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LT1618 Constant-Current/ Constant-Voltage 1.4MHz Step-Up DC/DC Converter
FEATURES
s s s s s s s
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
APPLICATIO S
s s s s
The LT(R)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. Available in the 10-Pin MSOP package, the LT1618 provides a complete solution for constant-current applications.
, LTC and LT are registered trademarks of Linear Technology Corporation.
LED Backlight Drivers USB Powered Boost/SEPIC Converters Input Current Limited Boost/SEPIC Converters Battery Chargers
TYPICAL APPLICATIO
USB to 12V Boost Converter (with Selectable 100mA/500mA Input Current Limit)
VIN 5V 0.1 L1 10H D1 VOUT 12V 7 SW LT1618 8 3.3V OFF ON 0V 20k 9 VIN SHDN IADJ GND 4 3.3V 100mA 500mA 0V 5 VC 10 2k 13k 10nF FB
90 85
2 C1 4.7F 3 ISN ISP
1 R2 107k
C2 4.7F
EFFICIENCY (%)
R1 909k
80 75 70 65 60
0
20
C1: TAIYO YUDEN JMK212BJ475 C2: TAIYO YUDEN EMK316BJ475 D1: ON SEMICONDUCTOR MBR0520 L1: SUMIDA CR43-100
1618 TA01a
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Efficiency Curve
60 80 100 120 140 160 40 LOAD CURRENT (mA)
1618 TA01b
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1
LT1618
ABSOLUTE
(Note 1)
AXI U RATI GS
PACKAGE/ORDER I FOR ATIO
TOP VIEW FB ISN ISP IADJ GND 1 2 3 4 5 10 9 8 7 6 VC SHDN VIN SW N/C
VIN, SHDN Voltage ................................................... 18V SW Voltage .............................................................. 36V ISP, ISN Voltage ...................................................... 36V IADJ Voltage ............................................................... 6V FB Voltage .............................................................. 1.5V VC Voltage .............................................................. 1.5V Junction Temperature ........................................... 125C Operating Temperature Range (Note 2) .. - 40C to 85C Storage Temperature Range ................. - 65C to 150C Lead Temperature (Soldering, 10 sec).................. 300C
ORDER PART NUMBER LT1618EMS MS10 PART MARKING LTNH
MS10 PACKAGE 10-LEAD PLASTIC MSOP TJMAX = 125C, JA = 160C/W
Consult LTC marketing for parts specified with wider operating temperature ranges.
The q denotes specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25C. VIN = 1.6V, VSHDN = 1.6V, unless otherwise noted.
PARAMETER Input Voltage Quiescent Current Reference Voltage Reference Voltage Line Regulation FB Pin Bias Current Error Amplifier Voltage Gain Error Amplifier Transconductance Error Amplifier Sink Current Error Amplifier Source Current Current Sense Voltage (ISP, ISN) ISP, ISN Pin Bias Currents (Note 3) (ISP, ISN) Common Mode Minimum Voltage Switching Frequency Maximum Switch Duty Cycle Switch Current Limit Switch VCESAT ISW = 1A VFB = 1V VFB = 0V
q
ELECTRICAL CHARACTERISTICS
CONDITIONS VSHDN = 1.6V, Not Switching VSHDN = 0V Measured at FB Pin
q
MIN 1.6
TYP 1.8 0.1
MAX 18 2.7 1 1.276 1.283 0.03 12
UNITS V mA A V V %/V nA V/V mho A A
1.250 1.243
1.263 1.263 0.01 2 180 160 15 30
1.6V < VIN < 18V VFB = 1.263V, VIN = 1.8V IC = 5A VFB = 1.35V, VC = 1V VFB = 1.10V, VC = 1V VFB = 0V, VIADJ = 0V VISP = 1.85V, VISN = 1.80V, VIADJ = 0V 1.25 88 1.5
q q
47.5
50 50 1.4 550 92 2.1 200
52.5 80 1.8 1.6
MHz kHz % A mV
2.8 260
2
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mV A V
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WW
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LT1618
The q denotes specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25C. VIN = 1.6V, VSHDN = 1.6V, unless otherwise noted.
PARAMETER Switch Leakage Current SHDN Pin Current Shutdown Threshold (SHDN Pin) Start-Up Threshold (SHDN Pin) 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 0C to 70C. Specifications over the - 40C to 85C operating 1 CONDITIONS Switch Off, VSW = 5V VSHDN = 1.6V MIN TYP 0.01 5 MAX 5 20 0.3 UNITS A A V V
ELECTRICAL CHARACTERISTICS
temperature range are assured by design, characterization, and correlation with statistical process controls. Note 3: Bias currents flow into the ISP and ISN pins.
