LT1618 - Constant-Current/Constant-Voltage 1.4MHz Step-Up DC/DC Converter

LT1618
Constant-Current/
Constant-Voltage 1.4MHz
Step-Up DC/DC Converter
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FEATURES
DESCRIPTIO
■
The LT®1618 step-up DC/DC converter combines a traditional voltage feedback loop and a unique current feedback
loop to operate as a constant-current, constant-voltage
source. This fixed frequency, current mode switcher operates from a wide input voltage range of 1.6V to 18V, and
the high switching frequency of 1.4MHz permits the use of
tiny, low profile inductors and capacitors. The current
sense voltage is set at 50mV and can be adjusted using the
IADJ pin.
■
■
■
■
■
■
Accurate Input/Output Current Control: ±5% Over
Temperature
Accurate Output Voltage Control: ±1%
Wide VIN Range: 1.6V to 18V
1.4MHz Switching Frequency
High Output Voltage: Up to 35V
Low VCESAT Switch: 200mV at 1A
Available in (3mm × 3mm × 0.8mm) 10-Pin DFN and
10-Pin MSOP Packages
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APPLICATIO S
■
■
■
LED Backlight Drivers
USB Powered Boost/SEPIC Converters
Input Current Limited Boost/SEPIC Converters
Battery Chargers
, LTC and LT are registered trademarks of Linear Technology Corporation.
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■
Available in the 10-Pin (3mm × 3mm) Exposed Pad DFN
and 10-pin MSOP packages, the LT1618 provides a complete solution for constant-current applications.
TYPICAL APPLICATIO
USB to 12V Boost Converter
(with Selectable 100mA/500mA Input Current Limit)
L1
10µH
C1
4.7µF
3
D1
2
7
ISN
SW
ISP
3.3V
OFF ON
0V
9
20k
IADJ GND
5
C2
4.7µF
R2
107k
SHDN
4
3.3V
100mA 500mA
0V
1
FB
VIN
90
85
R1
909k
LT1618
8
Efficiency Curve
VOUT
12V
VC
EFFICIENCY (%)
0.1Ω
VIN
5V
80
75
70
10
65
2k
13k
C1: TAIYO YUDEN JMK212BJ475
C2: TAIYO YUDEN EMK316BJ475
D1: ON SEMICONDUCTOR MBR0520
L1: SUMIDA CR43-100
10nF
60
0
20
60 80 100 120 140 160
40
LOAD CURRENT (mA)
1618 TA01a
1618 TA01b
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LT1618
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ABSOLUTE
AXI U RATI GS
(Note 1)
VIN, SHDN Voltage ................................................... 18V
SW Voltage .............................................................. 36V
ISP, ISN Voltage ...................................................... 36V
IADJ Voltage ............................................................... 6V
FB Voltage .............................................................. 1.5V
VC Voltage .............................................................. 1.5V
Junction Temperature ........................................... 125°C
Operating Temperature Range (Note 2) .. – 40°C to 85°C
Storage Temperature Range
MSOP ............................................... – 65°C to 150°C
DFN ................................................. – 65°C to 125°C
Lead Temperature (Soldering, 10 sec) (MSOP) .... 300°C
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PACKAGE/ORDER I FOR ATIO
TOP VIEW
FB
1
10 VC
ISN
2
9 SHDN
ISP
3
IADJ
4
7 SW
GND
5
6 SW
11
8 VIN
DD PACKAGE
10-LEAD (3mm × 3mm) PLASTIC DFN
TJMAX = 125°C, θJA = 43°C/W, θJC = 3°C/W
EXPOSED PAD (PIN 11) IS GND AND
MUST BE SOLDERED TO PCB
ORDER PART
NUMBER
LT1618EDD
ORDER PART
NUMBER
TOP VIEW
FB
ISN
ISP
IADJ
GND
DD PART
MARKING
1
2
3
4
5
10
9
8
7
6
VC
SHDN
VIN
SW
NC
LT1618EMS
MS PART
MARKING
MS PACKAGE
10-LEAD PLASTIC MSOP
TJMAX = 125°C, θJA = 160°C/W
LTNH
LAFQ
Consult LTC marketing for parts specified with wider operating temperature ranges.
ELECTRICAL CHARACTERISTICS
The ● denotes specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C. VIN = 1.6V, VSHDN = 1.6V, unless otherwise noted.
