LT3467AIS6#TRMPBF [Linear]
LT3467A - 1.1A Step-Up DC/DC Converter with Integrated Soft-Start; Package: SOT; Pins: 6; Temperature Range: -40°C to 85°C;型号: | LT3467AIS6#TRMPBF |
厂家: | Linear |
描述: | LT3467A - 1.1A Step-Up DC/DC Converter with Integrated Soft-Start; Package: SOT; Pins: 6; Temperature Range: -40°C to 85°C 开关 光电二极管 输出元件 |
文件: | 总18页 (文件大小:268K) |
中文: | 中文翻译 | 下载: | 下载PDF数据表文档文件 |
LT3467/LT3467A
1.1A Step-Up DC/DC
Converter with
Integrated Soft-Start
FEATURES
DESCRIPTION
The LT®3467/LT3467A switching regulators combine a
42V, 1.1A switch with a soft-start function. Pin compatible
n
1.3MHz Switching Frequency (LT3467)
n
2.1MHz Switching Frequency (LT3467A)
n
Low V
Switch: 330mV at 1.1A
with the LT1930, its low V
bipolar switch enables the
CESAT
CESAT
n
n
n
n
n
n
n
n
n
n
n
n
High Output Voltage: Up to 40V
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
constantfrequencycurrentmodePWMarchitectureresults
in low, predictable output noise that is easy to filter.
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
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/
LT3467Aareavailableinalowprofile(1mm)6-leadSOT-23
package and tiny 3mm × 2mm DFN package.
™
Low Profile (1mm) ThinSOT Package
Low Profile (0.75mm) 8-Lead (3mm × 2mm)
DFN Package
APPLICATIONS
n
Digital Cameras
n
White LED Power Supplies
n
Cellular Phones
n
Medical Diagnostic Equipment
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.
n
Local 5V or 12V Supplies
n
TFT-LCD Bias Supplies
n
xDSL Power Supplies
TYPICAL APPLICATION
Efficiency
95
Single Li-Ion Cell to 5V Boost Converter
90
V
= 4.2V
2.7μH
IN
V
85
80
75
70
65
60
55
50
IN
V
OUT
5V
2.6V TO
4.2V
V
= 3.3V
IN
V
= 2.6V
765mA AT V = 4.2V,
IN
IN
IN
IN
4.7μF
402k
133k
540mA AT V = 3.3V,
V
SW
IN
360mA AT V = 2.6V
SHDN
OFF ON
3.3pF
LT3467
SS
FB
GND
15μF
0.047μF
3467 TA01a
800
900
100
300 400 500
700
200
600
I
(mA)
OUT
3467 TA01b
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LT3467/LT3467A
ABSOLUTE MAXIMUM RATINGS (Note 1)
V Voltage................................................................16V
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)
IN
SW Voltage ................................................ –0.4V to 42V
FB Voltage................................................................2.5V
Current Into FB Pin .............................................. 1mA
SHDN Voltage ......................................................... 16V
Maximum Junction Temperature ......................... 125°C
TSOT................................................................. 300°C
PIN CONFIGURATION
TOP VIEW
TOP VIEW
FB
GND
SW
1
2
3
4
8
7
6
5
SHDN
SS
SW 1
GND 2
FB 3
6 V
IN
9
5 SS
VIN
4 SHDN
SW
GND
S6 PACKAGE