TYPICAL PERFOR A CE CHARACTERISTICS
Switch Saturation Voltage (VCE, SAT)
500
1.270
SATURATION VOLTAGE (mV)
400 TJ = 125C 300 TJ = 25C 200 TJ = -50C
FEEDBACK VOLTAGE (V)
VOLTAGE
PEAK CURRENT (A)
100
0
0
1.0 0.5 1.5 SWITCH CURRENT (A)
Current Sense Voltage (IADJ Pin = 0V)
52 CURRENT SENSE VOLTAGE (mV)
CURRENT SENSE VOLTAGE (mV) 60 50 40 30 20 10
51
QUIESCENT CURRENT (mA)
50
49
48 - 50 - 25
25 50 75 0 TEMPERATURE (C)
UW
2.0
1618 G01
FB Pin Voltage and Bias Current
4
Switch Current Limit
2.5
1.265
2
2.0
FB PIN BIAS CURRENT (nA)
1.5
1.260 CURRENT
0
1.0
1.255
-2
0.5
1.250 - 50 - 25
75 25 50 0 TEMPERATURE (C)
100
-4 125
0 - 50 - 25
75 25 50 0 TEMPERATURE (C)
100
125
1618 G02
1618 G03
Current Sense Voltage (VISP, ISN)
2.5
Quiescent Current
2.0
VIN = 18V VIN = 1.6V
1.5
1.0
0.5
100
125
0 0.0
0.2
0.4 0.6 0.8 1.0 1.2 IADJ PIN VOLTAGE (V)
1.4
1.6
0 - 50 - 25
25 50 75 0 TEMPERATURE (C)
100
125
1618 G04
1618 G05
1618 G06
3
LT1618 TYPICAL PERFOR A CE CHARACTERISTICS
Switching Frequency
1.8 1.7
SWITCHING FREQUENCY (MHz) 1.6 TJ = 25C 1.4
SWITCHING FREQUENCY (MHz)
SHDN PIN CURRENT (A)
1.6 1.5 1.4 1.3 1.2 1.1 1.0 - 50 - 25 75 25 50 0 TEMPERATURE (C) VIN = 18V VIN = 1.6V
PIN FUNCTIONS
FB (Pin 1): Feedback Pin. Set the output voltage by selecting values for R1 and R2 (see Figure 1): 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. VIN (Pin 8): Input Supply Pin. Bypass this pin with a capacitor to ground as close to the device as possible. SHDN (Pin 9): Shutdown Pin. Tie this pin higher than 1V to turn on the LT1618; tie below 0.3V to turn it off. VC (Pin 10): Compensation Pin for Error Amplifier. Connect a series RC from this pin to ground. Typical values are 2k and 10nF.
V R1 = R2 OUT - 1 1.263V
ISN (Pin 2): Current Sense (-) Pin. The inverting input to the current sense amplifier. ISP (Pin 3): Current Sense (+) Pin. The noninverting input to the current sense amplifier. 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.
4
UW
100
1618 G07
Frequency Foldback
50 45 40 35 30 25 20 15 10 5 0
SHDN Pin Current
1.2 1.0 0.8 0.6 0.4 0.2 0 0.8 0.4 0.6 1.0 FEEDBACK PIN VOLTAGE (V)
TJ = - 50C
TJ = 25C
TJ = 125C
125
0
0.2
1.2
1618 G08
0
5 15 10 SHUTDOWN PIN VOLTAGE (V)
20
1618 G09
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LT1618
BLOCK DIAGRA
VIN C1 9 SHDN 8 VIN 7 SW C2
DRIVER
S Q R A3
5 GND
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
W
L1 D1 RSENSE VOUT Q1 ISP 3 ISN 2 IADJ
+
0.02 x5 A1 x25
+ - +
-
1.4MHz OSCILLATOR
4
+ + -
A2
- - +
R1 1 1.263V R2 FB
10 VC RC CC
Figure 1. LT1618 Block Diagram
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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 25x 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
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 4.7H or 10H inductor will be a good choice for many LT1618 designs.