PARAMETER
CONDITIONS
MIN
Input Voltage
TYP
1.6
Quiescent Current
VSHDN = 1.6V, Not Switching
VSHDN = 0V
Reference Voltage
Measured at FB Pin
●
Reference Voltage Line Regulation
1.6V < VIN < 18V
FB Pin Bias Current
VFB = 1.263V, VIN = 1.8V
1.250
1.243
●
Error Amplifier Voltage Gain
MAX
UNITS
18
V
1.8
0.1
2.7
1
mA
µA
1.263
1.263
1.276
1.283
V
V
0.01
0.03
%/V
±2
±12
nA
180
V/V
Error Amplifier Transconductance
∆IC = ± 5µA
160
µmho
Error Amplifier Sink Current
VFB = 1.35V, VC = 1V
15
µA
Error Amplifier Source Current
VFB = 1.10V, VC = 1V
30
µA
Current Sense Voltage (ISP, ISN)
VFB = 0V, VIADJ = 0V
ISP, ISN Pin Bias Currents (Note 3)
VISP = 1.85V, VISN = 1.80V, VIADJ = 0V
●
47.5
50
52.5
mV
50
80
µA
1.8
V
1.6
MHz
kHz
(ISP, ISN) Common Mode Minimum Voltage
Switching Frequency
VFB = 1V
VFB = 0V
●
Maximum Switch Duty Cycle
Switch Current Limit
(Note 4)
1.25
1.4
550
88
92
1.5
2.1
%
2.8
A
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LT1618
ELECTRICAL CHARACTERISTICS
The ● denotes specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C. VIN = 1.6V, VSHDN = 1.6V, unless otherwise noted.
PARAMETER
CONDITIONS
Switch VCESAT
Switch Leakage Current
SHDN Pin Current
VSHDN = 1.6V
MIN
TYP
MAX
UNITS
ISW = 1A (Note 4)
200
260
mV
Switch Off, VSW = 5V
0.01
5
µA
5
20
µA
0.3
V
Shutdown Threshold (SHDN Pin)
Start-Up Threshold (SHDN Pin)
1
Note 1: Absolute Maximum Ratings are those values beyond which the life
of a device may be impaired.
Note 2: The LT1618 is guaranteed to meet performance specifications
from 0°C to 70°C. Specifications over the – 40°C to 85°C operating
V
temperature range are assured by design, characterization, and correlation
with statistical process controls.
Note 3: Bias currents flow into the ISP and ISN pins.
Note 4: Switch current limit and switch VCESAT for the DD package is
guaranteed by design and/or correlation to static test.
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TYPICAL PERFOR A CE CHARACTERISTICS
Switch Saturation Voltage
(VCE, SAT)
FB Pin Voltage and Bias Current
TJ = 125°C
300
TJ = 25°C
200
TJ = –50°C
100
0
0
1.0
0.5
1.5
SWITCH CURRENT (A)
2.0
1.265
2
VOLTAGE
1.260
0
CURRENT
1.255
–2
1.250
– 50 – 25
75
25
50
0
TEMPERATURE (°C)
100
Current Sense Voltage
(IADJ Pin = 0V)
1.0
0.5
0
– 50 – 25
–4
125
51
50
49
100
125
1618 G04
75
25
50
0
TEMPERATURE (°C)
100
Quiescent Current
60
2.5
50
2.0
40
30
20
10
0
0.0
0.2
0.4 0.6 0.8 1.0 1.2
IADJ PIN VOLTAGE (V)
125
1618 G03
QUIESCENT CURRENT (mA)
CURRENT SENSE VOLTAGE (mV)
CURRENT SENSE VOLTAGE (mV)
1.5
Current Sense Voltage
(VISP, ISN)
52
25
50
75
0
TEMPERATURE (°C)
2.0
1618 G02
1618 G01
48
– 50 – 25
2.5
PEAK CURRENT (A)
FEEDBACK VOLTAGE (V)
400
4
FB PIN BIAS CURRENT (nA)
SATURATION VOLTAGE (mV)
500
Switch Current Limit
1.270
1.4
1.6
1618 G05
VIN = 18V
VIN = 1.6V
1.5
1.0
0.5
0
– 50 – 25
25
50
75
0
TEMPERATURE (°C)
100
125
1618 G06
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TYPICAL PERFOR A CE CHARACTERISTICS
Switching Frequency
Frequency Foldback
1.8
1.6
1.7
1.4
SHDN Pin Current
50
1.6
1.5
VIN = 18V
1.4
VIN = 1.6V
1.3
1.2
45
1.2
SHDN PIN CURRENT (µA)
SWITCHING FREQUENCY (MHz)
SWITCHING FREQUENCY (MHz)
TJ = 25°C
1.0
0.8
0.6
0.4
0.2
1.1
1.0
– 50 – 25
100
125
35
30
TJ = 25°C
25
20
TJ = 125°C
15
10
5
0
75
25
50
0
TEMPERATURE (°C)
TJ = – 50°C
40
0
0
0.2
0.8
0.4
0.6
1.0
FEEDBACK PIN VOLTAGE (V)
1618 G07
1.2
1618 G08
0
5
15
10
SHUTDOWN PIN VOLTAGE (V)
20
1618 G09
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PIN FUNCTIONS (MS/DD)
FB (Pin 1/Pin 1): Feedback Pin. Set the output voltage by
selecting values for R1 and R2 (see Figure 1):
⎛ V
⎞
R1 = R2 ⎜ OUT – 1⎟
⎝ 1.263V ⎠
SW (NA/Pin 6): Switch Pin for DD Package. Connect this
pin to Pin 7.