6-LEAD PLASTIC TSOT-23
DDB PACKAGE
8-LEAD (3mm s 2mm) PLASTIC DFN
T
= 125°C, θ = 165°C/W, θ = 102°C/W
JA JC
JMAX
T
= 125°C, θ = 80°C/W
JA
JMAX
EXPOSED PAD (PIN 9) IS GND, MUST BE SOLDERED TO PCB
ORDER INFORMATION
LEAD FREE FINISH
LT3467EDDB#PBF
LT3467IDDB#PBF
LT3467AEDDB#PBF
LT3467AIDDB#PBF
LT3467IS6#PBF
LT3467ES6#PBF
LT3467AES6#PBF
LT3467AIS6#PBF
LEAD BASED FINISH
LT3467EDDB
TAPE AND REEL
PART MARKING*
LCPX
PACKAGE DESCRIPTION
TEMPERATURE RANGE
–40°C to 85°C
LT3467EDDB#TRPBF
LT3467IDDB#TRPBF
LT3467AEDDB#TRPBF
LT3467AIDDB#TRPBF
LT3467IS6#TRPBF
LT3467ES6#TRPBF
LT3467AES6#TRPBF
LT3467AIS6#TRPBF
TAPE AND REEL
8-Lead (3mm × 2mm) Plastic DFN
8-Lead (3mm × 2mm) Plastic DFN
8-Lead (3mm × 2mm) Plastic DFN
8-Lead (3mm × 2mm) Plastic DFN
6-Lead Plastic TSOT-23
LCPX
–40°C to 125°C
–40°C to 85°C
LCKD
LCKD
–40°C to 125°C
–40°C to 125°C
–40°C to 85°C
LTACH
LTACH
6-Lead Plastic TSOT-23
LTBCC
6-Lead Plastic TSOT-23
–40°C to 85°C
LTBCC
6-Lead Plastic TSOT-23
–40°C to 125°C
TEMPERATURE RANGE
–40°C to 85°C
PART MARKING*
LCPX
PACKAGE DESCRIPTION
LT3467EDDB#TR
LT3467IDDB#TR
8-Lead (3mm × 2mm) Plastic DFN
8-Lead (3mm × 2mm) Plastic DFN
8-Lead (3mm × 2mm) Plastic DFN
8-Lead (3mm × 2mm) Plastic DFN
6-Lead Plastic TSOT-23
LT3467IDDB
LCPX
–40°C to 125°C
–40°C to 85°C
LT3467AEDDB
LT3467AIDDB
LT3467AEDDB#TR
LT3467AIDDB#TR
LT3467IS6#TR
LCKD
LCKD
–40°C to 125°C
–40°C to 125°C
–40°C to 85°C
LT3467IS6
LTACH
LT3467ES6
LT3467ES6#TR
LTACH
6-Lead Plastic TSOT-23
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/
3467afe
2
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
TYP
MAX
2.4
UNITS
Minimum Operating Voltage
Maximum Operating Voltage
Feedback Voltage
2.2
V
V
16
1.230
1.220
1.255
1.270
1.280
V
V
l
l
FB Pin Bias Current
(Note 3)
10
50
2
nA
mA
μA
Quiescent Current
V
SHDN
V
SHDN
= 2.4V, Not Switching
1.2
Quiescent Current in Shutdown
Reference Line Regulation
Switching Frequency
= 0.5V, V = 3V
0.01
0.01
1
IN
2.6V ≤ V ≤ 16V
0.05
%/V
IN
LT3467
LT3467A
LT3467A
1
1.6
1.6
1.3
2.1
1.6
2.7
MHz
MHz
MHz
l
Maximum Duty Cycle
LT3467
LT3467
LT3467A
LT3467A
88
87
82
78
94
88
%
%
%
%
l
l
Minimum Duty Cycle
Switch Current Limit
10
%
At Minimum Duty Cycle
At Maximum Duty Cycle (Note 4)
1.4
0.8
1.8
1.2
2.5
1.9
A
A
Switch V
I
= 1.1A
= 5V
330
500
1
mV
μA
V
CESAT
SW
Switch Leakage Current
SHDN Input Voltage High
SHDN Input Voltage Low
SHDN Pin Bias Current
V
0.01
SW
2.4
0.5
V
V
V
= 3V
= 0V
16
0
32
0.1
μA
μA
SHDN
SHDN
SS Charging Current
V
= 0.5V
2
3
4.5
μA
SS
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 3: Current flows out of the pin.
Note 4: See Typical Performance Characteristics for guaranteed current
limit vs duty cycle.
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.
