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LT3479 3A, Full Featured DC/DC Converter with Soft-Start and Inrush Current Protection FEATURES
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DESCRIPTION
The LT(R)3479 is a current mode, fixed frequency step-up DC/DC converter with an internal 3A, 42V switch. Efficiencies of up to 89% can be achieved in typical applications. It features a programmable soft-start function to limit inductor current during start-up and inrush current protection to protect the LT3479 during shorts and line transients. Both inputs of the error amplifier are available to the user allowing positive and negative output voltages. Through an external resistor, the user can program the switching frequency from 200kHz to 3.5MHz. The low profile (0.75mm) 14-pin, 4mm x 3mm DFN package provides excellent thermal performance in a small footprint. The LT3479 is also available in a thermally enhanced 16-pin TSSOP package.
L, LT, LTC and LTM are registered trademarks of Linear Technology Corporation. All other trademarks are the property of their respective owners.
Wide Input Voltage Range: 2.5V to 24V 3A, 42V Internal Switch High Efficiency Power Conversion: Up to 89% Soft-Start Frequency Set by External Resistor: 200kHz to 3.5MHz Protection Against Input Short Circuits and Hot Plugging Low VCESAT Switch: 0.3V at 2.5A (Typical) Capable of Positive and Negative Outputs Available in Thermally Enhanced 14-Lead (4mm x 3mm) DFN and 16-Lead TSSOP Packages
APPLICATIONS
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High Power LED Driver DSL Modems Distributed Power
TYPICAL APPLICATION
5V to 12V Boost Converter
4.7H VIN 5V 2.2F VIN VS L SHDN LT3479 SS 10nF RT GND 17.8k FBP VC 10k 2.2nF
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5V to 12V Efficiency
VOUT 12V 0.8A 90 85 EFFICIENCY (%) 80 75 70 65 60
200k SW FBN 23.2k VREF
10F
0
0.2
0.4 IOUT (A)
0.6
0.8
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LT3479 ABSOLUTE MAXIMUM RATINGS
(Note 1)
SW, L, VS Voltages ................................................... 42V VIN, SHDN Voltages ................................................. 24V FBP FBN, VREF, RT, VC Voltages ................................. 2V , Junction Temperature .......................................... 125C
Operating Temperature Range (Note 2).... -40C to 85C Storage Temperature Range................... -65C to 125C Lead Temperature (Soldering, 10 sec) TSSOP .............................................................. 300C
PIN CONFIGURATION
TOP VIEW TOP VIEW SW SW L VS VIN RT SHDN 1 2 3 4 5 6 7 15 14 GND 13 GND 12 SS 11 VC 10 FBN 9 8 FBP VREF SW SW L VS VIN RT SHDN GND DE14 PACKAGE 14-LEAD (4mm 3mm) PLASTIC DFN TJMAX = 125C, JA = 43C/W EXPOSED PAD (PIN 15) IS PGND (MUST BE SOLDERED TO PCB) 1 2 3 4 5 6 7 8 17 16 GND 15 GND 14 GND 13 SS 12 VC 11 FBN 10 FBP 9 VREF
FE PACKAGE 16-LEAD PLASTIC TSSOP TJMAX = 125C, JA = 38C/W EXPOSED PAD (PIN 17) IS PGND (MUST BE SOLDERED TO PCB)
ORDER INFORMATION
LEAD FREE FINISH LT3479EDE#PBF LT3479EFE#PBF LEAD BASED FINISH LT3479EDE LT3479EFE TAPE AND REEL LT3479EDE#TRPBF LTC4263IDE#TRPBF TAPE AND REEL LT3479EDE#TR LT3479EFE#TR PART MARKING 3479 3479EFE PART MARKING 3479 3479EFE PACKAGE DESCRIPTION 14-Lead (4mm x 3mm) Plastic DFN 16-Lead Plastic TSSOP PACKAGE DESCRIPTION 14-Lead (4mm x 3mm) Plastic DFN 16-Lead Plastic TSSOP TEMPERATURE RANGE -40C to 85C -40C to 85C TEMPERATURE RANGE -40C to 85C -40C to 85C
Consult LTC Marketing for parts specified with wider operating temperature ranges. 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/
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LT3479 ELECTRICAL CHARACTERISTICS
PARAMETER Minimum Input Voltage Quiescent Current Reference Voltage Reference Voltage Line Regulation Maximum VREF Pin Current Soft-Start Pin Current FBP Pin Bias Current FBN Pin Bias Current Feedback Amplifier Offset Voltage Feedback Amplifier Voltage Gain Feedback Amplifier Transconductance Feedback Amplifier Sink Current Feedback Amplifier Source Current Switching Frequency VFBP = 1.25V, VFBN = 1.5V, VC = 0.5V VFBP = 1.25V, VFBN = 1V, VC = 0.5V RT = 17.8k RT = 113k RT = 1.78k RT = 17.8k VSHDN = 5V VSHDN = 0V 0.3 (Note 3) (Note 3) ISW = 1A (Note 3) SW = 40V 3.5 3
l
The l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25C. VIN = 2.5V, VSHDN = 2.5V.