SW (Pin 7/Pin 7): Switch Pin. This is the collector of the
internal NPN power switch. Minimize the metal trace area
connected to this pin to minimize EMI.
ISN (Pin 2/Pin 2): Current Sense (–) Pin. The inverting
input to the current sense amplifier.
VIN (Pin 8/Pin 8): Input Supply Pin. Bypass this pin with
a capacitor to ground as close to the device as possible.
ISP (Pin 3/Pin 3): Current Sense (+) Pin. The noninverting
input to the current sense amplifier.
SHDN (Pin 9/Pin 9): Shutdown Pin. Tie this pin higher
than 1V to turn on the LT1618; tie below 0.3V to turn it off.
IADJ (Pin 4/Pin 4): Current Sense Adjust Pin. A DC voltage
applied to this pin will reduce the current sense voltage. If
this adjustment is not needed, tie this pin to ground.
VC (Pin 10/Pin 10): Compensation Pin for Error Amplifier.
Connect a series RC from this pin to ground. Typical values
are 2kΩ and 10nF.
GND (Pin 5/Pin 5): Ground Pin. Tie this pin directly to local
ground plane.
Exposed Pad (NA/Pin 11): The Exposed Pad on the DD
package is GND and must be soldered to the PCB GND for
optimum thermal performance.
NC (Pin 6/NA): No Connection for MS Package.
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LT1618
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BLOCK DIAGRA
D1
L1
RSENSE
VIN
VOUT
C1
SHDN
VIN
9
C2
SW
7
8
Q1
DRIVER
+
0.02Ω
A1
×25
×5
–
+
1.4MHz
OSCILLATOR
+
S
3
–
2
ISN
4
IADJ
Σ
+
Q
R
ISP
+
A3
–
5
A2
–
–
+
R1
1
FB
1.263V
R2
10
VC
GND
RC
CC
Figure 1. LT1618 Block Diagram
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OPERATIO
The LT1618 uses a constant frequency, current mode
control scheme to provide excellent line and load regulation. Operation can be best understood by referring to the
Block Diagram in Figure 1. At the start of each oscillator
cycle, the SR latch is set, turning on power switch Q1. The
signal at the noninverting input of PWM comparator A3 is
a scaled-down version of the switch current (summed
together with a portion of the oscillator ramp). When this
signal reaches the level set by the output of error amplifier
A2, comparator A3 resets the latch and turns off the power
switch. In this manner, A2 sets the correct peak current
level to keep the output in regulation. If the error amplifier’s
output increases, more current is delivered to the output;
if it decreases, less current is delivered. A2 has two
inverting inputs, one from the voltage feedback loop, and
one from the current feedback loop. Whichever inverting
input is higher takes precedence, forcing the converter
into either a constant-current or a constant-voltage mode.
The LT1618 is designed to transition cleanly between the
two modes of operation. Current sense amplifier A1 senses
the voltage between the ISP and ISN pins and provides a
25× level-shifted version to error amplifier A2. When the
voltage between ISP and ISN reaches 50mV, the output of
A1 provides 1.263V to one of the noninverting inputs of A2
and the converter is in constant-current mode. If the
current sense voltage exceeds 50mV, the output of A1 will
increase causing the output of A2 to decrease, thus
reducing the amount of current delivered to the output. In
this manner the current sense voltage is regulated to
50mV. Similarly, if the FB pin increases above 1.263V, the
output of A2 will decrease to reduce the peak current level
and regulate the output (constant-voltage mode).
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LT1618
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APPLICATIONS INFORMATION
Inductor Selection
Several inductors that work well with the LT1618 are listed
in Table 1, although there are many other manufacturers
and devices that can be used. Consult each manufacturer
for more detailed information and for their entire selection
of related parts. Many different sizes and shapes are
available. Ferrite core inductors should be used to obtain
the best efficiency, as core losses at 1.4MHz are much
lower for ferrite cores than for the cheaper powdered-iron
ones. Choose an inductor that can handle the necessary
peak current without saturating, and ensure that the
inductor has a low DCR (copper-wire resistance) to minimize I2R power losses. A 4.7µH or 10µH inductor will be
a good choice for many LT1618 designs.
