LTC3426 1.2MHz Step-Up DC/DC Converter in SOT-23 U FEATURES DESCRIPTIO ■ The LTC®3426 step-up switching regulator generates an output voltage of up to 5.5V from an input voltage as low as 1.6V. Ideal for applications where space is limited, it switches at 1.2MHz, allowing the use of tiny, low cost and low profile external components. Its internal 2A, 100mΩ NMOS switch provides high efficiency even at heavy load, while the constant frequency, current mode architecture results in low, predictable output noise that is easy to filter. ■ ■ ■ ■ ■ ■ ■ ■ Internal 2A MOSFET Switch 1.2MHz Switching Frequency Integrated Soft-Start VIN Range: 1.6V to 4.3V Low RDS(ON) Switch: 100mΩ at 5V Output Delivers 5V at 800mA from a 3.3V Input Delivers 3.3V at 800mA from a 2.5V Input Uses Small, Low Profile External Components Low Profile (1mm) SOT-23 (ThinSOTTM) Package U APPLICATIO S ■ ■ ■ White LED Driver Supply Local 3.3V or 5V Supply Battery Back-Up Antiringing circuitry reduces EMI concerns by damping the inductor while in discontinuous mode, and internal soft-start eases inrush current worries. Internal frequency compensation is designed to accommodate ceramic output capacitors, further reducing noise. The device features very low shutdown current of 0.5µA. The LTC3426 is available in the 6-lead SOT-23 package. , LTC and LT 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. Protected by U.S. Patents, including 6498466, 6611131 U TYPICAL APPLICATIO 3.3V to 5V Boost Converter Efficiency 100 2.2µH VIN 3.3V VIN = 3.3V VOUT = 5V 95 VOUT VIN 10µF OFF ON VOUT 5V 800mA LTC3426 SHDN FB 22µF GND EFFICIENCY (%) 90 SW 85 80 75 70 65 60 3426 TA01 55 50 1 10 100 LOAD CURRENT (mA) 1000 3426 TA01b 3426f 1 LTC3426 W W W AXI U U ABSOLUTE RATI GS U U W PACKAGE/ORDER I FOR ATIO (Note 1) VIN Voltage ................................................. –0.3V to 6V SW Voltage .................................................. –0.3V to 6V SHDN, FB Voltage ....................................... –0.3V to 6V VOUT ........................................................... –0.3V to 6V Operating Temperature Range (Note 2) .. – 40°C to 85°C Storage Temperature Range ................. – 65°C to 125°C Lead Temperature (Soldering, 10 sec)................ 300°C ORDER PART NUMBER TOP VIEW 6 VIN SW 1 GND 2 LTC3426ES6 5 VOUT FB 3 4 SHDN S6 PART MARKING S6 PACKAGE 6-LEAD PLASTIC TSOT-23 TJMAX = 125°C, θJA = 165°C/W, θJC = 102°C/W LTAJT Consult LTC Marketing for parts specified with wider operating temperature ranges. U CO VERTER CHARACTERISTICS The ● denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. VIN = 1.8V, VOUT = 3.3V, unless otherwise specified. PARAMETER CONDITIONS MIN MAX UNITS Input Voltage Range SHDN = VIN 1.6 4.3 V 2.25 5 V Output Voltage Adjust Range ● Feedback Voltage 1.173 TYP 1.22 1.247 V 0.1 µA 1 µA 600 1000 µA 0.2 10 µA Feedback Input Current VFB = 1.23V Quiescent Current (Shutdown) VSHDN = 0V, Not Including Switch Leakage Quiescent Current SHDN = VIN, Not Switching Switch Leakage VSW = 5V Switch On Resistance VOUT = 3.3V VOUT = 5V 0.11 0.10 Ω Ω 2 2.3 A 80 85 % 0.85 1.2 ● Current Limit Maximum Duty Cycle VFB = 1.15V ● Switching