LT3590 - 48V Buck Mode LED Driver in SC70 and 2mm x 2mm DFN

LT3590
48V Buck Mode
LED Driver in SC70
and 2mm x 2mm DFN
DESCRIPTION
FEATURES
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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 ±5% Accuracy
CTRL Input Performs Dimming and Shutdown
91% Efficiency (10 LEDs, 50mA)
Requires Only 1μF Output Capacitor
8-Lead SC70 Package
6-Lead 2mm × 2mm DFN Package
APPLICATIONS
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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.
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.
, 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
50mA
VIN
48V
1μF
CONTROL
VIN
LED
470μH
CTRL
EFFICIENCY (%)
4Ω
80
70
60
LT3590
VREG
0.1μF
SW
GND
50
3590 TA01a
40
0
10
20
30
LED CURRENT (mA)
40
50
3590 TA01b
3590f
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LT3590
ABSOLUTE MAXIMUM RATINGS
(Note 1)
Input Voltage (VIN) ..................................... –0.3V to 55V
LED Voltage ............................................... –0.3V to 55V
CTRL Voltage ................................................. 0V to 6.0V
VREG Voltage ................................................. 0V to 4.0V
Operating Junction Temperature Range
(Note 2) ...............................................– 40°C to 85°C
Maximum Junction Temperature........................... 125°C
Storage Temperature Range...................– 65°C to 150°C
Lead Temperature (Soldering, 10 sec)
SC 8 Package Only ............................................ 300°C
PIN CONFIGURATION
TOP VIEW
SW 1
8 VIN
GND 2
7 LED
GND 3
6 VREG
GND 4
5 CTRL
6 VREG
CTRL 1
GND 2
TOP VIEW
7
SW 3
5 LED
4 VIN
SC8 PACKAGE
8-LEAD PLASTIC SC70
DC PACKAGE
6-LEAD (2mm × 2mm) PLASTIC DFN
TJMAX = 125°C, θJA = 65°C/W TO 85°C/W, θJC = 20°C/W
EXPOSED PAD (PIN 7) IS GND, MUST BE SOLDERED TO PCB
TJMAX = 125°C, θJA = 75°C/W TO 95°C/W
ORDER INFORMATION
LEAD FREE FINISH
TAPE AND REEL
PART MARKING
PACKAGE DESCRIPTION
TEMPERATURE RANGE
LT3590EDC#PBF
LT3590EDC#TRPBF
LCNZ
6-Lead (2mm × 2mm) Plastic DFN
–40°C to 85°C
LT3590ESC8#PBF
LT3590ESC8#TRPBF
LCPB
8-Lead Plastic SC70
–40°C to 85°C
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
Minimum Operating Voltage
TYP
MAX
UNITS
200
210
mV
4.5
●
LED Current Sense Voltage (VIN - VLED)
Sense Voltage Load Regulation
ΔILED = 10mA to 50mA
Quiescent Current ON, No Switching
VLED = 47.7V
Quiescent Current in Shutdown
VCTRL = 0V
190
5
Switching Frequency
●
650
Maximum Duty Cycle
●
90
80
Switch Current Limit
Switch VCESAT
ISW = 50mA
Switch Leakage Current
VSW = 48V
500
700
μA
15
20
μA
850
1050
kHz
%
115
1
150
2
μA
100
mV
V
150
CTRL Pin Bias Current
VCTRL = 1V, Current Out of Pin
LED Pin Bias Current
VLED = 47.8V
LDO Voltage VREG
IVREG = 1mA
LDO Load Regulation
ΔIVREG = 0mA to 1mA
LDO Current Limit
mV
100
3.1
nA
9
14
3.3
3.5
17
ISCHOTTKY = 50mA
Schottky Leakage Current
