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LT3479 3A, Full Featured DC/DC Converter with Soft-Start and Inrush Current Protection
FEATURES

DESCRIPTIO
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
APPLICATIO S

High Power LED Driver DSL Modems Distributed Power
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.
, LTC and LT are registered trademarks of Linear Technology Corporation.
TYPICAL APPLICATIO
4.7H VIN 5V 2.2F VIN VS L SHDN LT3479 SS 10nF RT GND 17.8k FBP VC 10k VREF SW FBN
5V to 12V Boost Converter
VOUT 12V 0.8A 200k 10F
90 85 EFFICIENCY (%) 80 75 70 65 60
23.2k
2.2nF
3479 TA01
0
0.2
U
5V to 12V Efficiency
0.4 IOUT (A)
3479 TA02
U
U
0.6
0.8
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1
LT3479
ABSOLUTE MAXIMUM RATINGS
SW, L, VS Voltages ................................................. 42V VIN, SHDN Voltages ................................................ 24V FBP, FBN, VREF, RT, VC Voltages ............................... 2V Junction Temperature .......................................... 125C
PACKAGE/ORDER INFORMATION
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
ORDER PART NUMBER LT3479EDE
DE PART MARKING 3479
DE14 PACKAGE 14-LEAD (4mm x 3mm) PLASTIC DFN TJMAX = 125C, JA = 35C/W EXPOSED PAD (PIN 15) IS PGND (MUST BE SOLDERED TO PCB)
Consult LTC Marketing for parts specified with wider operating temperature ranges.
The indicates specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25C. VIN = 2.5V, VSHDN = 2.5V.
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 0.9 160 2.7 FBP - FBN, VC = 1V -2 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 9 25 25 2 250 150 10 10 1 200 3.5 1.15 240 4.1 100 100 6
ELECTRICAL CHARACTERISTICS
CONDITIONS
2
U
U
W
WW
U
W
(Note 1)
Operating Temperature Range (Note 2) .. - 40C to 85C Storage Temperature Range ................. - 65C to 125C Lead Temperature (Soldering, 10 sec) TSSOP .............................................................. 300C
TOP VIEW SW SW L VS VIN RT SHDN GND 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
ORDER PART NUMBER LT3479EFE
FE PART MARKING 3479EFE
FE PACKAGE 16-LEAD PLASTIC TSSOP
TJMAX = 150C, JA = 35C/W EXPOSED PAD (PIN 17) IS PGND (MUST BE SOLDERED TO PCB)
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 MHz kHz MHz
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1.216
1.235 0.01
LT3479
The indicates specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25C. VIN = 2.5V, VSHDN = 2.5V.
PARAMETER Maximum Switch Duty Cycle SHDN Pin Current SHDN Pin Threshold Inductor Current Limit Switch Current Limit Switch VCESAT Switch Leakage Current (Note 3) (Note 3) ISW = 1A (Note 3) SW = 40V CONDITIONS RT = 17.8k VSHDN = 5V VSHDN = 0V 0.3 3.5 3
ELECTRICAL CHARACTERISTICS
MIN 84
TYP 93 30 0.1 1.5 5 4.5 120 0.2
MAX 60 1 2 6.5 6 200 5
UNITS % A A V A A mV A
Note 1: Absolute Maximum Ratings are those values beyond which the life to the device may be impaired. 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.