Table 1. Recommended Inductors L MAX PART (H) (m)
CDRH5D18-4R1 CDRH5D18-100 CR43-2R2 CR43-4R7 CR43-100 CR54-100 LQH3C1R0M24 LQH3C2R2M24 LQH3C4R7M24 4.1 10 2.2 4.7 10 10 1.0 2.2 4.7 57 124 71 109 182 100 78 126 260
HEIGHT (mm)
2.0 2.0 3.5 3.5 3.5 4.8 2.0 2.0 2.0
VENDOR
Sumida (847) 956-0666 www.sumida.com
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 4.7F to 10F output capacitor is sufficient for high output current designs. Converters with lower output currents may need only a 1F or 2.2F 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
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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 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. Recommended Ceramic Capacitor Manufacturers VENDOR PHONE URL
Taiyo Yuden Murata Kemet (408) 573-4150 (814) 237-1431 (408) 986-0424 www.t-yuden.com www.murata.com 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 UPS120 UPS130 UPS140 MBRM120 MBR0520 MBRM130 MBR0530 MBRM140 MBR0540 B120 B130 B140 B0520 B0530 B0540 0.5A PART VENDOR Microsemi PHONE/URL (510) 353-0822 www.microsemi.com
ON Semiconductor (800) 282-9855 www.onsemi.com Diodes, Inc (805) 446-4800 www.diodes.com
LT1618
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. Selecting RSENSE/Current Sense Adjustment 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,
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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 (2M) 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.
LT1618
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
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 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 2k and 10nF will be a good choice for many designs. For those wishing to optimize the compensation, use the 2k 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.
L1
VIN
8
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SWITCH NODE VOUT
HIGH FREQUENCY CIRCULATING PATH
LOAD
1618 * F03
Figure 3
LT1618
TYPICAL APPLICATIO S
4.5W Direct Broadcast Satellite (DBS) Power Supply with Short-Circuit Protection
L1 33H C2 1F D1 L3 2.2H
VIN 12V
0.068
2 3 8 9 ISN ISP LT1618 VIN SHDN IADJ GND C1 4.7F 4 5
SW
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
EFFICIENCY (%)
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7 FB VC
L2 33H
R1 100k C3 3.3F ADD 5V 3.3V R5 24.9k R2 10k C4 3.3F Q1 MMBT3904
R3 10k Q1 FMMT717 ZETEX
D2 MURS110 13.5V/18.5V
1
22kHz NETWORK TUNING R4 1k
10 RC 2k CC 33nF
RHCP LHCP 0V
(408) 573-4150 (408) 573-4150 (408) 573-4150 (800) 282-9855 (847) 956-0666 (847) 956-0666
1618 TA02a
Efficiency
80
75
70
65
60
0
50
100 150 200 LOAD CURRENT (mA)
250
300
1618 TA02b
9
LT1618
TYPICAL APPLICATIONS
2-Cell White LED Driver
VIN 1.6V TO 3V C1 4.7F 9 10kHz TO 50kHz PWM BRIGHTNESS ADJUST 8 VIN SHDN L1 4.7H D1 2.49 20mA
R3 5.1k
EFFICIENCY (%)
4
IADJ GND 5
C3 0.1F CC 0.1F 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
Li Ion White LED Driver
VIN 2.7V TO 5V C1 4.7F 9 10kHz TO 50kHz PWM BRIGHTNESS ADJUST 8 VIN SHDN L1 10H D1 2.49 20mA
EFFICIENCY (%)
R3 5.1k
4 IADJ GND 5
C3 0.1F CC 0.1F 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
High Power White LED Driver
VIN 2.7V TO 5V C1 4.7F 9 10kHz TO 50kHz PWM BRIGHTNESS ADJUST 8 VIN SHDN L1 10H D1 0.619 80mA
SW ISP ISN
2 R1 2M
EFFICIENCY (%)
R3 5.1k
4
LT1618 IADJ GND 5 FB VC 10 C2 1F CC 0.1F 1
