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FEATURES
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LT3467/LT3467A 1.1A Step-Up DC/DC Converter with Integrated Soft-Start DESCRIPTION
The LT(R)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. 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 x 2mm DFN package.
L, LT, LTC and LTM 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.
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: <1A Pin-for-Pin Compatible with the LT1930 and LT1613 Low Profile (1mm) ThinSOTTM Package Low Profile (0.75mm) 8-Lead (3mm x 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
TYPICAL APPLICATION
95
Efficiency
90 VOUT 5V 765mA AT VIN = 4.2V, 540mA AT VIN = 3.3V, 360mA AT VIN = 2.6V 3.3pF 85 EFFICIENCY (%) 80 75 70 65 60 55
3467 TA01a
Single Li-Ion Cell to 5V Boost Converter
VIN 2.6V TO 4.2V 4.7F OFF ON VIN SHDN LT3467 SS GND 2.7H
VIN = 4.2V VIN = 3.3V VIN = 2.6V
SW
402k
FB 133k 15F
0.047F
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 ......................... 125C Operating Temperature Range (Note 2) E Grade ................................................ -40C to 85C I Grade ............................................... -40C to 125C Storage Temperature Range................... -65C to 150C Lead Temperature (Soldering, 10 sec) TSOT................................................................. 300C
PIN CONFIGURATION
TOP VIEW FB 1 GND 2 SW 3 SW 4 9 8 7 6 5 SHDN SS VIN GND SW 1 GND 2 FB 3 TOP VIEW 6 VIN 5 SS 4 SHDN
DDB PACKAGE 8-LEAD (3mm 2mm) PLASTIC DFN TJMAX = 125C, JA = 80C/W EXPOSED PAD (PIN 9) IS GND, MUST BE SOLDERED TO PCB
S6 PACKAGE 6-LEAD PLASTIC TSOT-23 TJMAX = 125C, JA = 165C/W, JC = 102C/W
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 LT3467IDDB LT3467AEDDB LT3467AIDDB LT3467IS6 LT3467ES6 LT3467AES67 LT3467AIS67 TAPE AND REEL LT3467EDDB#TRPBF LT3467IDDB#TRPBF LT3467AEDDB#TRPBF LT3467AIDDB#TRPBF LT3467IS6#TRPBF LT3467ES6#TRPBF LT3467AES6#TRPBF LT3467AIS6#TRPBF TAPE AND REEL LT3467EDDB#TR LT3467IDDB#TR LT3467AEDDB#TR LT3467AIDDB#TR LT3467IS6#TR LT3467ES6#TR LT3467AES6#TR LT3467AIS67#TR PART MARKING* LCPX LCPX LCKD LCKD LTACH LTACH LTBCC LTBCC PART MARKING* LCPX LCPX LCKD LCKD LTACH LTACH LTBCC LTBCC PACKAGE DESCRIPTION 8-Lead (3mm x 2mm) Plastic DFN 8-Lead (3mm x 2mm) Plastic DFN 8-Lead (3mm x 2mm) Plastic DFN 8-Lead (3mm x 2mm) Plastic DFN 6-Lead Plastic TSOT-23 6-Lead Plastic TSOT-23 6-Lead Plastic TSOT-23 6-Lead Plastic TSOT-23 PACKAGE DESCRIPTION 8-Lead (3mm x 2mm) Plastic DFN 8-Lead (3mm x 2mm) Plastic DFN 8-Lead (3mm x 2mm) Plastic DFN 8-Lead (3mm x 2mm) Plastic DFN 6-Lead Plastic TSOT-23 6-Lead Plastic TSOT-23 6-Lead Plastic TSOT-23 6-Lead Plastic TSOT-23 TEMPERATURE RANGE -40C to 85C -40C to 125C -40C to 85C -40C to 125C -40C to 125C -40C to 85C -40C to 85C -40C to 125C TEMPERATURE RANGE -40C to 85C -40C to 125C -40C to 85C -40C to 125C -40C to 125C -40C to 85C -40C to 85C -40C to 125C
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
PARAMETER Minimum Operating Voltage Maximum Operating Voltage Feedback Voltage FB Pin Bias Current Quiescent Current Quiescent Current in Shutdown Reference Line Regulation Switching Frequency (Note 3) VSHDN = 2.4V, Not Switching VSHDN = 0.5V, VIN = 3V 2.6V VIN 16V LT3467 LT3467A LT3467A LT3467 LT3467 LT3467A LT3467A At Minimum Duty Cycle At Maximum Duty Cycle (Note 4) ISW = 1.1A VSW = 5V 2.4 0.5 VSHDN = 3V VSHDN = 0V VSS = 0.5V 2 16 0 3 32 0.1 4.5 1 1.6 1.6 88 87 82 78 1.4 0.8
l l
The l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25C. VIN = 3V, VSHDN = VIN unless otherwise noted. Specifications are for both the LT3467 and LT3467A unless otherwise noted.
