LINER LT3467A 1.1a step-up dc/dc converter with integrated soft-start Datasheet

LT3467/LT3467A
1.1A Step-Up DC/DC
Converter with
Integrated Soft-Start
DESCRIPTION
FEATURES
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The LT®3467/LT3467A switching regulators combine a
42V, 1.1A switch with a soft-start function. Pin compatible
with the LT1930, its low VCESAT bipolar switch enables the
device to deliver high current outputs in a small footprint.
The LT3467 switches at 1.3MHz, allowing the use of tiny,
low cost and low height inductors and capacitors. The
LT3467A switches at 2.1MHz, allowing the use of even
smaller components. High inrush current at start-up is
eliminated using the programmable soft-start function.
A single external capacitor sets the current ramp rate. A
constant frequency current mode PWM architecture results
in low, predictable output noise that is easy to filter.
1.3MHz Switching Frequency (LT3467)
2.1MHz Switching Frequency (LT3467A)
Low VCESAT Switch: 330mV at 1.1A
High Output Voltage: Up to 40V
Wide Input Range: 2.4V to 16V
Dedicated Soft-Start Pin
5V at 540mA from 3.3V Input (LT3467)
5V at 430mA from 3.3V Input (LT3467A)
12V at 270mA from 5V Input (LT3467)
12V at 260mA from 5V Input (LT3467A)
Uses Small Surface Mount Components
Low Shutdown Current: <1μA
Pin-for-Pin Compatible with the LT1930 and LT1613
Low Profile (1mm) ThinSOT™ Package
Low Profile (0.75mm) 8-Lead (3mm × 2mm)
DFN Package
The high voltage switch on the LT3467/LT3467A is rated
at 42V, making the devices ideal for boost converters up
to 40V as well as SEPIC and flyback designs. The LT3467
can generate 5V at up to 540mA from a 3.3V supply or
5V at 450mA from four alkaline cells in a SEPIC design.
The LT3467A can generate 5V at up to 430mA from a 3.3V
supply or 15V at 135mA from a 3.3V supply. The LT3467/
LT3467A are available in a low profile (1mm) 6-lead SOT-23
package and tiny 3mm × 2mm DFN package.
APPLICATIONS
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Digital Cameras
White LED Power Supplies
Cellular Phones
Medical Diagnostic Equipment
Local 5V or 12V Supplies
TFT-LCD Bias Supplies
xDSL Power Supplies
L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks of Linear
Technology Corporation. ThinSOT is a trademark of Linear Technology Corporation. All other
trademarks are the property of their respective owners.
TYPICAL APPLICATION
Efficiency
95
Single Li-Ion Cell to 5V Boost Converter
4.7μF
OFF ON
0.047μF
SW
VIN
SHDN
LT3467
SS
GND
VOUT
5V
765mA AT VIN = 4.2V,
540mA AT VIN = 3.3V,
360mA AT VIN = 2.6V
402k
3.3pF
FB
133k
15μF
VIN = 4.2V
85
EFFICIENCY (%)
2.7μH
VIN
2.6V TO
4.2V
90
80
VIN = 3.3V
VIN = 2.6V
75
70
65
60
55
3467 TA01a
50
100 200 300 400 500 600 700 800 900
IOUT (mA)
3467 TA01b
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LT3467/LT3467A
ABSOLUTE MAXIMUM RATINGS (Note 1)
VIN Voltage ................................................................16V
SW Voltage ................................................ –0.4V to 42V
FB Voltage ................................................................2.5V
Current Into FB Pin .............................................. ±1mA
SHDN Voltage ......................................................... 16V
Maximum Junction Temperature ......................... 125°C
Operating Junction Temperature Range (Note 2)
E Grade ................................................ –40°C to 85°C
I Grade ............................................... –40°C to 125°C
Storage Temperature Range................... –65°C to 150°C
Lead Temperature (Soldering, 10 sec)
TSOT................................................................. 300°C
PIN CONFIGURATION
TOP VIEW
FB 1
GND 2
SW 3
9
SW 4
TOP VIEW
8
SHDN
7
SS
SW 1
6 VIN
VIN
GND 2
5 SS
6
5
FB 3
GND
4 SHDN
S6 PACKAGE
6-LEAD PLASTIC TSOT-23
DDB PACKAGE
8-LEAD (3mm s 2mm) PLASTIC DFN
TJMAX = 125°C, θJA = 165°C/W, θJC = 102°C/W
TJMAX = 125°C, θJA = 80°C/W
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
LT3467EDDB#PBF
LT3467EDDB#TRPBF
LCPX
8-Lead (3mm × 2mm) Plastic DFN
–40°C to 85°C
LT3467IDDB#PBF
LT3467IDDB#TRPBF
LCPX
8-Lead (3mm × 2mm) Plastic DFN
–40°C to 125°C
LT3467AEDDB#PBF
LT3467AEDDB#TRPBF
LCKD
8-Lead (3mm × 2mm) Plastic DFN
–40°C to 85°C
LT3467AIDDB#PBF
LT3467AIDDB#TRPBF
LCKD
8-Lead (3mm × 2mm) Plastic DFN
–40°C to 125°C
LT3467IS6#PBF
LT3467IS6#TRPBF
LTACH
6-Lead Plastic TSOT-23
