LTC3440 - Micropower Synchronous Buck-Boost DC/DC Converter

LTC3440
Micropower Synchronous
Buck-Boost DC/DC Converter
Features
Description
Single Inductor
n Fixed Frequency Operation with Battery Voltages
Above, Below or Equal to the Output
n Synchronous Rectification: Up to 96% Efficiency
n 25µA Quiescent Current in Burst Mode® Operation
n Up to 600mA Continuous Output Current
n No Schottky Diodes Required (V
OUT < 4.3V)
nV
Disconnected
from
V
During
Shutdown
OUT
IN
n 2.5V to 5.5V Input and Output Range
n Programmable Oscillator Frequency
from 300kHz to 2MHz
n Synchronizable Oscillator
n Burst Mode Enable Control
n <1µA Shutdown Current
n Small Thermally Enhanced 10-Pin MSOP and
(3mm × 3mm) DFN Packages
The LTC®3440 is a high efficiency, fixed frequency, BuckBoost DC/DC converter that operates from input voltages
above, below or equal to the output voltage. The topology
incorporated in the IC provides a continuous transfer
function through all operating modes, making the product ideal for single lithium-ion, multicell alkaline or NiMH
applications where the output voltage is within the battery
voltage range.
n
Applications
n
n
n
n
The device includes two 0.19Ω N-channel MOSFET
switches and two 0.22Ω P-channel switches. Switching frequencies up to 2MHz are programmed with an
external resistor and the oscillator can be synchronized
to an external clock. Quiescent current is only 25µA in
Burst Mode operation, maximizing battery life in portable
applications. Burst Mode operation is user controlled and
can be enabled by driving the MODE/SYNC pin high. If the
MODE/SYNC pin has either a clock or is driven low, then
fixed frequency switching is enabled.
Other features include a 1µA shutdown, soft-start control, thermal shutdown and current limit. The LTC3440
is available in the 10-pin thermally enhanced MSOP and
(3mm × 3mm) DFN packages.
Palmtop Computers
Handheld Instruments
MP3 Players
Digital Cameras
L, LT, LTC, LTM, Linear Technology, Burst Mode 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
Li-Ion to 3.3V at 600mA Buck-Boost Converter
L1
10µH
Li-Ion
+
C1 *
10µF
2
1
SHDN/SS
FB
MODE/SYNC
VC
RT
RT
60.4k
*1 = Burst Mode OPERATION
0 = FIXED FREQUENCY
GND
R1
340k
9
C2
22µF
C5 1.5nF
10
5
R3
15k
EFFICIENCY (%)
4
SW1
SW2
LTC3440
6
7
VIN
VOUT
8
VOUT = 3.3V
98 IOUT = 100mA
96 fOSC = 1MHz
VOUT
3.3V
600mA
3
VIN = 2.7V TO 4.2V
Efficiency vs V­IN
100
94
92
90
88
86
84
R2
200k
82
80
C1: TAIYO YUDEN JMK212BJ106MG
C2: TAIYO YUDEN JMK325BJ226MM
L1: SUMIDA CDRH6D38-100
2.5
3440 TA01
3.0
3.5
4.0
VIN (V)
4.5
5.0
5.5
3440 TA02
3440fc
For more information www.linear.com/LTC3440
1
LTC3440
Absolute Maximum Ratings
(Note 1)
VIN, VOUT Voltage ........................................ – 0.3V to 6V
SW1, SW2 Voltage....................................... –0.3V to 6V
VC, RT, FB, SHDN/SS,
MODE/SYNC Voltage................................... –0.3V to 6V
Operating Temperature Range (Note 2)....–40°C to 85°C
Storage Temperature Range................... –65°C to 125°C
Lead Temperature (Soldering, 10 sec).................... 300°C
Pin Configuration
TOP VIEW
TOP VIEW
RT
1
10 VC
MODE/SYNC
2
9 FB
SW1
3
SW2
4
7 VIN
GND
5
6 VOUT
11
8 SHDN/SS
10
9
8
7
6
1
2
3
4
5
RT
MODE/SYNC
SW1
SW2
GND
VC
FB
SHDN/SS
VIN
VOUT
MS PACKAGE
10-LEAD PLASTIC MSOP
TJMAX = 125°C,
θJA = 130°C/W 1 layer board
θJA = 100°C/W 4 layer board
θJC = 45°C/W
DD PACKAGE
10-LEAD (3mm × 3mm) PLASTIC DFN
EXPOSED PAD (PIN 11) IS GND
MUST BE SOLDERED TO PCB
TJMAX = 125°C, θJA = 43°C/W, θJC = 3°C/W
Order Information
LEAD FREE FINISH
TAPE AND REEL
PART MARKING
PACKAGE DESCRIPTION
TEMPERATURE RANGE
LTC3440EDD#PBF
LTC3440EDD#TRPBF
LBKT
10-Lead (3mm × 3mm) Plastic DFN
–40°C to 85°C
LTC3440EMS#PBF
LTC3440EMS#TRPBF
LTNP
10-Lead Plastic MSOP
–40°C to 85°C
Consult LTC Marketing for parts specified with wider operating temperature ranges.
Consult LTC Marketing for information on nonstandard 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 ● denotes specifications that apply over the full operating
temperature range, otherwise specifications are at TA = 25°C. VIN = VOUT = 3.6V, RT = 60k, unless otherwise noted.
PARAMETER
CONDITIONS
MIN
TYP
MAX
2.4
UNITS
Input Start-Up Voltage
l
2.5
V
Input Operating Range
l
2.5
5.5
V
Output Voltage Adjust Range
l
2.5
5.5
V
Feedback Voltage
l
1.196
1.22
1.244
V
1
50
nA
Feedback Input Current
VFB = 1.22V
Quiescent Current, Burst Mode Operation
VC = 0V, MODE/SYNC = 3V (Note 3)
25
40
µA
Quiescent Current, Shutdown
SHDN = 0V, Not Including Switch Leakage
0.1
1
µA
Quiescent Current, Active
VC = 0V, MODE/SYNC = 0V (Note 3)
600
1000
µA
NMOS Switch Leakage
Switches B and C
0.1
5
µA
3440fc
2
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LTC3440
ELECTRICAL
CHARACTERISTICS
The
● denotes specifications that apply over the full operating temperature
range, otherwise specifications are at TA = 25°C. VIN = VOUT = 3.6V, RT = 60k, unless otherwise noted.
