LT3517IUF#PBF [Linear]
LT3517 - Full-Featured LED Driver with 1.5A Switch Current; Package: QFN; Pins: 16; Temperature Range: -40°C to 85°C;
| 型号： | LT3517IUF#PBF |
| 厂家： | 
Linear |
| 描述： | LT3517 - Full-Featured LED Driver with 1.5A Switch Current; Package: QFN; Pins: 16; Temperature Range: -40°C to 85°C 驱动 接口集成电路 |
| 文件： | 总20页 (文件大小：396K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
LT3517
Full-Featured LED Driver
with 1.5A Switch Current
Features
Description
The LT®3517 is a current mode DC/DC converter with an
internal 1.5A, 45V switch specifically designed to drive
LEDs. The LT3517 operates as a LED driver in boost,
buck mode and buck-boost mode. It combines a tradi-
tional voltage loop and a unique current loop to operate
as a constant-current source or constant-voltage source.
Programmableswitchingfrequencyallowsoptimizationof
theexternalcomponentsforefficiencyorcomponentsize.
n
5000:1 True Color PWM™ Dimming Ratio
n
1.5A, 45V Internal Switch
n
100mV High Side Current Sense
Open LED Protection
n
n
Adjustable Frequency: 250kHz to 2.5MHz
n
Wide Input Voltage Range:
n
Operation from 3V to 30V
Transient Protection to 40V
n
n
Operates in Boost, Buck Mode and Buck-Boost Mode The switching frequency of LT3517 can be synchronized
n
n
n
n
n
Gate Driver for PMOS LED Disconnect
Constant-Current and Constant-Voltage Regulation
CTRL Pin Provides 10:1 Analog Dimming
Low Shutdown Current: <1µA
Available in (4mm × 4mm) 16-Lead QFN and 16-Pin
TSSOP Packages
to an external clock signal. The LED current is externally
programmable with a 100mV sense resistor. The external
PWMinputprovidesupto5000:1LEDdimming.TheCTRL
pin provides further 10:1 dimming ratio.
The LT3517 is available in the tiny footprint 16-lead QFN
(4mm × 4mm) and the 16-pin TSSOP packages. The
LT3517 provides a complete solution for both constant-
voltage and constant-current applications.
L, LT, LTC, LTM, Burst Mode, Linear Technology and the Linear logo are registered trademarks
and True Color PWM is a trademark of Analog Devices, Inc. All other trademarks are the
property of their respective owners. Protected by U.S. Patents, including 7199560, 7321203,
7746300.
applications
n
Display Backlighting
Automotive and Avionic Lighting
Illumination
Scanners
n
n
n
typical application
1A Buck Mode LED Driver
Efficiency
100
CTRL = V
REF
10µF
15µH
100mΩ
PV
IN
90
24V
2.2µF
1A
80
70
ISP
ISN TG
V
IN
V
SW
IN
3.3V
2.2µF
SHDN
60
50
40
LT3517
V
CTRL
PWM
FB
SS
RT
REF
PWM
SYNC
TGEN V
VC GND
REF
0
20
40
60
80
100
16.9k
1MHz
PWM DUTY CYCLE (%)
0.1µF
0.1µF
3517 TA01b
3517 TA01a
3517fh
1
For more information www.linear.com/LT3517
LT3517
absolute MaxiMuM ratings
V , SHDN, PWM, TGEN (Note 3) .............................40V
IN
(Note 1)
Storage Temperature Range
SW, ISP, ISN, TG.......................................................45V
TG Pin Below ISP Pin................................................10V
FB, SYNC, SS, CTRL ...................................................6V
QFN....................................................–65°C to 150°C
TSSOP ...............................................–65°C to 150°C
Lead Temperature (Soldering, 10 sec)
VC, RT, V ................................................................3V
TSSOP ............................................................. 300°C
REF
Operating Junction Temperature Range (Notes 2,4)
LT3517E.............................................–40°C to 125°C
LT3517I..............................................–40°C to 125°C
LT3517H ............................................–40°C to 150°C
pin conFiguration
TOP VIEW
TOP VIEW
V
1
2
3
4
5
6
7
8
16
15
14
13
12
11
10
9
SW
SW
TG
IN
16 15 14 13
SHDN
SW
SW
1
2
3
4
12 FB
11 VC
V
REF
17
GND
RT
SYNC
SS
ISP
ISN
TGEN
FB
17
V
CTRL
10
9
IN
SHDN
PWM
5
6
7
8
PWM
CTRL
VC
UF PACKAGE
16-LEAD (4mm × 4mm) PLASTIC QFN
FE PACKAGE
16-LEAD PLASTIC TSSOP
T
JMAX
= 150°C, θ = 36°C/W
JA
T
JMAX
= 150°C, θ = 40°C/W, θ (PAD) = 10°C/W
JA JC
EXPOSED PAD (PIN 17) IS GND, MUST BE SOLDERED TO PCB
orDer inForMation http://www.linear.com/product/LT3517#orderinfo
LEAD FREE FINISH
LT3517EUF#PBF
LT3517IUF#PBF
LT3517HUF#PBF
LT3517EFE#PBF
LT3517IFE#PBF
LT3517HFE#PBF
TAPE AND REEL
PART MARKING*
PACKAGE DESCRIPTION
TEMPERATURE RANGE
–40°C to 125°C
–40°C to 125°C
–40°C to 150°C
–40°C to 125°C
–40°C to 125°C
–40°C to 150°C
LT3517EUF#TRPBF
LT3517IUF#TRPBF
LT3517HUF#TRPBF
LT3517EFE#TRPBF
LT3517IFE#TRPBF
LT3517HFE#TRPBF
3517
16-Lead (4mm × 4mm) Plastic QFN
16-Lead (4mm × 4mm) Plastic QFN
16-Lead (4mm × 4mm) Plastic QFN
16-Lead Plastic TSSOP
3517
3517
3517FE
3517FE
3517FE
16-Lead Plastic TSSOP
16-Lead Plastic TSSOP
Consult LTC Marketing for parts specified with wider operating temperature ranges. *The temperature grade is identified by a label on the shipping container.
