400
www.coilcraft.com
MSS5131
LPS4018-222
MSS6132
MOS6020
Murata
www.murata.com
LQH55D
LQH66S
Sumida
(847) 956-0666
www.sumida.com
CDRH4D22
CDRH4D28C
CDRH5D28
CDR6D23
TDK
(847) 803-6100
www.component.tdk.com
VLF5014ST
Toko
(408) 432-8282
www.tokoam.com
D53LC
D63LCB
Wurth
(201) 785-8800
www.we-online.com
WE-TPC Type LH, X
WE-PD Type XS
A small ceramic capacitor in parallel with a larger tantalum
capacitor may be used in demanding applications which
have large load transients. A feedforward capacitor across
the top resistor of the feedback divider (from VOUT to FB)
is usually required to improve transient response. A typical
value of 22pF 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. 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.
Output and Input Capacitor Selection
The internal loop compensation of the LTC3539 is designed
to be stable with output capacitor values of 10μF or greater.
Although ceramic capacitors are recommended, low ESR
(equivalent series resistance) tantalum capacitors may be
used as well.
Table 2. Capacitor Vendor Information
Low ESR capacitors should be used to minimize the
output voltage ripple. Multilayer ceramic capacitors are
an excellent choice as they have extremely low ESR and
are available in small footprints. A 22μF to 47μF output
capacitor is sufficient for output voltages of 3V or greater.
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
TYPICAL APPLICATIONS
1 Cell to 1.8V
1 Cell to 3.3V
2.2μH
VIN
1V TO 1.6V
2.2μH
VIN
0.9V TO 1.6V
2.2μF
VIN
VIN
MODE VOUT
SHDN
*AT HIGH LOAD CURRENTS, A
TANTALUM CAPACITOR WILL
IMPROVE PERFORMANCE.
22pF
FB
GND PGND
2.2μF
SW
VIN
LTC3539
1M
OFF ON
2.2μH
VIN
3V TO 4.5V
2.2μF
SW
LTC3539
PWM BURST
Li-Ion Cell to 5V
VOUT
1.8V
500mA
22μF*
x5
1.91M
3539 TA02
PWM BURST
MODE VOUT
1M
OFF ON
SHDN
22pF
FB
GND PGND
SW
LTC3539-2
VOUT
3.3V
350mA
22μF
x2
562k
3539 TA03
PWM BURST
MODE VOUT
1M
OFF ON
SHDN
22pF
FB
GND PGND
VOUT
5V
750mA
22μF
309k
3539 TA04
3539f
10
LTC3539/LTC3539-2
PACKAGE DESCRIPTION
DCB Package
8-Lead Plastic DFN (2mm × 3mm)
(Reference LTC DWG # 05-08-1718 Rev A)
0.70 ±0.05
1.35 ±0.05
3.50 ±0.05
1.65 ± 0.05
2.10 ±0.05
PACKAGE
OUTLINE
0.25 ± 0.05
0.45 BSC
1.35 REF
RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS
APPLY SOLDER MASK TO AREAS THAT ARE NOT SOLDERED
R = 0.115
TYP
R = 0.05
5
TYP
2.00 ±0.10
(2 SIDES)
0.40 ± 0.10
8
1.35 ±0.10
1.65 ± 0.10
3.00 ±0.10
(2 SIDES)
PIN 1 NOTCH
R = 0.20 OR 0.25
× 45° CHAMFER
PIN 1 BAR
TOP MARK
(SEE NOTE 6)
(DCB8) DFN 0106 REV A
4
0.200 REF
1
0.23 ± 0.05
0.45 BSC
0.75 ±0.05
1.35 REF
BOTTOM VIEW—EXPOSED PAD
0.00 – 0.05
NOTE:
1. DRAWING IS NOT A JEDEC PACKAGE OUTLINE
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
3539f
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.
11
LTC3539/LTC3539-2
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
LTC3402
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
LTC3421
3A ISW, 3MHz, Synchronous Step-Up DC/DC Converter 95% Efficiency VIN: 0.5V to 4.5V, VOUT(MAX) = 5.25V, IQ = 12μA, ISD <1μA,
with Output Disconnect
QFN24 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
1A/2A ISW, 3MHz, Synchronous Step-Up DC/DC
Converter
95% Efficiency VIN: 0.5V to 5.5V, VOUT(MAX) = 5.5V, IQ = 38μA, ISD <1μA,
10-Lead MS Package
LTC3426
2A ISW, 1.2MHz, 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 Converters with Output Disconnect
92% Efficiency VIN: 1.8V to 5V, VOUT(MAX) = 5.25V, ISD <1μA, 3mm × 3mm
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,
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,
DFN12 Package
LTC3458L
1.7A ISW, 1.5MHz, Synchronous Step-Up DC/DC
Converter with Output Disconnect, Automatic Burst
Mode Operation
94% Efficiency VOUT(MAX) = 6V, IQ = 12μA, DFN12 Package
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
LTC3525-3/
LTC3525-3.3/
LTC3525-5
400mA Micropower Synchronous Step-Up DC/DC
Converter with Output Disconnect
95% Efficiency VIN: 1V to 4.5V, VOUT(MAX) = 3.3V or 5V, IQ = 7μA, ISD <1μA,
SC-70 Package
LTC3525L-3
400mA Micropower Synchronous Step-Up DC/DC
Converter with Output Disconnect
95% Efficiency VIN: 0.88V to 4.5V, VOUT(MAX) = 3V, IQ = 7μA, ISD <1μA,
SC-70 Package
LTC3526/
LTC3526B
500mA, 1MHz Synchronous Step-Up DC/DC Converter 94% Efficiency VIN: 0.85V to 5V, VOUT(MAX) = 5.25V, IQ = 9μA, ISD <1μA,
2mm × 2mm DFN-6 Package
with Output Disconnect
LTC3526L
550mA, 1MHz Synchronous Step-Up DC/DC Converter 94% Efficiency VIN: 0.68V to 5V, VOUT(MAX) = 5.25V, IQ = 9μA, ISD <1μA,
with Output Disconnect
2mm × 2mm DFN-6 Package
LTC3527/
LTC3527-1
Dual 800mA/400mA, 1.2MHz/2.2MHz Synchronous
Step-Up DC/DC Converter with Output Disconnect
LTC3528/
LTC3528B
1A, 1MHz Synchronous Step-Up DC/DC Converter with 94% Efficiency VIN: 0.68V to 5V, VOUT(MAX) = 5.25V, IQ = 12μA, ISD <1μA,
2mm × 3mm DFN-8 Package
Output Disconnect
94% Efficiency VIN: 0.68V to 5V, VOUT(MAX) = 5.25V, IQ = 12μA, ISD <1μA,
3mm × 3mm QFN-16 Package
ThinSOT is a trademark of Linear Technology Corporation.
3539f
12 Linear Technology Corporation
LT 0408 • PRINTED IN USA
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408) 432-1900 ● FAX: (408) 434-0507
●
www.linear.com
© LINEAR TECHNOLOGY CORPORATION 2008