–40°C to 125°C
LT3467ES6#PBF
LT3467ES6#TRPBF
LTACH
6-Lead Plastic TSOT-23
–40°C to 85°C
LT3467AES6#PBF
LT3467AES6#TRPBF
LTBCC
6-Lead Plastic TSOT-23
–40°C to 85°C
LT3467AIS6#PBF
LT3467AIS6#TRPBF
LTBCC
6-Lead Plastic TSOT-23
–40°C to 125°C
LEAD BASED FINISH
TAPE AND REEL
PART MARKING*
PACKAGE DESCRIPTION
TEMPERATURE RANGE
LT3467EDDB
LT3467EDDB#TR
LCPX
8-Lead (3mm × 2mm) Plastic DFN
–40°C to 85°C
LT3467IDDB
LT3467IDDB#TR
LCPX
8-Lead (3mm × 2mm) Plastic DFN
–40°C to 125°C
LT3467AEDDB
LT3467AEDDB#TR
LCKD
8-Lead (3mm × 2mm) Plastic DFN
–40°C to 85°C
LT3467AIDDB
LT3467AIDDB#TR
LCKD
8-Lead (3mm × 2mm) Plastic DFN
–40°C to 125°C
LT3467IS6
LT3467IS6#TR
LTACH
6-Lead Plastic TSOT-23
–40°C to 125°C
LT3467ES6
LT3467ES6#TR
LTACH
6-Lead Plastic TSOT-23
–40°C to 85°C
LT3467AES67
LT3467AES6#TR
LTBCC
6-Lead Plastic TSOT-23
–40°C to 85°C
LT3467AIS67
LT3467AIS67#TR
LTBCC
6-Lead Plastic TSOT-23
–40°C to 125°C
Consult LTC Marketing for parts specified with wider operating temperature ranges. *The temperature grade is identified by a label on the shipping container.
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/
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LT3467/LT3467A
ELECTRICAL CHARACTERISTICS
The l denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C. VIN = 3V, VSHDN = VIN unless otherwise noted. Specifications are for both
the LT3467 and LT3467A unless otherwise noted.
PARAMETER
CONDITIONS
MIN
Minimum Operating Voltage
TYP
MAX
2.2
2.4
V
16
V
1.255
1.270
1.280
V
V
10
50
nA
Maximum Operating Voltage
Feedback Voltage
l
FB Pin Bias Current
(Note 3)
1.230
1.220
l
UNITS
Quiescent Current
VSHDN = 2.4V, Not Switching
1.2
2
mA
Quiescent Current in Shutdown
VSHDN = 0.5V, VIN = 3V
0.01
1
μA
Reference Line Regulation
2.6V ≤ VIN ≤ 16V
0.01
0.05
%/V
Switching Frequency
LT3467
LT3467A
LT3467A
1
1.6
1.6
1.3
2.1
1.6
2.7
MHz
MHz
MHz
88
87
82
78
94
Maximum Duty Cycle
LT3467
LT3467
LT3467A
LT3467A
l
l
l
Minimum Duty Cycle
%
%
%
%
88
10
Switch Current Limit
At Minimum Duty Cycle
At Maximum Duty Cycle (Note 4)
Switch VCESAT
ISW = 1.1A
Switch Leakage Current
VSW = 5V
SHDN Input Voltage High
1.4
0.8
%
1.8
1.2
2.5
1.9
A
A
330
500
mV
0.01
1
μA
2.4
V
SHDN Input Voltage Low
SHDN Pin Bias Current
VSHDN = 3V
VSHDN = 0V
SS Charging Current
VSS = 0.5V
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 LT3467E/LT3467AE are guaranteed to meet performance
specifications from 0°C to 85°C, junction temperature. Specifications over
the –40°C to 85°C operating junction temperature range are assured by
design, characterization and correlation with statistical process controls.
The LT3467I/LT3467AI are guaranteed over the full –40°C to 125°C
operating junction temperature range.
2
0.5
V
16
0
32
0.1
μA
μA
3
4.5
μA
Note 3: Current flows out of the pin.
Note 4: See Typical Performance Characteristics for guaranteed current
limit vs duty cycle.
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LT3467/LT3467A
TYPICAL PERFORMANCE CHARACTERISTICS
Quiescent Current vs Temperature
SHDN Current vs SHDN Voltage
FB Pin Voltage vs Temperature
1.6
1.4
1.26
140
1.25
120
1.2
0.8
0.6
ISHDN (μA)
VFB (V)
IQ (mA)
100
1.24
1.0
1.23
1.22
1.21
0
–40 –25 –10 5
0
20 35 50 65 80 95 110 125
TEMPERATURE (°C)
0
ILIM (A)
1.4
TA = 25°C
TA = 85°C
VCESAT
100mV/DIV
0.8
TA = –40°C
0.6
0.4
0.2
OSCILLATOR FREQUENCY (MHz)
2.25
TYPICAL
GUARANTEED
10
18
LT3467A
2.00
1.75
1.50
LT3467
1.25
1.00
0.75
0.50
20
30
40
50 60
DC (%)
70
80
3467 G05
90
SW CURRENT 200mA/DIV
0
–50
–25
0
25
Peak Switch Current
vs Soft-Start Voltage
2.0
TA = 25°C
100
Start-Up Waveform
(Figure 2 Circuit)
TA = 25°C
1.8
5
VSHDN
2V/DIV
SWITCH CURRENT (A)
1.6
4
3
2
1.4
1.2
VOUT
1V/DIV
1.0
0.8
0.6
0.4
1
ISUPPLY
0.5A/DIV
0.2
0
0
75
3467 G06
Soft-Start Current
vs Soft-Start Voltage
6
50
TEMPERATURE (°C)
3467 G04
ISS (μA)
16
0.25
0
0
14
2.50
TA = 25°C
1.0
8 10 12
VSHDN (V)
Oscillator Frequency
vs Temperature
2.0
1.2
6
3467 G03
Switch Saturation Voltage
vs Switch Current
Current Limit vs Duty Cycle
1.6
4
2
3467 G02
3467 G01
1.8
60
20
1.20
–40 –25 –10 5
20 35 50 65 80 95 110 125
TEMPERATURE (°C)
80
40
0.4
0.2
TA = 25°C
50 100 150 200 250 300 350 400 450 500
VSS (mV)
3467 G07
0
50 100 150 200 250 300 350 400 450 500
VSS (mV)
0.5ms/DIV
3467 G09
3467 G08
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LT3467/LT3467A
PIN FUNCTIONS
(DFN/TSOT)
FB (Pin 1/Pin 3): Feedback Pin. Reference voltage is 1.255V.