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LT3467/LT3467A
TYPICAL PERFORMANCE CHARACTERISTICS
Quiescent Current vs Temperature
FB Pin Voltage vs Temperature
SHDN Current vs SHDN Voltage
1.26
1.25
1.24
1.23
1.22
1.21
1.20
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0
140
120
100
80
T
= 25°C
A
60
40
20
0
–25 –10
5
20 35 50 65 80
TEMPERATURE (°C)
125
95 110
–25 –10
5
20 35 50 65 80
TEMPERATURE (°C)
125
95 110
–40
–40
0
2
4
6
12 14 16 18
8
10
V
(V)
SHDN
3467 G03
3467 G02
3467 G01
Switch Saturation Voltage
vs Switch Current
Oscillator Frequency
vs Temperature
Current Limit vs Duty Cycle
2.0
1.8
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0
2.50
2.25
2.00
1.75
1.50
1.25
1.00
0.75
0.50
0.25
0
T
= 25°C
A
LT3467A
TYPICAL
T
= 25°C
A
T
A
= 85°C
V
CESAT
LT3467
GUARANTEED
100mV/DIV
T
A
= –40°C
3467 G05
–25
0
25
50
75
10
50
70 80
–50
100
20 30 40
60
90
SW CURRENT 200mA/DIV
DC (%)
TEMPERATURE (°C)
3467 G04
3467 G06
Soft-Start Current
vs Soft-Start Voltage
Peak Switch Current
vs Soft-Start Voltage
Start-Up Waveform
(Figure 2 Circuit)
6
5
4
3
2
1
0
2.0
1.8
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0
T
= 25°C
T = 25°C
A
A
V
SHDN
2V/DIV
V
OUT
1V/DIV
I
SUPPLY
0.5A/DIV
3467 G09
0
50 100 150 200 250 300 350 400 450 500
(mV)
0
50 100 150 200 250 300 350 400 450 500
(mV)
0.5ms/DIV
V
V
SS
SS
3467 G07
3467 G08
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LT3467/LT3467A
PIN FUNCTIONS (DFN/TSOT)
FB(Pin1/Pin3):FeedbackPin.Referencevoltageis1.255V.
V
(Pin 6/Pin 6): Input Supply Pin. Must be locally
IN
Connect resistive divider tap here. Minimize trace area at
bypassed.
FB. Set V
= 1.255V(1 + R1/R2).
OUT
SS(Pin7/Pin5):Soft-StartPin.Placeasoft-startcapacitor
here. Upon start-up, 4μA of current charges the capacitor
to1.255V. Usealargercapacitorforslowerstart-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
SW
1.255V
REFERENCE
V
IN
+
–
COMPARATOR
–
A1
DRIVER
Q1
A2
R
Q
R
C
S
+
V
OUT
C
C
+
–
R1 (EXTERNAL)
0.01Ω
3
FB
R2 (EXTERNAL)
RAMP
GENERATOR
SHUTDOWN
SHDN
FB
GND
3467 F01
1.3MHz
OSCILLATOR*
*2.1MHz FOR LT3467A
Figure 1. Block Diagram
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LT3467/LT3467A
OPERATION
TheLT3467usesaconstantfrequency,current-modecon-
trol 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,
andissimplyanamplifiedversionofthedifferencebetween
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
monitoredandnotallowedtoexceedthemaximumswitch
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.
TheBlockDiagramfortheLT3467A(notshown)isidentical
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 ap-
plication is given by:
TheLT3467switchesat1.3MHz, allowingforsmallvalued
inductors to be used. 4.7μH or 10μH will usually suffice.
TheLT3467Aswitchesat2.1MHz,allowingforevensmaller
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
|VOUT |+|VD |–|V |
|VOUT |+|VD |–|VCESAT
IN
DC =
|
2
low DCR (copper-wire resistance) to minimize I R power
where V is the diode forward voltage drop and V
is
CESAT
D
losses.Notethatinsomeapplications,thecurrenthandling
requirements of the inductor can be lower, such as in the
SEPIC topology where each inductor only carries one-half
ofthetotalswitchcurrent.Forbetterefficiency,usesimilar
valuedinductorswithalargervolume.Manydifferentsizes
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.
in the worst case 330mV (at 1.1A)
TheLT3467andLT3467Acanbeusedathigherdutycycles,
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.