CONDITIONS
l
MIN
TYP 2.3 0.1 5
MAX 2.5 1 7.5 1.250 0.03 100
UNITS V A mA V %/V A A nA nA mV V/V S A A
VIN = 2.5V, VSHDN = 0V VIN = 2.5V, VSHDN = 2.5V, VC = 0.3V (Not Switching) Measured at VREF Pin 2.5V < VIN < 24V, VC = 0.3V Out of Pin SS = 0.5V, Out of Pin
l
1.216
1.235 0.01 9 25 25
100 100 6
FBP - FBN, VC = 1V
-2
2 250 150 10 10
0.9 160 2.7 84
1 200 3.5 93 30 0.1 1.5 5 4.5 120 0.2
1.15 240 4.1 60 1 2 6.5 6 200 5
MHz kHz MHz % A A V A A mV A
Maximum Switch Duty Cycle SHDN Pin Current SHDN Pin Threshold Inductor Current Limit Switch Current Limit Switch VCESAT Switch Leakage Current
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 LT3479 is guaranteed to meet performance specifications from 0C to 70C. Specifications over the -40C to 85C operating
temperature range are assured by design, characterization and correlation with statistical process controls. Note 3: Inductor Current Limit, Switch Current Limit and Switch VCESAT for DE package guaranteed by design and/or correlation to static test.
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LT3479 TYPICAL PERFORMANCE CHARACTERISTICS
Switch VCE(SAT)
0.5 6 INDUCTOR CURRENT LIMIT 0.4 125C 0.3 25C -50C 0.2 CURRENT (A) VCE(SAT) (V) 5 4 3 2 0.1 1 0 -50 -25 SWITCH CURRENT LIMIT VREF (V) 1.26 1.25 VIN = 24V 1.24 VIN = 2.5V 1.23 1.22 1.21 -50 -25
Inductor and Switch Current Limit
1.27
VREF
0 0 0.5 1 1.5 2 SWITCH CURRENT (A) 2.5 3
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50 25 75 0 TEMPERATURE (C)
100
125
0
25 50 75 100 125 150 TEMPERATURE (C)
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SHDN Pin Turn-On Threshold
1.750 50
SHDN Pin Current
6 -50C VIN PIN CURRENT (mA)
VIN Pin Current
VC = 0.3V
SHDN THRESHOLD (V)
1.625
SHDN PIN CURRENT (A)
40 5
30
25C
1.500
4
20
125C
1.375
10
3
1.250 -50
0 -25 75 0 25 50 TEMPERATURE (C) 100 125
0
4
8
12 VSHDN (V)
16
20
24
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2 -50 -25
0
25 50 75 100 125 150 TEMPERATURE (C)
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Soft-Start Pin Current
20 2.0
Oscillator Frequency
5 RT = 10k OFFSET VOLTAGE (mV)
Feedback Amplifier Offset Voltage
15 FREQUENCY (MHz)
1.6
4 VC = 0.5V 3
ISS (A)
1.2
RT = 15k
10
0.8
RT = 20k
2
VC = 1V
5 0.4
1
0 -50 -25
0
25 50 75 100 125 150 TEMPERATURE (C)
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0 -50 -25
0
25 50 75 100 125 150 TEMPERATURE (C)
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0 -50
-25
0 25 50 TEMPERATURE ( C)
75
100
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LT3479 PIN FUNCTIONS
(DFN/TSSOP)
SW (Pins 1, 2/Pins 1, 2): Switch Pins. Collector of the internal NPN power switch. Connect the inductor and diode here and minimize the metal trace area connected to this pin to minimize electromagnetic interference. L (Pin 3/Pin 3): Inductor Pin. Connect the inductor to this pin. VS (Pin 4/Pin 4): Inductor Supply. Must be locally bypassed. Powers the switch and the inductor. In case only one supply voltage is available, tie VIN and VS together. VIN (Pin 5/Pin 5): Input Supply. Must be locally bypassed. Powers the internal control circuitry. RT (Pin 6/Pin 6): Timing Resistor Pin. Adjusts the switching frequency. Do not leave this pin open. See Table 4 for RT values and switching frequencies. SHDN (Pin 7/Pin 7): Shutdown. Tie to 1.5V or greater to enable the device. Tie below 0.3V to turn off the device. VREF (Pin 8/Pin 9): Bandgap Voltage Reference. Internally set to 1.235V. Connect this pin to FBP if generating a positive output, or to an external resistor divider if generating a negative voltage. This pin can provide up to 100A of current and can be locally bypassed with a 100pF capacitor.