CONDITIONS MIN TYP 2.2 1.230 1.220 1.255 10 1.2 0.01 0.01 1.3 2.1 94 88 10 1.8 1.2 330 0.01 2.5 1.9 500 1 MAX 2.4 16 1.270 1.280 50 2 1 0.05 1.6 2.7 UNITS V V V V nA mA A %/V MHz MHz MHz % % % % % A A mV A V V A A A
l l l
Maximum Duty Cycle
Minimum Duty Cycle Switch Current Limit Switch VCESAT Switch Leakage Current SHDN Input Voltage High SHDN Input Voltage Low SHDN Pin Bias Current SS Charging Current
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 0C to 85C. Specifications over the -40C to 85C operating temperature range are assured by design, characterization and correlation with statistical process controls. The LT3467IS6 is guaranteed and tested over the full -40C to 125C operating temperature range.
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
1.6 1.4 1.2 ISHDN (A) 1.0 IQ (mA) 0.8 0.6 0.4 0.2 0 -40 -25 -10 5 20 35 50 65 80 95 110 125 TEMPERATURE (C)
3467 G01
FB Pin Voltage vs Temperature
1.26 1.25 1.24 VFB (V) 1.23 1.22 1.21 1.20 -40 -25 -10 5 140 120 100 80 60 40 20 0
SHDN Current vs SHDN Voltage
TA = 25C
20 35 50 65 80 95 110 125 TEMPERATURE (C)
3467 G02
0
2
4
6
8 10 12 VSHDN (V)
14
16
18
3467 G03
Current Limit vs Duty Cycle
2.0 1.8 1.6 1.4 ILIM (A) 1.2 1.0 0.8 0.6 0.4 0.2 0 10 20 30 40 50 60 DC (%) 70 80 90 GUARANTEED VCESAT 100mV/DIV TYPICAL TA = 25C
Switch Saturation Voltage vs Switch Current
2.50 2.25 OSCILLATOR FREQUENCY (MHz) 2.00 1.75 1.50 1.25 1.00 0.75 0.50 0.25
3467 G05
Oscillator Frequency vs Temperature
LT3467A
TA = 25C TA = 85C
LT3467
TA = -40C
SW CURRENT 200mA/DIV
0 -50
-25
0
25
50
75
100
3467 G06
TEMPERATURE (C)
3467 G04
Soft-Start Current vs Soft-Start Voltage
6 5 SWITCH CURRENT (A) 4 ISS (A) 3 2 1 0 TA = 25C 2.0 1.8 1.6 1.4 1.2 1.0 0.8 0.6 0.4 0.2 0 0 50 100 150 200 250 300 350 400 450 500 VSS (mV)
3467 G07
Peak Switch Current vs Soft-Start Voltage
TA = 25C VSHDN 2V/DIV
Start-Up Waveform (Figure 2 Circuit)
VOUT 1V/DIV
ISUPPLY 0.5A/DIV 0 50 100 150 200 250 300 350 400 450 500 VSS (mV)
3467 G08
0.5ms/DIV
3467 G09
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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). 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.
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, 4A of current charges the capacitor to 1.255V. Use a larger capacitor for slower start-up. Leave floating if not in use. SHDN (Pin 8/Pin 4): Shutdown Pin. Tie to 2.4V or more to enable device. Ground to shut down.