Connect resistive divider tap here. Minimize trace area at
FB. Set VOUT = 1.255V(1 + R1/R2).
VIN (Pin 6/Pin 6): Input Supply Pin. Must be locally
bypassed.
SS (Pin 7/Pin 5): Soft-Start Pin. Place a soft-start capacitor
here. Upon start-up, 4μA of current charges the capacitor
to 1.255V. Use a larger capacitor for slower start-up. Leave
floating if not in use.
GND (Pins 2, 5, 9/Pin 2): Ground. Tie directly to local
ground plane.
SW (Pins 3, 4/Pin 1): Switch Pin. (Collector of internal
NPN power switch) Connect inductor/diode here and
minimize the metal trace area connected to this pin to
minimize EMI.
SHDN (Pin 8/Pin 4): Shutdown Pin. Tie to 2.4V or more
to enable device. Ground to shut down.
BLOCK DIAGRAM
250k
SS
1.255V
REFERENCE
VIN
SW
+
–
A1
–
VOUT
COMPARATOR
DRIVER
RC
+
A2
R
CC
S
Q1
Q
+
R1 (EXTERNAL)
3
FB
0.01Ω
–
R2 (EXTERNAL)
RAMP
GENERATOR
SHUTDOWN
SHDN
FB
GND
1.3MHz
OSCILLATOR*
3467 F01
*2.1MHz FOR LT3467A
Figure 1. Block Diagram
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LT3467/LT3467A
OPERATION
The LT3467 uses a constant frequency, current-mode control scheme to provide excellent line and load regulation.
Refer to the Block Diagram. At the start of each oscillator
cycle, the SR latch is set which turns on the power switch
Q1. A voltage proportional to the switch current is added
to a stabilizing ramp and the resulting sum is fed into the
positive terminal of the PWM comparator A2. When this
voltage exceeds the level at the negative input of A2, the
SR latch is reset, turning off the power switch. The level
at the negative input of A2 is set by the error amplifier A1,
and is simply an amplified version of the difference between
the feedback voltage and the reference voltage of 1.255V.
In this manner, the error amplifier 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. Similarly, if the error decreases, less current
is delivered. The soft-start feature of the LT3467 allows
for clean start-up conditions by limiting the rate of voltage
rise at the output of comparator A1 which, in turn, limits
the peak switch current. The soft-start pin is connected
to a reference voltage of 1.255V through a 250k resistor,
providing 4μA of current to charge the soft-start capacitor.
Typical values for the soft-start capacitor range from 10nF
to 200nF. The LT3467 has a current limit circuit not shown
in the Block Diagram. The switch current is constantly
monitored and not allowed to exceed the maximum switch
current (typically 1.4A). If the switch current reaches
this value, the SR latch is reset regardless of the state
of comparator A2. This current limit protects the power
switch as well as the external components connected to
the LT3467.
The Block Diagram for the LT3467A (not shown) is identical
except that the oscillator frequency is 2.1MHz.
APPLICATIONS INFORMATION
Duty Cycle
Switching Frequency and Inductor Selection
The typical maximum duty cycle of the LT3467 is 94%
(88% for the LT3467A). The duty cycle for a given application is given by:
The LT3467 switches at 1.3 MHz, allowing for small valued
inductors to be used. 4.7μH or 10μH will usually suffice.
The LT3467A switches at 2.1MHz, allowing for even smaller
valued inductors to be used. 0.9μH to 6.8μH will usually
suffice. Choose an inductor that can handle at least 1.2A
without saturating, and ensure that the inductor has a
low DCR (copper-wire resistance) to minimize I2R power
losses. Note that in some applications, the current handling
requirements of the inductor can be lower, such as in the
SEPIC topology where each inductor only carries one-half
of the total switch current. For better efficiency, use similar
valued inductors with a larger volume. Many different sizes
and shapes are available from various manufacturers.
Choose a core material that has low losses at 1.3MHz,
(2.1MHz for the LT3467A) such as ferrite core.
DC =
| VOUT | +| VD | – | VIN |
| VOUT | +| VD | – | VCESAT |
where VD is the diode forward voltage drop and VCESAT is
in the worst case 330mV (at 1.1A)
The LT3467 and LT3467A can be used at higher duty cycles,
but must be operated in the discontinuous conduction
mode so that the actual duty cycle is reduced.
