LCPB [Linear]
48V Buck Mode LED Driver in SC70 and 2mm x 2mm DFN; 48V降压模式在SC70和采用2mm x 2mm DFN封装的LED驱动器
| 型号： | LCPB |
| 厂家： | 
Linear |
| 描述： | 48V Buck Mode LED Driver in SC70 and 2mm x 2mm DFN |
| 文件： | 总16页 (文件大小：216K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
LT3590
48V Buck Mode
LED Driver in SC70
and 2mm x 2mm DFN
DESCRIPTION
FEATURES
The LT®3590 is a fixed frequency buck mode converter
specifically designed to drive up to 10 LEDs in series from
a 48V DC source. Series connection of the LEDs provides
identical LED currents of up to 50mA, resulting in uniform
brightness and eliminating the need for ballast resistors.
A fixed frequency, current mode architecture results in
stable operation over a wide range of input voltage and
output voltage.
■
4.5V to 55V Input Voltage Range
■
Up to 50mA LED Current
■
80mA, 55V Switch
Internal Schottky Diode
15μA Supply Current in Shutdown
■
■
■
500μA Supply Current Operating, Not Switching
■
Switching Frequency: 850kHz
■
200mV Feedback Voltage with 5ꢀ Accuracy
■
CTRL Input Performs Dimming and Shutdown
The high switching frequency of 850kHz permits the use
of tiny, low profile inductors and capacitors. A single pin
performs both shutdown and accurate LED dimming
control. The power switch, Schottky diode and control
circuitry are all contained inside a space saving SC70
package or 2mm × 2mm DFN package to allow a small
converter footprint and lower parts cost.
■
91ꢀ Efficiency (10 LEDs, 50mA)
■
Requires Only 1μF Output Capacitor
■
8-Lead SC70 Package
■
6-Lead 2mm × 2mm DFN Package
APPLICATIONS
, LT, LTC and LTM are registered trademarks of Linear Technology Corporation.
All other trademarks are the property of their respective owners.
■
LED Fixed Signage
■
Traffic Signs
■
Neon Sign Replacement
TYPICAL APPLICATION
Buck Mode Driver for Ten White LEDs
Conversion Efficiency
100
1μF
90
80
70
50mA
4Ω
V
48V
IN
1μF
V
IN
LED
SW
470μH
60
CONTROL
CTRL
VREG
LT3590
GND
50
3590 TA01a
0.1μF
40
10
20
LED CURRENT (mA)
40
0
50
30
3590 TA01b
3590f
1
LT3590
ABSOLUTE MAXIMUM RATINGS
(Note 1)
Maximum Junction Temperature........................... 125°C
Storage Temperature Range...................–65°C to 150°C
Lead Temperature (Soldering, 10 sec)
Input Voltage (V )..................................... –0.3V to 55V
IN
LED Voltage ............................................... –0.3V to 55V
CTRL Voltage ................................................. 0V to 6.0V
VREG Voltage................................................. 0V to 4.0V
Operating Junction Temperature Range
SC 8 Package Only............................................ 300°C
(Note 2) ...............................................–40°C to 85°C
PIN CONFIGURATION
TOP VIEW
TOP VIEW
SW 1
GND 2
GND 3
GND 4
8 V
IN
6
5
4
VREG
LED
CTRL
GND
SW
1
2
3
7 LED
7
6 VREG
5 CTRL
V
IN
SC8 PACKAGE
8-LEAD PLASTIC SC70
DC PACKAGE
6-LEAD (2mm × 2mm) PLASTIC DFN
T
= 125°C, θ = 75°C/W TO 95°C/W
T
= 125°C, θ = 65°C/W TO 85°C/W, θ = 20°C/W
JMAX
JA
JMAX
JA
JC
EXPOSED PAD (PIN 7) IS GND, MUST BE SOLDERED TO PCB
ORDER INFORMATION
LEAD FREE FINISH
LT3590EDC#PBF
LT3590ESC8#PBF
TAPE AND REEL
PART MARKING
LCNZ
PACKAGE DESCRIPTION
6-Lead (2mm × 2mm) Plastic DFN
8-Lead Plastic SC70
TEMPERATURE RANGE
LT3590EDC#TRPBF
LT3590ESC8#TRPBF
–40°C to 85°C
–40°C to 85°C
LCPB
Consult LTC Marketing for parts specified with wider operating temperature ranges.
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/
3590f
2
LT3590
ELECTRICAL CHARACTERISTICS The ● denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C, VIN = 48V, VCTRL = 3.3V, unless otherwise noted.
