LT1618 Constant-Current/ Constant-Voltage 1.4MHz Step-Up DC/DC Converter U FEATURES ■ ■ ■ ■ ■ ■ ■ DESCRIPTIO Accurate Input/Output Current Control: ±5% Over Temperature Accurate Output Voltage Control: ±1% Wide VIN Range: 1.6V to 18V 1.4MHz Switching Frequency High Output Voltage: Up to 35V Low VCESAT Switch: 200mV at 1A Tiny 10-Pin MSOP Package The LT®1618 step-up DC/DC converter combines a traditional voltage feedback loop and a unique current feedback loop to operate as a constant-current, constant-voltage source. This fixed frequency, current mode switcher operates from a wide input voltage range of 1.6V to 18V, and the high switching frequency of 1.4MHz permits the use of tiny, low profile inductors and capacitors. The current sense voltage is set at 50mV and can be adjusted using the IADJ pin. U APPLICATIO S ■ ■ ■ LED Backlight Drivers USB Powered Boost/SEPIC Converters Input Current Limited Boost/SEPIC Converters Battery Chargers , LTC and LT are registered trademarks of Linear Technology Corporation. U ■ Available in the 10-Pin MSOP package, the LT1618 provides a complete solution for constant-current applications. TYPICAL APPLICATIO USB to 12V Boost Converter (with Selectable 100mA/500mA Input Current Limit) L1 10µH C1 4.7µF 3 D1 2 7 ISN SW ISP 3.3V OFF ON 0V 9 20k IADJ GND 5 C2 4.7µF R2 107k SHDN 4 3.3V 100mA 500mA 0V 1 FB VIN 90 85 R1 909k LT1618 8 Efficiency Curve VOUT 12V VC EFFICIENCY (%) 0.1Ω VIN 5V 80 75 70 10 65 2k 13k C1: TAIYO YUDEN JMK212BJ475 C2: TAIYO YUDEN EMK316BJ475 D1: ON SEMICONDUCTOR MBR0520 L1: SUMIDA CR43-100 10nF 60 0 20 60 80 100 120 140 160 40 LOAD CURRENT (mA) 1618 TA01a 1618 TA01b 1 LT1618 U W W W ABSOLUTE AXI U RATI GS U W U PACKAGE/ORDER I FOR ATIO (Note 1) VIN, SHDN Voltage ................................................... 18V SW Voltage .............................................................. 36V ISP, ISN Voltage ...................................................... 36V IADJ Voltage ............................................................... 6V FB Voltage .............................................................. 1.5V VC Voltage .............................................................. 1.5V Junction Temperature ........................................... 125°C Operating Temperature Range (Note 2) .. – 40°C to 85°C Storage Temperature Range ................. – 65°C to 150°C Lead Temperature (Soldering, 10 sec).................. 300°C ORDER PART NUMBER TOP VIEW FB ISN ISP IADJ GND 1 2 3 4 5 10 9 8 7 6 VC SHDN VIN SW N/C LT1618EMS MS10 PART MARKING MS10 PACKAGE 10-LEAD PLASTIC MSOP TJMAX = 125°C, θJA = 160°C/W LTNH Consult LTC marketing for parts specified with wider operating temperature ranges. ELECTRICAL CHARACTERISTICS The ● denotes specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. VIN = 1.6V, VSHDN = 1.6V, unless otherwise noted. PARAMETER CONDITIONS MIN Input Voltage TYP 1.6 Quiescent Current VSHDN = 1.6V, Not Switching VSHDN = 0V Reference Voltage Measured at FB Pin ● Reference Voltage Line Regulation 1.6V < VIN < 18V FB Pin Bias Current VFB = 1.263V, VIN = 1.8V 1.250 1.243 ● Error Amplifier Voltage Gain MAX UNITS 18 V 1.8 0.1 2.7 1 mA µA 1.263 1.263 1.276 1.283 V V 0.01 0.03 %/V ±2 ±12 nA 180 V/V Error Amplifier Transconductance ∆IC = ± 5µA 160 µmho Error Amplifier Sink Current VFB = 1.35V, VC = 1V 15 µA Error Amplifier Source Current VFB = 1.10V, VC = 1V Current Sense Voltage (ISP, ISN) VFB = 0V, VIADJ = 0V ISP, ISN Pin Bias Currents (Note 3) VISP = 1.85V, VISN = 1.80V, VIADJ = 0V 47.5 50 52.5 mV 50 80 µA (ISP, ISN) Common Mode Minimum Voltage Switching Frequency VFB = 1V VFB = 0V Maximum Switch Duty Cycle Switch VCESAT 2 1.25 ● Switch Current Limit ISW = 1A µA 30 ● 1.4 550 1.8 V 1.6 MHz kHz 88 92 1.5 2.1 2.8 % A 200 260 mV LT1618 ELECTRICAL CHARACTERISTICS The ● denotes specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. VIN = 1.6V, VSHDN = 1.6V, unless otherwise noted. PARAMETER CONDITIONS Switch Leakage Current Switch Off, VSW = 5V MIN SHDN Pin Current VSHDN = 1.6V TYP MAX 0.01 5 µA 5 20 µA 0.3 V Shutdown Threshold (SHDN Pin) Start-Up Threshold (SHDN Pin) UNITS 1 Note 1: Absolute Maximum Ratings are those values beyond which the life of a device may be impaired. Note 2: The LT1618 is guaranteed to meet performance specifications from 0°C to 70°C. Specifications over the – 40°C to 85°C operating V temperature range are assured by design, characterization, and correlation with statistical process controls. Note 3: Bias currents flow into the ISP and ISN pins. U W TYPICAL PERFOR A CE CHARACTERISTICS Switch Saturation Voltage (VCE, SAT) FB Pin Voltage and Bias Current TJ = 125°C 300 TJ = 25°C 200 TJ = –50°C 100 0 0 1.0 0.5 1.5 SWITCH CURRENT (A) 2.0 4 1.265 2 VOLTAGE 1.260 0 CURRENT 1.255 –2 1.250 – 50 – 25 75 25 50 0 TEMPERATURE (°C) 100 Current Sense Voltage (IADJ Pin = 0V) 1.0 0.5 0 – 50 – 25 –4 125 51 50 49 100 125 1618 G04 75 25 50 0 TEMPERATURE (°C) 2.5 50 2.0 40 30 20 10 0.2 0.4 0.6 0.8 1.0 1.2 IADJ PIN VOLTAGE (V) 125 Quiescent Current 60 0 0.0 100 1618 G03 QUIESCENT CURRENT (mA) CURRENT SENSE VOLTAGE (mV) CURRENT SENSE VOLTAGE (mV) 1.5 Current Sense Voltage (VISP, ISN) 52 25 50 75 0 TEMPERATURE (°C) 2.0 1618 G02 1618 G01 48 – 50 – 25 2.5 PEAK CURRENT (A) FEEDBACK VOLTAGE (V) 400 1.270 FB PIN BIAS CURRENT (nA) SATURATION VOLTAGE (mV) 500 Switch Current Limit 1.4 1.6 1618 G05 VIN = 18V VIN = 1.6V 1.5 1.0 0.5 0 – 50 – 25 25 50 75 0 TEMPERATURE (°C) 100 125 1618 G06 3 LT1618 U W TYPICAL PERFOR A CE CHARACTERISTICS Switching Frequency Frequency Foldback 1.8 1.6 1.7 1.4 SHDN Pin Current 50 1.6 1.5 VIN = 18V 1.4 VIN = 1.6V 1.3 1.2 45 1.2 SHDN PIN CURRENT (µA) SWITCHING FREQUENCY (MHz) SWITCHING FREQUENCY (MHz) TJ = 25°C 1.0 0.8 0.6 0.4 0.2 1.1 1.0 – 50 – 25 100 125 35 30 TJ = 25°C 25 20 TJ = 125°C 15 10 5 0 75 25 50 0 TEMPERATURE (°C) TJ = – 50°C 40 0 0 0.2 0.8 0.4 0.6 1.0 FEEDBACK PIN VOLTAGE (V) 1618 G07 1.2 1618 G08 0 5 15 10 SHUTDOWN PIN VOLTAGE (V) 20 1618 G09 U U U PIN FUNCTIONS FB (Pin 1): Feedback Pin. Set the output voltage by selecting values for R1 and R2 (see Figure 1): V R1 = R2 OUT – 1 1.263V GND (Pin 5): Ground Pin. Tie this pin directly to local ground plane. SW (Pin 7 ): Switch Pin. This is the collector of the internal NPN power switch. Minimize the metal trace area connected to this pin to minimize EMI. ISN (Pin 2): Current Sense (–) Pin. The inverting input to the current sense amplifier. VIN (Pin 8): Input Supply Pin. Bypass this pin with a capacitor to ground as close to the device as possible. ISP (Pin 3): Current Sense (+) Pin. The noninverting input to the current sense amplifier. SHDN (Pin 9): Shutdown Pin. Tie this pin higher than 1V to turn on the LT1618; tie below 0.3V to turn it off. IADJ (Pin 4): Current Sense Adjust Pin. A DC voltage applied to this pin will reduce the current sense voltage. If this adjustment is not needed, tie this pin to ground. VC (Pin 10): Compensation Pin for Error Amplifier. Connect