Frequency SHDN Input High SHDN Input Low SHDN Input Current 1.5 1 SHDN = 5.5V Note 1: Absolute Maximum Ratings are those values beyond which the life of a device may be impaired. Note 2: The LTC3426 is guaranteed to meet performance specifications from 0°C to 70°C. Specifications over the –40°C to 85°C operating temperature are assured by design, characterization and correlation with statistical process controls. MHz V 0.4 V 1 µA Note 3: This IC includes overtemperature protection that is intended to protect the device during momentary overload conditions. Junction temperature will exceed 125°C when overtemperature protection is active. Continuous operation above the specified maximum operating junction temperature may impair device reliability. 3426f 2 LTC3426 U W TYPICAL PERFOR A CE CHARACTERISTICS Oscillator Frequency vs Temperature Efficiency vs VIN EFFICIENCY (%) 1.3 1.2 FIGURE 1 CIRCUIT 98 TA = 25°C = 150mA I 96 VLOAD = 5V OUT 94 COUT = 22µF L = 2.2µH 92 FIGURE 1 CIRCUIT TA = 25°C VOUT = 5V 1.1 C OUT = 22µF L = 2.2µH IOUT(MAX) (A) 1.40 FREQUENCY (MHz) IOUT(MAX) vs VIN 1.3 100 90 88 0.9 0.7 86 1.1 84 0.5 82 1.0 –50 80 –30 –10 10 30 50 TEMPERATURE (°C) 70 1.8 90 2.2 2.6 3 VIN (V) 3.4 3.8 4.2 1.8 2.6 3 VIN (V) 3.4 3.8 4.2 3426 G03 FB Pin Voltage RDS(ON) vs Temperature Switching Waveforms 1.25 0.15 0.14 VOUT 500mV/DIV 1.24 0.12 FB VOLTAGE (V) 0.13 VOUT = 2.5V 0.11 0.10 VOUT = 5V 0.09 VOUT = 3.3V 0.08 0.07 1.23 SW 2V/DIV 1.22 IL 200mA/DIV 1.21 1.20 VIN = 1.8V VOUT = 3.3V COUT = 22µF L = 2.5µH 0.06 0.05 –50 2.2 LT1108 • TPC12 3426 G01 RDS(ON) (Ω) 0.3 –25 25 50 0 TEMPERATURE (°C) 75 100 1.19 –50 –25 0 25 50 TEMPERATURE (°C) 75 100 100ns/DIV 3426 G06 3426 G05 3426 G04 VOUT Transient Response SW Pin Antiringing Operation VOUT 500mV/DIV SW 1V/DIV IOUT 200mA/DIV IL 50mA/DIV 500mA 250mA IL 500mA/DIV VIN = 1.8V VOUT = 3.3V 100ns/DIV 3426 G07 VIN = 1.8V VOUT = 3.3V COUT = 22µF L = 2.5µH 40µs/DIV 3426 G08 3426f 3 LTC3426 U U U PI FU CTIO S SW (Pin 1): Switch Pin. Connect inductor between SW and VIN. A Schottky diode is connected between SW and VOUT. Keep these PCB trace lengths as short and wide as possible to reduce EMI and voltage overshoot. If the inductor current falls to zero, an internal 100Ω antiringing switch is connected from SW to VIN to minimize EMI. SHDN (Pin 4): Logic Controlled Shutdown Input. Typically, SHDN should be connected to VIN through a 1M pull-up resistor. GND (Pin 2): Signal and Power Ground. Provide a short direct PCB path between GND and the (–) side of the output capacitor(s). VOUT (Pin 5): Output Voltage Sense Input. The NMOS switch gate drive is derived from the greater of VOUT and VIN. FB (Pin 3): Feedback Input to the gm Error Amplifier. Connect resistor divider tap to this pin. The output voltage can be adjusted from 2.5V to 5V by: VIN (Pin 6): Input Supply. Must be locally bypassed. SHDN = High: Normal free running operation SHDN = Low: Shutdown, quiescent current < 1µA ⎛ R1⎞ VOUT = 1.22 • ⎜ 1 + ⎟ ⎝ R2 ⎠ W BLOCK DIAGRA 1.22V REFERENCE COMPARATOR + VIN SW 5 6 1 – A1 – VOUT RC A2 PWM LOGIC AND DRIVER + CC 3 FB + VOUT Σ – R1 (EXTERNAL) FB R2 (EXTERNAL) 0.02Ω RAMP GENERATOR SHDN 4 SHUTDOWN