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DESCRIPTION
1.1A Step-Up DC/DC Converter with Integrated Soft-Start The L T®3467/L T3467A switching regulators combine a 42V , 1.1A switch with a soft-start function. Pin compatible with the L T1930, its low V CESAT bipolar switch enables the device to deliver high current outputs in a small footprint. The L T3467 switches at 1.3MHz, allowing the use of tiny, low cost and low height inductors and capacitors. The L T3467A 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 fi lter . The high voltage switch on the L T3467/L T3467A is rated at 42V , making the devices ideal for boost converters up to 40V as well as SEPIC and fl yback designs. The L T3467 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 L T3467A can generate 5V at up to 430mA from a 3.3V supply or 15V at 135mA from a 3.3V supply. The L T3467/ L T3467A are available in a low profi le (1mm) 6-lead SOT-23 package and tiny 3mm × 2mm DFN package. L, L T , L TC, L TM, 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. Single Li-Ion Cell to 5V Boost Converter
FEATURES
APPLICATIONS
n 1.3MHz Switching Frequency (L T3467) n 2.1MHz Switching Frequency (L T3467A) n Low V CESAT Switch: 330mV at 1.1A n High Output Voltage: Up to 40V n Wide Input Range: 2.4V to 16V n Dedicated Soft-Start Pin n 5V at 540mA from 3.3V Input (L T3467) n 5V at 430mA from 3.3V Input (L T3467A) n 12V at 270mA from 5V Input (L T3467) n 12V at 260mA from 5V Input (L T3467A) n Uses Small Surface Mount Components n Low Shutdown Current: <1μA n Pin-for-Pin Compatible with the L T1930 and L T1613 n Low Profi le (1mm) ThinSOT™ Package n Low Profi le (0.75mm) 8-Lead (3mm × 2mm) n Digital Cameras n White LED Power Supplies n Cellular Phones n Medical Diagnostic Equipment n Local 5V or 12V Supplies n TFT-LCD Bias Supplies n xDSL Power Supplies GND VIN SW SS FB VIN 2.6V TO 4.2V 2.7μH 402k L T3467
3467 TA01a
15μF 3.3pF 4.7μF 133k VOUT 765mA AT VIN = 4.2V , 540mA AT VIN = 3.3V , 360mA AT VIN = 2.6V SHDNOFF ON 0.047μF IOUT (mA) EFFICIENCY (%) 600
3467 TA01b
100 900200 300 400 500 700 800 VIN = 3.3V VIN = 4.2V VIN = 2.6V Effi ciency
(Note 1) ORDER INFORMATION ABSOLUTE MAXIMUM RATINGS TOP VIEW DDB PACKAGE 8-LEAD (3mm s 2mm) PLASTIC DFN 1FB GND SW SW SHDN SS V IN GND TJMAX = 125°C, θJA = 80°C/W EXPOSED PAD (PIN 9) IS GND, MUST BE SOLDERED TO PCB
6 VIN
4 SHDN
TJMAX = 125°C, θJA = 165°C/W , θJC = 102°C/W PIN CONFIGURATION Operating Junction Temperature Range (Note 2) Lead Temperature (Soldering, 10 sec) LEAD FREE FINISH TAPE AND REEL PART MARKING* PACKAGE DESCRIPTION TEMPERATURE RANGE L T3467EDDB#PBF L T3467EDDB#TRPBF LCPX 8-Lead (3mm × 2mm) Plastic DFN –40°C to 85°C L T3467IDDB#PBF L T3467IDDB#TRPBF LCPX 8-Lead (3mm × 2mm) Plastic DFN –40°C to 125°C L T3467AEDDB#PBF L T3467AEDDB#TRPBF LCKD 8-Lead (3mm × 2mm) Plastic DFN –40°C to 85°C L T3467AIDDB#PBF L T3467AIDDB#TRPBF LCKD 8-Lead (3mm × 2mm) Plastic DFN –40°C to 125°C L T3467IS6#PBF L T3467IS6#TRPBF L TACH 6-Lead Plastic TSOT-23 –40°C to 125°C L T3467ES6#PBF L T3467ES6#TRPBF L TACH 6-Lead Plastic TSOT-23 –40°C to 85°C L T3467AES6#PBF L T3467AES6#TRPBF L TBCC 6-Lead Plastic TSOT-23 –40°C to 85°C L T3467AIS6#PBF L T3467AIS6#TRPBF L TBCC 6-Lead Plastic TSOT-23 –40°C to 125°C LEAD BASED FINISH TAPE AND REEL PART MARKING* PACKAGE DESCRIPTION TEMPERATURE RANGE L T3467EDDB L T3467EDDB#TR LCPX 8-Lead (3mm × 2mm) Plastic DFN –40°C to 85°C L T3467IDDB L T3467IDDB#TR LCPX 8-Lead (3mm × 2mm) Plastic DFN –40°C to 125°C L T3467AEDDB L T3467AEDDB#TR LCKD 8-Lead (3mm × 2mm) Plastic DFN –40°C to 85°C L