Consult LTC Marketing for information on non-standard lead based finish parts.
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/. Some packages are available in 500 unit reels through
designated sales channels with #TRMPBF suffix.
3517fh
2
For more information www.linear.com/LT3517
LT3517
electrical characteristics The l denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C. (Note 2) VIN = 5V, SHDN = 5V, PWM = 5V unless otherwise noted.
PARAMETER
Minimum V Operating Voltage
CONDITIONS
MIN
TYP
MAX
UNITS
3
V
V
IN
Maximum V Operating Voltage
Continuous Operation (Note 3)
30
96
IN
Current Sense Voltage (V – V
)
V
CTRL
V
CTRL
= 2V, V = 24V, VC = 1V
= 2V, V = 0V, VC = 1V
100
100
103
mV
mV
ISP
ISN
ISP
ISP
10% Scale Current Sense Voltage (V – V
)
ISN
V
CTRL
= 100mV, V = 24V, VC = 1V
9
mV
ISP
ISP
Current Sense Voltage Line Regulation
2V < V < 45V
0.03
%/V
ISP
V
Supply Current
PWM > 1.5V, VC = 0V
PWM = 0V
SHDN = 0V
6
4.5
0.1
10
1
mA
mA
µA
IN
l
Switching Frequency
R = 16.7k
0.85
2.25
220
1
2.5
250
1.15
2.7
270
MHz
MHz
kHz
T
R = 4.03k
T
R = 91.5k
T
RT Voltage
1
9
V
µA
µA
V
Soft-Start Pin Current
SYNC Pull-Down Current (Into the Pin)
SYNC Input Low
SS = 0.5V, Out of Pin
6
12
V
SYNC
= 2V
60
0.4
SYNC Input High
1.5
V
Maximum Duty Cycle
R = 91.5k (250kHz)
95
94
85
97
96
90
74
%
%
%
%
T
SYNC = 300kHz Clock Signal, R = 91.5k
T
l
R = 16.7k (1MHz)
T
R = 4.03k (2.5MHz)
T
Switch Current Limit
1.5
1.9
2.3
A
mV
µA
nA
µS
kΩ
nA
nA
V
Switch V
I
= 1A
300
CESAT
SW
Switch Leakage Current
CTRL Input Bias Current
Error Amplifier Transconductance
VC Output Impedance
V
= 45V, PWM = 0V
2
SW
Current Out of Pin, V
= 0.1V
20
550
1000
0
100
CTRL
VC Idle Input Bias Current
FB Pin Input Bias Current
FB Pin Threshold
PWM = 0V, VC = 1V
–20
20
Current Out of Pin, V = 0.5V
20
100
1.04
300
FB
l
l
0.98
1.01
ISP, ISN Idle Input Bias Current
ISP, ISN Full-Scale Input Bias Current
SHDN Voltage High
PWM = 0V, ISP = ISN = 24V
nA
µA
V
ISP Tied to ISN, V = 24V, V
= 2V
CTRL
20
60
60
ISP
1.2
1.2
SHDN Voltage Low
–40°C ≤ T ≤ 125°C
125°C < T ≤ 150°C
0.45
0.40
V
V
J
J
SHDN Pin Bias Current
PWM Input High Voltage
PWM Input Low Voltage
100
µA
V
l
–40°C ≤ T ≤ 125°C
125°C < T ≤ 150°C
0.45
0.40
V
V
J
J
PWM Pin Bias Current
120
µA
3517fh
3
For more information www.linear.com/LT3517
LT3517
The l denotes the specifications which apply over the full operating
electrical characteristics
temperature range, otherwise specifications are at TA = 25°C. (Note 2) VIN = 5V, SHDN = 5V, PWM = 5V unless otherwise noted.
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
V
TGEN Input High Voltage
TGEN Input Low Voltage
TGEN Pin Bias Current
1.5
0.4
200
2.04
0.03
V
TGEN = 5V
100
2
µA
V
l
V
REF
V
REF
Pin Voltage
I
= –100µA
1.96
REF
Pin Voltage Line Regulation
3V < V < 40V
%/V
ns
IN
Gate Turn-On Delay
Gate Turn-Off Delay
C
C
V
= 1nF Between ISP and TG
= 1nF Between ISP and TG
200
200
LOAD
LOAD
ns
Top Gate Drive V (V – V
)
TG
= 24V, TGEN = 5V
ISP
PWM = 0V
7
0
V
V
GS ISP
0.3
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 LT3517E is guaranteed to meet performance specifications
from 0°C to 125°C operating junction temperature range. Specifications
over the –40°C to 125°C operating junction temperature range are
assured by design, characterization and correlation with statistical
process controls. The LT3517I is guaranteed over the full –40°C to 125°C
operating junction temperature range. The LT3517H is guaranteed over
the full –40°C to 150°C operating junction temperature range. Operating
lifetime is derated at junction temperatures greater than 125°C.
Note 3: Absolute maximum voltage at V , SHDN, PWM and TGEN pins
is 40V for nonrepetitive 1 second transients and 30V for continuous
operation.
Note 4: This IC includes overtemperature protection that is intended
to protect the device during momentary overload conditions. Junction
temperature will exceed the maximum operating junction temperature
when overtemperature protection is active. Continuous operation above
the specified maximum operating junction temperature may impair device
reliability.