BLOCK DIAGRAM
250k SS VIN 1.255V REFERENCE
+
A1
SW COMPARATOR
-
VOUT R1 (EXTERNAL) FB R2 (EXTERNAL)
RC CC
RAMP GENERATOR SHUTDOWN SHDN FB 1.3MHz OSCILLATOR* GND
3467 F01
Figure 1. Block Diagram
+
*2.1MHz FOR LT3467A
-
A2 R S Q
DRIVER Q1
+
0.01
-
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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 4A 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 The typical maximum duty cycle of the LT3467 is 94% (88% for the LT3467A). The duty cycle for a given application is given by: DC = | VOUT | + | VD | - | VIN | | VOUT | + | VD | - | VCESAT | Switching Frequency and Inductor Selection The LT3467 switches at 1.3 MHz, allowing for small valued inductors to be used. 4.7H or 10H will usually suffice. The LT3467A switches at 2.1MHz, allowing for even smaller valued inductors to be used. 0.9H to 6.8H 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.
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 2.7H C1 4.7F OFF ON D1 R1 402k C4 3.3pF FB R2 133k C2 15F VOUT 5V 765mA AT VIN = 4.2V, 540mA AT VIN = 3.3V, 360mA AT VIN = 2.6V
VIN SHDN LT3467 SS GND
SW
C3 0.047F
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 TDK Murata FDK (847) 956-0666 (847) 803-6100 (714) 852-2001 (408) 432-8331 www.sumida.com www.tdk.com www.murata.com www.fdk.co.jp
VOUT 1V/DIV
Supply Current of Figure 2 During Start-Up Without Soft-Start Capacitor
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 4.7F to 15F output capacitor is sufficient for most applications, but systems with very low output currents may need only a 1F or 2.2F 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 1F to 4.7F 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 AVX Murata (408) 573-4150 (803) 448-9411 (714) 852-2001 www.t-yuden.com www.avxcorp.com www.murata.com
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. Z = 1 2 * 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).
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.
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LT3467/LT3467A APPLICATIONS INFORMATION
LOAD CURRENT 100mA/DIV AC COUPLED VOUT 200mV/DIV AC COUPLED
Layout Hints 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.
IL1 5A/DIV AC COUPLED 20s/DIV
3467 F03
Figure 3. Transient Response of Figure 8's Step-Up Converter without Phase Lead Capacitor
D1 VOUT LOAD CURRENT 100mA/DIV AC COUPLED VOUT 200mV/DIV AC COUPLED C2
1 2
L1
C1 VIN
6 5 4
CSS SS SHDN
GND
3
FB R2 R1
IL1 5A/DIV AC COUPLED 20s/DIV
3467 F04
C3
VOUT
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Figure 5a. Suggested Layout--ThinSOT
VOUT C3
Figure 4. Transient Response of Figure 8's Step-Up Converter with a 22pF Phase Lead Capacitor
Setting Output Voltage To set the output voltage, select the values of R1 and R2 (see Figure 2) according to the following equation.
GND
R1 R2 SHDN FB 1
2 8 7 6 5
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 = 94A.
CSS
C2 VOUT D1 L1
3 4
VIN 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 * * RL * COUT 1 2 * * RO * CC 1 2 * * RC * CC 1 2
Error Amp Pole: P2= Error Amp Zero: Z1= DC GAIN: A= 1.255 VOUT
2
* VIN * gma * RO * gmp * RL * 1
ESR Zero: Z2 = RHP Zero: Z3=
2 * * RESR * COUT VIN2 * RL
2 * * VOUT 2 * L fS 3
High Frequency Pole: P3> Phase Lead Zero : Z 4 =
gmp
VOUT CPL RESR COUT R1 RL
VC RC CC RO
+
gma
1.255V REFERENCE
1 2 * * R1 * CPL 1 Phase Lead Pole : P4 = R1 * R2 2 * * CPL * 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.
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
Figure 6. Boost Converter Equivalent Model
10
+ -
R2
3467 F06
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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.