FBP (Pin 9/Pin 10): The Noninverting Input to the Error Amplifier. Connect resistive divider tap here for negative output voltage. FBN (Pin 10/Pin 11): The Inverting Input to the Error Amplifier. Connect resistive divider tap here for positive output voltage. VC (Pin 11/Pin 12): Compensation Pin for Error Amplifier. Connect a series RC from this pin to GND. Typical values are 10k and 2.2nF. SS (Pin 12/Pin 13): Soft-Start. Place a soft-start capacitor here. Leave floating if not in use. GND (Pins 13, 14/Pins 8, 14, 15, 16): Ground. Tie directly to local ground plane. Exposed Pad (Pin 15/Pin 17): Power Ground. Must be connected to electrical PCB ground.
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LT3479 BLOCK DIAGRAM
RC CSS CC CS L1 D1 C1 FB SS FBP FEEDBACK AMPLIFIER INRUSH CURRENT PROTECTION COMPARATOR VS 8.5mW L SW R2 R1
+ -
+
FBN VC
+ -
36mV
-
VREF SHDN VIN CIN RT RT t t 1.25V REFERENCE ICON
+
pwmout
MASTER LATCH R S Q
DRIVER Q1
SLOPE
-
PWM COMPARATOR
+ -
GND
OSCILLATOR CURRENT LIMIT COMPARATOR
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LT3479 OPERATION
The LT3479 uses a fixed frequency, current mode control scheme to provide excellent line and load regulation. Operation can be best understood by referring to the Block Diagram. The start of each oscillator cycle sets the SR latch and turns on power switch Q1. The signal at the inverting input of the PWM comparator (SLOPE) is proportional to the sum of the switch current and oscillator ramp. When SLOPE exceeds VC (the output of the feedback amplifier), the PWM comparator resets the latch and turns off the power switch. In this manner, the feedback amplifier and PWM comparators set the correct peak current level to keep the output in regulation. The LT3479 also features a soft-start function. During start-up, 10A of current charges the external soft-start capacitor. The SS pin directly limits the rate of voltage rise on the VC pin, which in turn limits the peak switch current. The switch current is constantly monitored and not allowed to exceed the nominal value of 3A. If the switch current reaches 3A, the SR latch is reset regardless of the output of the PWM comparator. Current limit protects the power switch and external components. Soft-start plays an important role in applications where the switch will reach levels of 30V or higher. During startup, an overshoot in the switch current together with the presence of high switch voltage can overstress the switch. A properly used soft-start feature will greatly improve the robustness of such designs. In addition to soft-start, inrush current protection protects the LT3479 against shorts and line transients. During such faults, the inductor current can momentarily exceed 3A and damage the switch. Through an internal 8.5m resistor placed in series with the inductor, the inrush current protection comparator measures the inductor current. If it exceeds 5A, a soft-start cycle is initiated. The LT3479 will remain in the soft-start condition until the fault has passed.