IN
typical perForMance characteristics
Switch Current Limit
vs Duty Cycle
VISP – VISN Threshold vs VCTRL
Oscillator Frequency vs RT
2.0
1.5
1.0
0.5
0
10000
1000
100
120
T
= 25°C
V
V
= 5V
ISP
A
IN
= 24V
100 VC = 1V
T
A
= 25°C
80
60
40
20
0
T
= 25°C
20
A
1.0 1.2
(V)
0
40
60
80
100
0
0.2 0.4 0.6 0.8
1.4 1.6
1
10
(kΩ)
100
V
CTRL
DUTY CYCLE (%)
R
T
3518 G03
3517 G02
3518 G01
3517fh
4
For more information www.linear.com/LT3517
LT3517
typical perForMance characteristics
VISP – VISN Threshold
vs Temperature
Switch Current Limit
vs Temperature
Oscillator Frequency
vs Temperature
2.5
2.0
1.5
1.0
0.5
0
2.5
2.3
2.1
1.9
1.7
1.5
104
V
V
= 5V
V
= 5V
V
= 5V
= 6.04k
IN
IN
IN
T
= 24V
R
ISP
103
102
VC = 1V
V
= 2V
CTRL
101
100
99
98
97
96
–20
0
40 60 80 100 120 140 160
–40
20
–40 –20
0
20 40 60 80 100 120 140 160
TEMPERATURE (°C)
–40 –20
0
20 40 60 80 100 120 140 160
TEMPERATURE (°C)
TEMPERATURE (°C)
3517 G04
3518 G05
3517 G06
Reference Voltage
vs Temperature
Quiescent Current vs VIN
VISP – VISN Threshold vs VISP
105
104
103
102
101
100
99
2.02
2.01
2.00
1.99
8
7
6
5
4
3
2
1
0
T = 25°C
A
VC = 0V
V
V
A
= 2V
V
IN
= 5V
CTRL
IN
= 5V
T
= 25°C
VC = 1V
98
97
96
95
1.98
0
10
20
V
30
(V)
40
50
20
(V)
–40 –20
0
20 40 60 80 100 120 140 160
TEMPERATURE (°C)
0
10
30
40
V
ISP
IN
3517 G07
3517 G08
3517 G09
PMOS Turn-On
PMOS Turn-Off
FB Pin Threshold vs Temperature
1.04
1.03
1.02
V
= 5V
IN
5V
0V
5V
0V
PWM
PWM
1.01
1.00
0.99
0.98
40V
TG
30V
40V
TG
30V
3517 G11
3517 G11
V = 40V
ISP
200ns/DIV
V
ISP
= 40V
200ns/DIV
–40 –20
0
20 40 60 80 100 120 140 160
TEMPERATURE (°C)
3517 G10
3517fh
5
For more information www.linear.com/LT3517
LT3517
pin Functions
SW: Switch Pin. Minimize trace at this pin to reduce EMI.
CTRL: LED Current Adjustment Pin. Sets voltage across
sense resistor between ISP and ISN. Connect directly to
V : Input Supply Pin. Must be locally bypassed.
IN
V
REF
forfull-scalethresholdof100mV,orusesignalvalues
SHDN: Shutdown Pin. Tie to 1.5V or higher to enable
device or 0.4V or less to disable device.
betweenGNDand1VtomodulateLEDcurrent.TietheCTRL
pin to the V pin if not used.
REF
V
: Reference Output Pin. This pin can supply up to
REF
100µA.
VC: g Error Amplifier Output Pin. Stabilize the loop with
m
an RC network or compensating C.
RT: Switching Frequency Adjustment Pin. Set switching
frequencyusingaresistortoGND(seeTypicalPerformance
Characteristics for values). For SYNC function, choose
the resistor to program a frequency 20% slower than the
SYNC pulse frequency. Do not leave this pin open.
FB: Voltage Loop Feedback Pin. Works as overvoltage
protection for LED drivers. If FB is higher than 1V, the
main switch is turned off.
TGEN: Top Gate Enable Input Pin. Tie to 1.5V or higher
to enable the PMOS driver function. Tie the TGEN pin to
ground if TG function is not used. There is an equivalent
40k resistor from TGEN pin to ground internally.
SYNC: Frequency Synchronization Pin. Tie an external
clock signal here. R resistor should be chosen to pro-
T
gram a switching frequency 20% slower than SYNC pulse
frequency.Synchronization(powerswitchturn-on)occurs
a fixed delay after the rising edge of SYNC. Tie the SYNC
pin to ground if this feature is not used.
ISN: Current Sense (–) Pin. The inverting input to the
current sense amplifier.
ISP: Current Sense (+) Pin. The noninverting input to the
current sense amplifier. Also serves as positive rail for
TG pin driver.
SS: Soft-Start Pin. Place a soft-start capacitor here. Leave
the pin open if not in use.
TG: Top Gate Driver Output. An inverted PWM sig-
PWM: Pulse Width Modulated Input Pin. Signal low turns
nal drives series PMOS device between V
and
ISP
off channel, disables the main switch and makes the TG
(V – 7V). An internal 7V clamp protects the PMOS gate.
ISP
pin high. Tie the PWM pin to V pin or SHDN pin if not
REF
Leave TG unconnected if not used.
used. There is an equivalent 50k resistor from PWM pin
to ground internally.
GND: Exposed Pad (QFN Package). Solder paddle directly
to ground plane.