50 40 30 20 GAIN (dB) 10 0 -10 -20 -30 -40 -50 100 GAIN PHASE 1k 10k 100k FREQUENCY (Hz) 0 -45 -90 -135 PHASE (DEG) -180 -225 -270 -315 -360 -405 -450 1M
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Table 3. Bode Plot Parameters
PARAMETER RL COUT RESR RO CC CPL RC R1 R2 VOUT VIN gma gmp L fS VALUE 10.4 15 10 0.4 60 3.3 100 402 133 5 3.3 35 7.5 2.7 1.3* UNITS F m M pF pF k k k V V mho mho H MHz COMMENT Application Specific Application Specific Application Specific Not Adjustable Not Adjustable Adjustable Not Adjustable Adjustable Adjustable Application Specific Application Specific Not Adjustable Not Adjustable Application Specific Not Adjustable
Figure 7. Bode Plot of 3.3V to 5V Application
*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 2.2H D1 R1 501k C3 1.8pF FB R2 133k C2 15F VOUT 6V 275mA AT VIN = 2.7V 490mA AT VIN = 3.8V 590mA AT VIN = 4.2V 95 90 85 EFFICIENCY (%) 80 75 70 65 60 C1, C2: X5R OR X7R, 6.3V D1: ON SEMICONDUCTOR MBRM120 L1: SUMIDA CR43-2R2
3467 TA02
Li-Ion to 6V
VIN 2.7V TO 4.2V VIN C1 2.2F SHDN
VIN = 4.2V VIN = 3.8V VIN = 2.7V
SW
SHDN LT3467 SS GND
C4 0.047F
55 50 50 100 200 300 400 IOUT (mA) 500 600 700
3467 TA02b
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LT3467/LT3467A TYPICAL APPLICATIONS
4-Cell to 5V SEPIC Converter
L1 10H C1 2.2F SHDN 4-CELL BATTERY C4 0.047F C1, C3: X5R or X7R, 10V C2: X5R or X7R, 6.3V C3 1F D1 VOUT 5V 325mA AT VIN = 4V 400mA AT VIN = 5V 450mA AT VIN = 6.5V L2 10H 84.5k C2 10F
4V TO 6.5V
VIN SW SHDN LT3467 FB SS GND
255k
C5 4.7pF
D1: PHILIPS PMEG 2010 L1, L2: MURATA LQH32CN100K33L
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5V to 40V Boost Converter
L1 2.7H C1 4.7F SHDN D1 VOUT 40V 20mA R1 412k C2 1F R2 13.3k
VIN 5V
VIN SHDN LT3467 SS GND
SW
FB
C3 0.1F
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
L1 10H C1 2.2F OFF ON C4 1F
D1 15V 100mA
VIN 5V
VIN SHDN LT3467 SS
SW
C5 1F
R3 1 D2
R1 147k C2 2.2F R2 13.3k C3 2.2F
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FB GND
C6 0.047F
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 1
D4
-15V 100mA
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LT3467/LT3467A TYPICAL APPLICATIONS
9V, 18V, -9V Triple Output TFT-LCD Bias Supply with Soft-Start
D1 D2 C3 0.1F VIN 3.3V C1 2.2F VSHDN VIN SHDN LT3467 SS 3.3V 0V C7 0.1F 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 GND C2 0.1F D4 D3 C6 1F FB R2 20k L1 4.7H D5 9V 220mA SW R1 124k C5 10F 9V OUTPUT 5V/DIV -9V OUTPUT 5V/DIV C4 1F
18V 10mA
Start-Up Waveforms
18V OUTPUT 10V/DIV
IL1 0.5A/DIV
2ms/DIV
3467 TA06b
-9V 10mA
3467 TA06a
8V, 23V, -8V Triple Output TFT-LCD Bias Supply with Soft-Start
D1
D2 C3 0.1F
D3 C4 0.1F
D4 C5 0.1F
23V 10mA C6 1F
Start-Up Waveforms
8V OUTPUT 5V/DIV -8V OUTPUT 5V/DIV