T3467AIDDB L T3467AIDDB#TR LCKD 8-Lead (3mm × 2mm) Plastic DFN –40°C to 125°C L T3467IS6 L T3467IS6#TR L TACH 6-Lead Plastic TSOT-23 –40°C to 125°C L T3467ES6 L T3467ES6#TR L TACH 6-Lead Plastic TSOT-23 –40°C to 85°C L T3467AES67 L T3467AES6#TR L TBCC 6-Lead Plastic TSOT-23 –40°C to 85°C L T3467AIS67 L T3467AIS67#TR L TBCC 6-Lead Plastic TSOT-23 –40°C to 125°C Consult L TC Marketing for parts specifi ed with wider operating temperature ranges. *The temperature grade is identifi ed 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 specifi cations, go to: http://www.linear .com/tapeandreel/
ELECTRICAL CHARACTERISTICS
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 L T3467E/L T3467AE are guaranteed to meet performance specifi cations from 0°C to 85°C, junction temperature. Specifi cations over the –40°C to 85°C operating junction temperature range are assured by design, characterization and correlation with statistical process controls. The L T3467I/L T3467AI are guaranteed over the full –40°C to 125°C operating junction temperature range. The l denotes the specifi cations which apply over the full operating temperature range, otherwise specifi cations are at TA = 25°C. VIN = 3V , VSHDN = VIN unless otherwise noted. Specifi cations are for both the L T3467 and L T3467A unless otherwise noted. PARAMETER CONDITIONS MIN TYP MAX UNITS Minimum Operating Voltage 2.2 2.4 V Maximum Operating Voltage 16 V Feedback Voltage l 1.230 1.220 1.255 1.270 1.280 V V FB Pin Bias Current (Note 3) l 10 50 nA Quiescent Current V SHDN = 2.4V , Not Switching 1.2 2 mA Quiescent Current in Shutdown V SHDN = 0.5V , VIN = 3V 0.01 1 μA Reference Line Regulation 2.6V ≤ V IN ≤ 16V 0.01 0.05 %/V Switching Frequency L T3467 L T3467A L T3467A l 1.6 1.6 1.3 2.1 1.6 2.7 MHz MHz MHz Maximum Duty Cycle L T3467 L T3467 L T3467A L T3467A l l Minimum Duty Cycle 10 % Switch Current Limit 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 CESAT ISW = 1.1A 330 500 mV Switch Leakage Current V SW = 5V 0.01 1 μA SHDN Input Voltage High 2.4 V SHDN Input Voltage Low 0.5 V SHDN Pin Bias Current V SHDN = 3V VSHDN = 0V 0.1 μA μA SS Charging Current V SS = 0.5V 2 3 4.5 μA Note 3: Current fl ows out of the pin. Note 4: See Typical Performance Characteristics for guaranteed current limit vs duty cycle.
TYPICAL PERFORMANCE CHARACTERISTICS Current Limit vs Duty Cycle Switch Saturation Voltage vs Switch Current Oscillator Frequency vs Temperature Soft-Start Current vs Soft-Start Voltage Peak Switch Current vs Soft-Start Voltage Start-Up Waveform (Figure 2 Circuit) Quiescent Current vs Temperature FB Pin Voltage vs Temperature SHDN Current vs SHDN Voltage IQ (mA) TEMPERATURE (°C) –40 95 110
3467 G01
5–10 50 1.6 1.4 1.2 1.0 0.8 0.6 0.4 0.2 –25 35 20 65 80 125 VFB (V) TEMPERATURE (°C) –40 95 110
3467 G02
5–10 50 1.26 1.25 1.24 1.23 1.22 1.21 1.20 –25 35 20 65 80 125 VSHDN (V) ISHDN (μA) 140 120 100
3467 G03
TA = 25°C DC (%) ILIM (A) 2.0 1.8 1.6 1.4 1.2 1.0 0.8 0.6 0.4 0.2 30 50 60
3467 G04
TA = 25°C VCESAT 100mV/DIV SW CURRENT 200mA/DIV TA = 85°C TA = 25°C TA = –40°C
3467 G05
TEMPERATURE (°C) –50 OSCILLATOR FREQUENCY (MHz) 100
3467 G06
05 0–25 25 75 2.50 2.25 2.00 1.75 1.50 1.25 1.00 0.75 0.50 0.25 LT3467A LT3467 VSS (mV) 0 50 150 250 350 450 ISS (μA) 100 200 300 400
3467 G07
TA = 25°C VSS (mV) 0 50 150 250 350 450 SWITCH CURRENT (A) 2.0 1.8 1.6 1.4 1.2 1.0 0.8 0.6 0.4 0.2 100 200 300 400
3467 G08
TA = 25°C VSHDN 2V/DIV VOUT 1V/DIV ISUPPLY 0.5A/DIV 0.5ms/DIV
3467 G09
FB (Pin 1/Pin 3): Feedback Pin. Reference voltage is 1.255V . to enable device. Ground to shut down.