VR = 48V
μA
V
mV
1.5
Schottky Forward Drop
mA
mV
1.5
VCTRL to Shut Down IC
VCTRL to Turn on IC
mV
500
●
VCTRL for Full LED Current
V
mA
0.8
V
4
μA
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
(VCESAT)
0.7
–40°C
0.6
125°C
0.5
25°C
0.4
0.3
VCTRL = 0V
TA = 25°C
1.1
1.0
25°C
–40°C
0.9
0.8
125°C
0.7
0.6
0.4
20
60
40
80
SWITCH CURRENT (mA)
100
16
14
12
0
Quiescent Current
14
12
550
50
75
25
TEMPERATURE (°C)
100
125
50
40
60
500
450
1.5
VIN = 48V
1.0
VIN = 24V
0.5
400
0
30
VIN (V)
Schottky Leakage Current
SCHOTTKY LEAKAGE CURRENT (μA)
QUIESCENT CURRENT (μA)
16
20
10
2.0
VCTRL = 3.3V
TA = 25°C
18
0
3590 G03
600
VCTRL = 0V
VIN = 48V
10
–50 –25
10
100
200
50
150
SCHOTTKY FORWARD CURRENT (mA)
3590 G02
Shutdown Quiescent Current
vs Temperature
SHUTDOWN CURRENT (μA)
18
0.5
3590 G01
20
SHUTDOWN CURRENT (μA)
SCHOTTKY FORWARD DROP (V)
SWITCH SATURATION VOLTAGE (V)
20
1.2
0.8
0.2
Shutdown Quiescent
Current vs VIN
Schottky Forward Voltage Drop
0
10
20
30
VIN (V)
40
3590 G04
50
VIN = 4.5V
0
–50 –25
60
75
50
25
TEMPERATURE (°C)
0
125
3590 G06
3590 G05
Switching Waveform
100
Transient Response
CTRL
5V/DIV
IL
20mA/DIV
VSW
50V/DIV
IL
50mA/DIV
VSW
20V/DIV
ILED
50mA/DIV
1μs/DIV
VIN = 48V
ILED = 50mA
10 WHITE LEDs
L = 470μH (COILCRAFT)
3590 G07
VIN = 48V
ILED = 50mA
10 BLUE LEDs
40μs/DIV
3590 G08
3590f
4
LT3590
TYPICAL PERFORMANCE CHARACTERISTICS
Sense Voltage (VIN – VLED)
vs VCTRL
150
0.20
0.15
0.10
0.05
0
Switching Current Limit
vs Temperature
150
TA = 25°C
140
130
120
110
100
90
1
0.5
0
2
1.5
20
40
60
120
110
100
90
80
–50 –25
100
80
DUTY CYCLE (%)
Sense Voltage (VIN – VLED)
vs VIN
ILED = 50mA
10 WHITE LEDs
204 TA = 25°C
VIN-VLED (mV)
200
198
196
206
1000
204
950
202
200
198
196
194
0
10
20
40
30
VIN (V)
50
194
–50 –25
60
75
50
25
TEMPERATURE (°C)
0
100
800
750
700
–50 –25
3.25
VCTRL = 0V
ILED = 0V
20
30
VIN (V)
40
50
60
3590 G15
125
VCTRL = 3.3V
ILOAD = 1mA
3.35
3.30
3.30
VCTRL = 3.3V
ILED = 50mA
3.25
3.25
3.20
100
TREG (V)
VREG (V)
VCTRL = 3.3V
ILOAD = 1mA
50
75
25
TEMPERATURE (°C)
Internal Regulator
VREG vs Temperature
3.40
3.35
3.30
0
3590 G14
TA = 25°C
VCTRL = 0V
ILOAD = 0V
3.35
10
850
125
3.40
0
900
Internal Regulator
Load Regulation
3.40
TA = 25°C
VIN = 48V
3590 G13
3590 G12
Internal Regulator
Line Regulation
125
Switching Frequency over
Temperature
SWITCHING FREQUENCY (KHz)
206
100
3590 G11
Sense Voltage (VIN – VLED)
vs Temperature
202
75
50
25
TEMPERATURE (°C)
0
3590 G10
3590 G09
VIN-VLED (mV)
130
80
0
VCTRL (V)
VREG (V)
140
SWITCHING CURRENT LIMIT (mA)
VIN = 48V
ILED = 50mA
TA = 25°C
SWITCHING CURRENT LIMIT (mA)
SENSE VOLTAGE (VIN-VLED)
0.25
Switching Current Limit
vs Duty Cycle
3.20
0
0.2
0.6
0.4
ILOAD (mA)
0.8
1
3590 G16
3.20
–50
–25
75
0
25
50
TEMPERATURE (°C)
100
125
3590 G17
3590f
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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.