PARAMETER
CONDITIONS
MIN
4.5
TYP
MAX
UNITS
V
Minimum Operating Voltage
●
LED Current Sense Voltage (V -V
)
190
200
5
210
mV
mV
μA
μA
kHz
ꢀ
IN LED
Sense Voltage Load Regulation
Quiescent Current ON, No Switching
Quiescent Current in Shutdown
Switching Frequency
ΔI = 10mA to 50mA
LED
V
V
= 47.7V
500
15
700
20
LED
= 0V
CTRL
●
●
650
90
850
1050
Maximum Duty Cycle
Switch Current Limit
80
115
500
1
150
2
mA
mV
μA
V
Switch V
I
= 50mA
SW
CESAT
Switch Leakage Current
V
= 48V
SW
●
V
CTRL
V
CTRL
V
CTRL
for Full LED Current
to Shut Down IC
to Turn on IC
1.5
100
mV
mV
nA
μA
V
150
CTRL Pin Bias Current
LED Pin Bias Current
V
V
= 1V, Current Out of Pin
100
9
CTRL
= 47.8V
= 1mA
14
LED
LDO Voltage V
I
3.1
1.5
3.3
17
3.5
REG
VREG
LDO Load Regulation
LDO Current Limit
ΔI
= 0mA to 1mA
mV
mA
V
VREG
Schottky Forward Drop
Schottky Leakage Current
I
= 50mA
0.8
SCHOTTKY
V = 48V
4
μA
R
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 LT3590E is guaranteed to meet performance specifications
from 0°C to 85°C junction temperature. Specifications over the –40°C
to 85°C operating junction temperature range are assured by design,
characterization and correlation with statistical process controls.
3590f
3
LT3590
TYPICAL PERFORMANCE CHARACTERISTICS
Switch Saturation Voltage
Shutdown Quiescent
Current vs VIN
(VCESAT
)
Schottky Forward Voltage Drop
20
18
16
14
1.2
1.1
1.0
0.9
0.8
0.7
0.6
0.5
0.4
0.8
0.7
0.6
0.5
0.4
0.3
0.2
V
T
= 0V
CTRL
A
= 25°C
25°C
–40°C
125°C
–40°C
125°C
25°C
12
10
100
0
20
30
(V)
40
50
60
0
50
200
10
150
60
20
40
100
80
V
SCHOTTKY FORWARD CURRENT (mA)
IN
SWITCH CURRENT (mA)
3590 G02
3590 G01
3590 G03
Shutdown Quiescent Current
vs Temperature
Quiescent Current
Schottky Leakage Current
20
18
16
14
12
10
2.0
1.5
1.0
0.5
0
600
550
500
450
V
V
= 0V
CTRL
IN
V
A
= 3.3V
CTRL
= 48V
T
= 25°C
V
= 48V
IN
V
= 24V
IN
V
= 4.5V
50
IN
400
–25
0
50
75 100 125
0
10
20
30
(V)
40
50
60
–25
0
75 100 125
–50
25
–50
25
V
TEMPERATURE (°C)
TEMPERATURE (°C)
IN
3590 G04
3590 G06
3590 G05
Switching Waveform
Transient Response
CTRL
5V/DIV
I
L
20mA/DIV
V
SW
50V/DIV
I
L
V
SW
50mA/DIV
20V/DIV
I
LED
50mA/DIV
3590 G08
3590 G07
40μs/DIV
1μs/DIV
V
LED
10 BLUE LEDs
= 48V
V
LED
10 WHITE LEDs
= 48V
IN
IN
I
= 50mA
I
= 50mA
L = 470μH (COILCRAFT)
3590f
4
LT3590
TYPICAL PERFORMANCE CHARACTERISTICS
Sense Voltage (VIN – VLED
)
Switching Current Limit
vs Duty Cycle
Switching Current Limit
vs Temperature
vs VCTRL
150
140
130
120
110
100
90
150
140
130
0.25
0.20
0.15
0.10
0.05
0
V
= 48V
T = 25°C
A
IN
I
= 50mA
LED
T
= 25°C
A
120
110
100
90
80
80
–25
0
50
75 100 125
–50
25
20
40
60
100
1
0
80
0
0.5
2
1.5
TEMPERATURE (°C)
DUTY CYCLE (ꢀ)
V
(V)
CTRL
3590 G11
3590 G10
3590 G09
Sense Voltage (VIN – VLED
)
Sense Voltage (VIN – VLED
)
Switching Frequency over
Temperature
vs VIN
vs Temperature
206
204
202
200
198
196
194
206
204
202
1000
950
900
850
800
750
700
I
= 50mA
V
= 48V
IN
LED
10 WHITE LEDs
= 25°C
T
A
200
198
196
194
40
60
–25
0
50
75 100 125
0
10
20
30
(V)
50
–25
0
50
75 100 125
–50
25
–50
25
V
TEMPERATURE (°C)
TEMPERATURE (°C)
IN
3590 G14
3590 G13
3590 G12
Internal Regulator
Line Regulation
Internal Regulator
Load Regulation
Internal Regulator
VREG vs Temperature
3.40
3.35
3.30
3.25
3.20
3.40
3.35
3.30
3.25
3.20
3.40
3.35
3.30
3.25
T
= 25°C
V
I
= 3.3V
= 1mA
T
= 25°C
A
CTRL
LOAD
A
V
= 0V
= 0V
CTRL
LOAD
I
V
LED
= 0V
CTRL
I
= 0V
V
I
= 3.3V
V
I
= 3.3V
= 1mA
CTRL
LED
CTRL
LOAD
= 50mA
3.20
–50 –25
0
25
50
75 100 125
40
50
60
0.8
1
0
10
20
30
(V)
0
0.2
0.4
I
LOAD
0.6
(mA)
TEMPERATURE (°C)
V
IN
3590 G15
3590 G16
3590 G17
3590f
5
LT3590
PIN FUNCTIONS (SC70/DFN)
SW (Pin 1/Pin 3): Switch Pin. Minimize trace area at this
pin to minimize EMI. Connect the inductor at this pin.