Table 1. Recommended Inductors
L
MAX
PART
(µH)
(mΩ)
HEIGHT
(mm)
VENDOR
CDRH5D18-4R1
CDRH5D18-100
CR43-2R2
CR43-4R7
CR43-100
CR54-100
4.1
10
2.2
4.7
10
10
57
124
71
109
182
100
2.0
2.0
3.5
3.5
3.5
4.8
Sumida
(847) 956-0666
www.sumida.com
LQH3C1R0M24
LQH3C2R2M24
LQH3C4R7M24
1.0
2.2
4.7
78
126
260
2.0
2.0
2.0
Murata
(814) 237-1431
www.murata.com
Capacitor Selection
Low ESR (equivalent series resistance) capacitors should
be used at the output to minimize the output ripple voltage.
Multilayer ceramic capacitors are an excellent choice.
They have an extremely low ESR and are available in very
small packages. X5R and X7R dielectrics are preferred, as
these materials retain their capacitance over wider voltage
and temperature ranges than other dielectrics. A 4.7µF to
10µF output capacitor is sufficient for high output current
designs. Converters with lower output currents may need
only a 1µF or 2.2µF output capacitor. Solid tantalum or
OSCON capacitors can be used, but they will occupy more
board area than a ceramic and will have a higher ESR for
the same footprint device. Always use a capacitor with a
sufficient voltage rating.
Ceramic capacitors also make a good choice for the input
decoupling capacitor, which should be placed as close as
possible to the VIN pin of the LT1618. A 1µF to 4.7µF input
capacitor is sufficient for most applications. Table 2 shows
a list of several ceramic capacitor manufacturers. Consult
the manufacturers for detailed information on their entire
selection of ceramic parts.
Table 2. Recommended Ceramic Capacitor Manufacturers
VENDOR
PHONE
URL
Taiyo Yuden
(408) 573-4150
www.t-yuden.com
Murata
(814) 237-1431
www.murata.com
Kemet
(408) 986-0424
www.kemet.com
Diode Selection
Schottky diodes, with their low forward voltage drop and
fast switching speed, are the ideal choice for LT1618
applications. Table 3 shows several Schottky diodes that
work well with the LT1618. Many different manufacturers
make equivalent parts, but make sure that the component
chosen has a sufficient current rating and a voltage rating
greater than the output voltage. The diode conducts current only when the power switch is turned off (typically
less than half the time), so a 0.5A or 1A diode will be
sufficient for most designs. The companies below also
offer Schottky diodes with higher voltage and current
ratings.
Table 3. Recommended Schottky Diodes
1A PART
0.5A PART
VENDOR
PHONE/URL
UPS120
UPS130
UPS140
Microsemi
(510) 353-0822
www.microsemi.com
MBRM120 MBR0520
MBRM130 MBR0530
MBRM140 MBR0540
ON Semiconductor (800) 282-9855
www.onsemi.com
B120
B130
B140
Diodes, Inc
B0520
B0530
B0540
(805) 446-4800
www.diodes.com
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LT1618
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APPLICATIONS INFORMATION
Setting Output Voltage
To set the output voltage, select the values of R1 and R2
(see Figure 1) according to the following equation.
⎛V
⎞
R1 = R2 ⎜ OUT – 1⎟
⎝ 1.263 ⎠
For current source applications, use the FB pin for overvoltage protection. Pick R1 and R2 so that the output
voltage will not go too high if the load is disconnected or
if the load current drops below the preset value. Typically
choose R1 and R2 so that the overvoltage value will be
about 20% to 30% higher than the normal output voltage
(when in constant-current mode). This prevents the voltage loop from interfering with the current loop in current
source applications. For battery charger applications, pick
the values of R1 and R2 to give the desired end of charge
voltage.
the output of the error amplifier (the VC pin) will be pulled
down and the LT1618 will stop switching.
A pulse width modulated (PWM) signal can also be used
to adjust the current sense voltage; simply add an RC
filterto convert the PWM signal into a DC voltage for the
IADJ pin. If the IADJ pin is not used, it should be tied to
ground. Do not leave the pin floating.
For applications needing only a simple one-step current
sense adjustment, the circuit in Figure 2 works well. If a
large value resistor (≥2MΩ) is placed between the IADJ pin
and ground, the current sense voltage will reduce to about
25mV, providing a 50% reduction in current. Do not leave
the IADJ pin open. This method gives a well-regulated
current value in both states, and is controlled by a logic
signal without the need for a variable PWM or DC control
signal. When the NMOS transistor is on, the current sense
voltage will be 50mV, when it is off, the current sense
voltage will be reduced to 25mV.