VIN (Pin 8/Pin 4): Input Supply Pin. Must be locally bypassed.
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 voltage (VIN - VLED) ramps from 0mV to 200mV, controlling
the LBD current.
V − VLED
ILED = IN
R1
Exposed Pad (NA/Pin 7): Ground. The Exposed Pad
should be soldered to the PCB ground to achieve the
rated thermal performance.
BLOCK DIAGRAM
VIN
48V
VIN
R1
6.8Ω
C1
1μF
+
–
REG
+
VREG
EAMP
–
+
+
A = 6.25
LED
–
C2
1μF
C3
0.1μF
VREF
1.25V
START-UP
CONTROL
SW
–
+
L1
470μH
VOUT
PWM
R
S
Q
+
∑
ISNS
–
RAMP
GENERATOR
850kHz
OSCILLATOR
CTRL
GND
CONTROL
3590 F01
Figure 1. Block Diagram
3590f
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LT3590
OPERATION
The LT3590 uses a constant-frequency, current mode
control scheme to provide excellent line and load regulation. Operation can be best understood by referring to the
Block Diagram.
The maximum input voltage is limited by the absolute
maximum VIN rating of 55V.
At power-up, the bandgap reference, the start-up bias, 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 current is added to a stabilizing ramp and the resulting sum
is fed into the positive terminal of the PWM comparator.
When this voltage exceeds the level at the negative input of
the PWM comparator, the PWM logic turns off the power
switch. The level at the negative input of the PWM comparator is set by the error amplifier EAMP, and is simply
an amplified version of the difference between the VIN and
VLED 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.
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 15% of the input supply voltage. If
the LED voltage plus sense resistor is less than 15% 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.
The LT3590 enters into shutdown when CTRL is pulled
lower than 100mV.
Input Voltage Range
The minimum input voltage required to generate a particular
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:
DC =
VLED + VD
VIN – VSW + VD
Where VD is the forward voltage drop of the catch diode
(~0.8V) and VSW is the voltage drop of the internal switch
at maximum load (~0.5V). Given DCMAX = 0.9, this leads
to minimum input voltage of:
(V + V )
VIN(MIN) = LED D + VSW − VD
DCMAX
Pulse-Skipping
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 continuous 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. The photo in Figure 2 details circuit operation driving
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; far less spectral energy is contained in the ringing
than in the switch transitions. The ringing can be damped
by application of a 3kΩ resistor across the inductor, although this will degrade efficiency.
VSW
20V/DIV
IL
10mA/DIV
400ns/DIV
VIN = 48V
ILED = 2mA
10 WHITE LEDs
L = 470μH (MURATA)
3590 F02
Figure 2. Switching Waveforms
3590f
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LT3590
APPLICATIONS INFORMATION
Inductor Selection
Capacitor Selection
A 220μH inductor is recommended for most LT3590 applications with VIN < 25V and 470μH is recommended for
applications with VIN > 25V. Although small size and high
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.
The small size of ceramic capacitors make them ideal
for LT3590 applications. X5R and X7R types are recommended 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.
Table 1. Inductor Manufacturers
PART
SERIES
INDUCTANCE
RANGE (μH)
(RELEVANT TO
THIS PART)
DO1605
LPS4012
LPS3010
1812FS
MSS5131
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
Sumida
www.sumida.com
CDC4D20
100 TO 680
4.8 × 4.8 × 2.0
Toko
www.tokoam.com
LLQ1608
LLQ2012
100 TO 270
100 TO 680
Würth Elektronik
www.we-online.com
WE-PD2
TYPE M
WE-PD2
TYPE L
100 TO 220
5.2 × 5.8 × 4.5
100 to 470
7.0 × 7.8 × 5.0
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
VENDOR
Coilcraft
www.coilcraft.com
92
5.1 × 5.1 × 3.1
Table 2 shows a list of several ceramic capacitor manufacturers. Consult the manufacturers for detailed information
on their entire selection of ceramic parts.