3517fh
6
For more information www.linear.com/LT3517
LT3517
block DiagraM
LED ARRAY
C
IN
C
FILT
R
SENSE
PV
IN
SW
ISP
ISN
TG
TGEN
PWM
+
–
V
ISP
CURRENT
SENSE
AMPLIFIER
X10
V
– 7V
ISP
SHDN
MOSFET DRIVER
–
+
+
CTRL
A1
A2
ERROR
AMPLIFIER
1V
MAIN SWITCH
DRIVER
+
+
–
+
A3
Q1
POWER
SWITCH
A4
R
Q
1.01V
S
+
–
FB
PWM
COMPARATOR
+
VC
A8
GND
–
SS
SYNC
RAMP
GENERATOR
+
V
IN
A5
2.5MHz TO 250kHz
OSCILLATOR
100µA
1V
–
V
REF
V
IN
9µA
1V
+
–
+
+
–
SS
RT
A7
A6
Q2
2V
FREQ
ADJUST
V
IN
3517 F01
Figure 1. Buck Mode LED Driver
3517fh
7
For more information www.linear.com/LT3517
LT3517
operation
The LT3517 is a constant frequency, current mode regula-
tor with an internal power switch. Operation can be best
understoodbyreferringtotheBlockDiagraminFigure 1.At
the start of each oscillator cycle, the SR latch is set, which
turns on the Q1 power switch. A voltage proportional to
the switch current is added to a stabilizing ramp and the
resulting sum is fed into the positive terminal of the PWM
comparator, A4. When this voltage exceeds the level at the
negative input of A4, the SR latch is reset, turning off the
power switch. The level at the negative input of A4 is set
by the error amplifier A3. A3 has two inputs, one from the
voltage feedback loop and the other one from the current
loop.Whicheverfeedbackinputislowertakesprecedence,
and forces the converter into either constant-current or
constant-voltage mode. The LT3517 is designed to transi-
tion cleanly between these two modes of operation. The
through R
. If the error amplifier’s output increases,
SENSE
more current is delivered to the output; if it decreases,
less current is delivered. The current regulated in R
can be adjusted by changing the input voltage V
The current sense amplifier provides rail-to-rail current
sense operation. The FB voltage loop is implemented by
the amplifier A2. When the voltage loop dominates, the
error amplifier and the amplifier A2 regulate the FB pin to
1.01V (constant-voltage mode).
SENSE
.
CTRL
Dimming of the LED array is accomplished by pulsing the
LED current using the PWM pin. When the PWM pin is
low, switching is disabled and the error amplifier is turned
off so that it does not drive the VC pin. Also, all internal
loads on the VC pin are disabled so that the charge state
of the VC pin will be saved on the external compensation
capacitor. This feature reduces transient recovery time.
When the PWM input again transitions high, the demand
current for the switch returns to the value just before
PWM last transitioned low. To further reduce transient
recovery time, an external PMOS is used to disconnect
the LED array current loop when PWM is low, stopping
current sense amplifier senses the voltage across R
SENSE
and provides a pre-gain to amplifier A1. The output of A1
is simply an amplified version of the difference between
the voltage across R
and the lower of V
/10
CTRL
SENSE
or 100mV. In this manner, the error amplifier sets the
correct peak switch current level to regulate the current
C
FILT
from discharging.
applications inForMation
Dimming Control
minimum PWM low or high time should be at least four
switching cycles (2µs for f = 2MHz). Maximum PWM
SW
There are two methods to control the current source for
dimming using the LT3517. The first method uses the
PWM pin to modulate the current source between zero
and full current to achieve a precisely programmed aver-
age current. To make this method of current control more
accurate, the switch demand current is stored on the VC
node during the quiescent phase. This feature minimizes
recovery time when the PWM signal goes high. To further
improve the recovery time, a disconnect switch is used in
the LED current path to prevent the output capacitor from
discharging in the PWM signal low phase. The minimum
PWM on or off time will depend on the choice of operating
frequency through RT input pin or SYNC pin. When us-
ing the SYNC function, the SYNC and PWM signals must
have the aligned rising edges to achieve the optimized
high PWM dimming ratio. For best current accuracy, the
period is determined by the system and is unlikely to be
longer than 12ms. The maximum PWM dimming ratio
(PWM
) can be calculated from the maximum PWM
RATIO
period (t
) and the minimum PWM pulse width (t
)
MAX
MIN
as follows:
tMAX
tMIN
(1)
PWMRATIO
=
Example:
t
= 10ms, t = 2µs (f = 2MHz)
MIN SW
MAX
PWM
= 10ms/2µs = 5000:1
RATIO
The second method of dimming control uses the CTRL
pin to linearly adjust the current sense threshold during
3517fh
8
For more information www.linear.com/LT3517
LT3517
applications inForMation
the PWM high state. When the CTRL pin voltage is less
For a buck or a buck-boost configuration, the output
voltage is typically level-shifted to a signal with respect
to GND, as illustrated in the Figure 4. The output can be
expressed as:
than 1V, the LED current is:
VCTRL
10 •RSENSE
ILED
=
(2)
R1
R2
VOUT
=
•1.01V+ VBE(Q1)
(5)
When V
to be:
is higher than 1V, the LED current is clamped
(3)
CTRL
+
R1
R
SENSE
100mV
ILED
=
V
OUT
RSENSE
LED
ARRAY
–
Q2
LT3517
FB
The LED current programming feature possibly increases
total dimming range by a factor of ten.
R2
The CTRL pin should not be left open (tie to V
if not
3517 F04
REF
used). The CTRL pin can also be used in conjunction with
a PTC thermistor to provide overtemperature protection
for the LED load.
Figure 4
Inductor Selection
2V
V
REF
The inductor used with the LT3517 should have a satura-
tion current rating of 2A or greater. For buck mode LED
drivers, the inductor value should be chosen to give a
ripple current “ΔI” of ~30% to 40% of the LED current.