PARAMETER
CONDITIONS
TYP
MAX
PMOS Switch Leakage
Switches A and D
MIN
0.1
10
NMOS Switch On Resistance
Switches B and C
0.19
Ω
PMOS Switch On Resistance
Switches A and D
0.22
Ω
Input Current Limit
Maximum Duty Cycle
Boost (% Switch C On)
Buck (% Switch A On)
l
1
l
l
55
100
Minimum Duty Cycle
l
Frequency Accuracy
l
µA
A
75
%
%
0
0.8
MODE/SYNC Threshold
1
0.4
VMODE/SYNC = 5.5V
MODE/SYNC Input Current
UNITS
0.01
%
1.2
MHz
2
V
1
µA
Error Amp AVOL
90
dB
Error Amp Source Current
15
µA
Error Amp Sink Current
380
SHDN/SS Threshold
When IC is Enabled
When EA is at Maximum Boost Duty Cycle
SHDN/SS Input Current
VSHDN = 5.5V
Note 1: Absolute Maximum Ratings are those values beyond which the
life of the device may be impaired.
Note 2: The LTC3440E is guaranteed to meet performance specifications
from 0°C to 70°C. Specifications over the – 40°C to 85°C operating
0.4
l
µA
1
2.2
1.5
V
V
0.01
1
µA
temperature range are assured by design, characterization and
correlation with statistical process controls.
Note 3: Current measurements are performed when the outputs are not
switching.
TYPICAL PERFORMANCE CHARACTERISTICS
Li-Ion to 3.3V Efficiency
(fOSC = 300kHz)
Li-Ion to 3.3V Efficiency,
Power Loss (fOSC = 1MHz)
VIN = 2.5V
VIN = 3.3V
50
70
60
50
40
40
30
30
fOSC = 300kHz
20
0.1
10
100
1
OUTPUT CURRENT (mA)
1000
3440 G01
20
0.1
90
100
VIN = 4.2V
VIN = 2.5V
100
VIN = 3.3V
10
VIN = 3.3V
1
fOSC = 1MHz
10
100
1
OUTPUT CURRENT (mA)
0.1
1000
3440 G02
Burst Mode
OPERATION
80
EFFICIENCY (%)
70
60
80
VIN = 4.2V
Burst Mode
OPERATION
POWER LOSS (mW)
EFFICIENCY (%)
80
90
Burst Mode
OPERATION
EFFICIENCY (%)
90
1000
100
100
Li-Ion to 3.3V Efficiency
(fOSC = 2MHz)
70
60
50
VIN = 2.5V
VIN = 4.2V
VIN = 3.3V
40
30
20
0.1
fOSC = 2MHz
1
10
100
OUTPUT CURRENT (mA)
1000
3440 G03
3440fc
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3
LTC3440
Typical Performance Characteristics
Switch Pins on the Edge of
Buck/Boost and Approaching Boost
Switch Pins During Buck/Boost
Switch Pins on the Edge of
Buck/Boost and Approaching Buck
SW1
2V/DIV
SW1
2V/DIV
SW1
2V/DIV
SW2
2V/DIV
SW2
2V/DIV
SW2
2V/DIV
VIN = 3.78V
VOUT = 3.3V
IOUT = 250mA
50ns/DIV
VIN = 3.42V
VOUT = 3.3V
IOUT = 250mA
3440 G04
Switch Pins in Buck Mode
50ns/DIV
3440 G06
VOUT Ripple During Buck,
Buck/Boost and Boost Modes
Buck
VIN = 5V
SW1
2V/DIV
SW2
2V/DIV
VOUT
10mV/DIV
AC Coupled
Buck/Boost
VIN = 3.78V
Boost
VIN = 2.5V
SW2
2V/DIV
250ns/DIV
VIN = 2.5V
VOUT = 3.3V
IOUT = 250mA
3440 G07
Active Quiescent Current
VIN + VOUT CURRENT (µA)
500
450
–25
5
35
65
TEMPERATURE (°C)
L = 10µH
COUT = 22µF
IOUT = 250mA
fOSC = 1MHz
3440 G08
Burst Mode Quiescent Current
40
VIN = VOUT = 3.6V
400
–55
250ns/DIV
95
125
3440 G10
VIN = VOUT = 3.6V
30
20
10
–55
–25
5
35
65
TEMPERATURE (°C)
95
1µs/DIV
3440 G09
Error Amp Source Current
20
E/A SOURCE CURRENT (µA)
VIN = 5V
VOUT = 3.3V
IOUT = 250mA
VIN + VOUT CURRENT (µA)
VIN = 4.15V
VOUT = 3.3V
IOUT = 250mA
3440 G05
Switch Pins in Boost Mode
SW1
2V/DIV
550
50ns/DIV
125
3440 G11
VIN = VOUT = 3.6V
15
10
5
–55
–25
5
35
65
TEMPERATURE (°C)
95
125
3440 G12
3440fc
4
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LTC3440
Typical Performance Characteristics
Output Frequency
NMOS RDS(ON)
0.30
VIN = VOUT = 3.6V
VIN = VOUT = 3.6V
SWITCHES B AND C
0.25
NMOS RDS(ON) (Ω)
FREQUENCY (MHz)
1.05
Feedback Voltage
1.236
1.00
0.95
FEEDBACK VOLTAGE (V)
1.10
0.20
0.15
0.90
–55
–25
5
35
65
TEMPERATURE (°C)
95
0.10
–55
125
–25
5
35
65
TEMPERATURE (°C)
95
3440 G13
60
–55
–25
5
35
65
TEMPERATURE (°C)
95
0.30
VIN = VOUT = 3.6V
410
390
370
–25
5
35
65
TEMPERATURE (°C)
95
5
35
65
TEMPERATURE (°C)
95
125
3440 G19
DUTY CYCLE (%)
–25
5
35
65
TEMPERATURE (°C)
95
125
3440 G18
Current Limit
3000
VIN = VOUT = 3.6V
PEAK SWITCH
2500
CURRENT LIMIT (A)
MINIMUM START VOLTAGE (V)
–25
0.10
–55
125
Minimum Start Voltage
75
70
–55
0.20
0.15
2.40
VIN = VOUT = 3.6V
RT = 60k
125
VIN = VOUT = 3.6V
SWITCHES A AND D
3440 G17
Boost Max Duty Cycle
80
95
0.25
350
–55
125
85
5
35
65
TEMPERATURE (°C)
PMOS RDS(ON)
3440 G16
90
–25
3440 G15
PMOS RDS(ON) (Ω)
E/A SINK CURRENT (µA)
LINE REGULATION (dB)
430
70
1.196
–55
Error Amp Sink Current
VIN = VOUT = 2.5V TO 5.5V
80
1.216
3440 G14
Feedback Voltage Line Regulation
90
125
VIN = VOUT = 3V
2.35
2.30
2.25
–55
–25
5
35
65
TEMPERATURE (°C)
95
125
3440 G20
2000
AVERAGE INPUT
1500
1000
–55
–25
5
35
65
TEMPERATURE (°C)
95
125
3440 G21
3440fc
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5
LTC3440
Pin Functions
RT (Pin 1): Timing Resistor to Program the Oscillator
Frequency. The programming frequency range is 300kHz
to 2MHz.