a series RC from this pin to ground. Typical values are 2kΩ and 10nF. 4 LT1618 W BLOCK DIAGRA D1 L1 RSENSE VIN VOUT C1 SHDN VIN 9 C2 SW 7 8 Q1 DRIVER + ×5 0.02Ω – 1.4MHz OSCILLATOR + S 3 – 2 Σ + ISN 4 IADJ + Q R ISP + A1 ×25 A3 – 5 A2 – – + R1 1 FB 1.263V R2 10 VC GND RC CC Figure 1. LT1618 Block Diagram U OPERATIO The LT1618 uses a constant frequency, current mode control scheme to provide excellent line and load regulation. Operation can be best understood by referring to the Block Diagram in Figure 1. At the start of each oscillator cycle, the SR latch is set, turning on power switch Q1. The signal at the noninverting input of PWM comparator A3 is a scaled-down version of the switch current (summed together with a portion of the oscillator ramp). When this signal reaches the level set by the output of error amplifier A2, comparator A3 resets the latch and turns off the power switch. In this manner, A2 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; if it decreases, less current is delivered. A2 has two inverting inputs, one from the voltage feedback loop, and one from the current feedback loop. Whichever inverting input is higher takes precedence, forcing the converter into either a constant-current or a constant-voltage mode. The LT1618 is designed to transition cleanly between the two modes of operation. Current sense amplifier A1 senses the voltage between the ISP and ISN pins and provides a 25× level-shifted version to error amplifier A2. When the voltage between ISP and ISN reaches 50mV, the output of A1 provides 1.263V to one of the noninverting inputs of A2 and the converter is in constant-current mode. If the current sense voltage exceeds 50mV, the output of A1 will increase causing the output of A2 to decrease, thus reducing the amount of current delivered to the output. In this manner the current sense voltage is regulated to 50mV. Similarly, if the FB pin increases above 1.263V, the output of A2 will decrease to reduce the peak current level and regulate the output (constant-voltage mode). 5 LT1618 U W U U APPLICATIONS INFORMATION Inductor Selection Several inductors that work well with the LT1618 are listed in Table 1, although there are many other manufacturers and devices that can be used. Consult each manufacturer for more detailed information and for their entire selection of related parts. Many different sizes and shapes are available. Ferrite core inductors should be used to obtain the best efficiency, as core losses at 1.4MHz are much lower for ferrite cores than for the cheaper powdered-iron ones. Choose an inductor that can handle the necessary peak current without saturating, and ensure that the inductor has a low DCR (copper-wire resistance) to minimize I2R power losses. A 4.7µH or 10µH inductor will be a good choice for many LT1618 designs. Table 1. Recommended Inductors L MAX PART (µH) (mΩ) HEIGHT (mm) VENDOR CDRH5D18-4R1 CDRH5D18-100 CR43-2R2 CR43-4R7 CR43-100 CR54-100 4.1 10 2.2 4.7 10 10 57 124 71 109 182 100 2.0 2.0 3.5 3.5 3.5 4.8 Sumida (847) 956-0666 www.sumida.com LQH3C1R0M24 LQH3C2R2M24 LQH3C4R7M24 1.0 2.2 4.7 78 126 260 2.0 2.0 2.0 Murata (814) 237-1431 www.murata.com Capacitor Selection Low ESR (equivalent series resistance) capacitors should be used at the output to minimize the output ripple voltage. Multilayer ceramic capacitors are an excellent choice. They have an extremely low ESR and are available in very small packages. X5R and X7R dielectrics are preferred, as these materials retain their capacitance over wider voltage and temperature ranges than other dielectrics. A 4.7µF to 10µF output capacitor is sufficient for high output current designs. Converters with lower output currents may need only a 1µF or 2.2µF output capacitor. Solid tantalum or OSCON capacitors can be used, but they will occupy more board area than a ceramic and will have a higher ESR 6 forthe same footprint device. 