In the buck mode, the inductor value can be estimated
using the formula:
45.3k
49.9k
CTRL
5k
PTC
3517 F02
Figure 2
DBUCK • tSW(µs)• V – V
(
)
IN
LED
L µH =
( )
(6)
ΔI
Setting Output Voltage
VLED
V
IN
DBUCK
=
For a boost application, the output voltage can be set by
selecting the values of R1 and R2 (see Figure 3) according
to the following equation:
V
is the voltage across the LED string, V is the input
IN
LED
voltage to the converter, and t is the switching period.
SW
⎛
⎜
⎝
⎞
R1
R2
VOUT
=
+1 •1.01V
(4)
⎟
In the boost configuration, the inductor can be estimated
⎠
using the formula:
DBOOST • tSW(µs)• V
IN
V
(7)
OUT
L µH =
( )
ΔI
R1
LT3517
VLED – V
FB
IN
DBOOST
=
R2
VLED
3517 F03
Figure 3
3517fh
9
For more information www.linear.com/LT3517
LT3517
applications inForMation
Table 1 provides some recommended inductor vendors.
Table 1. Inductor Manufacturers
UseonlyceramiccapacitorswithX7R,X5Rorbetterdielec-
tric as they are best for temperature and DC bias stability
of the capacitor value. All ceramic capacitors exhibit loss
of capacitance value with increasing DC voltage bias, so it
maybenecessarytochooseahighervaluecapacitortoget
the required capacitance at the operation voltage. Always
check that the voltage rating of the capacitor is sufficient.
Table 2 shows some recommended capacitor vendors.
VENDOR
Sumida
Toko
PHONE
WEB
(408) 321-9660
(408) 432-8281
(561) 998-4100
(402) 563-6866
www.sumida.com
www.toko.com
www.cooperet.com
www.vishay.com
Cooper
Vishay
Table 2. Ceramic Capacitor Manufacturers
Input Capacitor Selection
VENDOR
Taiyo Yuden
AVX
PHONE
WEB
For proper operation, it is necessary to place a bypass
(408) 573-4150
(843) 448-9411
(770) 436-1300
(847) 803-6100
www.t-yuden.com
www.avxcorp.com
www.murata.com
www.tdk.com
capacitor to GND close to the V pin of the LT3517. A
IN
1µF or greater capacitor with low ESR should be used. A
Murata
TDK
ceramic capacitor is usually the best choice.
In the buck mode configuration, the capacitor at the input
to the power converter has large pulsed currents due to
the current returned though the Schottky diode when the
switchisoff. Forbestreliability, thiscapacitorshouldhave
low ESR and ESL and have an adequate ripple current
rating. The RMS input current is:
Loop Compensation
The LT3517 uses an internal transconductance error
amplifier whose VC output compensates the control loop.
The external inductor, output capacitor, and the compen-
sation resistor and capacitor determine the loop stability.
The inductor and output capacitor are chosen based on
performance, size and cost. The compensation resistor
and capacitor at VC are selected to optimize control loop
stability.FortypicalLEDapplications,a10nFcompensation
capacitor at VC is adequate and a series resistor is not
required.Acompensationresistormaybeusedtoincrease
the slew rate on the VC pin to maintain tighter regulation
IIN(RMS) =ILED • (1–D)•D
(8)
where D is the switch duty cycle. A 2.2µF ceramic type
capacitor is usually sufficient.
Output Capacitor Selection
The selection of output capacitor depends on the load
and converter configuration, i.e., step-up or step-down.
For LED applications, the equivalent resistance of the LED
is typically low, and the output filter capacitor should be
sized to attenuate the current ripple.
of LED current during fast transients on V or CTRL.
IN
Diode Selection
The Schottky diode conducts current during the interval
when the switch is turned off. Select a diode rated for
the maximum SW voltage. If using the PWM feature for
dimming, it is important to consider diode leakage, which
increaseswiththetemperature,fromtheoutputduringthe
PWM low interval. Therefore, choose the Schottky diode
with sufficiently low leakage current. Table 3 has some
recommended component vendors.
ToachievethesameLEDripplecurrent, therequiredfilter
capacitorvalueislargerintheboostandbuck-boostmode
applications than that in the buck mode applications. For
LED buck mode applications, a 1µF ceramic capacitor
is usually sufficient. For the LED boost and buck-boost
mode applications, a 2.2µF ceramic capacitor is usually
sufficient. Very high performance PWM dimming appli-
cations may require a larger capacitor value to support
the LED voltage during PWM transitions.
3517fh
10
For more information www.linear.com/LT3517
LT3517
applications inForMation
proper operation. One way to set the frequency is simply
connecting an external resistor between the RT pin and
GND. See Table 4 below or see the Oscillator Frequency vs
Table 3. Schottky Diodes
PART NUMBER
Diodes Inc.
DFLS160
V (V)
I
(A)
R
AVE
R graph in the Typical Performance Characteristics for
T
60
40
60
1
resistor values and corresponding switching frequencies.
Zetex
ZLLS1000TA
International Rectifier
10MQ060N
1
Table 4. Switching Frequency vs RT
Switching Frequency (kHz)
R ( kΩ )
T
1.5
250
500
90.9
39.2
16.9
9.53
6.04
4.02
Board Layout
1000
1500
2000
2500
The high speed operation of the LT3517 demands careful
attention to board layout and component placement. The
Exposed Pad of the package is the only GND terminal of
the IC and is also important for thermal management of
the IC. It is crucial to achieve a good electrical and thermal
contact between the Exposed Pad and the ground plane of
the board. To reduce electromagnetic interference (EMI),
it is important to minimize the area of the SW node. Use
a GND plane under SW and minimize the length of traces
in the high frequency switching path between SW and
GND through the diode and the capacitors. Since there is
a small DC input bias current to the ISN and ISP inputs,
resistanceinserieswiththeseinputsshouldbeminimized
and matched, otherwise there will be an offset. Finally,
The other way is to make the LT3517 synchronize with
an external clock via SYNC pin. For proper operation, a
resistor should be connected at the RT pin and be able
to generate a switching frequency 20% lower than the
external clock when external clock is absent.