V
= 1.255V (1+ R1/R2)
OUT
3467afe
6
LT3467/LT3467A
APPLICATIONS INFORMATION
L1
2.7μH
D1
V
V
OUT
IN
5V
765mA AT V = 4.2V,
2.6V TO 4.2V
C1
IN
R1
402k
4.7μF
540mA AT V = 3.3V,
IN
V
IN
SW
360mA AT V = 2.6V
IN
C4
3.3pF
SHDN
OFF ON
LT3467
SS
FB
C2
R2
133k
C3
GND
15μF
0.047μF
C1, C2: X5R OR X7R, 6.3V
3467 TA05a
D1: ON SEMICONDUCTOR MBRM120
L1: SUMIDA CR43-2R7
Figure 2. Single Li-Ion Cell to 5V Boost Converter (Same as 1st Page Application)
Supply Current of Figure 2 During Start-Up
Table 1. Inductor Manufacturers
Without Soft-Start Capacitor
Sumida
TDK
(847) 956-0666
(847) 803-6100
(714) 852-2001
(408) 432-8331
www.sumida.com
www.tdk.com
Murata
FDK
www.murata.com
www.fdk.co.jp
V
OUT
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 start-
up. 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
switchcurrentfromovershooting.Thispracticewillgreatly
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.
I
SUPPLY
0.5A/DIV
3467 AI01
0.1ms/DIV
Supply Current of Figure 2 During Start-Up
with a 47nF Soft-Start Capacitor
V
OUT
1V/DIV
I
SUPPLY
0.5A/DIV
3467 AI02
0.5ms/DIV
3467afe
7
LT3467/LT3467A
APPLICATIONS INFORMATION
Capacitor Selection
Aphaseleadzerocanbeintentionallyintroducedbyplacing
a capacitor (C4) in parallel with the resistor (R1) between
Low ESR (equivalent series resistance) capacitors should
beusedattheoutputtominimizetheoutputripplevoltage.
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.
V
and V as shown in Figure 2. The frequency of the
OUT
FB
zero is determined by the following equation.
1
ƒZ =
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.
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.
Diode Selection
A Schottky diode is recommendedforusewith 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 Semi-
conductor MBRM120 (a 20V diode) or the MBRM140 (a
40V diode).
Table 2. Ceramic Capacitor Manufacturers
Taiyo Yuden
AVX
(408) 573-4150
(803) 448-9411
(714) 852-2001
www.t-yuden.com
www.avxcorp.com
www.murata.com
Murata
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 ca-
pacitors, 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.
3467afe
8
LT3467/LT3467A
APPLICATIONS INFORMATION
LOAD CURRENT
100mA/DIV
AC COUPLED
Layout Hints
ThehighspeedoperationoftheLT3467/LT3467Ademands
careful attention to board layout. You will not get adver-
tised 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.
V
OUT
200mV/DIV
AC COUPLED
I
L1
5A/DIV
AC COUPLED
3467 F03
20μs/DIV
Figure 3. Transient Response of Figure 8’s Step-Up
Converter without Phase Lead Capacitor
L1
D1
C1
V
IN
V
OUT
LOAD CURRENT
C2
1
2
3
6
5
4
100mA/DIV
C
SS
AC COUPLED
SS
GND
SHDN
V
OUT
FB
200mV/DIV
R2
R1
AC COUPLED
I
L1
3467 F05a
5A/DIV
C3
V
OUT
AC COUPLED
3467 F04
20μs/DIV
Figure 5a. Suggested Layout—ThinSOT
Figure 4. Transient Response of Figure 8’s Step-Up
Converter with a 22pF Phase Lead Capacitor
V
OUT
C3
R1
Setting Output Voltage
R2
To set the output voltage, select the values of R1 and R2
(see Figure 2) according to the following equation.
SHDN
FB
1
2
3
4
8
7
6
5
GND
C
SS
VOUT
⎛
⎞
R1=R2
–1
C2
⎜
⎝
⎟
⎠
1.255V
V
OUT
V
IN
D1
A good value for R2 is 13.3k which sets the current in the
resistor divider chain to 1.255V/13.3k = 94μA.