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LT3479 APPLICATIONS INFORMATION
Capacitor Selection Low ESR (equivalent series resistance) ceramic capacitors should be used at the output to minimize the output ripple voltage. Use only X5R or X7R dielectrics, as these materials retain their capacitance over wider voltage and temperature ranges better than other dielectrics. A 4.7F to 10F output capacitor is sufficient for most high output current designs. Converters with lower output currents may need only a 1F or 2.2F output capacitor.
Table 1. Ceramic Capacitor Manufacturers
MANUFACTURER Taiyo Yuden AVX Murata PHONE (408) 573-4150 (803) 448-9411 (714) 852-2001 WEB www.t-yuden.com www.avxcorp.com www.murata.com
can pass a current larger than its rated value without damaging it. Aggressive designs where board space is precious will exceed the maximum current rating of the inductor to save board space. Consult each manufacturer to determine how the maximum inductor current is measured and how much more current the inductor can reliably conduct. Physically larger inductors provide better efficiency than smaller ones. Figure 1 shows a 3% to 4% efficiency gain in using a larger inductor in a 1MHz, 5V to 12V application. The efficiency of the TOKO FDV0630-4R7M, which measures 7mm x 7.7mm and 3 mm thick, peaks at 87%. The smaller Sumida CDRH4D28-4R7 which is 5mm x 5mm and 3mm thick yields a peak efficiency of 85% in an identical application. Thus, if board space is abundant, then larger inductors should be used to maximize efficiency.
90 85 80 EFFICIENCY (%) TOKO FDV0630-4R7 75 SUMIDA CDRH4D28-4R7 70 65 60 55 50 0 0.2 0.4 IOUT (A)
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Inductor Selection Several inductors that work well with the LT3479 are listed in Table 2. However, there are many other manufacturers and devices that can be used. Consult each manufacturer for more detailed information and their entire range of parts. Ferrite core inductors should be used to obtain the best efficiency. 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 suffice for most LT3479 applications. Inductor manufacturers specify the maximum current rating as the current where the inductance falls to some percentage of its nominal value--typically 65%. An inductor
Table 2. Suggested Inductors
MANUFACTURER PART NUMBER CDRH6D283R0 CDRH6D28100 CDRH4D284R7 LM N 05D B4R7M LM N 05D B100K LQH55DN4R7M01L LQH55DN100M01K FDV0630-4R7M IDC (A) 3 1.7 1.32 2.2 1.6 2.7 1.7 4.2 INDUCTANCE (H) 3 10 4.7 4.7 10 4.7 10 4.7
0.6
0.8
Figure 1. Efficiency vs Inductor Size
MAX DCR (m) 24 65 72 49 10 57 130 49
LxWxH (mm) 6.7 x 6.7 x 3.0 6.7 x 6.7 x 3.0 5.0 x 5.0 x 3.0 5.9 x 6.1 x 2.8 5.9 x 6.1 x 2.8 5.7 x 5.0 x 4.7 5.7 x 5.0 x 4.7 7.0 x 7.7 x 3.0
MANUFACTURER Sumida www.sumida.com Taiyo Yuden www.t-yuden.com Murata www.murata.com Toko www.toko.com
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LT3479 APPLICATIONS INFORMATION
Diode Selection Schottky diodes, with their low forward voltage drop and fast switching speed, are ideal for LT3479 applications. Table 3 lists several Schottky diodes that work well with the LT3479. The diode's average current rating must exceed the average output current. The diode's maximum reverse voltage must exceed the output voltage. The diode conducts current only when the power switch is turned off (typically less than 50% duty cycle), so a 3A diode is sufficient for most designs. The companies below also offer Schottky diodes with high voltage and current ratings.