TYPICAL PERFOR A CE CHARACTERISTICS
Switch VCE(SAT)
0.5
6 INDUCTOR CURRENT LIMIT 5
0.4 125C 25C -50C 0.2
CURRENT (A)
VCE(SAT) (V)
VREF (V)
0.3
0.1
0 0 0.5 1 1.5 2 SWITCH CURRENT (A) 2.5 3
3479 G01
SHDN Pin Turn-On Threshold
1.750 50
SHDN PIN CURRENT (A)
30
25C
1.500
VIN PIN CURRENT (mA)
SHDN THRESHOLD (V)
1.625
1.375
1.250 -50
-25
75 0 25 50 TEMPERATURE (C)
UW
100
3479 G04
Inductor and Switch Current Limit
1.27 1.26
SWITCH CURRENT LIMIT
VREF
4 3 2 1 0 -50 -25
1.25 VIN = 24V 1.24 VIN = 2.5V 1.23 1.22 1.21 -50 -25
50 25 75 0 TEMPERATURE (C)
100
125
0
25 50 75 100 125 150 TEMPERATURE (C)
3479 G03
3479 G02
SHDN Pin Current
6 -50C 40 5
VIN Pin Current
VC = 0.3V
4
20
125C
3
10
125
0
0
4
8
12 VSHDN (V)
16
20
24
3479 G05
2 -50 -25
0
25 50 75 100 125 150 TEMPERATURE (C)
3479 G06
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3
LT3479 TYPICAL PERFOR A CE CHARACTERISTICS
Soft-Start Pin Current
20 2.0 RT = 10k OFFSET VOLTAGE (mV)
15
FREQUENCY (MHz)
ISS (A)
10
5 0.4
0 -50 -25
0
25 50 75 100 125 150 TEMPERATURE (C)
3479 G07
PI FU CTIO S
(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.
4
UW
Oscillator Frequency
5
Feedback Amplifier Offset Voltage
1.6
4 VC = 0.5V 3
1.2
RT = 15k
0.8
RT = 20k
2
VC = 1V
1
0 -50 -25
0
25 50 75 100 125 150 TEMPERATURE (C)
3479 G08
0 -50
-25
0 25 50 TEMPERATURE (C)
75
100
3479 G09
U
U
U
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 DIAGRA
FBP
+ -
FEEDBACK AMPLIFIER
FBN
VREF SHDN VIN CIN RT RT t t 1.25V REFERENCE
OSCILLATOR
OPERATIO
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
W
RC CSS CC CS L1 D1 C1 FB SS INRUSH CURRENT PROTECTION COMPARATOR VS 8.5m L SW R2 R1
+
VC
+ -
36mV
-
ICON
+
pwmout
MASTER LATCH R S Q
DRIVER Q1
SLOPE
-
PWM COMPARATOR
+
CURRENT LIMIT COMPARATOR
-
GND
3479 BD
U
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. 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
APPLICATIO S I FOR ATIO
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
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
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 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
90 85 80
EFFICIENCY (%)
6
U
inductor 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.
TOKO FDV0630-4R7 75 SUMIDA CDRH4D28-4R7 70 65 60 55 50 0 0.2 0.4 IOUT (A)
3479 F01
W
UU
0.6
0.8
Figure 1. Efficiency vs Inductor Size
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LT3479
APPLICATIO S I FOR ATIO
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 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
3479 F02
VOUT
Figure 2. Positive Output Voltage Feedback Connections
U
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
3479 F03
W
UU
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 softstart 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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7
LT3479
APPLICATIO S I FOR ATIO
MINIMIZE THE AREA OF THIS TRACE
L1 CC
TO VS
TO VIN
CS CIN RT
TO GND
3479 F04
Figure 4. Suggested Board Layout
IL 2A/DIV
VOUT 5V/DIV
0.2ms/DIV
3479 F05
Figure 5. Start-Up with No Soft-Start Capacitor
IL 2A/DIV
VOUT 5V/DIV 0.2ms/DIV
3479 F06
Figure 6. Start-Up with CSS = 22nF
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8
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TO VOUT D COUT SW SW L VS VIN RT SHDN LT3479 GND GND SS VC FBN FBP VREF R1 CSS RC R2 TO SHDN PLACE VIAS AROUND EXPOSED PAD TO ENHANCE THERMAL PERFORMANCE
W
UU
Switching Frequency 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 2.5 2 1.5 1 0.5 0.2 RT (k) 1.78 2.87 4.32 6.49 10.2 17.8 39.2 113
LT3479
APPLICATIO S I FOR ATIO
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. 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
3.5 3.0 SWITCH FREQUENCY (MHz) 2.5 2.0 1.5 1.0
0.5 0 0.1 VSS 2V/DIV 10 RT (k) 100
3479 F07
Figure 7. Switch Frequency
90 85 80 EFFICIENCY (%) 75 70 65 60 55 50 0 0.2 0.4 IOUT (A)
3479 F08
1MHz 2MHz
0.6
0.8
Figure 8. Efficiency vs Switching Frequency
3479 F11
U
external inductor senses the inductor current at all times. When it exceeds 5A, a soft-start cycle is initiated. Figure 9 shows an output short circuit 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. 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.