AND SOFT-START 1.2MHz OSCILLATOR 2 3426 F01 GND Figure 1 3426f 4 LTC3426 U OPERATIO The LTC3426 is a monolithic 1.2MHz boost converter housed in a 6-lead SOT-23 package. The device features fixed frequency, current mode PWM control for excellent line and load regulation. The low RDS(ON) NMOS switch enables the device to maintain high efficiency over a wide range of load current. Operation of the feedback loop which sets the peak inductor current to keep the output in regulation can be best understood by referring to the Block Diagram in Figure 1. At the start of each clock cycle a latch in the PWM logic is set and the NMOS switch is turned on. The sum of a voltage proportional to the switch current and a slope compensating voltage ramp is fed to the positive input to the PWM comparator. When this voltage exceeds either a voltage proportional to the 2A current limit or the PWM control voltage, the latch in the PWM logic is reset and NMOS switch is turned off. The PWM control voltage at the output of the error amplifier is the amplified and compensated difference between the feedback voltage on the FB pin and the internal reference voltage of 1.22V. If the control voltage increases, more current is delivered to the output. When the control voltage exceeds the ILIMIT reference voltage, the peak current is limited to a minimum of 2A. The current limit helps protect the LTC3426 internal switch and external components connected to it. If the control voltage decreases, less current is delivered to the output. During load transients control voltage may decrease to the point where no switching occurs until the feedback voltage drops below the reference. The LTC3426 has an integrated soft-start feature which slowly ramps up the feedback control node from 0V. The soft-start is initiated when SHDN is pulled high. U W U U APPLICATIO S I FOR ATIO Setting the Output Voltage The output voltage, VOUT, is set by a resistive divider from VOUT to ground. The divider tap is tied to the FB pin. VOUT is set by the formula: ⎛ R1⎞ VOUT = 1.22 • ⎜ 1 + ⎟ ⎝ R2 ⎠ Inductor Selection The LTC3426 can utilize small surface mount inductors due to its 1.2MHz switching frequency. A 1.5µH or 2.2µH inductor will be the best choice for most LTC3426 applications. Larger values of inductance will allow greater output current capability by reducing the inductor ripple current. Increasing the inductance above 3.3µH will increase component size while providing little improvement in output current capability. The inductor current ripple is typically set for 20% to 40% of the maximum inductor current (IP). High frequency ferrite core inductor materials reduce frequency dependent power losses compared to cheaper powdered iron types, improving efficiency. The inductor should have low DCR (DC resistance) to reduce the I2R power losses, and must be able to handle the peak inductor current without saturating. Several inductor manufacturers are listed in Table 1. Table 1. Inductor Manufacturers TDK www.tdk.com Sumida www.sumida.com Murata www.murata.com Output and Input Capacitor Selection Low ESR (equivalent series resistance) capacitors should be used