Table 3. Suggested Diodes
MANUFACTURER MAX MAX REVERSE PART NUMBER CURRENT (A) VOLTAGE (V) MANUFACTURER UPS340 UPS315 B220 B230 B240 B320 B330 B340 SBM340 3 3 2 2 2 3 3 3 3 40 15 20 30 40 20 30 40 40 Microsemi www.microsemi.com Diodes, Inc www.diodes.com
Setting Negative Output Voltages To set a negative output voltage, select the values of R3 and R4 (see Figure 3) according to the following equation: R3 VOUT = -1.235V R4
-VOUT R3 FBP LT3479 VREF FBN
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R4
Figure 3. Negative Output Voltage Feedback Connections
Board Layout As with all switching regulators, careful attention must be paid to the PCB board layout and component placement. 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 high frequency switching path is essential. Minimize the length and area of all traces connected to the SW pin and always use a ground plane under the switching regulator to minimize interplane coupling. The signal path including the switch, output diode D1 and output capacitor COUT, contains nanosecond rise and fall times and should be kept as short as possible. Recommended component placement is shown in Figure 4. Soft-Start For many applications, it is necessary to minimize the inrush current at start-up. The built-in soft-start circuit significantly reduces the start-up current spike and output voltage overshoot. A typical value is 10nF for 1.65ms. Figure 5 shows the start-up output voltage and inductor current waveforms in a typical application without a soft-start capacitor. Notice the output voltage overshoot and the large initial current. The addition of a 22nF capacitor eliminates the output overshoot and reduces the peak inductor current (Figure 6).
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Setting Positive Output Voltages To set a positive output voltage, select the values of R1 and R2 (see Figure 2) according to the following equation: R1 VOUT = 1.235V 1 + R2
FBP LT3479 VREF R1 FBN R2
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VOUT
Figure 2. Positive Output Voltage Feedback Connections
9
LT3479 APPLICATIONS INFORMATION
MINIMIZE THE AREA OF THIS TRACE TO VOUT
D
COUT L1 CC
SW SW TO VS L VS VIN TO VIN CS CIN RT RT SHDN LT3479
GND GND SS VC FBN FBP VREF R1 CSS RC
R2 TO GND
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TO SHDN
PLACE VIAS AROUND EXPOSED PAD TO ENHANCE THERMAL PERFORMANCE
Figure 4. Suggested Board Layout
Switching Frequency
IL 2A/DIV
VOUT 5V/DIV 0.2MS/DIV
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The switching frequency of the LT3479 is set by an external resistor attached to the RT pin. Do not leave this pin open. A resistor must always be connected for proper operation. See Table 4 and Figure 7 for resistor values and corresponding frequencies.
Table 4. Switching Frequency
SWITCHING FREQUENCY (MHz) 3.5 3 RT (k) 1.78 2.87 4.32 6.49 10.2 17.8 39.2 113
Figure 5. Start-Up with No Soft-Start Capacitor
IL 2A/DIV
2.5 2 1.5 1
VOUT 5V/DIV 0.2ms/DIV
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0.5 0.2
Figure 6. Start-Up with CSS = 22nF
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LT3479 APPLICATIONS INFORMATION
Increasing switching frequency reduces output voltage ripple but also reduces efficiency. The user should set the frequency for the maximum tolerable output voltage ripple. Figure 8 shows a reduction in efficiency of about 4% between 1MHz and 2MHz operation in a typical application. Inrush Current Protection The LT3479 features a novel inductor current sensing circuit that protects the LT3479 during hot plugging and short circuits. An internal resistor in series with the external inductor senses the inductor current at all times. When it exceeds 5A, a soft-start cycle is initiated. Figure 9
3.5 3.0 SWITCH FREQUENCY (MHz) 2.5 2.0 1.5 1.0 0.5 0 0.1 VSW 10V/DIV IL 4V/DIV VSS 2V/DIV VOUT 20V/DIV 20s/DIV
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shows an output overload with inrush current protection disabled. Notice that soft-start remains high, and that the inductor current does not return to zero. Figure 10 illustrates the benefits of inrush current protection. The output short initiates a new soft start cycle reducing the inductor current. After the fault has passed, the inductor current slowly returns to its equilibrium value. To ensure bond wire integrity, the inductor current should not exceed 8A for more than 10ms. Bypassing the 8.5m inductor current sense resistor disables inrush current protection. Connect the inductor supply trace and bypass capacitor to the L pin and leave the VS pin open to disable this feature.