In general, a lower switching frequency should be used
where either very high or very low switching duty cycle
operationisrequired,orhighefficiencyisdesired.Selection
of a higher switching frequency will allow use of smaller
value external components and yield a smaller solution
size and profile.
the bypass capacitor on the V supply to the LT3517
IN
should be placed as close as possible to the V terminal
IN
Thermal Considerations
of the device.
The LT3517 is rated to a maximum input voltage of 30V
for continuous operation, and 40V for nonrepetitive one
second transients. Careful attention must be paid to the
internal power dissipation of the LT3517 at higher input
voltagestoensurethatthemaximumjunctiontemperature
is not exceeded. This junction limit is especially important
whenoperatingathighambienttemperatures.TheExposed
Pad on the bottom of the package must be soldered to a
ground plane. This ground should then be connected to
an internal copper ground plane with thermal vias placed
directlyunderthepackagetospreadouttheheatdissipated
by the LT3517.
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
outputvoltageovershoot.Atypicalvalueforthesoft-start
capacitor is 0.1µF.
Switching Frequency
There are two methods to set the switching frequency of
LT3517. Both methods require a resistor connected at RT
pin. Do not leavetheRT pin open. Also, donotload thispin
with a capacitor. A resistor must always be connected for
3517fh
11
For more information www.linear.com/LT3517
LT3517
typical applications
Buck Mode 1A LED Driver
2000:1 PWM Dimming at 120Hz
C3
10µF
R
SENSE
M1
100mΩ
PV
IN
24V
C2
2.2µF
L1
15µH
PWM
1A
5V/DIV
D1
ISP
ISN TG
V
I
IN
LED
V
SW
IN
3.3V
1A/DIV
C1
2.2µF
SHDN
LT3517
V
I
CTRL
PWM
FB
SS
RT
REF
L
1A/DIV
PWM
3517 TA02b
1µs/DIV
SYNC
PV = 24V
TGEN V
VC GND
IN
OSC
LED
REF
C4
f
I
= 1MHz
= 1A
R
16.9k
1MHz
T
C5
0.1µF
0.1µF
3517 TA02a
C1: KEMET C0805C225K4RAC
C2: MURATA GRM31MR71E225KA93
C3: MURATA GRM32DR71E106KA12B
C4, C5: MURATA GRM21BR71H104KA01B
D1: DIODES DFLS160
L1: TOKO B992AS-150M
LEDS: LUXEON K2 (WHITE)
M1: ZETEX ZXMP6A13FTA
350mA, 5V to 12V Boost Converter with Accurate Input Current Limit
R
L1
SENSE
Efficiency
D1
100mΩ 6.8µH
V
OUT
V
IN
12V
90
80
70
60
50
5V
350mA
C1
2.2µF
R1
549k
ISP TG ISN
SW
FB
V
IN
CTRL
PWM
SHDN
TGEN
C2
10µF
LT3517
GND
SHDN
SYNC
RT
R2
49.9k
V
REF
VC
SS
R3
10k
C4
10nF
R
6.04k
2MHz
T
C3
0.1µF
50
100
150
200
(mA)
250
300
350
I
LOAD
3517 TA03b
3517 TA03a
C1: KEMET C0805C225K4RAC
C2: KEMET C1206C106K4RAC
C3: MURATA GRM21BR71H104KA01B
C4: MURATA GCM033R71A103KA03
D1: ZETEX ZLLS1000TA
L1: TOKO B992AS-6R8N
3517fh
12
For more information www.linear.com/LT3517
LT3517
typical applications
Buck-Boost Mode LED Driver
L1
6.8µH
D1
V
IN
8V TO 16V
C5
0.22µF
R1
3.92M
SHDN
V
IN
SW
FB
R2
124k
300mA
PWM
PWM
TGEN
LT3517
ISP
R
SENSE
V
REF
C1
2.2µF
330mΩ
CTRL
ISN
TG
M1
C2
4.7µF
SYNC
VC
RT SS
GND
R
T
6.04k
2MHz
3517 TA04a
C4
0.1µF
C3
0.1µF
C1: KEMET C0806C225K4RAC
C2: KEMET C1206C475K3RAC
C3, C4: MURATA GRM21BR71H104KA01B
C5: MURATA GRM21BR71H224KA01B
D1: DIODE DFLS160
L1: TOKO B992AS-6R8N
LEDS: LUXEON I (WHITE)
M1: ZETEX ZXMP6A13FTA
Efficiency
5000:1 PWM Dimming at 100Hz
90
80
70
60
50
40
30
20
V
= 12V
IN
CTRL = V
REF
PWM
5V/DIV
I
LED
200mA/DIV
I
L
1A/DIV
3517 TA04b
500ns/DIV
= 12V
V
f
I
IN
= 2MHz
OSC
LED
= 300mA
0
20
40
60
80
100
PWM DUTY CYCLE (%)
3517 TA04c
3517fh
13
For more information www.linear.com/LT3517
LT3517
typical applications
Low Side Current Sensing Load Dump Protected Buck-Boost Mode LED Driver
L1
6.8µH
D1
V
IN
8V TO 16V
C5
0.22µF
R1
3.92M
SHDN
V
IN
SW
FB
R2
124k
PWM
PWM
TGEN
LT3517
RT SS
ISP
V
R
REF
SENSE
330mΩ
CTRL
SYNC
C1
2.2µF
C2
4.7µF
ISN
TG
D1: DIODES DFLS160
L1: TOKO B992AS-6R8N
M1
VC
GND
C1: KEMET C0806C225K4RAC
C2: KEMET C1206C475K3RAC
C3: MURATA GRM21BR71H104KA01B
C4: MURATA GRM219R71H333KAQ01B
C5: MURATA GRM21BR71H224KA01B
M1: ZETEX ZXMP6A13FTA
300mA
R3
R
T
10k 6.04k
2MHz
C4
33nF
C3
0.1µF
3517 TA05a
LEDs: LUXEON I (WHITE)
Efficiency
5000:1 PWM Dimming at 100Hz
90
80
70
60
50
40
30
20
V
= 12V
IN
CTRL = V
REF
PWM
5V/DIV
I
LED
200mA/DIV
I
L
1A/DIV
3517 TA05b
500ns/DIV
V
= 12V
IN
f
I
= 2MHz
OSC
LED
= 300mA
0
20
40
60
80
100
PWM DUTY CYCLE (%)
3517 TA05c
Load Dump Response
V
V
10V/DIV
ISP
10V/DIV
IN
V
ISP
15V TO 40V
V
15V TO 40V
IN
V
REF GND
REF GND
ISP
I
I
200mA/DIV
LED
V
IN
1A/DIV
L
3517 TA05d
5ms/DIV
Raises From 15V to 40V in 5ms.