fOSC =
6 • 1010
Hz
RT
MODE/SYNC (Pin 2): MODE/SYNC = External CLK : Synchronization of the internal oscillator. A clock frequency
of twice the desired switching frequency and with a pulse
width between 100ns and 2µs is applied. The oscillator
free running frequency is set slower than the desired
synchronized switching frequency to guarantee sync.
The oscillator RT component value required is given by:
RT =
GND (Pin 5): Signal and Power Ground for the IC.
VOUT (Pin 6): Output of the Synchronous Rectifier. A filter
capacitor is placed from VOUT to GND.
VIN (Pin 7): Input Supply Pin. Internal VCC for the IC. A
ceramic bypass capacitor as close to the VIN pin and GND
(Pin 5) is required.
SHDN/SS (Pin 8): Combined Soft-Start and Shutdown.
Grounding this pin shuts down the IC. Tie to >1.5V to
enable the IC and >2.5V to ensure the error amp is not
clamped from soft-start. An RC from the shutdown command signal to this pin will provide a soft-start function
by limiting the rise time of the VC pin.
FB (Pin 9): Feedback Pin. Connect resistor divider tap
here. The output voltage can be adjusted from 2.5V to
5.5V. The feedback reference voltage is typically 1.22V.
8 • 1010
fSW
where fSW = desired synchronized switching frequency.
SW1 (Pin 3): Switch Pin Where the Internal Switches
A and B are Connected. Connect inductor from SW1 to
SW2. An optional Schottky diode can be connected from
SW1 to ground. Minimize trace length to keep EMI down.
SW2 (Pin 4): Switch Pin Where the Internal Switches C
and D are Connected. For applications with output voltages
over 4.3V, a Schottky diode is required from SW2 to VOUT
to ensure the SW pin does not exhibit excess voltage.
VC (Pin 10): Error Amp Output. A frequency compensation network is connected from this pin to the FB pin to
compensate the loop. See the section “Compensating the
Feedback Loop” for guidelines.
Exposed Pad (Pin 11, DFN Package Only): Ground. This
pin must be soldered to the PCB and electrically connected
to ground.
3440fc
6
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LTC3440
Block Diagram
SW1
3
7
SW D
6
REVERSE
CURRENT
LIMIT
SUPPLY
CURRENT
LIMIT
UVLO
PWM
LOGIC
AND
OUTPUT
PHASING
–
ERROR
AMP
+
1.22V
R1
–
PWM
COMPARATORS
9
+
10
1
FB
CLAMP
–
–
+
2.4V
ISENSE
AMP
+
2.7A
VOUT
2.5V TO 5.5V
VOUT
–0.4A
SW C
–
+
GATE
DRIVERS
AND
ANTICROSS
CONDUCTION
–
SW B
RT
SW2
SW A
+
RT
4
+
VIN
2.5V TO 5.5V
VC
OSC
R2
SYNC
SLEEP
Burst Mode
OPERATION
CONTROL
SHUTDOWN
8
SHDN/SS
RSS
VIN
5µs DELAY
CSS
MODE/SYNC 2
1 = Burst Mode
OPERATION
0 = FIXED FREQUENCY
5
GND
3440 BD
3440fc
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7
LTC3440
Operation
The LTC3440 provides high efficiency, low noise power
for applications such as portable instrumentation. The
LTC proprietary topology allows input voltages above,
below or equal to the output voltage by properly phasing
the output switches. The error amp output voltage on the
VC pin determines the output duty cycle of the switches.
Since the VC pin is a filtered signal, it provides rejection
of frequencies from well below the switching frequency.
The low RDS(ON), low gate charge synchronous switches
provide high frequency pulse width modulation control at
high efficiency. Schottky diodes across the synchronous
switch D and synchronous switch B are not required, but
provide a lower drop during the break-before-make time
(typically 15ns). The addition of the Schottky diodes will
improve peak efficiency by typically 1% to 2% at 600kHz.
High efficiency is achieved at light loads when Burst Mode
operation is entered and when the IC’s quiescent current
is a low 25µA.
Error Amp
Low Noise Fixed Frequency Operation
Output Switch Control
Oscillator
The frequency of operation is user programmable and is
set through a resistor from the RT pin to ground where:
 6e10 
f =
Hz
R


T
An internally trimmed timing capacitor resides inside the
IC. The oscillator can be synchronized with an external
clock applied to the MODE/SYNC pin. A clock frequency
of twice the desired switching frequency and with a pulse
width between 100ns and 2µs is applied. The oscillator
RT component value required is given by:
RT =
8 • 1010
fSW
The error amplifier is a voltage mode amplifier. The loop
compensation components are configured around the
amplifier to provide loop compensation for the converter.
The SHDN/SS pin will clamp the error amp output, VC, to
provide a soft-start function.
Supply Current Limit
The current limit amplifier will shut PMOS switch A off
once the current exceeds 2.7A typical. The current amplifier delay to output is typically 50ns.
Reverse Current Limit
The reverse current limit amplifier monitors the inductor
current from the output through switch D. Once a negative inductor current exceeds – 400mA typical, the IC will
shut off switch D.
Figure 1 shows a simplified diagram of how the four internal
switches are connected to the inductor, VIN, VOUT and GND.
Figure 2 shows the regions of operation for the LTC3440
as a function of the internal control voltage, VCI. The VCI
voltage is a level shifted voltage from the output of the
error amp (VC pin) (see Figure 5). The output switches are
properly phased so the transfer between operation modes
is continuous, filtered and transparent to the user. When
VIN approaches VOUT the Buck/Boost region is reached
where the conduction time of the four switch region is
typically 150ns. Referring to Figures 1 and 2, the various
regions of operation will now be described.
VIN
VOUT
7
6
PMOS A
where fSW = desired synchronized switching frequency.