10 RT (k)
100
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Figure 9. Output Overload with Inrush Current Protection Enabled
Figure 7. Switching Frequency
90 85 80 EFFICIENCY (%) 75 70 65 60 55 1MHz 2MHz
VSW 10V/DIV IL 4V/DIV VSS 2V/DIV VOUT 20V/DIV 20s/DIV
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Figure 10. Output Overload with Inrush Current Protection Disabled
VIN VOUT 0.5
50 0 0.2 0.4 IOUT (A)
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0.6
0.8
LT3479 BOOST REGULATOR
Figure 8. Efficiency vs Switching Frequency
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Figure 11. Circuit for Output Overload
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LT3479 TYPICAL APPLICATIONS
5V to 12V/800mA 1MHz Boost Converter
L1 4.7H C1 2.2F VIN VS L SHDN LT3479 SS RT 10nF GND 17.8k FBP VC 10k 50 2.2nF
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Efficiency
90 VOUT 12V 0.8A EFFICIENCY (%) 85 80 75 70 65 60 55 0 0.2 0.4 IOUT (A)
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D1 C2 10F
VIN 5V
200k SW FBN 23.2k VREF
0.6
0.8
C1: TAIYO YUDEN LMK316BJ225MD C2: AVX 1206 YD106MAT D1: DIODES INC B320A L1: TOKO FDV0630-4R7M
5V to 12V/800mA 500kHz Boost Converter
L1 10H C1 2.2F D1 C2 10F 90 VOUT 12V 0.8A EFFICIENCY (%) 85 80 75 70 65 60 55 10nF 39.2k 4.7k 50 10nF
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Efficiency
VIN 5V
200k VIN VS L SHDN LT3479 SS RT GND FBP VC VREF SW FBN 23.2k
0
0.2
0.4 IOUT (A)
0.6
0.8
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C1: TAIYO YUDEN LMK316BJ225MD C2: AVX 1206 YD106MAT D1: DIODES INC. B320A L1: SUMIDA CDRH8D43-100
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LT3479 TYPICAL APPLICATIONS
3.3V to 8V/900mA Boost Converter
L1 4.7H C1 2.2F VIN VS L SHDN LT3479 SS RT 10nF GND 17.8k FBP VC 4.3k 50 10nF
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Efficiency
90 VOU 8V 0.9A EFFICIENCY (%) 85 80 75 70 65 60 55 0 0.2 0.4 IOUT (A)
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D1 C2 10F
VIN 3.3V
169k SW FBN 30.9k VREF
0.6
0.8
C1: TAIYO YUDEN LMK316BJ225MD C2: AVX 1206 YD106MAT D1: DIODES INC B320A L1: TOKO FDV0630-4R7M
5V to -5V/600mA Inverting DC/DC Converter
L1 4.7H C1 2.2F VIN VS L SHDN LT3479 SS RT 10nF GND 17.8k FBN VC 1k 15nF
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Efficiency
90
C2 2.2F
D2 D1
VIN 5V
EFFICIENCY (%)
SW FBP 100k VREF 100pF
402k
C3 10F
VOUT -5V 600mA
85 80 75 70 65 60 55 50 0 0.2 0.4 IOUT (A)
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D3
0.6
0.8
C1, C2: TAIYO YUDEN LMK316BJ225MD C3: AVX 1206 YD106MAT D1, D2: DIODES INC B320A D3: CENTRAL SEMI, CMDSH-3-LTC L1: TOKO FDV0630-4R7M
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LT3479 TYPICAL APPLICATIONS
500mA, 12 White LED Driver