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 VIN pin of the LT1618. 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. Recommended Ceramic Capacitor Manufacturers VENDOR PHONE URL Taiyo Yuden (408) 573-4150 www.t-yuden.com Murata (814) 237-1431 www.murata.com Kemet (408) 986-0424 www.kemet.com Diode Selection Schottky diodes, with their low forward voltage drop and fast switching speed, are the ideal choice for LT1618 applications. Table 3 shows several Schottky diodes that work well with the LT1618. Many different manufacturers make equivalent parts, but make sure that the component chosen has a sufficient current rating and a voltage rating greater than the output voltage. The diode conducts current only when the power switch is turned off (typically less than half the time), so a 0.5A or 1A diode will be sufficient for most designs. The companies below also offer Schottky diodes with higher voltage and current ratings. Table 3. Recommended Schottky Diodes 1A PART 0.5A PART VENDOR PHONE/URL UPS120 UPS130 UPS140 Microsemi (510) 353-0822 www.microsemi.com MBRM120 MBR0520 MBRM130 MBR0530 MBRM140 MBR0540 ON Semiconductor (800) 282-9855 www.onsemi.com B120 B130 B140 Diodes, Inc B0520 B0530 B0540 (805) 446-4800 www.diodes.com LT1618 U W U U APPLICATIONS INFORMATION Setting Output Voltage To set the output voltage, select the values of R1 and R2 (see Figure 1) according to the following equation. V R1 = R2 OUT – 1 1.263 For current source applications, use the FB pin for overvoltage protection. Pick R1 and R2 so that the output voltage will not go too high if the load is disconnected or if the load current drops below the preset value. Typically choose R1 and R2 so that the overvoltage value will be about 20% to 30% higher than the normal output voltage (when in constant-current mode). This prevents the voltage loop from interfering with the current loop in current source applications. For battery charger applications, pick the values of R1 and R2 to give the desired end of charge voltage. the output of the error amplifier (the VC pin) will be pulled down and the LT1618 will stop switching. A pulse width modulated (PWM) signal can also be used to adjust the current sense voltage; simply add an RC filterto convert the PWM signal into a DC voltage for the IADJ pin. If the IADJ pin is not used, it should be tied to ground. Do not leave the pin floating. For applications needing only a simple one-step current sense adjustment, the circuit in Figure 2 works well. If a large value resistor (≥2MΩ) is placed between the IADJ pin and ground, the current sense voltage will reduce to about 25mV, providing a 50% reduction in current. Do not leave the IADJ pin open. This method gives a well-regulated current value in both states, and is controlled by a logic signal without the need for a variable PWM or DC control signal. When the NMOS transistor is on, the current sense voltage will be 50mV, when it is off, the current sense voltage will be reduced to 25mV. Selecting RSENSE/Current