For example to achieve a 1.2MHz synchronized switching
frequency the applied clock frequency to the MODE/SYNC
pin is set to 2.4MHz and the timing resistor, RT, is set to
66.5k (closest 1% value).
PMOS D
SW1
SW2
3
4
NMOS B
VOUT
NMOS C
3440 F01
Figure 1. Simplified Diagram of Output Switches
3440fc
8
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LTC3440
Operation
75%
DMAX
BOOST
V4 (≈2.05V)
The input voltage, VIN, where the four switch region begins
is given by:
A ON, B OFF
BOOST REGION
PWM CD SWITCHES
DMIN
BOOST
DMAX
BUCK
FOUR SWITCH PWM
V2 (≈1.55V)
The point at which the four switch region ends is given by:
D ON, C OFF
PWM AB SWITCHES BUCK REGION
VIN = VOUT(1 – D) = VOUT(1 – 150ns • f) V
V1 (≈0.9V)
0%
3440 F02
INTERNAL
CONTROL
VOLTAGE, VCI
Figure 2. Switch Control vs Internal Control Voltage, VCI
Buck Region (VIN > VOUT)
Switch D is always on and switch C is always off during
this mode. When the internal control voltage, VCI, is above
voltage V1, output A begins to switch. During the off time of
switch A, synchronous switch B turns on for the remainder
of the time. Switches A and B will alternate similar to a
typical synchronous buck regulator. As the control voltage increases, the duty cycle of switch A increases until
the maximum duty cycle of the converter in Buck mode
reaches DMAX _BUCK, given by:
VOUT
V
1– (150ns • f)
V3 (≈1.65V)
BUCK/BOOST REGION
DUTY
CYCLE
VIN =
DMAX _BUCK = 100 – D4SW %
where D4SW = duty cycle % of the four switch range.
D4SW = (150ns • f) • 100 %
where f = operating frequency, Hz.
Beyond this point the “four switch,” or Buck/Boost region
is reached.
Buck/Boost or Four Switch (VIN ~ VOUT)
When the internal control voltage, VCI, is above voltage V2,
switch pair AD remain on for duty cycle DMAX_BUCK, and
the switch pair AC begins to phase in. As switch pair AC
phases in, switch pair BD phases out accordingly. When
the VCI voltage reaches the edge of the Buck/Boost range,
at voltage V3, the AC switch pair completely phase out the
BD pair, and the boost phase begins at duty cycle D4SW.
Boost Region (VIN < VOUT)
Switch A is always on and switch B is always off during this mode. When the internal control voltage, VCI, is
above voltage V3, switch pair CD will alternately switch
to provide a boosted output voltage. This operation is
typical to a synchronous boost regulator. The maximum
duty cycle of the converter is limited to 75% typical and
is reached when VCI is above V4.
Burst Mode Operation
Burst Mode operation is when the IC delivers energy to
the output until it is regulated and then goes into a sleep
mode where the outputs are off and the IC is consuming
only 25µA. In this mode the output ripple has a variable
frequency component that depends upon load current.
During the period where the device is delivering energy to
the output, the peak current will be equal to 400mA typical
and the inductor current will terminate at zero current for
each cycle. In this mode the maximum average output
current is given by:
IOUT(MAX)BURST ≈
0.1• VIN
A
VOUT + VIN
Burst Mode operation is user controlled, by driving the
MODE/SYNC pin high to enable and low to disable.
The peak efficiency during Burst Mode operation is less
than the peak efficiency during fixed frequency because
the part enters full-time 4-switch mode (when servicing
the output) with discontinuous inductor current as illustrated in Figures 3 and 4. During Burst Mode operation,
the control loop is nonlinear and cannot utilize the control
voltage from the error amp to determine the control mode,
3440fc
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9
LTC3440
Operation
Burst Mode Operation to Fixed Frequency Transient
Response
therefore full-time 4-switch mode is required to maintain
the Buck/Boost function. The efficiency below 1mA
becomes dominated primarily by the quiescent current and
not the peak efficiency. The equation is given by:
Efficiency Burst ≈
When transitioning from Burst Mode operation to fixed
frequency, the system exhibits a transient since the modes
of operation have changed. For most systems this transient
is acceptable, but the application may have stringent input
current and/or output voltage requirements that dictate
a broad-band voltage loop to minimize the transient.
Lowering the DC gain of the loop will facilitate the task
(10M FB to VC) at the expense of DC load regulation. Type
3 compensation is also recommended to broad band the
loop and roll off past the two pole response of the LC of
the converter (see Closing the Feedback Loop).
(ηbm) • ILOAD
25µA +ILOAD
where (ηbm) is typically 79% during Burst Mode operation for an ESR of the inductor of 50mΩ. For 200mΩ of
inductor ESR, the peak efficiency (ηbm) drops to 75%.
VIN
VOUT
7
6
3
+
dI ≈ VIN
dT L
D
–
L
SW1
4
IINDUCTOR
A
SW2
B
C
400mA
0mA
3440 F03
T1
5
GND
Figure 3. Inductor Charge Cycle During Burst Mode Operation
VIN
VOUT
7
6
3
SW1
–
dI ≈ – VOUT
L
dT
+
L
B
D
4
SW2
C
IINDUCTOR
A
400mA
0mA
T2
3440 F04
5
GND
Figure 4. Inductor Discharge Cycle During Burst Mode Operation
3440fc
10
For more information www.linear.com/LTC3440
LTC3440
Operation
Soft-Start
The soft-start function is combined with shutdown.
When the SHDN/SS pin is brought above typically 1V,
the IC is enabled but the EA duty cycle is clamped from
the VC pin. A detailed diagram of this function is shown
in Figure 5. The components RSS and CSS provide a
slow ramping voltage on the SHDN/SS pin to provide a
soft-start function.