V
IN
3517fh
14
For more information www.linear.com/LT3517
LT3517
typical applications
Boost 100mA LED Driver with LED Open Protection
L1
22µH
D1
V
IN
8V TO 16V
R1
1M
SHDN V
SW
IN
FB
R2
30.1k
ISP
PWM
TGEN
PWM
R
SENSE
1Ω
LT3517
RT SS
V
ISN
TG
REF
CTRL
SYNC
M1
C1
2.2µF
C2
2.2µF
LED1
LED2
VC
GND
R
T
100mA
16.9k
1MHz
C4
0.1µF
C3
0.1µF
LED10
3517 TA06a
C1, C2: KEMET C1206C225K2RAC
C3, C4: MURATA GRM21BR71H104KA01B
D1: DIODES DFLS160
L1: COILCRAFT DS3316P-223
LEDS: CREE XLAMP 7090
M1: ZETEX ZXMP6A13FTA
Efficiency
3000:1 PWM Dimming at 100Hz
90
80
70
60
50
40
30
20
PWM
5V/DIV
V
= 12V
IN
I
LED
CTRL = V
REF
100mA/DIV
I
L
500mA/DIV
3517 TA06b
1µs/DIV
= 12V
V
f
I
IN
= 1MHz
OSC
LED
= 100mA
0
20
40
60
80
100
PWM DUTY CYCLE (%)
3517 TA06c
3517fh
15
For more information www.linear.com/LT3517
LT3517
typical application
5.5V SEPIC Converter with Short-Circuit Protection
Efficiency
C5
L1
R
SENSE
10µF
D1
90
80
70
60
50
40
30
4.3µH
V
0.22Ω
OUT
V
IN
5.5V
3V
350mA
C2
10µF
C2
2.2µF
R1
L2
221k
4.3µH
V
IN
PWM
SW
FB
CTRL
SYNC
SHDN
TGEN
TG
ISP
ISN
RT
SHDN
LT3517
V
REF
R2
49.9k
VC
GND
SS
R3
10k
C4
R
T
C3
0.1µF
6.04k
2MHz
0
50 100 150 200 250 300 350
I
(mA)
LOAD
10nF
3517 TA07b
3517 TA07a
C1: KEMET C0805C225K4RAC
C2, C5: KEMET C1206C106K4RAC
C3: MURATA GRM21BR71H104KA01B
C4: MURATA GCM033R71A103KA03
D1: ZETEX ZLLS1000TA
L1, L2: TOKO B992AS-4R3N
3517fh
16
For more information www.linear.com/LT3517
LT3517
package Description
Please refer to http://www.linear.com/product/LT3517#packaging for the most recent package drawings.
UF Package
16-Lead Plastic QFN (4mm × 4mm)
(Reference LTC DWG # 05-08-1692 Rev Ø)
0.72 0.05
4.35 0.05
2.90 0.05
2.15 0.05
(4 SIDES)
PACKAGE OUTLINE
0.30 0.05
0.65 BSC
RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS
BOTTOM VIEW—EXPOSED PAD
PIN 1 NOTCH R = 0.20 TYP
OR 0.35 × 45° CHAMFER
0.75 0.05
R = 0.115
TYP
4.00 0.10
(4 SIDES)
15
16
0.55 0.20
PIN 1
TOP MARK
(NOTE 6)
1
2
2.15 0.10
(4-SIDES)
(UF16) QFN 10-04
0.200 REF
0.30 0.05
0.65 BSC
0.00 – 0.05
NOTE:
1. DRAWING CONFORMS TO JEDEC PACKAGE OUTLINE MO-220 VARIATION (WGGC)
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
3517fh
17
For more information www.linear.com/LT3517
LT3517
package Description
Please refer to http://www.linear.com/product/LT3517#packaging for the most recent package drawings.