Selecting RSENSE/Current Sense Adjustment
LT1618
Use the following formula to choose the correct current
sense resistor value (for constant current operation).
RSENSE = 50mV/IMAX
For designs needing an adjustable current level, the IADJ
pin is provided. With the IADJ pin tied to ground, the
nominal current sense voltage is 50mV (appearing between the ISP and ISN pins). Applying a positive DC
voltage to the IADJ pin will decrease the current sense
voltage according to the following formula:
VISENSE =
1.263V – (0.8)VIADJ
25
For example, if 1V is applied to the IADJ pin, the current
sense voltage will be reduced to about 18mV. This
adjustability allows the regulated current to be reduced
without changing the current sense resistor (e.g. to adjust
brightness in an LED driver or to reduce the charge current
in a battery charger). If the IADJ pin is taken above 1.6V,
IADJ
FULL
CURRENT
2M
1618 F02
Figure 2
Considerations When Sensing Input Current
In addition to regulating the DC output current for currentsource applications, the constant-current loop of the
LT1618 can also be used to provide an accurate input
current limit. Boost converters cannot provide output
short-circuit protection, but the surge turn-on current can
be drastically reduced using the LT1618’s current sense
at the input. SEPICs, however, have an output that is DCisolated from the input, so an input current limit not only
helps soft-start the output but also provides excellent
short-circuit protection.
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LT1618
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APPLICATIONS INFORMATION
When sensing input current, the sense resistor should be
placed in front of the inductor (between the decoupling
capacitor and the inductor) as shown in the circuits in the
Typical Applications section. This will regulate the average
inductor current and maintain a consistent inductor ripple
current, which will, in turn, maintain a well regulated input
current. Do not place the sense resistor between the input
source and the input decoupling capacitor, as this may
allow the inductor ripple current to vary widely (even
though the average input current and the average inductor
current will still be regulated). Since the inductor current
is a triangular waveform (not a DC waveform like the
output current) some tweaking of the compensation
values (RC and CC on the VC pin) may be required to ensure
a clean inductor ripple current while the constant-current
loop is in effect. For these applications, the constantcurrent loop response can usually be improved by reducing the RC value, or by adding a capacitor (with a value of
approximately CC /10) in parallel with the RC and CC
compensation network.
Frequency Compensation
The LT1618 has an external compensation pin (VC), which
allows the loop response to be optimized for each application. An external resistor and capacitor (or sometimes just
a capacitor) are placed at the VC pin to provide a pole and
a zero (or just a pole) to ensure proper loop compensation.
Numerous other poles and zeroes are present in the closed
L1
loop transfer function of a switching regulator, so the VC
pin pole and zero are positioned to provide the best loop
response. A thorough analysis of the switching regulator
control loop is not within the scope of this data sheet, and
will not be presented here, but values of 2kΩ and 10nF will
be a good choice for many designs. For those wishing to
optimize the compensation, use the 2kΩ and 10nF as a
starting point. For LED backlight applications where a
pulse-width modulation (PWM) signal is used to drive
the IADJ pin, the resistor is usually not included in the
compensation network. This helps to provide additional
filtering of the PWM signal at the output of the error
amplifier (the VC pin).
Switch Node Considerations
To maximize efficiency, switch rise and fall times are made
as short as possible. To prevent radiation and high frequency resonance problems, proper layout of the high
frequency switching path is essential. Keep the output
switch (SW pin), diode and output capacitor as close
together as possible. Minimize the length and area of all
traces connected to the switch pin, and always use a
ground plane under the switching regulator to minimize
interplane coupling. The high speed switching current
path is shown in Figure 3. The signal path including the
switch, output diode and output capacitor contains nanosecond rise and fall times and should be kept as short as
possible.