C1
L1
3467 F05b
Figure 5b. Suggested Layout—DFN
3467afe
9
LT3467/LT3467A
APPLICATIONS INFORMATION
Compensation—Theory
From Figure 6, the DC gain, poles and zeroes can be
calculated as follows:
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 under-
stand and adjust the voltage feedback loop.
2
Output Pole: P1=
2• π •RL •COUT
1
Error Amp Pole: P2=
2• π •RO •CC
1
Error Amp Zero: Z1=
2• π •RC •CC
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 re-
1.255
1
2
DC GAIN: A=
• V •gma •R •gmp •RL •
IN
O
2
VOUT
1
ESR Zero: Z2=
placed by the equivalent transconductance amplifier gmp
.
2• π •RESR •COUT
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.
V
2 •RL
IN
RHP Zero: Z3=
2• π • VOUT2 •L
fS
3
High Frequency Pole: P3>
–
1
g
Phase Lead Zero: Z4 =
mp
V
OUT
2• π •R1•CPL
+
C
R
R
L
PL
ESR
1
C
OUT
1.255V
REFERENCE
Phase LeadPole:P4 =
+
–
R1•R2
R1+R2
V
C
g
2• π •CPL •
ma
R1
R2
R
C
R
O
C
C
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.
3467 F06
C : COMPENSATION CAPACITOR
C
C
C
: OUTPUT CAPACITOR
: PHASE LEAD CAPACITOR
OUT
PL
ma
mp
g
g
: TRANSCONDUCTANCE AMPLIFIER INSIDE IC
: POWER STAGE TRANSCONDUCTANCE AMPLIFIER
R : COMPENSATION RESISTOR
C
L
O
R : OUTPUT RESISTANCE DEFINED AS V
DIVIDED BY I
LOAD(MAX)
OUT
R : OUTPUT RESISTANCE OF g
ma
R1, R2: FEEDBACK RESISTOR DIVIDER NETWORK
: OUTPUT CAPACITOR ESR
R
ESR
Figure 6. Boost Converter Equivalent Model
3467afe
10
LT3467/LT3467A
APPLICATIONS INFORMATION
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.
Table 3. Bode Plot Parameters
PARAMETER
VALUE
10.4
15
UNITS
Ω
COMMENT
R
L
Application Specific
Application Specific
Application Specific
Not Adjustable
Not Adjustable
Adjustable
C
μF
OUT
50
40
0
R
10
mΩ
MΩ
pF
ESR
–45
R
0.4
60
30
–90
O
C
C
20
–135
–180
–225
–270
–315
–360
–405
–450
10
C
3.3
100
402
133
5
pF
PL
0
R
kΩ
kΩ
kΩ
V
Not Adjustable
Adjustable
C
–10
–20
–30
–40
–50
R1
R2
Adjustable
V
Application Specific
Application Specific
Not Adjustable
Not Adjustable
Application Specific
Not Adjustable
OUT
GAIN
PHASE
V
3.3
35
V
IN
100
1k
10k
100k
1M
g
g
μmho
mho
μH
ma
FREQUENCY (Hz)
7.5
2.7
1.3*
mp
3467 F07
L
Figure 7. Bode Plot of 3.3V to 5V Application
f
MHz
S
*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
Li-Ion to 6V
95
L1
D1
2.2μH
V