3467 F01
Figure 1. Block Diagram
The L T3467 uses a constant frequency, current-mode con- 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 amplifi er A1, and is simply an amplifi ed version of the difference between the feedback voltage and the reference voltage of 1.255V . In this manner , the error amplifi er sets the correct peak current level to keep the output in regulation. If the error amplifi er’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 L T3467 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 L T3467 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 L T3467. The Block Diagram for the L T3467A (not shown) is identical except that the oscillator frequency is 2.1MHz. Duty Cycle The typical maximum duty cycle of the L T3467 is 94% (88% for the L T3467A). The duty cycle for a given ap- plication is given by: where VD is the diode forward voltage drop and VCESAT is in the worst case 330mV (at 1.1A) The L T3467 and L T3467A 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. V OUT = 1.255V (1+ R1/R2) Switching Frequency and Inductor Selection The L T3467 switches at 1.3 MHz, allowing for small valued inductors to be used. 4.7μH or 10μH will usually suffi ce. The L T3467A switches at 2.1MHz, allowing for even smaller valued inductors to be used. 0.9μH to 6.8μH will usually suffi ce. 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 I 2R 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 effi ciency, 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 L T3467A) such as ferrite core.
3467 TA05a
Figure 2. Single Li-Ion Cell to 5V Boost Converter (Same as 1st Page Application) Table 1. Inductor Manufacturers the soft-start capacitor range from 10nF to 200nF .
3467 AI01
3467 AI02
be used at the output to minimize the output ripple voltage. use a capacitor with a suffi cient voltage rating. Table 2. Ceramic Capacitor Manufacturers zero is determined by the following equation.
3467 F03
Figure 3. T ransient Response of Figure 8’s Step-Up
3467 F04
Figure 4. T ransient Response of Figure 8’s Step-Up (see Figure 2) according to the following equation. resistor divider chain to 1.255V/13.3k = 94μA. plane for better thermal performance.
3467 F05a
3467 F05b
stand and adjust the voltage feedback loop. contribution of the various elements in the loop is critical. with proper external component selection.
3467 F06
Figure 6. Boost Converter Equivalent Model
Table 3. Bode Plot Parameters adequate. The crossover frequency is 37kHz.
3467 F07
Figure 7. Bode Plot of 3.3V to 5V Application
3467 TA02
3467 TA02b
4-Cell to 5V SEPIC Converter GND VIN SW SHDN FB 4V TO 6.5V D1L1 10μH 10μH 255k LT3467
3467 TA03
2.2μF 0.047μF 4-CELL BATTERY C2 10μF 1μF 84.5k VOUT 325mA AT V IN = 4V 400mA AT VIN = 5V 450mA AT VIN = 6.5V C1, C3: X5R or X7R, 10V C2: X5R or X7R, 6.3V SHDN SS 4.7pF D1: PHILIPS PMEG 2010 L1, L2: MURATA LQH32CN100K33L 5V to 40V Boost Converter GND VIN SW SHDN FB VIN D1L1 2.7μH 412k LT3467
3467 TA04a
1μF 4.7μF 0.1μF 13.3k VOUT 40V 20mA C1: X5R or X7R, 6.3V C2: X5R or X7R, 50V D1: ON SEMICONDUCTOR, MBRM140 L1: SUMIDA CD43-2R7 SHDN SS ±15V Dual Output Converter with Output Disconnect GND VIN SW SS FB VIN 1μF 10μH 147kC5 1μF 0.047μF LT3467 D3 D4
3467 TA05