SWITCH
NODE
VOUT
VIN
HIGH
FREQUENCY
CIRCULATING
PATH
LOAD
1618 • F03
Figure 3
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LT1618
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TYPICAL APPLICATIO S
4.5W Direct Broadcast Satellite (DBS) Power Supply with Short-Circuit Protection
0.068Ω
3
2
7
ISN
SW
9
FB
VIN
4
5
R3
10k Q1
FMMT717
ZETEX
R1
100k
1
C3
3.3µF
SHDN
IADJ GND
C1
4.7µF
L2
33µH
ISP
LT1618
8
L3
2.2µH
D1
ADD 5V
3.3V
VC
10
RC
2k
R5
24.9k
R2
10k
D2
MURS110
13.5V/18.5V
C4
3.3µF
22kHz
NETWORK
TUNING
Q1
MMBT3904
RHCP LHCP
0V
R4
1k
CC
33nF
C1: TAIYO YUDEN EMK316BJ475
C2: TAIYO YUDEN TMK316BJ105
C3, C4: TAIYO YUDEN TMK325BJ335
D1: ON SEMICONDUCTOR MBRM140
L1, L2: SUMIDA CR54-330
L3: SUMIDA CR43-2R2
(408) 573-4150
(408) 573-4150
(408) 573-4150
(800) 282-9855
(847) 956-0666
(847) 956-0666
1618 TA02a
Efficiency
80
75
EFFICIENCY (%)
VIN
12V
C2
1µF
L1
33µH
70
65
60
0
50
100
150
200
LOAD CURRENT (mA)
250
300
1618 TA02b
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LT1618
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TYPICAL APPLICATIONS
2-Cell White LED Driver
L1
4.7µH
VIN
1.6V TO 3V
C1
4.7µF
9
10kHz TO 50kHz
PWM
BRIGHTNESS
ADJUST
D1
8
7
VIN
SW
SHDN
ISP
4
2
R1
2M
LT1618
IADJ
1
FB
VC
GND
5
20mA
3
ISN
R3
5.1k
2.49Ω
10
C2
1µF
C3
0.1µF
R2
160k
CC
0.1µF
C1: TAIYO YUDEN JMK212BJ475
C2: TAIYO YUDEN EMK316BJ105
D1: ON SEMICONDUCTOR MBR0520
L1: SUMIDA CLQ4D10-4R7
(408) 573-4150
(408) 573-4150
(800) 282-9855
(847) 956-0666
1618 • TA03
2-Cell Luxeon LED Driver
L1
10µH
VIN
1.8V TO 3V
9
D1
8
7
VIN
SW
SHDN
ISP
ISN
C1
1µF
4
0.15Ω
3
2
LT1618
IADJ
FB
VC
GND
5
350mA
332k
1
D2
10
100nF
C1, C2: TAIYO YUDEN JMK107BJ105KA
D1: ON SEMICONDUCTOR MBR0520
D2: LUMILEDS LXHL-BW02
L1: SUMIDA CR43-100
C2
1µF
124k
1618 • TA12
sn1618 1618fas
10
LT1618
U
TYPICAL APPLICATIONS
Li Ion White LED Driver
L1
10µH
VIN
2.7V TO 5V
C1
4.7µF
9
10kHz TO 50kHz
PWM
BRIGHTNESS
ADJUST
D1
8
7
VIN
SW
SHDN
ISP
ISN
R3
5.1k
LT1618
4
IADJ
GND
2.49Ω
20mA
3
2
R1
2M
1
FB
VC
5
10
C2
1µF
C3
0.1µF
R2
100k
CC
0.1µF
C1: TAIYO YUDEN JMK212BJ475
C2: TAIYO YUDEN TMK316BJ105
D1: ON SEMICONDUCTOR MBR0530
L1: SUMIDA CLQ4D10-100
(408) 573-4150
(408) 573-4150
(800) 282-9855
(847) 956-0666
1618 • TA04
White LED Driver for 20 LEDs
L1
10µH
VIN
2.7V TO 5V
C1
4.7µF
9
10kHz TO 50kHz
PWM
BRIGHTNESS
ADJUST
D1
8
7
VIN
SW
SHDN
ISP
ISN
R3
5.1k
4
0.619Ω
3
2
R1
2M
LT1618
IADJ
FB
VC
GND
5
1
10
C2
1µF
C3
0.1µF
CC
0.1µF
C1: TAIYO YUDEN JMK212BJ475
C2: TAIYO YUDEN TMK316BJ105
D1: ON SEMICONDUCTOR MBR0530
L1: SUMIDA CR43-100
80mA
(408) 573-4150
(408) 573-4150
(800) 282-9855
(847) 956-0666
R2
121k
51Ω
51Ω
51Ω
51Ω
1618 • TA05
sn1618 1618fas
11
LT1618
U
TYPICAL APPLICATIONS
USB to 5V SEPIC Converter
VIN
5V
C1
4.7µF
3
C3
0.47µF
L1
10µH
0.1Ω
VOUT