VREG (Pin 6/Pin 6): Internally Generated 3.3V Regulated
Output Pin. Must be locally bypassed with a 0.1μF X5R
capacitor.
GND (Pins 2, 3, 4/Pin 2): Ground Pins. All ground pins
should be tied directly to local ground plane. Proper
soldering of these pins to the PCB ground is required to
achieve the rated thermal performance.
LED (Pin 7/Pin 5): Connection point for the anode of the
highest LED and the sense resistor.
V
(Pin 8/Pin 4): Input Supply Pin. Must be locally by-
IN
CTRL (Pin 5/Pin 1): Dimming and Shutdown Pin.
Connect it below 100mV to disable the switcher. As the
pin voltage is ramped from 0V to 1.5V, the feedback volt-
passed.
Exposed Pad (NA/Pin 7): Ground. The Exposed Pad
should be soldered to the PCB ground to achieve the
rated thermal performance.
age (V -V ) ramps from 0mV to 200mV, controlling
IN LED
the LBD current.
V − VLED
IN
ILED
=
R1
BLOCK DIAGRAM
V
48V
IN
V
IN
R1
6.8Ω
C1
1μF
–
+
+
–
A = 6.25
–
+
+
LED
REG
EAMP
C2
1μF
VREG
C3
0.1μF
VREF
1.25V
L1
470μH
START-UP
CONTROL
SW
–
+
V
OUT
R
Q
PWM
S
+
–
ISNS
∑
RAMP
GENERATOR
850kHz
OSCILLATOR
CTRL
GND
3590 F01
CONTROL
Figure 1. Block Diagram
3590f
6
LT3590
OPERATION
The LT3590 uses a constant-frequency, current mode
control scheme to provide excellent line and load regula-
tion. Operation can be best understood by referring to the
Block Diagram.
The maximum input voltage is limited by the absolute
maximum V rating of 55V.
IN
Pulse-Skipping
For LED strings with a low number of LEDs (1, 2, or 3),
the LT3590 can drive currents without pulse-skipping as
long as the voltage across the LED and sense resistor is
greater than roughly 15ꢀ of the input supply voltage. If
the LED voltage plus sense resistor is less than 15ꢀ of
the input supply, the device will begin skipping pulses.
This will result in some low frequency ripple, although
the LED current remains regulated on an average basis
down to zero.
Atpower-up, thebandgapreference, thestart-upbias, and
the regulator are turned on. If CTRL is pulled higher than
150mV, the switching converter sub-blocks including the
oscillator, the PWM comparator and the error amplifier
are also turned on. At the start of each oscillator cycle,
the power switch Q1 is turned on. Current flows through
the inductor and the switch to ground, ramping up as the
switch stays on. A voltage proportional to the switch cur-
rent is added to a stabilizing ramp and the resulting sum
is fed into the positive terminal of the PWM comparator.