V
IN
90
85
80
75
70
65
60
55
50
V
= 4.2V
OUT
6V
IN
2.7V TO 4.2V
R1
275mA AT V = 2.7V
V
= 3.8V
IN
IN
501k
V
SW
490mA AT V = 3.8V
IN
IN
V
= 2.7V
IN
590mA AT V = 4.2V
IN
C1
C3
1.8pF
SHDN
SHDN
LT3467
2.2μF
SS
FB
C2
15μF
C4
0.047μF
R2
133k
GND
C1, C2: X5R OR X7R, 6.3V
3467 TA02
D1: ON SEMICONDUCTOR MBRM120
L1: SUMIDA CR43-2R2
50 100
300 400 500 600 700
(mA)
200
I
OUT
3467 TA02b
3467afe
11
LT3467/LT3467A
TYPICAL APPLICATIONS
4-Cell to 5V SEPIC Converter
C3
1μF
L1
10μH
D1
4V TO 6.5V
V
OUT
5V
C1
325mA AT V = 4V
IN
2.2μF
400mA AT V = 5V
IN
450mA AT V = 6.5V
V
SW
IN
C5
4.7pF
IN
SHDN
SHDN
255k
4-CELL
BATTERY
LT3467
L2
10μH
C2
10μF
SS
FB
C4
0.047μF
GND
84.5k
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
D1
V
OUT
V
IN
40V
20mA
5V
C1
4.7μF
V
SW
IN
R1
412k
SHDN
SHDN
LT3467
SS
C2
1μF
FB
C3
0.1μF
R2
13.3k
GND
C1: X5R or X7R, 6.3V
C2: X5R or X7R, 50V
3467 TA04a
D1: ON SEMICONDUCTOR, MBRM140
L1: SUMIDA CD43-2R7
15V Dual Output Converter with Output Disconnect
C4
1μF
L1
10μH
D1
V
15V
IN
5V
100mA
C1
R3
1Ω
R1
147k
2.2μF
C5
1μF
V
SW
IN
OFF ON
SHDN
D2
C2
2.2μF
LT3467
SS
FB
C6
0.047μF
R2
13.3k
GND
C3
2.2μF
C1: X5R or X7R, 6.3V
R4
1Ω
D3
D4
C2 TO C5: X5R or X7R, 16V
D1 TO D4: PHILIPS PMEG 2005
L1: SUMIDA CR43-100
–15V
100mA
3467 TA05
3467afe
12
LT3467/LT3467A
TYPICAL APPLICATIONS
9V, 18V, –9V Triple Output TFT-LCD Bias Supply with Soft-Start
D1
D2
18V
10mA
C4
1μF
C3
0.1μF
Start-Up Waveforms
L1
4.7μH
D5
V
9V
220mA
IN
9V OUTPUT
5V/DIV
3.3V
C1
2.2μF
–9V OUTPUT
5V/DIV
V
SW
IN
R1
124k
V
SHDN
SHDN
LT3467
C5
10μF
SS
FB
3.3V
GND
R2
20k
0V
18V OUTPUT
10V/DIV
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
I
L1
D4
D3
0.5A/DIV
3467 TA06b
2ms/DIV
C6
1μF
–9V
10mA
3467 TA06a
8V, 23V, –8V Triple Output TFT-LCD Bias Supply with Soft-Start
D1
D2
D3
D4
23V
10mA
C3
0.1μF
C4
0.1μF
C5
0.1μF
C6
1μF
Start-Up Waveforms
L1
4.7μH
D7
V
8V OUTPUT
5V/DIV
–8V OUTPUT
5V/DIV
8V
IN
3.3V
SHDN
3.3V
270mA
C1
R1
V
SW
2.2μF
IN
113k
V
SHDN
LT3467
C7
10μF
SS
FB
GND
R2
21k
23V OUTPUT
10V/DIV
0V
C9
C2
0.1μF
0.1μF
C1: X5R OR X7R, 6.3V
I
L1
0.5A/DIV
D5
D6
C2 TO C4, C7, C8: X5R OR X7R, 10V
C5: X5R OR X7R, 16V
3467 TA07b
2ms/DIV
C8
C6: X5R OR X7R, 25V
1μF
D1 TO D6: PHILIPS BAT54S OR EQUIVALENT
D7: PHILIPS PMEG 2005
–8V
10mA
L1: PANASONIC ELT5KT4R7M