Setting Output Voltage
R1 and R2 determine the output voltage.
VOUT = 1.255V (1+ R1/R2)
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LT3467/LT3467A
APPLICATIONS INFORMATION
VIN
2.6V TO 4.2V
L1
2.7μH
C1
4.7μF
OFF ON
SW
VIN
SHDN
LT3467
SS
C3
0.047μF
D1
R1
402k
C4
3.3pF
VOUT
5V
765mA AT VIN = 4.2V,
540mA AT VIN = 3.3V,
360mA AT VIN = 2.6V
FB
GND
C2
15μF
R2
133k
C1, C2: X5R OR X7R, 6.3V
D1: ON SEMICONDUCTOR MBRM120
L1: SUMIDA CR43-2R7
3467 TA05a
Figure 2. Single Li-Ion Cell to 5V Boost Converter (Same as 1st Page Application)
Table 1. Inductor Manufacturers
Sumida
(847) 956-0666
www.sumida.com
TDK
(847) 803-6100
www.tdk.com
Murata
(714) 852-2001
www.murata.com
FDK
(408) 432-8331
www.fdk.co.jp
Supply Current of Figure 2 During Start-Up
Without Soft-Start Capacitor
VOUT
1V/DIV
Soft-Start
The soft-start feature provides a way to limit the inrush
current drawn from the supply upon start-up. An internal
250k resistor charges the external soft-start capacitor
to 1.255V. After the capacitor reaches 0.15V the rate of
voltage rise at the output of the comparator A1 tracks the
rate of voltage rise of the soft-start capacitor. This limits
the inrush current drawn from the supply during startup. The soft-start feature plays another important role in
applications where the switch will reach levels of 30V or
higher. During start-up, excessively high switch current,
together with the presence of high voltage can overstress
the switch. A properly used soft-start feature will keep the
switch current from overshooting. This practice will greatly
improve the robustness of such designs. Once the part is
shut down, the soft-start capacitor is quickly discharged
to 0.4V, then slowly discharged through the 250k resistor
to ground. If the part is to be shut down and re-enabled in
a short period of time while soft-start is used, you must
ensure that the soft-start capacitor has enough time to
discharge before re-enabling the part. Typical values of
the soft-start capacitor range from 10nF to 200nF.
ISUPPLY
0.5A/DIV
0.1ms/DIV
3467 AI01
Supply Current of Figure 2 During Start-Up
with a 47nF Soft-Start Capacitor
VOUT
1V/DIV
ISUPPLY
0.5A/DIV
0.5ms/DIV
3467 AI02
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LT3467/LT3467A
APPLICATIONS INFORMATION
Capacitor Selection
Low ESR (equivalent series resistance) capacitors should
be used at the output to minimize the output ripple voltage.
Multi-layer ceramic capacitors are an excellent choice,
as they have extremely low ESR and are available in very
small packages. X5R dielectrics are preferred, followed
by X7R, as these materials retain the capacitance over
wide voltage and temperature ranges. A 4.7μF to 15μF
output capacitor is sufficient for most applications, but
systems with very low output currents may need only a
1μF or 2.2μF output capacitor. Solid tantalum or OS-CON
capacitors can be used, but they will occupy more board
area than a ceramic and will have a higher ESR. 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 LT3467. 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. Ceramic Capacitor Manufacturers
Taiyo Yuden
(408) 573-4150
www.t-yuden.com
AVX
(803) 448-9411
www.avxcorp.com
Murata
(714) 852-2001
www.murata.com
The decision to use either low ESR (ceramic) capacitors
or the higher ESR (tantalum or OS-CON) capacitors can
affect the stability of the overall system. The ESR of any
capacitor, along with the capacitance itself, contributes
a zero to the system. For the tantalum and OS-CON capacitors, this zero is located at a lower frequency due to
the higher value of the ESR, while the zero of a ceramic
capacitor is at a much higher frequency and can generally
be ignored.
A phase lead zero can be intentionally introduced by placing
a capacitor (C4) in parallel with the resistor (R1) between
VOUT and VFB as shown in Figure 2. The frequency of the
zero is determined by the following equation.
ƒZ =
1
2π • R1• C4
By choosing the appropriate values for the resistor and
capacitor, the zero frequency can be designed to improve
the phase margin of the overall converter. The typical
target value for the zero frequency is between 35kHz
to 55kHz. Figure 3 shows the transient response of the
step-up converter from Figure 8 without the phase lead
capacitor C4. Although adequate for many applications,
phase margin is not ideal as evidenced by 2-3 “bumps”
in both the output voltage and inductor current. A 22pF
capacitor for C4 results in ideal phase margin, which is
revealed in Figure 4 as a more damped response and less
overshoot.
Diode Selection
A Schottky diode is recommended for use with the LT3467
and the LT3467A. The Philips PMEG 2005 is a very good
choice. Where the switch voltage exceeds 20V, use the
PMEG 3005 (a 30V diode). Where the switch voltage
exceeds 30V, use the PMEG 4005 (a 40V diode). These
diodes are rated to handle an average forward current of
0.5A. In applications where the average forward current
of the diode exceeds 0.5A, a Philips PMEG 2010 rated at
1A is recommended. For higher efficiency, use a diode
with better thermal characteristics such as the On Semiconductor MBRM120 (a 20V diode) or the MBRM140 (a
40V diode).