Whenthisvoltageexceedsthelevelatthenegativeinputof
the PWM comparator, the PWM logic turns off the power
switch. The level at the negative input of the PWM com-
parator is set by the error amplifier EAMP, and is simply
Discontinuous Current Mode
The CTRL pin, in conjunction with the sense resistor,
can be used to program the LED current as discussed
under Applications Information. The LT3590 can drive a
10-LED string at 10mA LED current operating in continu-
ous conduction mode, using the recommended external
components shown in the front page application circuit
with the sense resistor equal to 10Ω. As current is further
reduced, the regulator enters discontinuous conduction
mode.ThephotoinFigure2detailscircuitoperationdriving
ten LEDs at 2mA load. During the discharge phase, the
inductor current reaches zero. After the inductor current
reaches zero, the SW pin exhibits ringing due to the LC
tank circuit formed by the inductor in combination with
the switch and the diode capacitance. This ringing is not
harmful;farlessspectralenergyiscontainedintheringing
than in the switch transitions. The ringing can be damped
by application of a 3kΩ resistor across the inductor, al-
though this will degrade efficiency.
an amplified version of the difference between the V and
IN
V
LED
voltage and the bandgap reference. In this manner,
the error amplifier sets the correct peak current level in
inductor L1 to keep the output in regulation. The CTRL
pin is used to adjust the reference voltage.
The LT3590 enters into shutdown when CTRL is pulled
lower than 100mV.
Input Voltage Range
Theminimuminputvoltagerequiredtogenerateaparticular
output voltage in an LT3590 application is limited by either
its 4.5V limit or by its maximum duty cycle. The duty cycle
is the fraction of time that the internal switch is on and is
determined by the input and output voltages:
VLED + VD
DC =
V
V – VSW + VD
SW
IN
20V/DIV
Where V is the forward voltage drop of the catch diode
D
(~0.8V) and V is the voltage drop of the internal switch
SW
I
L
at maximum load (~0.5V). Given DC
= 0.9, this leads
10mA/DIV
MAX
to minimum input voltage of:
3590 F02
400ns/DIV
(VLED + VD)
DCMAX
V
LED
10 WHITE LEDs
= 48V
IN
V
=
+ VSW − VD
I
= 2mA
IN(MIN)
L = 470μH (MURATA)
Figure 2. Switching Waveforms
3590f
7
LT3590
APPLICATIONS INFORMATION
Inductor Selection
Capacitor Selection
A 220μH inductor is recommended for most LT3590 ap-
The small size of ceramic capacitors make them ideal
for LT3590 applications. X5R and X7R types are recom-
mended because they retain their capacitance over wider
voltage and temperature ranges than other types such as
Y5V or Z5U. A 1μF input capacitor and a 0.1μF regulator
capacitor are sufficient for most applications. For the
output capacitor, 1μF is generally recommended, but if
the voltage across the capacitor exceeds 10V, a 0.47μF
capacitor may be used instead. For applications driving
one or two LEDs a 2.2μF output capacitor is needed.
plications with V < 25V and 470μH is recommended for
IN
applications with V > 25V. Although small size and high
IN
efficiency are major concerns, the inductor should have
low core losses at 850kHz and low DCR (copper wire
resistance). Several manufacturers and inductor series
that meet these criteria are listed in Table 1. The efficiency
comparison of different inductors is shown in Figure 3.
Table 1. Inductor Manufacturers
INDUCTANCE
RANGE (μH)
(RELEVANT TO
THIS PART)
Table 2 shows a list of several ceramic capacitor manufac-
turers. Consultthemanufacturersfordetailedinformation
on their entire selection of ceramic parts.
PART
SERIES
DIMENSIONS
(mm)
VENDOR
Coilcraft
DO1605
LPS4012
LPS3010
1812FS
100 TO 680
100 TO 680
100 TO 330
100 TO 680
100 TO 390
5.4 × 4.2 × 1.8
4.0 × 4.0 × 1.2
3.0 × 3.0 × 0.9
www.coilcraft.com
Table 2: Recommended Ceramic Capacitor Manufacturers
Taiyo Yuden
(408) 573-4150
www.t-yuden.com
MSS5131
5.1 × 5.1 × 3.1
4.8 × 4.8 × 2.0
Sumida
www.sumida.com
CDC4D20
100 TO 680
AVX
(803) 448-9411
www.avxcorp.com
Murata
Kemet
(714) 852-2001
Toko
LLQ1608
LLQ2012
100 TO 270
100 TO 680
www.murata.com
www.tokoam.com
(408) 986-0424
www.kemet.com
Würth Elektronik
www.we-online.com
WE-PD2
TYPE M
WE-PD2
TYPE L
100 TO 220
5.2 × 5.8 × 4.5
7.0 × 7.8 × 5.0
100 to 470
Coiltronics
www.cooperet.com
CTX32C
100 to 330
2.5 × 3.2 × 2.2
Murata
www.murata.com
LQH32M
LQH43M
100 to 560
100 to 680
3.2 × 2.5 × 2.0
4.5 × 3.2 × 2.0
92
TDK SLF70145-471MR22-PF
V
= 48V
IN
MURATA QH32CN471K23
MURATA LQH43CN471K03
COILCRAFT LP06013-474KLB
COILCRAFT 1008PS-474KLB
COILCRAFT LPS4012-474ML
10 LEDs
FRONT PAGE
APPLICATION
CIRCUIT
90
88
86
84
40
50
0
10
20
30
LED CURRENT (mA)
3590 F03
Figure 3. Efficiency Comparison of Different Inductors
3590f
8
LT3590
APPLICATIONS INFORMATION
Programming LED Current
Using a DC Voltage
Forsomeapplications,thepreferredmethodofbrightness
control is a variable DC voltage to adjust the LED current.