L1 4.7H C1 2.2F VIN VS L ON SHDN SS LT3479 SW M1 FBN VREF 124k FBP RT 10nF GND VC 10k 2.2nF C1, C2: TAIYO YUDEN LMK316BJ225MD D1: PHILIPS PMEG 2010 D2, D3: LUMILEDS LXHL-PW01 L1: SUMIDA CDRH4D28-4R7 M1: VISHAY SILICONIX Si2302ADS 10k
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D1 D2 D3 ON C2 2.2F
VIN 2.8V TO 4.2V
600mA
0.15
7.5k
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LT3479 TYPICAL APPLICATIONS
500mA, 12 White LED Driver
L1 10H C1 4.7F D2 VIN VS L SHDN SS LT3479 SW 100k FBN VREF 93.1k FBP RT 10nF GND VC 10k 3.3nF C1: TAIYO YUDEN EMK316BJ475ML C2: TAIYO YUDEN TMK325BJ475ML D1: DIODES INC B330B D2: LUMILEDS LXHL-NW99 L1: SUMIDA CDRH8D28-100 ILED 500mA 0.150
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D1
VIN 8V TO 16V
VOUT 16V TO 24V C2 4.7F
5.9k 1 1
17.8k
Efficiency
100 VIN = 12V VIN = 16V VIN = 8V 80
90 EFFICIENCY (%)
70
60
50
0
0.1
0.2
0.3 IOUT (A)
0.4
0.5
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LT3479 TYPICAL APPLICATIONS
8V, 16V, -8V Triple Output Power Supply for TFTLCD Panels
D2B C5 0.1F C3 1F 16V 10mA 8V 700mA 100k VIN VS L SHDN LT3479 SS 10nF RT GND 17.8k FBP VC 10k D3B 2.2nF C1: AVX 0805ZD475MAT C2: AVX 1210YD226MAT C3 TO C6: X5R/X7R 10V D1: MBRM120 OR EQUIVALENT D2, D3: BAT54S OR EQUIVALENT L1: SUMIDA CDRH4D28-3R3 D3A VREF C4 1F -8V 10mA SW FBN C6 0.1F 18.7k C2 22F
VIN 2.8V TO 4.2V
L1 3.3H C1 4.7F
D1
D2A
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Efficiency
100
90 EFFICIENCY (%)
80
70
60
50 0 0.1 0.2 0.3 0.4 0.5 LOAD CURRENT (A) 0.6 0.7
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LT3479 TYPICAL APPLICATIONS
1A Dual Tracking Power Supply with Adjustable Outputs
L1 15H 4.7F 16V VIN VS L SHDN SHDN SS LT3479 SW 470pF FBN VREF 5.76k FBP RT GND VC 10nF 10.2k 4.99k 3.3nF 470pF L3 15H 4.7F 16V VIN VS L SHDN SS LT3479 SW FBN VREF FBP RT GND VC 4.99k 3.3nF
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1F 16V
D1
VIN 10V TO 14V
VOUT 7V TO 10V 1A 30F 16V 10.2k
L2 15H
VCTRL 0V-2.5V 26.1k
1.13k
10k
1F 16V
L4 15H 30F 16V
11.3k VOUT -7V TO -10V 1A
D2
D3 D1, D2: DIODES INC DFLS230 2A, 30V D3: PHILIPS 1PS79SB62 L1-L4: SUMIDA CDRH6D38-150 ALL CAPACITORS X5R/X7R DIELECTRIC OR EQUIVALENT
20nF
10.2k
Efficiency
80 75 EFFICIENCY (%) 70 VIN = 14V, VOUT = 7V 65 60 55 50 VIN =14V, VOUT = 10V VIN =10V, VOUT = 7V
0
0.2
0.4 0.6 IOUT (A)
0.8
1.0
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LT3479 PACKAGE DESCRIPTION
DE Package 14-Lead Plastic DFN (4mm x 3mm)
(Reference LTC DWG # 05-08-1708)
0.65
0.05
3.50
0.05 2.20
1.70 0.05 0.05 (2 SIDES) PACKAGE OUTLINE 0.25 0.50 BSC 3.30 0.05 (2 SIDES) RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS 4.00 0.10 (2 SIDES) R = 0.20 TYP R = 0.115 TYP 8 14 0.38 0.10 0.05
3.00 0.10 (2 SIDES) PIN 1 TOP MARK (SEE NOTE 6)
1.70 0.10 (2 SIDES) PIN 1 NOTCH
(DE14) DFN 1203
7 0.200 REF 0.75 0.05 3.30 0.10 (2 SIDES)
1 0.25 0.05 0.50 BSC
0.00 - 0.05