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LT3467/LT3467A
APPLICATIONS INFORMATION
Layout Hints
LOAD CURRENT
100mA/DIV
AC COUPLED
VOUT
200mV/DIV
AC COUPLED
IL1
5A/DIV
AC COUPLED
20μs/DIV
3467 F03
The high speed operation of the LT3467/LT3467A demands
careful attention to board layout. You will not get advertised performance with careless layout. Figure 5a shows
the recommended component placement for the ThinSOT
package. Figure 5b shows the recommended component
placement for the DFN package. Note the vias under the
Exposed Pad. These should connect to a local ground
plane for better thermal performance.
Figure 3. Transient Response of Figure 8’s Step-Up
Converter without Phase Lead Capacitor
L1
D1
C1
VIN
VOUT
LOAD CURRENT
100mA/DIV
AC COUPLED
C2
GND
VOUT
200mV/DIV
AC COUPLED
1
6
2
5
3
4
CSS
SS
SHDN
FB
R2
R1
IL1
5A/DIV
AC COUPLED
C3
20μs/DIV
3467 F04
VOUT
3467 F05a
Figure 5a. Suggested Layout—ThinSOT
Figure 4. Transient Response of Figure 8’s Step-Up
Converter with a 22pF Phase Lead Capacitor
VOUT
C3
Setting Output Voltage
R1
To set the output voltage, select the values of R1 and R2
(see Figure 2) according to the following equation.
R2
SHDN
GND
⎞
⎛ V
R1= R2 ⎜ OUT – 1⎟
⎝ 1.255V ⎠
A good value for R2 is 13.3k which sets the current in the
resistor divider chain to 1.255V/13.3k = 94μA.
FB 1
8
2
7
3
6
4
5
C2
VOUT
CSS
VIN
D1
L1
C1
3467 F05b
Figure 5b. Suggested Layout—DFN
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LT3467/LT3467A
APPLICATIONS INFORMATION
Compensation—Theory
Like all other current mode switching regulators, the
LT3467/LT3467A needs to be compensated for stable
and efficient operation. Two feedback loops are used in
the LT3467/LT3467A: a fast current loop which does not
require compensation, and a slower voltage loop which
does. Standard Bode plot analysis can be used to understand and adjust the voltage feedback loop.
As with any feedback loop, identifying the gain and phase
contribution of the various elements in the loop is critical.
Figure 6 shows the key equivalent elements of a boost
converter. Because of the fast current control loop, the
power stage of the IC, inductor and diode have been replaced by the equivalent transconductance amplifier gmp.
gmp acts as a current source where the output current is
proportional to the VC voltage. Note that the maximum
output current of gmp is finite due to the current limit
in the IC.
From Figure 6, the DC gain, poles and zeroes can be
calculated as follows:
Output Pole: P1=
2
2 • π • RL • COUT
Error Amp Pole: P2=
1
2 • π • RO • CC
Error Amp Zero: Z1=
1
2 • π • RC • CC
DC GAIN: A=
1.255
VOUT
ESR Zero: Z2 =
RHP Zero: Z3=
2
• VIN • gma • RO • gmp • RL •
1
2 • π • RESR • COUT
VIN 2 • RL
2 • π • VOUT 2 • L
High Frequency Pole: P3>
–
gmp
VOUT
+
CPL
+
VC
gma
RC
RO
CC
RESR
COUT
1.255V
REFERENCE
R1
–
R2
3467 F06
CC: COMPENSATION CAPACITOR
COUT: OUTPUT CAPACITOR
CPL: PHASE LEAD CAPACITOR
gma: TRANSCONDUCTANCE AMPLIFIER INSIDE IC
gmp: POWER STAGE TRANSCONDUCTANCE AMPLIFIER
RC: COMPENSATION RESISTOR
RL: OUTPUT RESISTANCE DEFINED AS VOUT DIVIDED BY ILOAD(MAX)
RO: OUTPUT RESISTANCE OF gma
R1, R2: FEEDBACK RESISTOR DIVIDER NETWORK
RESR: OUTPUT CAPACITOR ESR
1
2
Phase Lead Zero: Z4 =
RL
Phase Lead Pole: P4 =
fS
3
1
2 • π • R1• CPL
1
2 • π • CPL •
R1• R2
R1+ R2
The current mode zero is a right-half plane zero which can
be an issue in feedback control design, but is manageable
with proper external component selection.
Figure 6. Boost Converter Equivalent Model
3467afe
10
LT3467/LT3467A
APPLICATIONS INFORMATION
Table 3. Bode Plot Parameters
PARAMETER
VALUE
UNITS
COMMENT
RL
10.4
Ω
Application Specific
15
μF
Application Specific
50
0
COUT
40
–45
RESR
10
mΩ
Application Specific
30
–90
RO
0.4
MΩ
Not Adjustable
20
–135
CC
60
pF
Not Adjustable
10
–180
0
–225
–10
–270
–20
–315
–30
–360
–40
GAIN
PHASE
–50
100
1k
PHASE (DEG)
GAIN (dB)
Using the circuit of Figure 2 as an example, the following
table shows the parameters used to generate the Bode
plot shown in Figure 7.