ERROR AMP
VIN
15µA
+
VOUT
1.22V
R1
FB
–
9
TO PWM
COMPARATORS
R2
CP1
VC
SOFT-START
CLAMP
10
VCI
SHDN/SS
RSS
ENABLE SIGNAL
8
3440 F05
CSS
+
CHIP
ENABLE
–
1V
Figure 5. Soft-Start Circuitry
APPLICATIONS INFORMATION
COMPONENT SELECTION
L1
D1
Inductor Selection
LTC3440
1
RT
2
MODE/SYNC
3
SW1
4
5
SW2
D2
GND
VC 10
FB
9
SHDN/SS
8
VIN
7
VOUT
6
R1
R2
VIN
L>
C1
MULTIPLE
VIAS
C2
The high frequency operation of the LTC3440 allows the
use of small surface mount inductors. The inductor current ripple is typically set to 20% to 40% of the maximum
inductor current. For a given ripple the inductance terms
are given as follows:
VOUT
L>
GND
3440 F06
Figure 6. Recommended Component Placement. Traces
Carrying High Current are Direct. Trace Area at FB and VC Pins
are Kept Low. Lead Length to Battery Should be Kept Short
(
)
VIN(MIN) • VOUT – VIN(MIN)
f • IOUT(MAX) • Ripple • VOUT
(
VOUT • VIN(MAX) – VOUT
)
μH,
f • IOUT(MAX) • Ripple • VIN(MAX)
μH
where f = operating frequency, MHz
3440fc
For more information www.linear.com/LTC3440
11
LTC3440
APPLICATIONS INFORMATION
Ripple = allowable inductor current ripple
(e.g., 0.2 = 20%)
VIN(MIN) = minimum input voltage, V
VIN(MAX) = maximum input voltage, V
VOUT = output voltage, V
IOUT(MAX) = maximum output load current
The output capacitance is usually many times larger in
order to handle the transient response of the converter. For
a rule of thumb, the ratio of the operating frequency to the
unity-gain bandwidth of the converter is the amount the
output capacitance will have to increase from the above
calculations in order to maintain the desired transient
response.
For high efficiency, choose an inductor with a high frequency core material, such as ferrite, to reduce core loses. The
inductor should have low ESR (equivalent series resistance)
to reduce the I2R losses, and must be able to handle the
peak inductor current without saturating. Molded chokes
or chip inductors usually do not have enough core to support the peak inductor currents in the 1A to 2A region. To
minimize radiated noise, use a toroid, pot core or shielded
bobbin inductor. See Table 1 for suggested components
and Table 2 for a list of component suppliers.
The other component of ripple is due to the ESR (equivalent series resistance) of the output capacitor. Low ESR
capacitors should be used to minimize output voltage
ripple. For surface mount applications, Taiyo Yuden ceramic
capacitors, AVX TPS series tantalum capacitors or Sanyo
POSCAP are recommended.
Table 1. Inductor Vendor Information
SUPPLIER PHONE
Coilcraft
FAX
WEB SITE
(847) 639-6400 (847) 639-1469
(561) 241-9339
www.coiltronics.com
Murata
USA:
(814) 238-0490
www.murata.com
Sumida
Output Capacitor Selection
The bulk value of the capacitor is set to reduce the ripple
due to charge into the capacitor each cycle. The steady
state ripple due to charge is given by:
%Ripple _ Buck =
SUPPLIER
PHONE
AVX
(803) 448-9411 (803) 448-1943 www.avxcorp.com
FAX
WEB SITE
Sanyo
(619) 661-6322 (619) 661-1055 www.sanyovideo.com
Taiyo Yuden (408) 573-4150 (408) 573-4159 www.t-yuden.com
www.japanlink.com/
USA:
(847) 956-0666 (847) 956-0702 sumida
Japan:
81(3) 3607-5111 81(3) 3607-5144
%Ripple _ Boost =
Since the VIN pin is the supply voltage for the IC it is
recommended to place at least a 4.7µF, low ESR bypass
capacitor.
Table 2. Capacitor Vendor Information
www.coilcraft.com
Coiltronics (561) 241-7876
USA:
(814) 237-1431
(800) 831-9172
Input Capacitor Selection
(
)
%
(
)
%
IOUT(MAX) • VOUT – VIN(MIN) • 100
COUT • VOUT2 • f
IOUT(MAX) • VIN(MAX) – VOUT • 100
COUT • VIN(MAX) • VOUT • f
Optional Schottky Diodes
To achieve a 1%-2% efficiency improvement above 50mW,
Schottky diodes can be added across synchronous
switches B (SW1 to GND) and D (SW2 to VOUT ). The
Schottky diodes will provide a lower voltage drop during
the break-before-make time (typically 15ns) of the NMOS to
PMOS transition. General purpose diodes such as a 1N914
are not recommended due to the slow recovery times and
will compromise efficiency. If desired a large Schottky
diode, such as an MBRM120T3, can be used from SW2 to
VOUT. A low capacitance Schottky diode is recommended
from GND to SW1 such as a Phillips PMEG2010EA or
equivalent.
where COUT = output filter capacitor, F
3440fc
12
For more information www.linear.com/LTC3440
LTC3440
APPLICATIONS INFORMATION
Output Voltage > 4.3V
Closing the Feedback Loop
A Schottky diode from SW to VOUT is required for output
voltages over 4.3V. The diode must be located as close to
the pins as possible in order to reduce the peak voltage
on SW2 due to the parasitic lead and trace inductance.
The LTC3440 incorporates voltage mode PWM control. The
control to output gain varies with operation region (Buck,
Boost, Buck-Boost), but is usually no greater than 15. The
output filter exhibits a double pole response is given by:
1
fFILTER _ POLE =
Hz (in Buck mode)
2 • π • L • COUT
Input Voltage > 4.5V
For applications with input voltages above 4.5V which could
exhibit an overload or short-circuit condition, a 2Ω/1nF
series snubber is required between the SW1 pin and GND.
A Schottky diode such as the Phillips PMEG2010EA or
equivalent from SW1 to VIN should also be added as close
to the pins as possible. For the higher input voltages VIN
bypassing becomes more critical, therefore, a ceramic
bypass capacitor as close to the VIN and GND pins as
possible is also required.
Operating Frequency Selection
There are several considerations in selecting the operating frequency of the converter. The first is, what are
the sensitive frequency bands that cannot tolerate any
spectral noise? For example, in products incorporating RF
communications, the 455kHz IF frequency is sensitive to
any noise, therefore switching above 600kHz is desired.
Some communications have sensitivity to 1.1MHz and in
that case a 2MHz converter frequency may be employed.
Other considerations are the physical size of the converter
and efficiency. As the operating frequency goes up, the
inductor and filter capacitors go down in value and size.
The trade off is in efficiency since the switching losses due
to gate charge are going up proportional with frequency.
Additional quiescent current due to the output switches
GATE charge is given by:
Buck: 500e –12 • VIN • F
Boost: 250e –12 • (VIN + VOUT ) • F
Buck/Boost: F • (750e –12 • VIN + 250e –12 • VOUT )
where F = switching frequency
fFILTER_POLE =
VIN
Hz (in Boost mode)
2 • VOUT • π • L •COUT
Where L is in Henries and COUT is the output filter capacitor in Farads.