The CTRL pin voltage can be modulated to set the dim-
ming of the LED string. As the voltage on the CTRL pin
increases from 0V to 1.5V, the LED current increases from
The feedback resistor (R1 in Figure 1) and the sense volt-
age (V - V ) control the LED current.
IN LED
V − VLED
IN
ILED
=
R1
0 to I . As the CTRL pin voltage increases beyond 1.5V,
LED
The CTRL pin controls the sense reference voltage as
shown in the Typical Performance Characteristics. For
CTRL higher than 1.5V, the sense reference is 200mV,
which results in full LED current. In order to have accu-
rate LED current, precision resistors are preferred (1ꢀ
is recommended). The formula and table for R1 selection
are shown below.
it has no effect on the LED current.
The LED current can be set by:
200mV
ILED
=
,when VCTRL > 1.5V
R1
VCTRL
6.25 •R1
ILED
=
,when VCTRL < 1.25V
200mV
ILED
R1=
Feedback voltage variation versus control voltage is
shown in Figure 4.
Table 3. R1 Theoretical Value for 200mV Sense
I
(mA)
R1 (Ω)
20
LED
Using a Filtered PWM Signal
10
20
30
40
50
10
A variable duty cycle PWM can be used to control the
brightness of the LED string. The PWM signal is filtered
(Figure 5) by a RC network and fed to the CTRL pin.
6.8
5.0
4.0
The corner frequency of R1, C1 should be much lower
than the frequency of the PWM signal. R1 needs to be
much smaller than the internal impedance in the CTRL
pin which is 100kΩ.
Dimming Control
Therearethreedifferenttypesofdimmingcontrolcircuits.
The LED current can be set by modulating the CTRL pin
with a DC voltage, a filtered PWM signal or directly with
a PWM signal.
LT3590
R1
10k
PWM
kHz TYP
CTRL
C1
1μF
0.25
0.20
0.15
0.10
0.05
0
3590 F05
Figure 5. Dimming Control Using a Filtered PWM Signal
0.5
1.0
1.5
0
2.0
V
(V)
CTRL
3590 F04
Figure 4. Dimming and Shutdown Using CTRL Pin
3590f
9
LT3590
APPLICATIONS INFORMATION
Direct PWM Dimming
48V input voltage. The achievable dimming range for this
application and 100Hz PWM frequency can be determined
using the following method.
Changing the forward current flowing in the LEDs not only
changestheintensityoftheLEDs,italsochangesthecolor.
The chromaticity of the LEDs changes with the change in
forward current. Many applications cannot tolerate any
shift in the color of the LEDs. Controlling the intensity of
the LEDs with a direct PWM signal allows dimming of the
LEDs without changing the color. In addition, direct PWM
dimming offers a wider dimming range to the user.
Example:
ƒ =100Hz, tSETTLE = 50μs
1
1
tPERIOD
=
=
= 0.01s
ƒ 100
Dimming the LEDs via a PWM signal essentially involves
turning the LEDs on and off at the PWM frequency. The
typical human eye has a limit of ~60 frames per second.
By increasing the PWM frequency to ~80Hz or higher,
the eye will interpret that the pulsed light source is con-
tinuously on. Additionally, by modulating the duty cycle
(amount of “on-time”), the intensity of the LEDs can be
controlled. The color of the LEDs remains unchanged in
this scheme since the LED current value is either zero or
a constant value.
tPERIOD
tSETTLE 50μs
0.01s
Dim Range=
=
= 200:1
tSETTLE
tPERIOD
50μs
0.01s
Min Duty Cycle =
•100=
•100= 0.5%
Duty Cycle Range =100%→0.5% at 100Hz
Thecalculationsshowthatfora100Hzsignalthedimming
range is 200 to 1. In addition, the minimum PWM duty
cycle of 0.5ꢀ ensures that the LED current has enough
time to settle to its final value. Figure 7 shows the dim-
ming range achievable for three different frequencies with
a settling time of 50μs.