VIN 3.3V C1 2.2F VSHDN VIN
L1 4.7H
D7 8V 270mA SW R1 113k C7 10F R2 21k 23V OUTPUT 10V/DIV
SHDN LT3467 SS GND C9 0.1F
FB
3.3V 0V
C2 0.1F D5 D6
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
IL1 0.5A/DIV C8 1F
3467 TA07a
2ms/DIV
3467 TA07b
-8V 10mA
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13
LT3467/LT3467A TYPICAL APPLICATIONS
Single Li-Ion Cell to 5V Boost Converter
VIN 2.6V TO 4.2V C1 4.7F VIN OFF ON L1 0.9H D1 R1 8.06k C4* 75pF VOUT 5V 600mA AT VIN = 4.2V 360mA AT VIN = 3.3V 250mA AT VIN = 2.6V 95 90 85 EFFICIENCY (%) 80 75 70 65 60
3467 TA09a
Efficiency
SW
SHDN LT3467A SS FB GND R2 2.67k
VIN = 3.3V VIN = 2.6V
VIN = 4.2V
C3 0.047F
C2* 22F
C1, C2: X5R OR X7R, 6.3V D1: PHILIPS PMEG 2010 L1: FDK MIPW3226D0R9M *C2 CAN BE 10F IN A 1210 OR LARGER PACKAGE WITH THE ADDITION OF C4, OTHERWISE C4 IS OPTIONAL
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 1.5H D1 R1 8.06k C4 56pF C2 10F VOUT 5V 430mA AT VIN = 3.3V 270mA AT VIN = 2.6V 90 85 80 EFFICIENCY (%) 75 70 65 60 C1, C2: X5R OR X7R, 6.3V D1: PHILIPS PMEG 2010 L1: FDK MIP3226D1R5M
3467 TA08a
Efficiency
VIN 2.6V TO 3.3V C1 4.7F VIN OFF ON
SW
SHDN LT3467A SS FB GND R2 2.67k
VIN = 2.6V
VIN = 3.3V
C3 0.047F
55 50 50 100 150 200 250 300 350 400 450 500 IOUT (mA)
3467 TA08b
3.3V to 15V, 135mA Step-Up Converter
L1 6.8H D1 R1 16.5k C4 68pF R2 1.5k C2 2.2F 90 VOUT 15V 135mA EFFICIENCY (%) 80 70 60 50 40 30
Efficiency
VIN 3.3V C1 4.7F VIN OFF ON
SW
SHDN LT3467A SS FB GND
C3 0.047F
C1: X5R OR X7R, 6.3V C2: X5R OR X7R, 16V D1: PHILIPS PMEG 2010 L1: SUMIDA CMD4D13-6R8MC
3467 TA10a
20
40
60
80 100 IOUT (mA)
120
140
160
3467 TA10b
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14
LT3467/LT3467A PACKAGE DESCRIPTION
DDB Package 8-Lead Plastic DFN (3mm x 2mm)
(Reference LTC DWG # 05-08-1702 Rev B)
0.61 0.05 (2 SIDES) 0.70 0.05 2.55 0.05 1.15 0.05 PACKAGE OUTLINE 0.25 0.05 0.50 BSC 2.20 0.05 (2 SIDES) RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS 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 PIN 1 BAR TOP MARK (SEE NOTE 6) 2.00 0.10 (2 SIDES) 0.56 0.05 (2 SIDES) 0.75 0.05 0.25 PIN 1 R = 0.20 OR 0.25 45 CHAMFER
(DDB8) DFN 0905 REV B
3.00 0.10 (2 SIDES)
R = 0.05 TYP
R = 0.115 TYP 5
0.40 8
0.10
0.200 REF
4 0.05 2.15 0.05 (2 SIDES)
1 0.50 BSC
0 - 0.05
BOTTOM VIEW--EXPOSED PAD
S6 Package 6-Lead Plastic TSOT-23
(Reference LTC DWG # 05-08-1636)
0.62 MAX 0.95 REF 2.90 BSC (NOTE 4)
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
0.95 BSC
0.30 - 0.45 6 PLCS (NOTE 3)
0.80 - 0.90 0.20 BSC 1.00 MAX DATUM `A' 0.01 - 0.10
0.30 - 0.50 REF
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
0.09 - 0.20 (NOTE 3)
1.90 BSC
S6 TSOT-23 1005