The output filter zero is given by:
1
fFILTER _ ZERO =
Hz
2 • π • RESR • COUT
where RESR is the capacitor equivalent series resistance.
A troublesome feature in Boost mode is the right-half
plane zero (RHP), and is given by:
VIN 2
fRHPZ =
Hz
2 • π •IOUT • L • VOUT
The loop gain is typically rolled off before the RHP zero
frequency.
A simple Type I compensation network can be incorporated
to stabilize the loop but at a cost of reduced bandwidth
and slower transient response. To ensure proper phase
margin, the loop requires to be crossed over a decade
before the LC double pole.
The unity-gain frequency of the error amplifier with the
Type I compensation is given by:
fUG =
1
Hz
2 • π • R1• CP1
Most applications demand an improved transient response
to allow a smaller output filter capacitor. To achieve a higher
bandwidth, Type III compensation is required. Two zeros
are required to compensate for the double-pole response.
3440fc
For more information www.linear.com/LTC3440
13
LTC3440
APPLICATIONS INFORMATION
1
fPOLE1 ≈
as the traces and external components. Following the
recommendations for output voltage >4.3V and input
voltage >4.5V will improve this condition. Additional
short-circuit protection can be accomplished with some
external circuitry.
Hz
2 • π •32e3 •R1• CP1
Which is extremely close to DC
1
Hz
fZERO1=
2 • π •R Z • CP1
1
Hz
fZERO2 =
2 • π •R1 • CZ 1
1
Hz
2 • π •R Z • CP 2
fPOLE2 =
VOUT
+
1.22V
ERROR
AMP
R1
FB
–
9
CP1
VC
10
R2
3440 F07
Figure 7. Error Amplifier with Type I Compensation
Restart Circuit
VOUT
+
ERROR
AMP
–
1.22V
R1
CZ1
FB
9
VC
10
CP1
RZ
In an overload or short-circuit condition the LTC3440 voltage loop opens and the error amp control voltage on the VC
pin slams to the upper clamp level. This condition forces
boost mode operation in order to attempt to provide more
output voltage and the IC hits a peak switch current limit of
2.7A. When switch current limit is reached switches B and
D turn on for the remainder of the cycle to reverse the volts
• seconds on the inductor. Although this prevents current
run away, this condition produces four switch operation
producing a current foldback characteristic and the average input current drops. The IC is trimmed to guarantee
greater than 1A average input current to meet the maximum
load demand, but in a short-circuit or overload condition
the foldback characteristic will occur producing higher
peak switch currents. To minimize this affect during this
condition the following circuits can be utilized.
For a sustained short-circuit the circuit in Figure 9 will force
a soft-start condition. The only design constraint is that
R2/C2 time constant must be longer than the soft-start
components R1/C1 to ensure start-up.
R2
CP2
VIN
3440 F08
R1
1M
Figure 8. Error Amplifier with Type III Compensation
SOFT-START
SO/SS
Short-Circuit Improvements
The LTC3440 is current limited to 2.7A peak to protect the
IC from damage. At input voltages above 4.5V a current
limit condition may produce undesirable voltages to the
IC due to the series inductance of the package, as well
C1
4.7nF
R2
1M
D1
1N4148
M2
NMOS
VN2222
C2
10nF
M1
NMOS
VN2222
VOUT
3440 F09
Figure 9. Soft-Start Reset Circuitry for a Sustained Short-Circuit
3440fc
14
For more information www.linear.com/LTC3440
LTC3440
APPLICATIONS INFORMATION
Simple Average Input Current Control
INPUT_VOLTAGE
A simple average current limit circuit is shown in
Figure 10. Once the input current of the IC is above approximately 1A, Q1 will start sourcing current into the FB
pin and lower the output voltage to maintain the average
input current. Since the voltage loop is utilized to perform
average current limit, the voltage control loop is maintained and the VC voltage does not slam. The averaging
function of current comes from the fact that voltage loop
compensation is also used with this circuit.
V1
C1
10µF
Q1
2N3906
R1
0.5Ω
VIN_PIN
FB_PIN
Figure 10. Simple Input Current Control
Utilizing the Voltage Loop
TYPICAL APPLICATIONS
3-Cell to 3.3V at 600mA Converter
L1
4.7µH
D2
C3
33pF
D1
4
SW1
SW2
LTC3440
6
7
VIN
VOUT
3
VIN = 2.7V TO 4.5V
8
3 CELLS
C1 *
10µF
2
1
MODE/SYNC
RT
FB
VC
GND
RT f
OSC = 1.5MHz
45.3k
*1 = Burst Mode OPERATION
0 = FIXED FREQUENCY
R1
340k
9
10
R3 15k
C2
22µF
C4 150pF
5
R5
10k
R2
200k
C5 10pF
C1: TAIYO YUDEN JMK212BJ106MG
C2: TAIYO YUDEN JMK325BJ226MM
D1, D2: CENTRAL SEMICONDUCTOR CMDSH2-3