The time it takes for the LED current to reach its pro-
grammed value sets the achievable dimming range for a
given PWM frequency. For example, the settling time of
the LED current in Figure 6 is approximately 50μs for a
PWM
5V/DIV
100Hz
V
SW
20V/DIV
1kHz
10kHz
I
LED
20mA/DIV
3590 F06
V
= 48V
2ms/DIV
IN
1
10
100
1000
4 LEDs
PWM DIMMING RANGE
3590 F07
Figure 6. Direct PWM Dimming Waveforms
Figure 7. Dimming Range Comparison
of Three PWM Frequencies
3590f
10
LT3590
APPLICATIONS INFORMATION
The dimming range can be further extended by changing
the amplitude of the PWM signal. The height of the PWM
signalsetsthecommandedsensevoltageacrossthesense
resistor through the CTRL pin. In this manner both analog
dimming and direct PWM dimming extend the dimming
range for a given application. The color of the LEDs no
longer remains constant because the forward current of
the LED changes with the height of the CTRL signal. For
the ten LED application described above, the LEDs can be
dimmedfirst,modulatingthedutycycleofthePWMsignal.
Once the minimum duty cycle is reached, the height of the
PWMsignalcanbedecreasedbelow1.5Vdownto150mV.
The use of both techniques together allows the average
LED current for the ten LED application to be varied from
50mA down to less than 50μA.
Internal Voltage Regulator
The LT3590 has a 3.3V onboard voltage regulator capable
of sourcing up to 1mA of current for use by an external
device. This feature may be used to power-up a controller
from the LT3590. The 3.3V is available even during shut-
down. It is required to place a 0.1μF capacitor from V
to ground. The regulator current is limited to 1.5mA.
REG
Board Layout Considerations
As with all switching regulators, careful attention must be
paid to the PCB board layout and component placement.
To prevent electromagnetic interference (EMI) problems,
proper layout of high frequency switching paths is essen-
tial. Minimize the length and area of all traces connected
to the switching node pin (SW). Keep the sense voltage
pins (V and LED) away from the switching node. Place
IN
the output capacitor, C2, next to the V pin. Always use
IN
a ground plane under the switching regulator to minimize
interplanecoupling.Recommendedcomponentplacement
is shown in Figure 8.
C3
GND
GND
C3
V
V
REG
REG
GND
GND
CTRL
CTRL
V
V
REG
REG
CTRL
1
2
3
6
5
4
CTRL
5
6
7
8
4
3
2
1
7
V
V
IN
IN
V
IN
V
IN
LED
C1
C2
C1
R1
GND
SW
C2
L1
R1
OUT
OUT
L1
LED
SW
3590 F08
(a) SC70 Package
(b) 2mm × 2mm DFN Package
Figure 8. Recommended Component Placement
3590f
11
LT3590
TYPICAL APPLICATIONS
48V Supply for 6 LED String, 50mA Current
Conversion Efficiency
100
90
80
70
60
50
40
C2
1μF
R1
4Ω
50mA
V
48V
6
IN
LEDs
C1
1μF
V
IN
LED
SW
L1
CONTROL
>1.5V
CTRL
VREG
470μH
LT3590
GND
3590 TA02a
C3
0.1μF
10
20
LED CURRENT (mA)
40
0
0
0
50
30
3590 TA02b
L1: MURATA LQH32CN221K03
48V Supply for 5 LED String, 30mA Current