2.2μF 2.2μF 2.2μF 13.3k –15V 100mA 15V 100mA C1: X5R or X7R, 6.3V C2 TO C5: X5R or X7R, 16V D1 TO D4: PHILIPS PMEG 2005 L1: SUMIDA CR43-100 SHDNOFF ON
9V , 18V , –9V T riple Output TFT-LCD Bias Supply with Soft-Start GND VIN SW FB VIN 3.3V D5L1 4.7μH 124k LT3467
3467 TA06a
10μF 1μFC1 2.2μF 0.1μF 1μF 20k 220mA –9V 10mA 18V 10mA 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 SS VSHDN SHDN 3.3V 0V C7 0.1μF 0.1μF IL1 0.5A/DIV 9V OUTPUT 5V/DIV 18V OUTPUT 10V/DIV –9V OUTPUT 5V/DIV 2ms/DIV
3467 TA06b
8V , 23V , –8V T riple Output TFT-LCD Bias Supply with Soft-Start IL1 0.5A/DIV 8V OUTPUT 5V/DIV 23V OUTPUT 10V/DIV –8V OUTPUT 5V/DIV 2ms/DIV
3467 TA07b
3.3V D7L1 4.7μH 113k LT3467
3467 TA07a
10μF 1μFC1 2.2μF 0.1μF 1μF 21k 270mA –8V 10mA 23V 10mA 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 3.3V 0V C9 0.1μF 0.1μF 0.1μF 0.1μF D3 D4 SHDNVSHDN
2.6V TO 4.2V D1L1 0.9μH 8.06k L T3467A
3467 TA09a
C2* 22μF C4* 75pF 4.7μF 2.67k VOUT 600mA AT V IN = 4.2V 360mA AT VIN = 3.3V 250mA AT VIN = 2.6V 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 SS 0.047μF OFF ON IOUT (mA) EFFICIENCY (%) 400
3467 TA09b
10050 150 250 350 450200 300 500 VIN = 3.3V VIN = 4.2V VIN = 2.6V Single Li-Ion Cell to 5V Boost Converter Effi ciency 2.6V-3.3V to 5V Boost Converter Effi ciency GND VIN SW SHDN FB VIN 2.6V TO 3.3V D1L1 1.5μH 8.06k LT3467A
3467 TA08a
10μF 56pF 4.7μF 2.67k VOUT 430mA AT V IN = 3.3V 270mA AT VIN = 2.6V C1, C2: X5R OR X7R, 6.3V D1: PHILIPS PMEG 2010 L1: FDK MIP3226D1R5M SS 0.047μF OFF ON IOUT (mA) EFFICIENCY (%) 400
3467 TA08b
10050 150 250 350 450200 300 500 VIN = 3.3V VIN = 2.6V 3.3V to 15V , 135mA Step-Up Converter Effi ciency GND VIN SW SHDN FB VIN 3.3V D1L1 6.8μH 16.5k L T3467A
3467 TA10a
2.2μF 68pF 4.7μF 1.5k VOUT 15V 135mA C1: X5R OR X7R, 6.3V C2: X5R OR X7R, 16V D1: PHILIPS PMEG 2010 L1: SUMIDA CMD4D13-6R8MC SS 0.047μF OFF ON IOUT (mA) EFFICIENCY (%)
3467 TA10b
40 80 10020 60 120 140 160
8-Lead Plastic DFN (3mm × 2mm) (Reference L TC DWG # 05-08-1702 Rev B) 2.00 p0.10 (2 SIDES) 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 0.40 p 0.10 BOTTOM VIEW—EXPOSED PAD 0.56 p 0.05 (2 SIDES) 0.75 p0.05 R = 0.115 TYPR = 0.05 TYP 2.15 p0.05 (2 SIDES) 3.00 p0.10 (2 SIDES) PIN 1 BAR TOP MARK (SEE NOTE 6)
0.200 REF
0 – 0.05 (DDB8) DFN 0905 REV B 0.25 p 0.05 2.20 p0.05 (2 SIDES) RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS 0.61 p0.05 (2 SIDES) 1.15 p0.05 0.70 p0.05 2.55 p0.05 PACKAGE OUTLINE 0.25 p 0.05
0.50 BSC
R = 0.20 OR 0.25 s 45o CHAMFER
1.50 – 1.75 (NOTE 4)2.80 BSC 0.30 – 0.45
6 PLCS (NOTE 3)
DATUM ‘A’ 0.09 – 0.20 (NOTE 3) S6 TSOT-23 1005
2.90 BSC
(NOTE 4)
0.95 BSC
1.90 BSC
0.80 – 0.90
1.00 MAX
0.01 – 0.100.20 BSC 0.30 – 0.50 REF PIN ONE ID 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
3.85 MAX
0.62 MAX 0.95 REF RECOMMENDED SOLDER PAD LAYOUT PER IPC CALCULATOR 1.4 MIN2.62 REF
1.22 REF
(Reference L TC DWG # 05-08-1636) PACKAGE DESCRIPTION
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.
REVISION HISTORY
REV DATE DESCRIPTION PAGE NUMBER E 04/10 Updated Note 2 in Absolute Maximum Ratings and Electrical Characteristics 2, 3 (Revision history begins at Rev E)
No RSENSE is a trademark of Linear Technology Corporation.
3467 F08a
3467 F08b
Figure 8. 5V to 12V , 270mA Step-Up Converter
3467 F09b
3467 F09a
Figure 9. 5V to 12V , 260mA Step-Up Converter