–405
–450
1M
10k
100k
FREQUENCY (Hz)
3467 F07
Figure 7. Bode Plot of 3.3V to 5V Application
CPL
3.3
pF
Adjustable
RC
100
kΩ
Not Adjustable
R1
402
kΩ
Adjustable
R2
133
kΩ
VOUT
5
V
Application Specific
Adjustable
VIN
3.3
V
Application Specific
gma
35
μmho
Not Adjustable
gmp
7.5
mho
Not Adjustable
L
2.7
μH
fS
1.3*
MHz
Application Specific
Not Adjustable
*2.1MHz for LT3467A
From Figure 7, the phase is –138° when the gain reaches
0dB giving a phase margin of 42°. This is more than
adequate. The crossover frequency is 37kHz.
TYPICAL APPLICATIONS
Lithium-Ion to 6V Step-Up DC/DC Converter
L1
2.2μH
SW
VIN
C1
2.2μF
SHDN
C4
0.047μF
SHDN
LT3467
SS
95
D1
R1
501k
C3
1.8pF
VOUT
6V
275mA AT VIN = 2.7V
490mA AT VIN = 3.8V
590mA AT VIN = 4.2V
FB
GND
R2
133k
C2
15μF
90
VIN = 4.2V
85
EFFICIENCY (%)
VIN
2.7V TO 4.2V
Li-Ion to 6V
VIN = 3.8V
VIN = 2.7V
80
75
70
65
60
C1, C2: X5R OR X7R, 6.3V
D1: ON SEMICONDUCTOR MBRM120
L1: SUMIDA CR43-2R2
3467 TA02
55
50
50 100
200
300 400
IOUT (mA)
500
600
700
3467 TA02b
3467afe
11
LT3467/LT3467A
TYPICAL APPLICATIONS
4-Cell to 5V SEPIC Converter
C3
1μF
L1
10μH
4V TO 6.5V
C1
2.2μF
SHDN
4-CELL
BATTERY
D1
VIN
SW
SHDN
LT3467
FB
SS
255k
GND
84.5k
C4
0.047μF
VOUT
5V
325mA AT VIN = 4V
400mA AT VIN = 5V
450mA AT VIN = 6.5V
C5
4.7pF
L2
10μH
C2
10μF
D1: PHILIPS PMEG 2010
L1, L2: MURATA LQH32CN100K33L
C1, C3: X5R or X7R, 10V
C2: X5R or X7R, 6.3V
3467 TA03
5V to 40V Boost Converter
L1
2.7μH
VIN
5V
C1
4.7μF
SHDN
D1
SW
VIN
SHDN
LT3467
SS
C3
0.1μF
VOUT
40V
20mA
R1
412k
C2
1μF
FB
R2
13.3k
GND
C1: X5R or X7R, 6.3V
C2: X5R or X7R, 50V
D1: ON SEMICONDUCTOR, MBRM140
L1: SUMIDA CD43-2R7
3467 TA04a
±15V Dual Output Converter with Output Disconnect
VIN
5V
C4
1μF
L1
10μH
C1
2.2μF
OFF ON
SHDN
LT3467
SS
C6
0.047μF
15V
100mA
SW
VIN
D1
C5
1μF
R3
1Ω
R1
147k
D2
C2
2.2μF
FB
R2
13.3k
GND
C1: X5R or X7R, 6.3V
C2 TO C5: X5R or X7R, 16V
D1 TO D4: PHILIPS PMEG 2005
L1: SUMIDA CR43-100
D3 R4
1Ω
D4
C3
2.2μF
3467 TA05
–15V
100mA
3467afe
12
LT3467/LT3467A
TYPICAL APPLICATIONS
9V, 18V, –9V Triple Output TFT-LCD Bias Supply with Soft-Start
D1
D2
C3
0.1μF
L1
4.7μH
VIN
3.3V
C1
2.2μF
VIN
9V
220mA
SW
3.3V
9V OUTPUT
5V/DIV
–9V OUTPUT
5V/DIV
R1
124k
C5
10μF
FB
SS
0V
Start-Up Waveforms
D5
SHDN
LT3467
VSHDN
18V
10mA
C4
1μF
GND
C2
0.1μF
C7
0.1μF
C1: X5R OR X7R, 6.3V
C2,C3, C5, C6: X5R OR X7R, 10V
C4: X5R OR X7R, 25V
D1 TO D4: PHILIPS BAT54S OR EQUIVALENT
D5: PHILIPS PMEG 2005
L1: PANASONIC ELT5KT4R7M
R2
20k
18V OUTPUT
10V/DIV
IL1
0.5A/DIV
D4
D3
C6
1μF
–9V
10mA
2ms/DIV
3467 TA06b
3467 TA06a
8V, 23V, –8V Triple Output TFT-LCD Bias Supply with Soft-Start
D1
D2
D3
C3
0.1μF
L1
4.7μH
VIN
3.3V
C1
2.2μF
SHDN
LT3467
SS
VSHDN
3.3V
0V
C4
0.1μF
C5
0.1μF
23V
10mA
C6
1μF
Start-Up Waveforms
D7
8V
270mA
R1
113k
SW
VIN
D4
C7
10μF
FB
GND
C9
0.1μF
C1: X5R OR X7R, 6.3V
C2 TO C4, C7, C8: X5R OR X7R, 10V
C5: X5R OR X7R, 16V
C6: X5R OR X7R, 25V
D1 TO D6: PHILIPS BAT54S OR EQUIVALENT
D7: PHILIPS PMEG 2005
L1: PANASONIC ELT5KT4R7M
8V OUTPUT
5V/DIV
–8V OUTPUT
5V/DIV
C2
0.1μF
R2
21k
23V OUTPUT
10V/DIV
IL1
0.5A/DIV
D5
D6
C8
1μF
3467 TA07a
2ms/DIV