Conversion Efficiency
100
90
80
70
60
50
40
C2
1μF
R1
6.8Ω
30mA
V
48V
IN
C1
1μF
V
IN
LED
SW
L1
470μH
CONTROL
>1.5V
CTRL
VREG
LT3590
GND
3590 TA03a
C3
0.1μF
20
LED CURRENT (mA)
30
5
10
15
25
3590 TA03b
L1: MURATA LQH32CN-391
24V Supply for a 5 LED String, 30mA Current
Conversion Efficiency
100
90
80
70
60
50
40
C2
1μF
R1
6.8Ω
30mA
V
24V
IN
C1
1μF
V
IN
LED
SW
L1
220μH
CONTROL
>1.5V
CTRL
VREG
LT3590
GND
3590 TA04a
C3
0.1μF
20
LED CURRENT (mA)
30
5
10
15
25
3590 TA04b
L1: MURATA LQH32CN-221
3590f
12
LT3590
TYPICAL APPLICATIONS
12V or 24V Supply for a Single LED, 50mA Current
Conversion Efficiency
80
75
70
65
C2
2.2μF
12V
24V
R1
4Ω
50mA
V
IN
12V OR 24V
60
55
C1
1μF
V
IN
LED
SW
L1
CONTROL
>1.5V
CTRL
VREG
220μH
50
45
40
LT3590
GND
3590 TA05a
C3
0.1μF
10
20
LED CURRENT (mA)
40
0
50
30
3590 TA05b
48V Supply for Two Strings of 10 LEDs, 25mA Current
Conversion Efficiency
100
90
C2
1μF
25mA
25mA
R1
4Ω
80
70
60
50
40
V
IN
48V
C1
1μF
V
IN
LED
SW
L1
CONTROL
>1.5V
CTRL
VREG
0
5
10
15
20
25
470μH
LT3590
GND
LED CURRENT (mA)
3590 TA06b
3590 TA06a
C3
0.1μF
12V Supply for a 3 LED String, 50mA Current
Conversion Efficiency
C2
100
90
80
70
60
50
40
1μF
R1
4Ω
50mA
V
IN
12V
C1
1μF
V
IN
LED
SW
L1
CONTROL
>1.5V
CTRL
VREG
220μH
LT3590
GND
3590 TA07a
C3
0.1μF
10
20
LED CURRENT (mA)
40
0
50
30
3590 TA07b
L1: MURATA LQH32CN-221
3590f
13
LT3590
PACKAGE DESCRIPTION
DC Package
6-Lead Plastic DFN (2mm × 2mm)
(Reference LTC DWG # 05-08-1703)
R = 0.115
TYP
0.56 0.05
(2 SIDES)
0.38 0.05
4
6
0.675 0.05
2.50 0.05
0.61 0.05
(2 SIDES)
2.00 0.10
(4 SIDES)
1.15 0.05
PIN 1 BAR
TOP MARK
(SEE NOTE 6)
PIN 1
PACKAGE
OUTLINE
CHAMFER OF
EXPOSED PAD
(DC6) DFN 1103
3
1
0.25 0.05
0.25 0.05
0.50 BSC
0.50 BSC
0.75 0.05
0.200 REF
1.37 0.05
(2 SIDES)
1.42 0.05
(2 SIDES)
RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS
0.00 – 0.05
BOTTOM VIEW—EXPOSED PAD
NOTE:
1. DRAWING TO BE MADE A JEDEC PACKAGE OUTLINE M0-229 VARIATION OF (WCCD-2)
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
3590f
14
LT3590
PACKAGE DESCRIPTION
SC8 Package
8-Lead Plastic SC70
(Reference LTC DWG # 05-08-1639 Rev Ø)
0.30
MAX
0.50
REF
1.80 – 2.20
(NOTE 4)
PIN 8
1.00 REF
INDEX AREA
(NOTE 6)
1.15 – 1.35
1.80 – 2.40
2.8 BSC 1.8 REF
(NOTE 4)
PIN 1
RECOMMENDED SOLDER PAD LAYOUT
PER IPC CALCULATOR
0.15 – 0.27
8 PLCS (NOTE 3)
0.50 BSC
0.10 – 0.40
0.80 – 1.00
0.00 – 0.10
REF
1.00 MAX
GAUGE PLANE
0.15 BSC
0.26 – 0.46
SC8 SC70 0905 REV Ø
0.10 – 0.18
(NOTE 3)
NOTE:
1. DIMENSIONS ARE IN MILLIMETERS
2. DRAWING NOT TO SCALE
5. MOLD FLASH SHALL NOT EXCEED 0.254mm
6. DETAILS OF THE PIN 1 IDENTIFIER ARE OPTIONAL,
BUT MUST BE LOCATED WITHIN THE INDEX AREA
7. EIAJ PACKAGE REFERENCE IS EIAJ SC-70 AND JEDEC MO-203
VARIATION BA
3. DIMENSIONS ARE INCLUSIVE OF PLATING
4. DIMENSIONS ARE EXCLUSIVE OF MOLD FLASH
AND METAL BURR
3590f
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.