Sense Adjustment LT1618 Use the following formula to choose the correct current sense resistor value (for constant current operation). RSENSE = 50mV/IMAX For designs needing an adjustable current level, the IADJ pin is provided. With the IADJ pin tied to ground, the nominal current sense voltage is 50mV (appearing between the ISP and ISN pins). Applying a positive DC voltage to the IADJ pin will decrease the current sense voltage according to the following formula: VISENSE = 1.263V – (0.8)VIADJ 25 For example, if 1V is applied to the IADJ pin, the current sense voltage will be reduced to about 18mV. This adjustability allows the regulated current to be reduced without changing the current sense resistor (e.g. to adjust brightness in an LED driver or to reduce the charge current in a battery charger). If the IADJ pin is taken above 1.6V, IADJ FULL CURRENT 2M 1618 F02 Figure 2 Considerations When Sensing Input Current In addition to regulating the DC output current for currentsource applications, the constant-current loop of the LT1618 can also be used to provide an accurate input current limit. Boost converters cannot provide output short-circuit protection, but the surge turn-on current can be drastically reduced using the LT1618’s current sense at the input. SEPICs, however, have an output that is DCisolated from the input, so an input current limit not only helps soft-start the output but also provides excellent short-circuit protection. 7 LT1618 U U W U APPLICATIONS INFORMATION When sensing input current, the sense resistor should be placed in front of the inductor (between the decoupling capacitor and the inductor) as shown in the circuits in the Typical Applications section. This will regulate the average inductor current and maintain a consistent inductor ripple current, which will, in turn, maintain a well regulated input current. Do not place the sense resistor between the input source and the input decoupling capacitor, as this may allow the inductor ripple current to vary widely (even though the average input current and the average inductor current will still be regulated). Since the inductor current is a triangular waveform (not a DC waveform like the output current) some tweaking of the compensation values (RC and CC on the VC pin) may be required to ensure a clean inductor ripple current while the constant-current loop is in effect. For these applications, the constantcurrent loop response can usually be improved by reducing the RC value, or by adding a capacitor (with a value of approximately CC /10) in parallel with the RC and CC compensation network. Frequency Compensation The LT1618 has an external compensation pin (VC), which allows the loop response to be optimized for each application. An external resistor and capacitor (or sometimes just a capacitor) are placed at the VC pin to provide a pole and a zero (or just a pole) to ensure proper loop compensation. Numerous other poles and zeroes are present in the closed L1 loop transfer function of a switching regulator, so the VC pin pole and zero are positioned to provide the best loop response. A thorough analysis of the switching regulator control loop is not within the scope of this data sheet, and will not be presented here, but values of 2kΩ and 10nF will be a good choice for many designs. For those wishing to optimize the compensation, use the 2kΩ and 10nF as a starting point. For LED backlight applications where a pulse-width