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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
LT3467/LT3467A TYPICAL APPLICATIONS
VIN 5V L1 4.7H C1 2.2F SHDN D1 R1 115k
Efficiency
VOUT 12V 270mA C4* 22pF 90 85 80 EFFICIENCY (%) C2 10F 75 70 65 60 55 50 50 100 150 200 250 IOUT (mA) 300 350
VIN SHDN LT3467 SS GND
SW
FB R2 13.3k
C3 0.047F C1: X5R OR X7R, 6.3V C2: X5R OR X7R, 16V D1: PHILIPS PMEG 2010 L1: SUMIDA CR43-4R7 *OPTIONAL
3467 F08a
Figure 8. 5V to 12V, 270mA Step-Up Converter
L1 3.3H D1 R1 115k C4 12pF R2 13.3k C2 10F VOUT 12V 260mA
3467 F08b
Efficiency
95 90 85 EFFICIENCY (%) 80 75 70 65 60 55 50 50 100 150 200 IOUT (mA) 250 300
3467 F09b
VIN 5V C1 4.7F VIN OFF ON
SW
SHDN LT3467A SS FB GND
C3 0.047F
C1: X5R OR X7R, 6.3V C2: X5R OR X7R, 16V D1: PHILIPS PMEG 2010 L1: SUMIDA CDRH4D18-3R3
3467 F09a
Figure 9. 5V to 12V, 260mA Step-Up Converter
RELATED PARTS
PART NUMBER LT1615/LT1615-1 LT1618 LTC1700 LTC1871 LT1930/LT1930A LT1946/LT1946A LT1961 LTC3400/ LTC3400B LTC3401 LTC3402 LT3464 DESCRIPTION 300mA/80mA (ISW), High Efficiency Step-Up DC/DC Converter 1.5A (ISW), 1.25MHz, High Efficiency Step-Up DC/DC Converter No RSENSETM, 530kHz, Synchronous Step-Up DC/DC Controller 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 600mA (ISW), 1.2MHz, Synchronous Step-Up DC/DC Converter 1A (ISW), 3MHz, Synchronous Step-Up DC/DC Converter 2A (ISW), 3MHz, Synchronous Step-Up DC/DC Converter COMMENTS VIN: 1V to 15V, VOUT(MAX) = 34V, IQ = 20A, ISD < 1A, ThinSOT Package 90% Efficiency, VIN: 1.6V to 18V, VOUT(MAX) = 35V, IQ = 1.8mA, ISD < 1A, MS Package 95% Efficiency, VIN: 0.9V to 5V, IQ = 200A, ISD < 10A, MS Package 92% Efficiency, VIN: 2.5V to 36V, IQ = 250A, ISD < 10A, MS Package High Efficiency, VIN: 2.6V to 16V, VOUT(MAX) = 34V, IQ = 4.2mA/5.5mA, ISD < 1A, ThinSOT Package High Efficiency, VIN: 2.45V to 16V, VOUT(MAX) = 34V, IQ = 3.2mA, ISD < 1A, MS8 Package 90% Efficiency, VIN: 3V to 25V, VOUT(MAX) = 35V, IQ = 0.9mA, ISD < 6A, MS8E Package 92% Efficiency, VIN: 0.85V to 5V, VOUT(MAX) = 5V, IQ = 19A/300A, ISD < 1A, ThinSOT Package 97% Efficiency, VIN: 0.5V to 5V, VOUT(MAX) = 5.5V, IQ = 38A, ISD < 1A, MS Package 97% Efficiency, VIN: 0.5V to 5V, VOUT(MAX) = 5.5V, IQ = 38A, ISD < 1A, MS Package VIN: 2.3V to 10V, VOUT(MAX) = 34V, IQ = 25A, ISD < 1A, ThinSOT Package
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85mA (ISW), High Efficiency Step-Up DC/DC Converter with Integrated Schottky and PNP Disconnect No RSENSE is a trademark of Linear Technology Corporation.
16 Linear Technology Corporation
(408) 432-1900 FAX: (408) 434-0507
LT 1208 REV D * PRINTED IN USA
1630 McCarthy Blvd., Milpitas, CA 95035-7417
www.linear.com
(c) LINEAR TECHNOLOGY CORPORATION 2003

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