5V
2
7
ISN
SW
3.3V
OFF ON
0V
9
L2
10µH
ISP
20k
4
3.3V
100mA 500mA
0V
5
75
C2
10µF
R2
107k
SHDN
IADJ GND
R1
316k
1
FB
VIN
Efficiency
80
LT1618
8
D1
VC
10
EFFICIENCY (%)
IIN
65
2k
13k
70
10nF
60
C1: TAIYO YUDEN JMK212BJ475
C2: TAIYO YUDEN JMK316BJ106
C3: TAIYO YUDEN EMK212BJ474
D1: ON SEMICONDUCTOR MBR0520
L1: SUMIDA CR43-100
(408) 573-4150
(408) 573-4150
(408) 573-4150
(800) 282-9855
(847) 956-0666
0
50
100 150 200 250
LOAD CURRENT (mA)
300
350
1618 F09b
1618 • TA09a
USB SEPIC During Start-Up
USB SEPIC Start-Up with Output Shorted
VOUT
2V/DIV
VOUT
2V/DIV
IIN
50mA/DIV
50mA/DIV
1ms/DIV
1618 TA10
1ms/DIV
1618 TA11
sn1618 1618fas
12
LT1618
U
TYPICAL APPLICATIO S
12V Boost Converter with 500mA Input Current Limit
IL1
L1
10µH
0.1Ω
3
8
9
VOUT
12V
2
7
ISN
SW
VIN = 5V
1
FB
5
C2
4.7µF
R2
107k
SHDN
4
85
R1
909k
LT1618
VIN
Efficiency
90
ISP
IADJ GND
C1
4.7µF
D1
VC
10
2k
EFFICIENCY (%)
VIN
1.8V TO 5V
80
VIN = 3.3V
75
70
65
10nF
60
C1: TAIYO YUDEN JMK212BJ475
C2: TAIYO YUDEN EMK316BJ475
D1: ON SEMICONDUCTOR MBR0520
L1: SUMIDA CR43-100
(408) 573-4150
(408) 573-4150
(800) 282-9855
(847) 956-0666
12V Boost Converter Start-Up with Input Current Limit
(VIN = 1.8V, ILOAD = 40mA)
0
20
60 80 100 120 140 160
L0AD CURRENT (mA)
40
1618 TA06b
1618 • TA06a
12V Boost Converter Start-Up without Input Current Limit
(VIN = 1.8V, ILOAD = 40mA)
VOUT
5V/DIV
VOUT
5V/DIV
ILI
200mA/DIV
ILI
200mA/DIV
50µs/DIV
1618 TA07
50µs/DIV
1618 TA08
sn1618 1618fas
13
LT1618
U
PACKAGE DESCRIPTIO
DD Package
10-Lead Plastic DFN (3mm × 3mm)
(Reference LTC DWG # 05-08-1698)
0.675 ±0.05
3.50 ±0.05
1.65 ±0.05
2.15 ±0.05 (2 SIDES)
PACKAGE
OUTLINE
0.25 ± 0.05
0.50
BSC
2.38 ±0.05
(2 SIDES)
RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS
3.00 ±0.10
(4 SIDES)
R = 0.115
TYP
0.38 ± 0.10
6
10
5
1
1.65 ± 0.10
(2 SIDES)
PIN 1
TOP MARK
(SEE NOTE 6)
0.200 REF
(DD10) DFN 1103
0.25 ± 0.05
0.50 BSC
0.75 ±0.05
0.00 – 0.05
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
sn1618 1618fas
14
LT1618
U
PACKAGE DESCRIPTIO
MS Package
10-Lead Plastic MSOP
(Reference LTC DWG # 05-08-1661)
0.889 ± 0.127
(.035 ± .005)
5.23
(.206)
MIN
3.20 – 3.45
(.126 – .136)
3.00 ± 0.102
(.118 ± .004)
(NOTE 3)
0.50
0.305 ± 0.038
(.0197)
(.0120 ± .0015)
BSC
TYP
RECOMMENDED SOLDER PAD LAYOUT
0.254
(.010)
0.497 ± 0.076
(.0196 ± .003)
REF
10 9 8 7 6
3.00 ± 0.102
(.118 ± .004)
(NOTE 4)
4.90 ± 0.152
(.193 ± .006)
DETAIL “A”
0° – 6° TYP
GAUGE PLANE
1 2 3 4 5
0.53 ± 0.152
(.021 ± .006)
DETAIL “A”
0.86
(.034)
REF
1.10
(.043)
MAX
0.18
(.007)
SEATING
PLANE
0.17 – 0.27
(.007 – .011)
TYP
0.50
(.0197)
BSC
0.127 ± 0.076
(.005 ± .003)
MSOP (MS) 0603
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
sn1618 1618fas
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.