3467 TA07a
3467afe
13
LT3467/LT3467A
TYPICAL APPLICATIONS
Single Li-Ion Cell to 5V Boost Converter
Efficiency
L1
95
90
85
80
75
70
65
60
55
50
D1
0.9μH
V
V
IN
OUT
5V
2.6V TO 4.2V
R1
600mA AT V = 4.2V
IN
8.06k
V
SW
360mA AT V = 3.3V
IN
C1
4.7μF
V
IN
= 4.2V
IN
250mA AT V = 2.6V
IN
V
= 3.3V
IN
C4*
75pF
SHDN
OFF ON
C3
V
= 2.6V
IN
LT3467A
SS
FB
C2*
22μF
R2
GND
0.047μF
2.67k
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
50 100 150 200 250 300 350 400 450 500
(mA)
I
OUT
3467 TA09b
2.6V-3.3V to 5V Boost Converter
Efficiency
90
85
80
75
70
65
60
55
50
L1
D1
1.5μH
V
V
IN
OUT
5V
2.6V TO 3.3V
R1
430mA AT V = 3.3V
270mA AT V = 2.6V
IN
IN
V
= 3.3V
IN
8.06k
V
SW
C1
IN
V
= 2.6V
IN
4.7μF
C4
56pF
SHDN
LT3467A
OFF ON
C3
SS
FB
C2
10μF
GND
R2
0.047μF
2.67k
C1, C2: X5R OR X7R, 6.3V
D1: PHILIPS PMEG 2010
L1: FDK MIP3226D1R5M
3467 TA08a
50 100 150 200 250 300 350 400 450 500
(mA)
I
OUT
3467 TA08b
3.3V to 15V, 135mA Step-Up Converter
Efficiency
90
80
70
60
50
40
30
L1
D1
6.8μH
V
OUT
V
IN
15V
135mA
3.3V
R1
16.5k
V
SW
C1
4.7μF
IN
C4
68pF
SHDN
LT3467A
OFF ON
C3
SS
FB
C2
2.2μF
R2
GND
1.5k
0.047μF
C1: X5R OR X7R, 6.3V
C2: X5R OR X7R, 16V
D1: PHILIPS PMEG 2010
3467 TA10a
L1: SUMIDA CMD4D13-6R8MC
140
20
40
60
80 100 120
160
I
(mA)
OUT
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)
R = 0.115
0.40 p 0.10
3.00 p0.10
(2 SIDES)
TYP
5
R = 0.05
TYP
8
0.70 p0.05
2.55 p0.05
1.15 p0.05
2.00 p0.10
PIN 1 BAR
TOP MARK
PIN 1
(2 SIDES)
R = 0.20 OR
0.25 s 45o
(SEE NOTE 6)
PACKAGE
OUTLINE
0.56 p 0.05
(2 SIDES)
CHAMFER
4
1
(DDB8) DFN 0905 REV B
0.25 p 0.05
0.25 p 0.05
0.75 p0.05
0.200 REF
0.50 BSC
0.50 BSC
2.20 p0.05
2.15 p0.05
(2 SIDES)
(2 SIDES)
0 – 0.05
RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS
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)
2.90 BSC
(NOTE 4)
0.62
MAX
0.95
REF
1.22 REF
1.4 MIN
1.50 – 1.75
2.80 BSC
3.85 MAX 2.62 REF
(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
DATUM ‘A’
0.01 – 0.10
1.00 MAX
0.30 – 0.50 REF
1.90 BSC
0.09 – 0.20
(NOTE 3)
S6 TSOT-23 1005
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
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 representa-
tion that the interconnection of its circuits as described herein will not infringe on existing patent rights.