FE Package
16-Lead Plastic TSSOP (4.4mm)
(Reference LTC DWG # 05-08-1663 Rev L)
Exposed Pad Variation BA
4.90 – 5.10*
(.193 – .201)
2.74
(.108)
2.74
(.108)
16 1514 13 12 1110
9
6.60 ±0.10
4.50 ±0.10
2.74
(.108)
6.40
(.252)
BSC
SEE NOTE 4
2.74
(.108)
0.45 ±0.05
1.05 ±0.10
0.65 BSC
5
7
8
1
2
3
4
6
RECOMMENDED SOLDER PAD LAYOUT
1.10
(.0433)
MAX
4.30 – 4.50*
(.169 – .177)
0.25
REF
0° – 8°
0.65
(.0256)
BSC
0.09 – 0.20
(.0035 – .0079)
0.50 – 0.75
(.020 – .030)
0.05 – 0.15
(.002 – .006)
0.195 – 0.30
FE16 (BA) TSSOP REV L 0117
(.0077 – .0118)
TYP
NOTE:
1. CONTROLLING DIMENSION: MILLIMETERS 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
MILLIMETERS
(INCHES)
2. DIMENSIONS ARE IN
3. DRAWING NOT TO SCALE
3517fh
18
For more information www.linear.com/LT3517
LT3517
revision history (Revision history begins at Rev C)
REV
DATE
4/10
7/10
DESCRIPTION
PAGE NUMBER
C
Added H-grade to Order Information Section
Added conditions to ISP, ISN Idle Input Bias Current parameters
2
3
7
3
D
Changed V current sense to 9µA in Figure 1
IN
E
F
01/11 Updated Electrical Characteristics
04/12 Subscript added to V Pin Label
1
2
C
R changed to RT in ABS Max Table, QFM Max Temp changed to 150°C
T
Added Operating in Note 2
Clarified Application Schematics
Package Diagram Updated
4
15, 16
18
G
H
04/13 Clarified Application schematic
15
03/17 Clarified T
2
J(MAX)
3517fh
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 representa-
tion that the interconnection of its circuits as described herein will not infringe on existing patent rights.
19
LT3517
relateD parts
PART NUMBER
DESCRIPTION
COMMENTS
V : 5V to 18V, V
LT1618
Constant Current, 1.4MHz, 1.5A Boost Converter
= 36V, Dimming = Analog/PWM, I < 1µA,
OUT(MAX) SD
IN
MSOP10 Package
LT3003
3-Channel LED Ballaster with PWM Dimming
V : 3V to 48V, Dimming = 3000:1 True Color PWM, I < 5µA,
IN
SD
MSOP10 Package
LT3474
36V, 1A (I ), 2MHz, Step-Down LED Driver
V : 4V to 36V, V
SD
= 13.5V, Dimming = 400:1 True Color PWM,
LED
IN
OUT(MAX)
I
< 1µA, TSSOP16E Package
LT3475
Dual 1.5A (I ), 36V 2MHz Step-Down LED Driver
V : 4V to 36V, V
SD
= 13.5V, Dimming = 3000:1 True Color PWM,
LED
IN
OUT(MAX)
I
< 1µA, TSSOP20E Package
LT3476
Quad-Output 1.5A, 36V, 2MHz High Current LED Driver
with 1000:1 Dimming
V : 2.8V to 16V, V
SD
= 36V, Dimming = 1000:1 True Color PWM,
IN
OUT(MAX)
I
< 10µA, 5mm × 7mm QFN Package
LT3477
3A, 42V, 3MHz Boost, Buck-Boost, Buck LED Driver
V : 2.5V to 25V, V
= 40V, Dimming = Analog/PWM, I < 1µA,
IN
OUT(MAX)
SD
QFN, TSSOP20E Packages
LT3478/LT3478-1
LT3479
4.5A, 42V, 2.5MHz High Current LED Driver with 3000:1 V : 2.8V to 36V, V
= 42V, Dimming = 3000:1 True Color PWM,
OUT(MAX)
IN
Dimming
I
< 3µA, TSSOP16E Packages
SD
3A, Full -Featured DC/DC Converter with Soft-Start and
Inrush Current Protection
V : 2.5V to 24V, V
= 40V, I = 6.5mA, I < 1µA,
OUT(MAX) Q SD
IN
DFN and TSSOP Packages
V : 2.5V to 24V, V = 36V, Dimming = 1000:1 True Color PWM,
OUT(MAX)
LT3486
Dual 1.3A, 2MHz High Current LED Driver
IN
I
< 1µA, 5mm × 3mm DFN, TSSOP16E
SD
LT3496
Triple-Output LED Driver
V : 3V to 40V, V
SD
= 45V, Dimming = 3000:1 True Color PWM,
IN
OUT(MAX)
I
< 10µA, 4mm × 5mm QFN Package
LT3518
Full-Featured LED Driver with 2.3A Switch Current
48V Buck Mode 50mA LED Driver
16-Channel Buck LED Driver Mode
High Current LED Controller
V : 3V to 40V, V
SD
= 45V, Dimming = 3000:1 True Color PWM,
IN
OUT(MAX)
I
< 1µA, 4mm × 4mm QFN Package and TSSOP Package
LT3590
V : 4.5V to 55V, Drives Up to 10 LEDs, 200:1 Dimming,
IN
I
SO
= 15mA, 2mm × 2mm DFN SC70
LT3595
V : 4.5V to 45V, Drives Up to 160 LEDs, 5000:1 Dimming,
IN
5mm × 9mm QFN
LTC®3783
V : 3V to 36V, V
= Ext FET, Dimming = 3000:1 True Color PWM,
OUT(MAX)
IN
SD
I
< 20µA, 5mm × 4mm QFN10, TSSOP16E Packages
3517fh
LT 0317 • PRINTED IN USA
www.linear.com/LT3517
20
LINEAR TECHNOLOGY CORPORATION 2017
相关型号：
LT3517IUF#TRPBF
LT3517 - Full-Featured LED Driver with 1.5A Switch Current; Package: QFN; Pins: 16; Temperature Range: -40°C to 85°C
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LT3518EFE
LT3518 - Full-Featured LED Driver with 2.3A Switch Current; Package: TSSOP; Pins: 16; Temperature Range: -40°C to 85°C
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LT3518EFE#PBF
LT3518 - Full-Featured LED Driver with 2.3A Switch Current; Package: TSSOP; Pins: 16; Temperature Range: -40°C to 85°C
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LT3518EFE#TRPBF
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