LT3467/LT3467A 1.1A Step-Up DC/DC Converter with Integrated Soft-Start DESCRIPTION FEATURES n n n n n n n n n n n n n n n 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 n n n n n n n 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 3467afe 1 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/ 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 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. 3467afe 3 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 3467afe 4 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 3467afe 5 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) 3467afe 6 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 3467afe 7 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). 3467afe 8 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 3467afe 9 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