15
LT1618
U
TYPICAL APPLICATIONS
Li-Ion Buck-Boost Mode Luxeon LED Driver
Buck Mode Luxeon LED Driver
D2
350mA
0.15Ω
L1
3.3µH
VIN
3.2V TO 5V
2
9
C1
4.7µF
D2
D1
D1
3
7
ISP
SW
L1
47µH
2
7
ISN
SW
100k
ISN
LT1618
8
700mA
0.07Ω
VIN
16V
1
FB
VIN
C2
4.7µF
SHDN
10k
IADJ GND
4
C1
4.7µF
5
3
9
VC
10
ISP
LT1618
8
SHDN
IADJ GND
4
10nF
C1: TAIYO YUDEN JMK212BJ475KG
C2: TAIYO YUDEN EMK316BJ475ML
D1: ON SEMICONDUCTOR MBRM120
D2: LUMILEDS DS25
L1: NEC PLC-07453R3
1
FB
VIN
5
VC
10
10k
1618 TA13
220pF
2.2nF
C1: TAIYO YUDEN TMK325BJ475MN
D1: PHILIPS PMEG2010
D2: LUMILEDS DS45
L1: TOKO D104C
1618 TA14
RELATED PARTS
PART NUMBER
DESCRIPTION
COMMENTS
LT1613
550mA (ISW), 1.4MHz, High Efficiency Step-Up DC/DC Converter
VIN: 0.9V to 10V, VOUT(MAX) = 34V, IQ = 3mA, ISD < 1µA,
ThinSOTTM Package
LT1615/LT1615-1
300mA/80mA (ISW), Constant Off-Time, High Efficiency Step-Up
DC/DC Converter
VIN: 1.2V to 15V, VOUT(MAX) = 34V, IQ = 20µA, ISD < 1µA,
ThinSOT Package
LT1930/LT1930A
1A (ISW), 1.2MHz/2.2MHz, High Efficiency Step-Up
DC/DC Converter
VIN: 2.6V to 16V, VOUT(MAX) = 34V, IQ = 4.2mA/5.5mA,
ISD < 1µA, ThinSOT Package
LT1932
Constant Current, 1.2MHz, High Efficiency White LED
Boost Regulator
VIN: 1V to 10V, VOUT(MAX) = 34V, IQ = 1.2mA, ISD < 1µA,
ThinSOT Package
LT1944/LT1944-1
(Dual)
Dual Output 350mA/100mA (ISW), Constant Off-Time,
High Efficiency Step-Up DC/DC Converter
VIN: 1.2V to 15V, VOUT(MAX) = 34V, IQ = 20µA, ISD < 1µA,
MS Package
LT1945 (Dual)
Dual Output, Pos/Neg, 350mA (ISW), Constant Off-Time,
High Efficiency Step-Up DC/DC Converter
VIN: 1.2V to 15V, VOUT(MAX) = ±34V, IQ = 20µA, ISD < 1µA,
MS Package
LT1961
1.5A (ISW), 1.25MHz, High Efficiency Step-Up DC/DC Converter
VIN: 3V to 25V, VOUT(MAX) = 35V, IQ = 0.9mA, ISD < 6µA,
MS8E Package
LTC3401/LTC3402 1A/2A (ISW), 3MHz, Synchronous Step-Up DC/DC Converter
VIN: 0.5V to 5V, VOUT(MAX) = 6V, IQ = 38µA, ISD < 1µA,
MS Package
LT3461/LT3461A
0.3A (ISW), 1.3MHz/3MHz, High Efficiency Step-Up DC/DC
Converter with Integrated Schottky
VIN: 2.5V to 16V, VOUT(MAX) = 38V, IQ = 2.8mA, ISD < 1µA,
SC70 and ThinSOT Packages
LT3463/LT3463A
250mA (ISW), Boost/Inverter Dual, Micropower DC/DC Converter
with Integrated Schottky Diodes
VIN: 2.4V to 15V, VOUT(MAX) = ±40V, IQ = 40µA, ISD < 1µA,
DFN Package
LT3464
0.08A (ISW), High Efficiency Step-Up DC/DC Converter with
Integrated Schottky, Output Disconnect
VIN: 2.3V to 10V, VOUT(MAX) = 34V, IQ = 25µA, ISD < 1µA,
ThinSOT Package
LT3465/LT3465A
Constant Current, 1.2MHz/2.7MHz, High Efficiency White LED
Boost Regulator with Integrated Schottky Diode
VIN: 2.7V to 16V, VOUT(MAX) = 34V, IQ = 1.9mA, ISD < 1µA,
ThinSOT Package
LT3467/LT3467A
1.1A (ISW), 1.3MHz/2.1MHz, High Efficiency Step-Up DC/DC
Converter with Integrated Soft-Start
VIN: 2.4V to 16V, VOUT(MAX) = 40V, IQ = 1.2mA, ISD < 1µA,
ThinSOT Package
ThinSOT is a trademark of Linear Technology Corporation.
sn1618 1618fas
16
Linear Technology Corporation
LT/TP 0504 1K REV A • PRINTED IN USA
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408) 432-1900 ● FAX: (408) 434-0507
●
www.linear.com
© LINEAR TECHNOLOGY CORPORATION 2001