L1: SUMIDA CDR43-4R7M
3440 TA03a
3-Cell to 3.3V Efficiency
100
90
80
EFFICIENCY (%)
+
SHDN/SS
VOUT
3.3V
600mA
70
60
50
40
Burst Mode
OPERATION
VIN = 2.7V
VIN = 4.5V
VIN = 3.3V
30
20
10
fOSC = 1.5MHz
0
1
0.1
10
100
OUTPUT CURRENT (mA)
1000
3440 TA03b
3440fc
For more information www.linear.com/LTC3440
15
LTC3440
TYPICAL APPLICATIONS
3-Cell to 5V Boost Converter with Output Disconnect
L1
10µH
VIN = 2.7V TO 4.5V
7
R4 1M
3
CELLS
+
C1
10µF
SD
8
2
C3 *
0.1µF
1
D1**
4
SW1
SW2
LTC3440
6
VIN
VOUT
SHDN/SS
FB
MODE/SYNC
VC
RT
90
80
9
C2**
22µF
15k
10
5
GND
100
R1
619k
C4
1.5nF
RT
= 1MHz
f
60.4k OSC
*1 = Burst Mode OPERATION
0 = FIXED FREQUENCY
** LOCATE COMPONENTS AS
CLOSE TO IC AS POSSIBLE
VOUT
5V
300mA
EFFICIENCY (%)
3
3-Cell to 5V Boost Efficiency
R2
200k
VIN = 4.5V
Burst Mode
OPERATION
VIN = 3.6V
70
VIN = 2.7V
60
50
40
30
20
10
C1: TAIYO YUDEN JMK212BJ106MG
C2: TAIYO YUDEN JMK325BJ226MM
D1: ON SEMICONDUCTOR MBRM120T3
L1: SUMIDA CDRH4D28-100
fOSC = 1MHz
0
1
0.1
10
100
OUTPUT CURRENT (mA)
3440 TA06a
1000
3440 TA06b
Low Profile (<1.1mm) Li-Ion to 3.3V at 200mA Converter
L1
4.7µH
VOUT
3.3V
200mA
4
SW1
SW2
LTC3440
6
7
VIN
VOUT
3
VIN = 2.5V TO 4.2V
8
Li-Ion
+
C1 *
4.7µF
2
1
SHDN/SS
FB
MODE/SYNC
RT
VC
GND
R1
340k
9
C2
4.7µF
10
R3
15k
5
RT
30.1k
*1 = Burst Mode OPERATION
0 = FIXED FREQUENCY
fOSC = 2MHz
C4
1.5nF
R2
200k
C1: TAIYO YUDEN JMK212BJ475MG
C2: TAIYO YUDEN JMK212BJ475MG
L1: COILCRAFT LPO1704-472M
3440 TA04a
Efficiency
100
90
EFFICIENCY (%)
80
Burst Mode
OPERATION
70
60
50
40
VIN = 2.5V
VIN = 4.2V
VIN = 3.3V
30
20
10
0
0.1
1
10
100
OUTPUT CURRENT (mA)
1000
3440 TA04b
3440fc
16
For more information www.linear.com/LTC3440
LTC3440
TYPICAL APPLICATIONS
Efficiency of the WCDMA
Power Amp Power Supply
WCDMA Power Amp Power Supply with Dynamic Voltage Control
L1
3.3µH
D1**
VIN = 2.5V TO 4.2V
8
Li-Ion
+
C1
*
10µF
2
1
SHDN/SS
FB
MODE/SYNC
RT
VC
GND
R1
340k
10
R3 15k
C4 150pF
IOUT = 100mA
94
92
IOUT = 250mA
90
88
IOUT = 600mA
86
84
5
C1, C2: TAIYO YUDEN JMK212BJ106MM
D1: ON SEMICONDUCTOR MBRM120T3
L1: SUMIDA CDRH4D28-3R3
82
C2**
10µF
R2
200k
C5 10pF
RT
30.1k fOSC = 2MHz
*1 = Burst Mode OPERATION
0 = FIXED FREQUENCY
** LOCATE COMPONENTS AS
CLOSE TO IC AS POSSIBLE
R5
10k
R6
200k
9
VOUT = 3.4V
96
EFFICIENCY (%)
3
98
VOUT
0.4V TO 5V
C3
33pF
4
SW1
SW2
LTC3440
6
7
VIN
VOUT
100
VOUT = 3.3V – 1.7V • (VDAC – 1.22V)
DAC
80
2.5
3
4
3.5
INPUT VOLTAGE (V)
4.5
5
3440 TA07b
3440 TA07a
GSM Modem Powered from USB or PCMCIA with 500mA Input Current Limit
L1
10µH
VIN
2.5V TO 5.5V
USB/PCMCIA POWER
500mA MAX
VOUT
3.6V
2A
(PULSED)
4
SW1
SW2
LTC3440
6
7
VIN
VOUT
3
RS
0.1Ω
8
C1 *
10µF
2
1
SHDN/SS
FB
MODE/SYNC
VC
RT
GND
RT
60.4k
R6
130k
9
5
1/2 LT1490A
–
+
–
C5
10nF
2N3906
ICURRENTLIMIT = 1.22 • R4
R5 • RS
C6 TO C9
470µF
×4
1/2 LT1490A
10
+
R4
1k
1N914
R1
392k
R2
200k
R5
24k
C1: TAIYO YUDEN JMK212BJ106MG
C2: TAIYO YUDEN JMK325BJ226MM
L1: SUMIDA CDRH-4D28-100
*1 = Burst Mode OPERATION
0 = FIXED FREQUENCY
3440 TA08
3440fc
For more information www.linear.com/LTC3440
17
LTC3440
Package Description
Please refer to http://www.linear.com/designtools/packaging/ for the most recent package drawings.
DD Package
10-Lead Plastic DFN (3mm × 3mm)
(Reference LTC DWG # 05-08-1699 Rev C)
R = 0.125
TYP
0.40 ±0.10
6
10
0.70 ±0.05
3.55 ±0.05
1.65 ±0.05
2.15 ±0.05 (2 SIDES)
3.00 ±0.10
(4 SIDES)
PACKAGE
OUTLINE
0.25 ±0.05
1.65 ±0.10
(2 SIDES)
PIN 1 NOTCH
R = 0.20 OR
0.35 × 45°
CHAMFER
PIN 1
TOP MARK
(SEE NOTE 6)
5
0.75 ±0.05
0.200 REF
0.50
BSC
2.38 ±0.05
(2 SIDES)
0.00 – 0.05
RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS
1
(DD) DFN REV C 0310
0.25 ±0.05
0.50 BSC
2.38 ±0.10
(2 SIDES)
BOTTOM VIEW—EXPOSED PAD
NOTE:
1. DRAWING TO BE MADE A JEDEC PACKAGE OUTLINE M0-229 VARIATION OF (WEED-2).
CHECK THE LTC WEBSITE DATA SHEET FOR CURRENT STATUS OF VARIATION ASSIGNMENT
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
MS Package
10-Lead Plastic MSOP
(Reference LTC DWG # 05-08-1661 Rev F)
3.00 ±0.102
(.118 ±.004)
(NOTE 3)
0.889 ±0.127
(.035 ±.005)
5.10
(.201)
MIN
3.20 – 3.45
(.126 – .136)
0.50
0.305 ±0.038
(.0197)
(.0120 ±.0015)
BSC
TYP
RECOMMENDED SOLDER PAD LAYOUT
0.254
(.010)
10 9 8 7 6
3.00 ±0.102
(.118 ±.004)
(NOTE 4)
4.90 ±0.152
(.193 ±.006)
DETAIL “A”
0.497 ±0.076
(.0196 ±.003)
REF
0° – 6° TYP
GAUGE PLANE
1 2 3 4 5
0.53 ±0.152
(.021 ±.006)
0.18
(.007)
SEATING
PLANE
0.86
(.034)
REF
1.10
(.043)
MAX
DETAIL “A”
0.17 – 0.27
(.007 – .011)
TYP
NOTE:
1. DIMENSIONS IN MILLIMETER/(INCH)
2. DRAWING NOT TO SCALE
3. DIMENSION DOES NOT INCLUDE MOLD FLASH, PROTRUSIONS OR GATE BURRS.
MOLD FLASH, PROTRUSIONS OR GATE BURRS SHALL NOT EXCEED 0.152mm (.006") PER SIDE
4. DIMENSION DOES NOT INCLUDE INTERLEAD FLASH OR PROTRUSIONS.
INTERLEAD FLASH OR PROTRUSIONS SHALL NOT EXCEED 0.152mm (.006") PER SIDE
5. LEAD COPLANARITY (BOTTOM OF LEADS AFTER FORMING) SHALL BE 0.102mm (.004") MAX
0.50
(.0197)
BSC
0.1016 ±0.0508
(.004 ±.002)
MSOP (MS) 0213 REV F
3440fc
18
For more information www.linear.com/LTC3440
LTC3440
Revision History
(Revision history begins at Rev C)
REV
DATE
DESCRIPTION
C
8/14
Modified filter pole equation in Closing the Feedback Loop section
PAGE NUMBER
13
3440fc
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.
For more
information
www.linear.com/LTC3440
19
LTC3440
Typical Application
Li-Ion to 3.3V at 600mA Buck-Boost Converter
Efficiency
100
L1
10µH
VIN = 2.7V TO 4.2V
7
8
Li-Ion
+
C1 *
10µF
2
1
4
SW1
SW2
LTC3440
6
VIN
VOUT
SHDN/SS
FB
MODE/SYNC
VC
RT
GND
80
R1
340k
9
C2
22µF
C5 1.5nF
10
R3
15k
5
RT
60.4k
*1 = Burst Mode OPERATION
0 = FIXED FREQUENCY
90
EFFICIENCY (%)
3
VOUT
3.3V
600mA
70
60
50
VIN = 4.2V
VIN = 3.3V
40
30
20
R2
200k
C1: TAIYO YUDEN JMK212BJ106MG
C2: TAIYO YUDEN JMK325BJ226MM
L1: SUMIDA CDRH6D38-100
Burst Mode
OPERATION
10
0
0.1
3440 TA01
1.0
10
100
OUTPUT CURRENT (mA)
1000
3440 TA05
Related Parts
PART NUMBER
DESCRIPTION
COMMENTS
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550mA(ISW ), 1.4MHz, High Efficiency Step-Up
DC/DC Converter
90% Efficiency, VIN: 0.9V to 10V, VOUT(MIN) = 34V, IQ = 3mA,
ISD = <1µA, ThinSOT™ Package
LT1618
1.5A(ISW ), 1.25MHz, High Efficiency Step-Up DC/
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90% Efficiency, VIN: 1.6V to 18V, VOUT(MIN) = 35V, IQ = 1.8mA,
ISD = <1µA, MS10 Package
LTC1877
600mA(IOUT ), 550kHz, Synchronous Step-Down
DC/DC Converter
95% Efficiency, VIN: 2.7V to 10V, VOUT(MIN) = 0.8V, IQ = 10µA,
ISD = <1µA, MS8 Package
LTC1878
600mA(IOUT ), 550kHz, Synchronous Step-Down
DC/DC Converter
95% Efficiency, VIN: 2.7V to 6V, VOUT(MIN) = 0.8V, IQ = 10µA,
ISD = <1µA, MS8 Package
LTC1879
1.2A(IOUT ), 550kHz, Synchronous Step-Down DC/ 95% Efficiency, VIN: 2.7V to 10V, VOUT(MIN) = 0.8V, IQ = 15µA,
DC Converter
ISD = <1µA, TSSOP16 Package
LT1961
1.5A(ISW ), 1.25MHz, High Efficiency Step-Up DC/
DC Converter
90% Efficiency, VIN: 3V to 25V, VOUT(MIN) = 35V, IQ = 0.9mA,
ISD = 6µA, MS8E Package
LTC3400/LTC3400B
600mA(ISW ), 1.2MHz, Synchronous Step-Up DC/
DC Converter
92% Efficiency, VIN: 0.85V to 5V, VOUT(MIN) = 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(MIN) = 6V, IQ = 38µA,
ISD = <1µA, MS10 Package
LTC3402
2A(ISW ), 3MHz, Synchronous Step-Up
DC/DC Converter
97% Efficiency, VIN: 0.5V to 5V, VOUT(MIN) = 6V, IQ = 38µA,
ISD = <1µA, MS10 Package
LTC3405/LTC3405A
300mA(IOUT ), 1.5MHz, Synchronous Step-Down
DC/DC Converter
95% Efficiency, VIN: 2.7V to 6V, VOUT(MIN) = 0.8V, IQ = 20µA,
ISD = <1µA, ThinSOT Package
LTC3406/LTC3406B
600mA(IOUT ), 1.5MHz, Synchronous Step-Down
DC/DC Converter
95% Efficiency, VIN: 2.5V to 5.5V, VOUT(MIN) = 0.6V, IQ = 20µA,
ISD = <1µA, ThinSOT Package
LTC3411
1.25A(IOUT ), 4MHz, Synchronous Step-Down DC/
DC Converter
95% Efficiency, VIN: 2.5V to 5.5V, VOUT(MIN) = 0.8V, IQ = 60µA,
ISD = <1µA, MS10 Package
LTC3412
2.5A(IOUT ), 4MHz, Synchronous Step-Down DC/
DC Converter
95% Efficiency, VIN: 2.5V to 5.5V, VOUT(MIN) = 0.8V, IQ = 60µA,
ISD = <1µA, TSSOP16E Package
LTC3441/LTC3443
1.2A(IOUT ), 1MHz/0.6MHz, Micropower
Synchronous Buck-Boost DC/DC Converter
95% Efficiency, VIN: 2.4V to 5.5V, VOUT(MIN): 2.4V to 5.25V, IQ = 25µA,
ISD = <1µA, DFN Package
3440fc
20 Linear Technology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
For more information www.linear.com/LTC3440
(408) 432-1900 ● FAX: (408) 434-0507
●
www.linear.com/LTC3440
LT 0814 REV C • PRINTED IN USA
 LINEAR TECHNOLOGY CORPORATION 2001