VSW 10V/DIV IL 4V/DIV VOUT 20V/DIV 20s/DIV
3479 F09
W
UU
Figure 9. Output Short with Inrush Current Protection Enabled
VSW 10V/DIV
IL 4V/DIV VSS 2V/DIV VOUT 20V/DIV 20s/DIV
3479 F10
Figure 10. Output Short with Inrush Current Protection Disabled
VIN
VOUT 0.5
LT3479 BOOST REGULATOR
Figure 11
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9
LT3479
TYPICAL APPLICATIO S
800mA, 5V to 12V Boost Converter
L1 4.7H C1 2.2F VIN VS L SHDN LT3479 SS RT 10nF GND 17.8k FBP VC 10k 2.2nF
3479 TA03
VIN 5V
SW FBN 23.2k VREF
EFFICIENCY (%)
C1: TAIYO YUDEN LMK316BJ225MD C2: AVX 1206 YD106MAT D1: DIODES INC B320A L1: TOKO FDV0630-4R7M
500kHz, 800mA, 5V to 12V Boost Converter
L1 10H C1 2.2F D1 C2 10F
VIN 5V
VIN VS L SHDN LT3479 SS RT GND 39.2k
SW FBN 23.2k VREF FBP VC 4.7k 10nF
3479 TA04
EFFICIENCY (%)
10nF
C1: TAIYO YUDEN LMK316BJ225MD C2: AVX 1206 YD106MAT D1: DIODES INC. B320A L1: SUMIDA CDRH8D43-100
10
U
D1
200k
C2 10F
VOUT 12V 0.8A
Efficiency
90 85 80 75 70 65 60 55 50 0 0.2 0.4 IOUT (A)
3479 TA03b
0.6
0.8
VOUT 12V 0.8A
Efficiency
90 85 80 75 70 65 60 55 50 0 0.2 0.4 IOUT (A)
3479 TA04b
200k
0.6
0.8
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LT3479
TYPICAL APPLICATIO S
900mA, 3.3V to 8V Boost Converter
L1 4.7H C1 2.2F VIN VS L SHDN LT3479 SS RT 10nF GND 17.8k FBP VC 4.3k 10nF
3479 TA05
VIN 3.3V
SW FBN 30.9k VREF
EFFICIENCY (%)
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
3479 TA06
C2 2.2F
VIN 5V
SW FBP 100k 100pF VREF
EFFICIENCY (%)
C1, C2: TAIYO YUDEN LMK316BJ225MD C3: AVX 1206 YD106MAT D1, D2: DIODES INC B320A L1: TOKO FDV0630-4R7M
U
D1 C2 10F
VOUT 8V 0.9A
Efficiency
90
169k
80
70
60
50 0 0.15 0.3 0.45 0.6 IOUT (A) 0.75 0.9
3479 TA05b
D2 D1 402k
C3 10F
VOUT -5V 600mA
Efficiency
80 75 70 65 60 55 50 0 0.15 0.3 IOUT (A) 0.45 0.6
3479 TA06b
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11
LT3479
TYPICAL APPLICATIO S
83% Efficient, 5W Lumileds LuxeonTM 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: LUMILEDS LXCL-PWF2 L1: SUMIDA CDRH4D28-4R7 M1: VISHAY SILICONIX Si2302ADS 10k
3479 TA07
VIN 2.8V TO 4.2V
Luxeon is a trademark of Lumileds Lighting U.S. LLC.