15
LT3590
TYPICAL APPLICATION
Conversion Efficiency
24V Supply for 6 LED String, 50mA Current
C2
1μF
100
95
R1
4Ω
50mA
90
85
V
IN
24V
C1
80
75
1μF
V
IN
LED
L1
CONTROL
>1.5V
CTRL
VREG
220μH
70
65
60
LT3590
GND
SW
3590 TA08a
C3
0.1μF
0
10
20
LED CURRENT (mA)
40
50
30
3590 TA08b
L1: MURATA LQH32CN-221
RELATED PARTS
PART NUMBER DESCRIPTION
COMMENTS
V : 1.0V to 10.0V, V
LT1932
LT3003
LT3465/A
LT3466/-1
LT3474
LT3475
LT3476
LT3478/-1
LT3486
LT3491
LT3496
LT3497
LT3498
LT3517
LT3518
LT3591
Constant Current, 1.2MHz, High Efficiency White LED Boost
Regulator
= 34V, Dimming Analog/PWM,
OUT(MAX)
IN
I
< 1μA, ThinSOT™ Package
SD
Three Channel LED Ballaster with PWM Dimming
V : 3.0V to 48.0V, Dimming 3,000:1 True Color PWM™,
IN
I
<5μA, MSOP-10 Package
SD
Constant Current, 1.2/2.7MHz, High Efficiency White LED Boost
Regulator with Integrated Schottky Diode
V : 2.7V to 16.0V, V
SD
= 34V, Dimming Analog/PWM,
IN
OUT(MAX)
I
<1μA, ThinSOT Package
Dual Constant Current, 2MHz, High Efficiency White LED Boost
Regulator with Integrated Schottky Diode
V : 2.7V to 24.0V, V
= 40V, Dimming 5mA, I <16μA,
IN
OUT(MAX)
SD
3mm × 3mm DFN-10
36V, 1A (I ), 2MHz,Step-Down LED Driver
V : 4.0V to 36V, V
= 13.5V, Dimming 400:1 True Color
LED
IN
OUT(MAX)
PWM, I <1μA, TSSOP16E Package
SD
Dual 1.5A(I ), 36V, 2MHz, Step-Down LED Driver
V : 4.0V to 36V, V
= 13.5V, Dimming 3,000:1 True Color
LED
IN
OUT(MAX)
PWM, I <1μA, TSSOP20E Package
SD
Quad Output 1.5A, 2MHz High Current LED Driver with 1,000:1
Dimming
V : 2.8V to 16.0V, V
= 36.0V, Dimming 1,000:1 True
IN
OUT(MAX)
Color PWM, I <10μA, 5mm × 7mm QFN-10
SD
4.5A, 2MHz High Current LED Driver with 3,000:1 Dimming
V : 2.8V to 36.0V, V
= 40.0V, Dimming 1,000:1 True
IN
OUT(MAX)
Color PWM, I <10μA, 5mm × 7mm QFN-10
SD
Dual 1.3A, 2MHz High Current LED Driver
V : 2.5V to 24.0V, V
= 36.0V, Dimming 1,000:1 True
IN
OUT(MAX)
Color PWM, I <1μA, 5mm × 3mm DFN, TSSOP-16E Package
SD
Constant Current, 2.3MHz, High Efficiency White LED Boost
Regulator with Integrated Schottky Diode
V : 2.5V to 12.0V, V
= 27V, Dimming 300:1 True Color
IN
OUT(MAX)
PWM, I <8μA, 2mm × 2mm DFN-6, SC70 Package
SD
Triple Output 750mA, 2.1 MHz High Current LED Driver with 3,000:1 V : 3.0V to 30.0V, V
Dimming
= 40.0, Dimming 3,000:1 True
IN
OUT(MAX)
Color PWM, I <1μA, 4mm × 5mm QFN-28
SD
Dual 2.3MHz, Full Function LED Driver with Integrated Schottkys and V : 2.5V to 10.0V, V
250:1 True Color PWM Dimming
= 32, Dimming 250:1 True Color
IN
OUT(MAX)
PWM, I <12μA, 2mm × 3mm DFN-10
SD
20mA LED Driver and OLED Driver Integrated Schottkys
V : 2.5 to 12.0V, V
SD
= 32, Dimming Analog/PWM,
IN
OUT(MAX)
I
<8.5μA, 2mm × 3mm DFN-12
1.3A, 2.5MHz High Current LED Driver with 3,000:1 Dimming
2.3A, 2.5MHz High Current LED Driver with 3,000:1 Dimming
V : 3.0V to 30.0V, Dimming 3,000:1 True Color PWM, I <1μA,
IN
SD
4mm × 4mm QFN-16
V : 3.0V to 30.0V, Dimming 3,000:1 True Color PWM, I <1μA,
IN
SD
4mm × 4mm QFN-16
Constant Current, 1MHz, High Efficiency White LED Boost Regulator V : 2.5V to 12.0V, V
with Integrated Schottky Diode and 80:1 True Color PWM Dimming
= 40, Dimming 80:1 True Color
IN
OUT(MAX)
PWM, I <9μA, 2mm × 3mm DFN-8
SD
ThinSOT and True Color PWM are trademarks of Linear Technology Corporation.
3590f
LT 0707 • PRINTED IN USA
LinearTechnology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
16
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© LINEAR TECHNOLOGY CORPORATION 2007
(408) 432-1900 FAX: (408) 434-0507 www.linear.com
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