C3 0.1F
C1: TAIYO YUDEN JMK212BJ475 C2: TAIYO YUDEN TMK316BJ105 D1: ON SEMICONDUCTOR MBR0530 L1: SUMIDA CR43-100
(408) 573-4150 (408) 573-4150 (800) 282-9855 (847) 956-0666
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Efficiency
7 SW ISP ISN LT1618 FB VC 10 C2 1F R2 160k 1 3 2 R1 2M
80 75 70 VIN = 3V 65 60 55 50 45 40 0 5 10 LED CURRENT (mA)
1618 TA03b
1618 * TA03a
VIN = 1.6V
15
20
Efficiency
80 75
7 SW ISP ISN LT1618 FB VC 10 C2 1F R2 100k 3 2 1 R1 2M
70 65 60 55 50 45 40 0 5 10
VIN = 4.2V VIN = 3.3V VIN = 2.7V
15
20
1618 TA03b
LED CURRENT (mA)
1618 * TA04a
Efficiency
90 85 VIN = 5V
3
80 75 70 65 60
R2 121k 51 51 51 51
VIN = 3.3V
VIN = 2.7V
55 50 10 20 30 40 50 60 70 80 OUTPUT CURRENT (mA)
1618 TA05b
1618 * TA05a
LT1618
TYPICAL APPLICATIO S
12V Boost Converter with 500mA Input Current Limit
VIN 1.8V TO 5V IL1 0.1 L1 10H D1 VOUT 12V 2 3 8 9 ISN ISP LT1618 VIN SHDN IADJ GND C1 4.7F 4 5 VC 10 2k 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 40 60 80 100 120 140 160 L0AD CURRENT (mA)
1618 TA06b
FB
EFFICIENCY (%)
12V Boost Converter Start-Up with Input Current Limit (VIN = 1.8V, ILOAD = 40mA)
VOUT 5V/DIV
ILI 200mA/DIV
50s/DIV
PACKAGE DESCRIPTIO
0.007 (0.18) 0.021 0.006 (0.53 0.015)
0 - 6 TYP SEATING PLANE 0.007 - 0.011 (0.17 - 0.27) 0.193 0.006 (4.90 0.15) 0.118 0.004** (3.00 0.102)
* 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.
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Efficiency
90 VIN = 5V
7 SW R1 909k 1 R2 107k C2 4.7F
85 80 75 70 65 VIN = 3.3V
1618 * TA06a
12V Boost Converter Start-Up without Input Current Limit (VIN = 1.8V, ILOAD = 40mA)
VOUT 5V/DIV
ILI 200mA/DIV
1618 TA07
50s/DIV
1618 TA08
MS10 Package 10-Lead Plastic MSOP
(Reference LTC DWG # 05-08-1661)
0.043 (1.10) MAX 0.034 (0.86) REF 0.118 0.004* (3.00 0.102) 10 9 8 7 6
0.0197 (0.50) BSC
0.005 0.002 (0.13 0.05)
12345
MSOP (MS10) 1100
11
LT1618
TYPICAL APPLICATIONS
USB to 5V SEPIC Converter
IIN VIN 5V 0.1 L1 10H C3 0.47F D1 VOUT 5V 2 C1 4.7F 3 8 3.3V OFF ON 0V 9 20k ISN ISP LT1618 VIN SHDN IADJ GND 4 3.3V 100mA 500mA 0V 5 VC 10 2k 13k 10nF FB 1 R2 107k 7 SW
EFFICIENCY (%)
C1: TAIYO YUDEN JMK212BJ475 C2: TAIYO YUDEN JMK316BJ106 C3: TAIYO YUDEN EMK212BJ474 D1: ON SEMICONDUCTOR MBR0520 L1: SUMIDA CR43-100
USB SEPIC During Start-Up
VOUT 2V/DIV
VOUT 2V/DIV
IIN 50mA/DIV
1618 TA10
1ms/DIV
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Burst Mode is a trademark of Linear Technology Corporation.
12
Linear Technology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408)432-1900 q FAX: (408) 434-0507 q www.linear-tech.com
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Efficiency
80
L2 10H
R1 316k C2 10F
75
70
65
60
(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 Start-Up with Output Shorted
50mA/DIV
1ms/DIV
1618 TA11
COMMENTS 3.3V at 75mA from 1 Cell, MSOP Package 1.5V Minimum, Precise Control of Peak Current Limit 3.3V at 200mA from 2 Cells; 600kHz Fixed Frequency 3V at 30mA from 1V; 1.7MHz Fixed Frequency -5V at 150mA from 5V Input. ThinSOT Package 5V at 200mA from 3.3V Input. ThinSOT Package 20V at 12mA from 2.5V Input. ThinSOT Package -15V at 12mA from 2.5V Input. ThinSOT Package 5V at 450mA from 3.3V. ThinSOT Package Drives 6 White LEDs from 2.7V
1618f LT/TP 0801 2K * PRINTED IN USA
(c) LINEAR TECHNOLOGY CORPORATION 2001

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