modulation (PWM) signal is used to drive the IADJ pin, the resistor is usually not included in the compensation network. This helps to provide additional filtering of the PWM signal at the output of the error amplifier (the VC pin). Switch Node Considerations To maximize efficiency, switch rise and fall times are made as short as possible. To prevent radiation and high frequency resonance problems, proper layout of the highfrequency switching path is essential. Keep the output switch (SW pin), diode and output capacitor as close together as possible. Minimize the length and area of all traces connected to the switch pin, and always use a ground plane under the switching regulator to minimize interplane coupling. The high speed switching current path is shown in Figure 3. The signal path including the switch, output diode and output capacitor contains nanosecond rise and fall times and should be kept as short as possible. SWITCH NODE VOUT VIN HIGH FREQUENCY CIRCULATING PATH LOAD 1618 • F03 Figure 3 8 LT1618 U TYPICAL APPLICATIO S 4.5W Direct Broadcast Satellite (DBS) Power Supply with Short-Circuit Protection 3 2 7 ISN SW 9 FB VIN 4 5 R3 10k Q1 FMMT717 ZETEX R1 100k 1 C3 3.3µF SHDN IADJ GND C1 4.7µF L2 33µH ISP LT1618 8 L3 2.2µH D1 ADD 5V 3.3V VC 10 RC 2k R5 24.9k R2 10k D2 MURS110 13.5V/18.5V C4 3.3µF 22kHz NETWORK TUNING Q1 MMBT3904 RHCP LHCP 0V R4 1k CC 33nF C1: TAIYO YUDEN EMK316BJ475 C2: TAIYO YUDEN TMK316BJ105 C3, C4: TAIYO YUDEN TMK325BJ335 D1: ON SEMICONDUCTOR MBRM140 L1, L2: SUMIDA CR54-330 L3: SUMIDA CR43-2R2 (408) 573-4150 (408) 573-4150 (408) 573-4150 (800) 282-9855 (847) 956-0666 (847) 956-0666 1618 TA02a Efficiency 80 75 EFFICIENCY (%) VIN 12V C2 1µF L1 33µH 0.068Ω 70 65 60 0 50 100 150 200 LOAD CURRENT (mA) 250 300 1618 TA02b 9 LT1618 U TYPICAL APPLICATIONS 2-Cell White LED Driver L1 4.7µH VIN 1.6V TO 3V 2.49Ω 20mA Efficiency 9 8 7 VIN SW SHDN ISP 80 4 70 2 ISN R3 5.1k 75 3 R1 2M LT1618 IADJ 1 FB VC GND 5 EFFICIENCY (%) C1 4.7µF 10kHz TO 50kHz PWM BRIGHTNESS ADJUST D1 10 C3 0.1µF C2 1µF R2 160k VIN = 3V 65 VIN = 1.6V 60 55 50 45 CC 0.1µF 40 5 0 C1: TAIYO YUDEN JMK212BJ475 C2: TAIYO YUDEN EMK316BJ105 D1: ON SEMICONDUCTOR MBR0520 L1: SUMIDA CLQ4D10-4R7 (408) 573-4150 (408) 573-4150 (800) 282-9855 (847) 956-0666 10 15 20 LED CURRENT (mA) 1618 TA03b 1618 • TA03a Li Ion White LED Driver L1 10µH VIN 2.7V TO 5V 2.49Ω 20mA Efficiency 80 9 8 7 VIN SW SHDN ISP ISN R3 5.1k LT1618 4 IADJ GND 75 3 2 R1 2M 1 FB VC 5 10 C2 1µF C3 0.1µF VIN = 4.2V 70 EFFICIENCY (%) C1 4.7µF 10kHz TO 50kHz PWM BRIGHTNESS ADJUST D1 VIN = 3.3V 65 VIN = 2.7V 60 55 50 R2 100k 45 CC 0.1µF 40 5 0 10 15 20 LED CURRENT (mA) C1: TAIYO YUDEN JMK212BJ475 C2: TAIYO YUDEN TMK316BJ105 D1: ON SEMICONDUCTOR MBR0530 L1: SUMIDA CLQ4D10-100 (408) 573-4150 (408) 573-4150 (800) 282-9855 (847) 956-0666 1618 TA03b 1618 • TA04a High Power White LED Driver L1 10µH VIN 2.7V TO 5V 0.619Ω Efficiency 80mA 90 9 8 7 VIN SW SHDN ISP ISN R3 5.1k 4 85 VIN = 5V 80 3 2 R1 2M LT1618 IADJ FB VC GND 5 EFFICIENCY (%) C1 4.7µF 10kHz TO 50kHz PWM BRIGHTNESS ADJUST D1 1 C2 1µF CC 0.1µF 70 VIN = 2.7V 65 60 10 C3 0.1µF VIN = 3.3V 75 R2 121k 55 51Ω 51Ω 51Ω 51Ω 50 10 20 30 40 50 60 70 80 OUTPUT CURRENT (mA) C1: TAIYO YUDEN JMK212BJ475 C2: TAIYO YUDEN TMK316BJ105 D1: ON SEMICONDUCTOR MBR0530 L1: SUMIDA CR43-100 10 (408) 573-4150 (408) 573-4150 (800) 282-9855 (847) 956-0666 1618 TA05b 1618 • TA05a LT1618 U TYPICAL APPLICATIO S 12V Boost Converter with 500mA Input Current Limit IL1 