to minimize the output voltage ripple. Multilayer ceramic capacitors are an excellent choice as they have extremely low ESR and are available in small footprints. A 15µF to 30µF output capacitor is sufficient for most applications. X5R and X7R dielectric materials are preferred for their ability to maintain capacitance over wide voltage and temperature ranges. Low ESR input capacitors reduce input switching noise and reduce the peak current drawn from the input supply. It follows that ceramic capacitors are also a good choice for input decoupling and should be located as close as 3426f 5 LTC3426 U W U U APPLICATIO S I FOR ATIO possible to the device. A 10µF input capacitor is sufficient for most applications. Table 2 shows a list of several ceramic capacitor manufacturers. Consult the manufacturers for detailed information in their entire selection of ceramic parts. Table 2. Ceramic Capacitor Manufacturers Taiyo Yuden PCB Layout Guidelines The high speed operation of the LTC3426 demands careful attention to board layout. You will not get advertised performance with careless layout. Figure 2 shows the recommended component placement. A large ground pin copper area will help to lower the chip temperature. www.t-yuden.com Murata www.murata.com TDK www.component.tdk.com Diode Selection A Schottky diode is recommended for use with the LTC3426. Use of a low forward voltage diode such as the ON Semiconductor MBRA210LT3 is recommended. A Schottky diode rated at 2A is recommended for use with the LTC3426. VIN 1 SW VIN 6 2 GND VOUT 5 3 FB 4 SHDN VOUT 3426 F02 Figure 2. Recommended Component Placement for Single Layer Board 3426f 6 LTC3426 U TYPICAL APPLICATIO S Efficiency L1 2.2µH 100 D1 95 VIN 3.3V VOUT VIN C1 10µF OFF ON R1 95.3k 1% LTC3426 SHDN FB VOUT 5V 800mA C2 22µF R2 30.9k 1% GND EFFICIENCY (%) 90 SW 85 80 75 70 65 60 55 C1: TAIYO YUDEN X5R JMK212BJ475ML C2: TAIYO YUDEN X5R JMK316BJ226ML D1: ON SEMICONDUCTOR MBRA210LT3 L1: COILCRAFT D03316P-222 3426 TA02a 50 1 10 100 LOAD CURRENT (mA) 1000 3426 TA02b Efficiency L1 1.5µH 100 D1 VIN 1.8V VOUT VIN C1 10µF OFF ON LTC3426 SHDN GND FB R1 64.9k 1% R2 61.9k 1% C1: TDK C1608X5R0J106M C2: TAIYO YUDEN JMK316BJ226ML D1: ON SEMICONDUCTOR MBRM120LT3 L1: TDK RLF7030T-1R5N6R1 VOUT 2.5V 800mA C2 22µF EFFICIENCY (%) 90 SW 80 70 60 3426 TA03a 50 1 10 100 LOAD CURRENT (mA) 1000 3426 TA03b 3426f 7 LTC3426 U TYPICAL APPLICATIO S Efficiency 100 L1 2.2µH VIN 3V TO 4.2V D1 95 VOUT VIN C1 10µF OFF ON R1 95.3k 1% LTC3426 SHDN FB R2 30.9k 1% GND C1: TDK C1608X5R0J475M C2: TAIYO YUDEN JMK316BJ226ML D1: ON SEMICONDUCTOR MBR120VLSFT1 L1: SUMIDA CDRH4D28-2R2 2 VOUT 5V 750mA AT 3V C2 22µF EFFICIENCY (%) 90 SW VIN = 4.2V 85 80 VIN = 3V 75 70 65 60 55 3426 TA04a 50 1 10 100 LOAD CURRENT (mA) 1000 3426 TA04b Efficiency 100 L1 2.5µH VIN 2.5V D1 SW VIN C1 10µF OFF ON VOUT LTC3426 SHDN GND FB R1 75k 1% R2 44.2k 1% C1: TDK C1608X5R0J106 C2: TAIYO YUDEN JMK316BJ266 D1: ON SEMICONDUCTOR MBRM120LT3 L1: SUMIDA CDRH5D28-2R5 2 VOUT 3.3V 800mA C2 22µF EFFICIENCY (%) 90 80 70 60 3426 TA05a 50 1 10 100 LOAD CURRENT (mA) 1000 3426 TA05b 3426f 8 LTC3426 U TYPICAL APPLICATIO S Efficiency 100 L1 1.5µH D1 VIN 