BOTTOM VIEW--EXPOSED PAD NOTE: 1. DRAWING PROPOSED TO BE MADE VARIATION OF VERSION (WGED-3) IN JEDEC PACKAGE OUTLINE MO-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
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18
LT3479 PACKAGE DESCRIPTION
FE Package 16-Lead Plastic TSSOP (4.4mm)
(Reference LTC DWG # 05-08-1663)
Exposed Pad Variation BC
3.58 (.141) 4.90 - 5.10* (.193 - .201) 3.58 (.141) 16 1514 13 12 1110 9
6.60
0.10 4.50 0.10
SEE NOTE 4
2.94 (.116) 0.45 0.05 1.05 0.65 BSC 0.10
6.40 2.94 (.252) (.116) BSC
RECOMMENDED SOLDER PAD LAYOUT
12345678 1.10 (.0433) MAX
0 -8
4.30 - 4.50* (.169 - .177)
0.25 REF
0.09 - 0.20 (.0035 - .0079)
0.50 - 0.75 (.020 - .030)
0.65 (.0256) BSC
NOTE: 1. CONTROLLING DIMENSION: MILLIMETERS MILLIMETERS 2. DIMENSIONS ARE IN (INCHES) 3. DRAWING NOT TO SCALE
0.195 - 0.30 (.0077 - .0118) TYP
0.05 - 0.15 (.002 - .006)
FE16 (BC) TSSOP 0204
4. RECOMMENDED MINIMUM PCB METAL SIZE FOR EXPOSED PAD ATTACHMENT *DIMENSIONS DO NOT INCLUDE MOLD FLASH. MOLD FLASH SHALL NOT EXCEED 0.150mm (.006") PER SIDE
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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.
19
LT3479 TYPICAL APPLICATION
Lumiled Driver for Photo Flash with Output Disconnnect
VIN 3.3V TO 4.2V L1 4.7H C1 2.2F VIN VS L ON SHDN LT3479 SS RT 10nF 7.5k GND FBP VC 10k 2.2nF FLASH MODE ILED = 500mA C1, C2: TAIYO YUDEN LMK316BJ225MD D1: PHILIPS PMEG2010 D2, D3: LUMILEDS LXHL-PW01 L1: SUMIDA CDRH4D28-4R7 M1: VISHAY SILICONIX Si2302ADS 10k VREF 115k 0.2 SW FBN D1 D2 D3 M1 ON ILED 500mA/100mA C2 2.2F
2.49k TORCH MODE ILED = 100mA
3479 TA09
Lumileds Start-Up
Lumileds Torch/Flash Transition
VOUT 1V/DIV
ILED 0.2A/DIV
INDUCTOR CURRENT 0.5A/DIV
3479 TA09b
VOUT AC-COUPLED 500mV/DIV
0.2ms/DIV
ILED 500mA
50s/DIV 100mA 500mA
3479 TA09c
RELATED PARTS
PART NUMBER LT1618 LTC(R)3216 LTC3436 LTC3453 LT3466 DESCRIPTION Constant Current, Constant Voltage 1.4MHz, High Efficiency Boost Regulator 1A Low Noise High Current LED Charge Pump with Independent Torch/Flash Current Control 3A (ISW), 1MHz, 34V Step-Up DC/DC Converter Synchronous Buck-Boost High Power White LED Driver Dual Constant Current, 2MHz, High Efficiency White LED Boost Regulator with Integrated Schottky Diode COMMENTS VIN: 1.6V to 18V, VOUT(MAX) = 5.5V, IQ = 2.5mA, ISD = <1A, QFN16 Package VIN: 2.9V to 4.4V, VOUT(MAX) = 5.5V, IQ = 300A, ISD = <1A, DFN12 Package VIN: 3V to 25V, VOUT(MAX) = 34V, IQ = 0.9mA, ISD = <6A, TSSOP16E Package VIN: 2.7V to 5.5V, VOUT(MAX) = 5.5V, IQ = 2.5mA, ISD = <1A, QFN16 Package VIN: 2.7V to 24V, VOUT(MAX) = 40V, IQ = 5mA, ISD = <16A, DFN Package
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20 Linear Technology Corporation
(408) 432-1900 FAX: (408) 434-0507
LT 0808 REV B * PRINTED IN USA
1630 McCarthy Blvd., Milpitas, CA 95035-7417
www.linear.com
(c) LINEAR TECHNOLOGY CORPORATION 2004

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