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D1 C2 2.2F
D2 600mA ON
0.15
7.5k
LT3479
TYPICAL APPLICATIO S
500mA, 12 White LED Driver
L1 10H C1 4.7F D2 VIN VS L SHDN SS LT3479 SW 100k FBN VREF 5.9k 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 93.1k ILED 500mA 0.150
3479 TA08
VIN 8V TO 16V
EFFICIENCY (%)
U
D1
VOUT 16V TO 24V C2 4.7F
17.8k
Efficiency
100
90
VIN = 12V VIN = 16V
80 VIN = 8V 70
60
50
0
0.125
0.25 IOUT (A)
0.375
0.5
3479 TA08b
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13
LT3479
PACKAGE DESCRIPTIO
3.50 0.05
1.70 0.05 2.20 0.05 (2 SIDES) PACKAGE OUTLINE 0.25 0.05 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
PIN 1 TOP MARK (SEE NOTE 6) 7 0.200 REF 0.75 0.05 3.30 0.10 (2 SIDES) 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
14
U
DE Package 14-Lead Plastic DFN (4mm x 3mm)
(Reference LTC DWG # 05-08-1708)
0.65 0.05 3.00 0.10 (2 SIDES) 1.70 0.10 (2 SIDES) PIN 1 NOTCH
(DE14) DFN 1203
1 0.25 0.05 0.50 BSC
0.00 - 0.05
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LT3479
PACKAGE DESCRIPTIO
3.58 (.141)
6.60 0.10 4.50 0.10
SEE NOTE 4
0.65 BSC
RECOMMENDED SOLDER PAD LAYOUT
4.30 - 4.50* (.169 - .177)
0.09 - 0.20 (.0035 - .0079)
0.50 - 0.75 (.020 - .030)
NOTE: 1. CONTROLLING DIMENSION: MILLIMETERS MILLIMETERS 2. DIMENSIONS ARE IN (INCHES) 3. DRAWING NOT TO SCALE
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.
U
FE Package 16-Lead Plastic TSSOP (4.4mm)
(Reference LTC DWG # 05-08-1663)
Exposed Pad Variation BC
4.90 - 5.10* (.193 - .201) 3.58 (.141) 16 1514 13 12 1110 9
2.94 (.116) 0.45 0.05 1.05 0.10
6.40 2.94 (.252) (.116) BSC
12345678 1.10 (.0433) MAX
0 - 8
0.25 REF
0.65 (.0256) BSC
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
3479f
15
LT3479
TYPICAL APPLICATIO
VIN 3.3V TO 4.2V
Lumileds Start-Up
VOUT 1V/DIV
INDUCTOR CURRENT 0.5A/DIV 0.2ms/DIV
3479 TA04b
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
16
Linear Technology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408) 432-1900 FAX: (408) 434-0507
U
Lumiled Driver for Photo Flash with Output Disconnnect
L1 4.7H C1 2.2F VIN VS L ON SHDN LT3479 SS RT 10nF 7.5k GND FBP VC 2.49k 10k 2.2nF FLASH MODE ILED = 500mA C1, C2: TAIYO YUDEN LMK316BJ225MD D1: PHILIPS PMEG2010 D2: LUMILEDS LXCL-PWF2 L1: SUMIDA CDRH4D28-4R7 M1: VISHAY SILICONIX Si2302ADS 10k TORCH MODE ILED = 100mA VREF 115k 0.2 SW FBN M1 ON ILED 500mA/100mA D1 C2 2.2F D2
3479 TA09
Lumileds Torch/Flash Transition
ILED 0.2A/DIV
VOUT AC-COUPLED 500mV/DIV
50s/DIV ILED 500mA 100mA 500mA
3479 TA04c
3479f LT/TP 1004 1K * PRINTED IN THE USA
www.linear.com
(c) LINEAR TECHNOLOGY CORPORATION 2004

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