17
LT3467/LT3467A
TYPICAL APPLICATIONS
L1
Efficiency
D1
4.7μH
V
OUT
V
90
85
80
75
70
65
60
55
50
IN
12V
5V
C1
2.2μF
270mA
R1
115k
V
SW
IN
C4*
22pF
SHDN
SHDN
C2
10μF
LT3467
SS
FB
C3
0.047μF
R2
13.3k
GND
C1: X5R OR X7R, 6.3V
C2: X5R OR X7R, 16V
D1: PHILIPS PMEG 2010
L1: SUMIDA CR43-4R7
*OPTIONAL
3467 F08a
300
50
100
150
200
(mA)
250
350
Figure 8. 5V to 12V, 270mA Step-Up Converter
I
OUT
3467 F08b
Efficiency
L1
D1
3.3μH
V
OUT
V
IN
5V
95
90
85
80
75
70
65
60
55
50
12V
260mA
R1
115k
V
SW
C1
4.7μF
IN
C4
12pF
SHDN
OFF ON
C3
LT3467A
GND
SS
FB
C2
10μF
R2
0.047μF
13.3k
C1: X5R OR X7R, 6.3V
C2: X5R OR X7R, 16V
3467 F09a
D1: PHILIPS PMEG 2010
L1: SUMIDA CDRH4D18-3R3
Figure 9. 5V to 12V, 260mA Step-Up Converter
50
100
150
200
250
300
I
(mA)
OUT
3467 F09b
RELATED PARTS
PART NUMBER
DESCRIPTION
COMMENTS
V : 1V to 15V, V
LT1615/LT1615-1 300mA/80mA (I ), High Efficiency Step-Up DC/DC Converter
= 34V, I = 20μA, I < 1μA,
SW
IN
OUT(MAX)
Q
SD
ThinSOT Package
LT1618
1.5A (I ), 1.25MHz, High Efficiency Step-Up DC/DC Converter
90% Efficiency, V : 1.6V to 18V, V
= 35V, I = 1.8mA,
SW
IN
OUT(MAX) Q
I
< 1μA, MS Package
SD
Q
LTC1700
No R
™, 530kHz, Synchronous Step-Up DC/DC Controller
SENSE
95% Efficiency, V : 0.9V to 5V, I = 200μA, I < 10μA,
IN SD
MS Package
LTC1871
Wide Input Range, 1MHz, No R
Flyback and SEPIC Controller
Current Mode Boost,
92% Efficiency, V : 2.5V to 36V, I = 250μA, I < 10μA,
SENSE
IN
Q
SD
MS Package
High Efficiency, V : 2.6V to 16V, V
LT1930/LT1930A
LT1946/LT1946A
LT1961
1A (I ), 1.2MHz/2.2MHz, High Efficiency Step-Up
= 34V,
SW
IN
OUT(MAX)
DC/DC Converter
I = 4.2mA/5.5mA, I < 1μA, ThinSOT Package
Q SD
1.5A (I ), 1.2MHz/2.7MHz, High Efficiency Step-Up
High Efficiency, V : 2.45V to 16V, V
SD
= 34V, I = 3.2mA,
OUT(MAX) Q
SW
IN
DC/DC Converter with Soft-Start
I
< 1μA, MS8 Package
1.5A (I ), 1.25MHz, High Efficiency Step-Up DC/DC Converter
90% Efficiency, V : 3V to 25V, V
SD
= 35V, I = 0.9mA,
OUT(MAX) Q
SW
IN
I
< 6μA, MS8E Package
LTC3400/
LTC3400B
600mA (I ), 1.2MHz, Synchronous Step-Up DC/DC Converter
92% Efficiency, V : 0.85V to 5V, V
= 5V,
SW
IN
OUT(MAX)
I = 19μA/300μA, I < 1μA, ThinSOT Package
Q
SD
LTC3401
LTC3402
LT3464
1A (I ), 3MHz, Synchronous Step-Up DC/DC Converter
97% Efficiency, V : 0.5V to 5V, V
SD
= 5.5V, I = 38μA,
Q
SW
IN
OUT(MAX)
I
< 1μA, MS Package
2A (I ), 3MHz, Synchronous Step-Up DC/DC Converter
97% Efficiency, V : 0.5V to 5V, V
SD
= 5.5V, I = 38μA,
Q
SW
IN
OUT(MAX)
I
< 1μA, MS Package
85mA (I ), High Efficiency Step-Up DC/DC Converter with
V : 2.3V to 10V, V
= 34V, I = 25μA, I < 1μA,
OUT(MAX) Q SD
SW
IN
Integrated Schottky and PNP Disconnect
ThinSOT Package
No R
is a trademark of Linear Technology Corporation.
SENSE
3467afe
LT 0410 REV E • PRINTED IN USA
LinearTechnology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
18
●
●
© LINEAR TECHNOLOGY CORPORATION 2003
(408) 432-1900 FAX: (408) 434-0507 www.linear.com
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