3467 TA07b
–8V
10mA
3467afe
13
LT3467/LT3467A
TYPICAL APPLICATIONS
Single Li-Ion Cell to 5V Boost Converter
L1
0.9μH
SW
VIN
C1
4.7μF
95
D1
R1
8.06k
C4*
75pF
SHDN
LT3467A
SS
FB
OFF ON
C3
0.047μF
VOUT
5V
600mA AT VIN = 4.2V
360mA AT VIN = 3.3V
250mA AT VIN = 2.6V
C2*
22μF
R2
2.67k
GND
90
85
EFFICIENCY (%)
VIN
2.6V TO 4.2V
Efficiency
80
VIN = 3.3V
VIN = 4.2V
VIN = 2.6V
75
70
65
60
C1, C2: X5R OR X7R, 6.3V
D1: PHILIPS PMEG 2010
L1: FDK MIPW3226D0R9M
*C2 CAN BE 10μF IN A 1210 OR LARGER PACKAGE WITH
THE ADDITION OF C4, OTHERWISE C4 IS OPTIONAL
3467 TA09a
55
50
50 100 150 200 250 300 350 400 450 500
IOUT (mA)
3467 TA09b
2.6V-3.3V to 5V Boost Converter
L1
1.5μH
SW
VIN
C1
4.7μF
OFF ON
90
D1
VOUT
5V
430mA AT VIN = 3.3V
270mA AT VIN = 2.6V
R1
8.06k
C4
56pF
SHDN
LT3467A
SS
FB
C3
0.047μF
C2
10μF
R2
2.67k
GND
85
80
EFFICIENCY (%)
VIN
2.6V TO 3.3V
Efficiency
VIN = 2.6V
75
VIN = 3.3V
70
65
60
C1, C2: X5R OR X7R, 6.3V
D1: PHILIPS PMEG 2010
L1: FDK MIP3226D1R5M
3467 TA08a
55
50
50 100 150 200 250 300 350 400 450 500
IOUT (mA)
3467 TA08b
3.3V to 15V, 135mA Step-Up Converter
VIN
C1
4.7μF
OFF ON
C3
0.047μF
SW
C1: X5R OR X7R, 6.3V
C2: X5R OR X7R, 16V
D1: PHILIPS PMEG 2010
L1: SUMIDA CMD4D13-6R8MC
VOUT
15V
135mA
R1
16.5k
SHDN
LT3467A
SS
FB
GND
90
D1
C4
68pF
R2
1.5k
C2
2.2μF
3467 TA10a
80
EFFICIENCY (%)
L1
6.8μH
VIN
3.3V
Efficiency
70
60
50
40
30
20
40
60
80 100
IOUT (mA)
120
140
160
3467 TA10b
3467afe
14
LT3467/LT3467A
PACKAGE DESCRIPTION
DDB Package
8-Lead Plastic DFN (3mm × 2mm)
(Reference LTC DWG # 05-08-1702 Rev B)
0.61 p0.05
(2 SIDES)
3.00 p0.10
(2 SIDES)
R = 0.115
TYP
5
R = 0.05
TYP
0.40 p 0.10
8
0.70 p0.05
2.55 p0.05
1.15 p0.05
PACKAGE
OUTLINE
0.25 p 0.05
0.50 BSC
2.20 p0.05
(2 SIDES)
PIN 1 BAR
TOP MARK
(SEE NOTE 6)
0.200 REF
RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS
2.00 p0.10
(2 SIDES)
0.56 p 0.05
(2 SIDES)
0.75 p0.05
0 – 0.05
4
0.25 p 0.05
1
PIN 1
R = 0.20 OR
0.25 s 45o
CHAMFER
(DDB8) DFN 0905 REV B
0.50 BSC
2.15 p0.05
(2 SIDES)
BOTTOM VIEW—EXPOSED PAD
NOTE:
1. DRAWING CONFORMS TO VERSION (WECD-1) IN JEDEC PACKAGE OUTLINE M0-229
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
3467afe
15
LT3467/LT3467A
PACKAGE DESCRIPTION
S6 Package
6-Lead Plastic TSOT-23
(Reference LTC DWG # 05-08-1636)
0.62
MAX
2.90 BSC
(NOTE 4)
0.95
REF
1.22 REF
3.85 MAX 2.62 REF
1.4 MIN
2.80 BSC
1.50 – 1.75
(NOTE 4)
PIN ONE ID
RECOMMENDED SOLDER PAD LAYOUT
PER IPC CALCULATOR
0.30 – 0.45
6 PLCS (NOTE 3)
0.95 BSC
0.80 – 0.90
0.20 BSC
0.01 – 0.10
1.00 MAX
DATUM ‘A’
0.30 – 0.50 REF
0.09 – 0.20
(NOTE 3)
NOTE:
1. DIMENSIONS ARE IN MILLIMETERS
2. DRAWING NOT TO SCALE
3. DIMENSIONS ARE INCLUSIVE OF PLATING
4. DIMENSIONS ARE EXCLUSIVE OF MOLD FLASH AND METAL BURR
5. MOLD FLASH SHALL NOT EXCEED 0.254mm
6. JEDEC PACKAGE REFERENCE IS MO-193
1.90 BSC
S6 TSOT-23 1005
3467afe
16
LT3467/LT3467A
REVISION HISTORY
(Revision history begins at Rev E)
REV
DATE
DESCRIPTION
PAGE NUMBER
E
04/10
Updated Note 2 in Absolute Maximum Ratings and Electrical Characteristics
2, 3
3467afe
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.