L1 10µH 0.1Ω 3 8 9 D1 VOUT 12V 2 7 ISN SW VIN = 5V 1 FB C2 4.7µF R2 107k SHDN IADJ GND 5 85 R1 909k LT1618 4 C1 4.7µF 90 ISP VIN Efficiency EFFICIENCY (%) VIN 1.8V TO 5V VC 10 2k 80 VIN = 3.3V 75 70 65 10nF 60 C1: TAIYO YUDEN JMK212BJ475 C2: TAIYO YUDEN EMK316BJ475 D1: ON SEMICONDUCTOR MBR0520 L1: SUMIDA CR43-100 (408) 573-4150 (408) 573-4150 (800) 282-9855 (847) 956-0666 0 20 60 80 100 120 140 160 L0AD CURRENT (mA) 40 1618 TA06b 1618 • TA06a 12V Boost Converter Start-Up with Input Current Limit (VIN = 1.8V, ILOAD = 40mA) 12V Boost Converter Start-Up without Input Current Limit (VIN = 1.8V, ILOAD = 40mA) VOUT 5V/DIV VOUT 5V/DIV ILI 200mA/DIV ILI 200mA/DIV 50µs/DIV 1618 TA07 50µs/DIV 1618 TA08 U PACKAGE DESCRIPTIO MS10 Package 10-Lead Plastic MSOP (Reference LTC DWG # 05-08-1661) 0.034 (0.86) REF 0.043 (1.10) MAX 0.007 (0.18) 0.118 ± 0.004* (3.00 ± 0.102) 10 9 8 7 6 0° – 6° TYP 0.021 ± 0.006 (0.53 ± 0.015) SEATING PLANE 0.007 – 0.011 (0.17 – 0.27) 0.0197 (0.50) BSC 0.005 ± 0.002 (0.13 ± 0.05) 0.118 ± 0.004** (3.00 ± 0.102) 0.193 ± 0.006 (4.90 ± 0.15) * DIMENSION DOES NOT INCLUDE MOLD FLASH, PROTRUSIONS OR GATE BURRS. MOLD FLASH, PROTRUSIONS OR GATE BURRS SHALL NOT EXCEED 0.006" (0.152mm) PER SIDE ** DIMENSION DOES NOT INCLUDE INTERLEAD FLASH OR PROTRUSIONS. INTERLEAD FLASH OR PROTRUSIONS SHALL NOT EXCEED 0.006" (0.152mm) PER SIDE 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. 1 2 3 4 5 MSOP (MS10) 1100 11 LT1618 U TYPICAL APPLICATIONS USB to 5V SEPIC Converter VIN 5V C1 4.7µF 3 C3 0.47µF L1 10µH 0.1Ω VOUT 5V 2 7 ISN SW 3.3V OFF ON 0V 9 L2 10µH ISP 20k 4 5 75 C2 10µF R2 107k SHDN IADJ GND R1 316k 1 FB VIN Efficiency 80 LT1618 8 D1 VC 10 EFFICIENCY (%) IIN 65 2k 3.3V 100mA 500mA 0V 13k 70 10nF 60 C1: TAIYO YUDEN JMK212BJ475 C2: TAIYO YUDEN JMK316BJ106 C3: TAIYO YUDEN EMK212BJ474 D1: ON SEMICONDUCTOR MBR0520 L1: SUMIDA CR43-100 (408) 573-4150 (408) 573-4150 (408) 573-4150 (800) 282-9855 (847) 956-0666 0 50 100 150 200 250 LOAD CURRENT (mA) 300 350 1618 F09b 1618 • TA09a USB SEPIC During Start-Up USB SEPIC Start-Up with Output Shorted VOUT 2V/DIV VOUT 2V/DIV IIN 50mA/DIV 50mA/DIV 1ms/DIV 1618 TA10 1ms/DIV 1618 TA11 RELATED PARTS PART NUMBER DESCRIPTION COMMENTS LT1307 Single Cell Micropower 600kHz PWM DC/DC Converter 3.3V at 75mA from 1 Cell, MSOP Package TM LT1316 Burst Mode LT1317 2-Cell Micropower DC/DC with Low Battery Detector Operation DC/DC with Programmable Current Limit 3.3V at 200mA from 2 Cells; 600kHz Fixed Frequency 1.5V Minimum, Precise Control of Peak Current Limit LT1610 Single Cell Micropower DC/DC Converter 3V at 30mA from 1V; 1.7MHz Fixed Frequency LT1611 Inverting 1.4MHz Switching Regulator in 5-Lead ThinSOT –5V at 150mA from 5V Input. ThinSOT Package LT1613 1.4MHz Switching Regulator in 5-Lead ThinSOT 5V at 200mA from 3.3V Input. ThinSOT Package LT1615 Micropower DC/DC Converter in 5-Lead ThinSOT 20V at 12mA from 2.5V Input. ThinSOT Package LT1617 Micropower Inverting DC/DC Converter in 5-Lead ThinSOT –15V at 12mA from 2.5V Input. ThinSOT Package LT1930/LT1930A 1.2/2.2MHz Boost DC/DC Converter in ThinSOT 5V at 450mA from 3.3V. ThinSOT Package LT1932 Constant-Current DC/DC LED Driver in ThinSOT Drives 6 White LEDs from 2.7V Burst Mode is a trademark of Linear Technology Corporation. 12 Linear Technology Corporation 1618f LT/TP 0801 2K • PRINTED IN USA 1630 McCarthy Blvd., Milpitas, CA 95035-7417 (408)432-1900 ● FAX: (408) 434-0507 ● www.linear-tech.com LINEAR TECHNOLOGY CORPORATION 2001