1.8V VOUT VIN C1 10µF OFF ON R1 75k 1% LTC3426 SHDN FB R2 44.2k 1% GND C1: TDK C1608X5R0J106M C2: TAIYO YUDEN JMK316BJ226ML D1: ON SEMICONDUCTOR MBRM120LT3 L1: TDK RLF7030T-1R5N6R1 VOUT 3.3V 540mA C2 22µF EFFICIENCY (%) 90 SW 80 70 60 3426 TA06a 50 1 10 100 LOAD CURRENT (mA) 1000 3426 TA06b Efficiency 90 L1 2.2µH VIN 1.8V D1 SW VOUT VIN C1 10µF OFF ON LTC3426 SHDN GND FB R1 95.3k 1% R2 30.9k 1% C1: TDK C1608X5R0J475M C2: TAIYO YUDEN JMK316BJ226ML D1: ON SEMICONDUCTOR MBR120VLSFT1 L1: SUMIDA CDRH4D28-2R2 2 VOUT 5V 400mA C2 22µF EFFICIENCY (%) 80 70 60 50 3426 TA07a 40 1 10 100 LOAD CURRENT (mA) 1000 3426 TA07b 3426f 9 LTC3426 U TYPICAL APPLICATIO S Efficiency L1 2.5µH VIN 2.5V 100 D1 VIN C1 10µF OFF ON VOUT LTC3426 SHDN GND FB R1 95.3k 1% R2 30.9k 1% C1: TDK C1608X5R0J106 C2: TAIYO YUDEN JMK316BJ266 D1: ON SEMICONDUCTOR MBRM120LT3 L1: SUMIDA CDRH5D28-2R5 VOUT 5V 550mA C2 22µF EFFICIENCY (%) 90 SW 80 70 60 3426 TA08a 50 1 10 100 LOAD CURRENT (mA) 1000 3426 TA08b 3426f 10 LTC3426 U PACKAGE DESCRIPTIO 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 NOTE: 1. DIMENSIONS ARE IN MILLIMETERS 2. DRAWING NOT TO SCALE 3. DIMENSIONS ARE INCLUSIVE OF PLATING 0.09 – 0.20 (NOTE 3) 1.90 BSC S6 TSOT-23 0302 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 3426f 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. 11 LTC3426 RELATED PARTS PART NUMBER LT1613 LT1946/LT1946A LTC3400/LTC3400B LTC3401/LTC3402 LTC3421 LTC3425 LTC3429 LTC3436 LTC3459 LTC3464 DESCRIPTION 550mA (ISW), 1.4MHz, High Efficiency Step-Up DC/DC Converter 1.5A (ISW), 1.2MHz/2.7MHz, High Efficiency Step-Up DC/DC Converter 600mA (ISW), 1.2MHz, Synchronous Step-Up DC/DC Converter 1A/2A (ISW), 3MHz, Synchronous Step-Up DC/DC Converter 3A (ISW), 3MHz, Synchronous Step-Up DC/DC Converter with Output Disconnect 5A (ISW), 8MHz, 4-Phase Synchronous Step-Up DC/DC Converter with Output Disconnect 600mA (ISW), 550kHz, Synchronous Step-Up DC/DC Converter with Soft-Start/Output Disconnect 3A (ISW), 1MHz, High Efficiency Step-Up DC/DC Converter COMMENTS 90% Efficiency, VIN: 0.9V to 10V, VOUT(MAX) = 34V, IQ = 3mA, ISD < 1µA, ThinSOT High Efficiency, VIN: 2.45V to 16V, VOUT(MAX) = 34V, IQ = 3.2mA, ISD < 1µA, MS8 92% Efficiency, VIN: 0.5V to 5V, VOUT(MAX) = 5V, IQ = 19µA/300µA, ISD < 1µA, ThinSOT 97% Efficiency, VIN: 0.5V to 5V, VOUT(MAX) = 5.5V, IQ = 38µA, ISD < 1µA, MS10 95% Efficiency, VIN: 0.5V to 4.5V, VOUT(MAX) = 5.25V, IQ = 12µA, ISD < 1µA, QFN24 95% Efficiency, VIN: 0.5V to 4.5V, VOUT(MAX) = 5.25V, IQ = 12µA, ISD < 1µA, QFN32 90% Efficiency, VIN: 0.5V to 4.3V, VOUT(MAX) = 5V, IQ = 20µA, ISD < 1µA, ThinSOT VIN: 3V to 25V, VOUT(MAX) = 34V, IQ = 0.9mA, ISD < 6µA, TSSOP16E 75mA (ISW), 10V Micropower Synchronous Boost Converter in ThinSOT 85mA (ISW), High Efficiency Step-Up DC/DC Converter with Schottky and PNP Disconnect VIN: 1.5V to 5.5V, VOUT(MAX) = 10V, IQ = 10µA, ISD < 1µA, ThinSOT VIN: 2.3V to 10V, VOUT(MAX) = 34V, IQ = 25µA, ISD < 1µA, ThinSOT 3426f 12 Linear Technology Corporation LT/TP 1104 1K • PRINTED IN THE USA 1630 McCarthy Blvd., Milpitas, CA 95035-7417 (408) 432-1900 ● FAX: (408) 434-0507 ● www.linear.com © LINEAR TECHNOLOGY CORPORATION 2004