17
LT3467/LT3467A
TYPICAL APPLICATIONS
L1
4.7μH
C1
2.2μF
VIN
SHDN
VOUT
12V
270mA
R1
115k
SW
SHDN
LT3467
SS
C3
0.047μF
Efficiency
D1
C4*
22pF
FB
C1: X5R OR X7R, 6.3V
C2: X5R OR X7R, 16V
D1: PHILIPS PMEG 2010
L1: SUMIDA CR43-4R7
*OPTIONAL
85
80
C2
10μF
R2
13.3k
GND
90
EFFICIENCY (%)
VIN
5V
75
70
65
60
3467 F08a
55
50
Figure 8. 5V to 12V, 270mA Step-Up Converter
VIN
OFF ON
C3
0.047μF
D1
SW
VOUT
12V
260mA
R1
115k
200
250
IOUT (mA)
300
350
3467 F08b
90
85
SHDN
LT3467A
SS
FB
GND
150
95
C4
12pF
C2
10μF
R2
13.3k
C1: X5R OR X7R, 6.3V
C2: X5R OR X7R, 16V
D1: PHILIPS PMEG 2010
L1: SUMIDA CDRH4D18-3R3
3467 F09a
EFFICIENCY (%)
C1
4.7μF
100
Efficiency
L1
3.3μH
VIN
5V
50
80
75
70
65
60
55
Figure 9. 5V to 12V, 260mA Step-Up Converter
50
50
100
150
200
IOUT (mA)
250
300
3467 F09b
RELATED PARTS
PART NUMBER
LT1615/LT1615-1
DESCRIPTION
300mA/80mA (ISW), High Efficiency Step-Up DC/DC Converter
LT1618
1.5A (ISW), 1.25MHz, High Efficiency Step-Up DC/DC Converter
LTC1700
No RSENSE™, 530kHz, Synchronous Step-Up DC/DC Controller
LTC1871
Wide Input Range, 1MHz, No RSENSE Current Mode Boost,
Flyback and SEPIC Controller
1A (ISW), 1.2MHz/2.2MHz, High Efficiency Step-Up
DC/DC Converter
1.5A (ISW), 1.2MHz/2.7MHz, High Efficiency Step-Up
DC/DC Converter with Soft-Start
1.5A (ISW), 1.25MHz, High Efficiency Step-Up DC/DC Converter
LT1930/LT1930A
LT1946/LT1946A
LT1961
LTC3400/
LTC3400B
LTC3401
600mA (ISW), 1.2MHz, Synchronous Step-Up DC/DC Converter
LTC3402
2A (ISW), 3MHz, Synchronous Step-Up DC/DC Converter
1A (ISW), 3MHz, Synchronous Step-Up DC/DC Converter
85mA (ISW), High Efficiency Step-Up DC/DC Converter with
Integrated Schottky and PNP Disconnect
No RSENSE is a trademark of Linear Technology Corporation.
LT3464
COMMENTS
VIN: 1V to 15V, VOUT(MAX) = 34V, IQ = 20μA, ISD < 1μA,
ThinSOT Package
90% Efficiency, VIN: 1.6V to 18V, VOUT(MAX) = 35V, IQ = 1.8mA,
ISD < 1μA, MS Package
95% Efficiency, VIN: 0.9V to 5V, IQ = 200μA, ISD < 10μA,
MS Package
92% Efficiency, VIN: 2.5V to 36V, IQ = 250μA, ISD < 10μA,
MS Package
High Efficiency, VIN: 2.6V to 16V, VOUT(MAX) = 34V,
IQ = 4.2mA/5.5mA, ISD < 1μA, ThinSOT Package
High Efficiency, VIN: 2.45V to 16V, VOUT(MAX) = 34V, IQ = 3.2mA,
ISD < 1μA, MS8 Package
90% Efficiency, VIN: 3V to 25V, VOUT(MAX) = 35V, IQ = 0.9mA,
ISD < 6μA, MS8E Package
92% Efficiency, VIN: 0.85V to 5V, VOUT(MAX) = 5V,
IQ = 19μA/300μA, ISD < 1μA, ThinSOT Package
97% Efficiency, VIN: 0.5V to 5V, VOUT(MAX) = 5.5V, IQ = 38μA,
ISD < 1μA, MS Package
97% Efficiency, VIN: 0.5V to 5V, VOUT(MAX) = 5.5V, IQ = 38μA,
ISD < 1μA, MS Package
VIN: 2.3V to 10V, VOUT(MAX) = 34V, IQ = 25μA, ISD < 1μA,
ThinSOT Package
3467afe
18 Linear Technology Corporation
LT 0410 REV E • PRINTED IN USA
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408) 432-1900 ● FAX: (408) 434-0507
●
www.linear.com
© LINEAR TECHNOLOGY CORPORATION 2003
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