Table 2: Recommended Ceramic Capacitor Manufacturers
Taiyo Yuden
(408) 573-4150
www.t-yuden.com
AVX
(803) 448-9411
www.avxcorp.com
Murata
(714) 852-2001
www.murata.com
Kemet
(408) 986-0424
www.kemet.com
4.5 × 3.2 × 2.0
TDK SLF70145-471MR22-PF
MURATA QH32CN471K23
MURATA LQH43CN471K03
COILCRAFT LP06013-474KLB
COILCRAFT 1008PS-474KLB
COILCRAFT LPS4012-474ML
VIN = 48V
10 LEDs
FRONT PAGE
APPLICATION
CIRCUIT
90
EFFICIENCY (%)
DIMENSIONS
(mm)
88
86
84
0
10
30
20
LED CURRENT (mA)
40
50
3590 F03
Figure 3. Efficiency Comparison of Different Inductors
3590f
8
LT3590
APPLICATIONS INFORMATION
Programming LED Current
Using a DC Voltage
The feedback resistor (R1 in Figure 1) and the sense voltage (VIN - VLED) control the LED current.
For some applications, the preferred method of brightness
control is a variable DC voltage to adjust the LED current.
The CTRL pin voltage can be modulated to set the dimming of the LED string. As the voltage on the CTRL pin
increases from 0V to 1.5V, the LED current increases from
0 to ILED. As the CTRL pin voltage increases beyond 1.5V,
it has no effect on the LED current.
ILED =
VIN − VLED
R1
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 accurate LED current, precision resistors are preferred (1%
is recommended). The formula and table for R1 selection
are shown below.
200mV
R1 =
ILED
Table 3. R1 Theoretical Value for 200mV Sense
ILED (mA)
R1 (Ω)
10
20
200mV
,when VCTRL > 1.5V
R1
V
= CTRL ,when VCTRL < 1.25V
6.25 • R1
ILED =
ILED
Feedback voltage variation versus control voltage is
shown in Figure 4.
Using a Filtered PWM Signal
20
10
30
6.8
40
5.0
50
4.0
Dimming Control
There are three different types of dimming control circuits.
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.
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.
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.
LT3590
R1
10k
PWM
kHz TYP
0.25
CTRL
C1
1μF
3590 F05
0.20
VIN-VLED (V)
The LED current can be set by:
Figure 5. Dimming Control Using a Filtered PWM Signal
0.15
0.10
0.05
0
0
0.5
1.0
1.5
2.0
VCTRL (V)
3590 F04
Figure 4. Dimming and Shutdown Using CTRL Pin
3590f
9
LT3590
APPLICATIONS INFORMATION
Direct PWM Dimming
Changing the forward current flowing in the LEDs not only
changes the intensity of the LEDs, it also changes the color.
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.
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 continuously 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.
The time it takes for the LED current to reach its programmed 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
48V input voltage. The achievable dimming range for this
application and 100Hz PWM frequency can be determined
using the following method.
Example:
ƒ = 100Hz, t SETTLE = 50μs
tPERIOD =
1
1
=
= 0.01s
ƒ 100
Dim Range =
tPERIOD 0.01s
=
= 200 : 1
t SETTLE 50μs
Min Duty Cycle =
t SETTLE
50μs
• 100 =
• 1000 = 0.5%
tPERIOD
0.01s
Duty Cycle Range = 100% → 0.5% at 100Hz
The calculations show that for a 100Hz signal the dimming
range is 200 to 1. In addition, the minimum PWM duty
cycle of 0.5% ensures that the LED current has enough
time to settle to its final value. Figure 7 shows the dimming range achievable for three different frequencies with
a settling time of 50μs.
PWM
5V/DIV
100Hz
VSW
20V/DIV
1kHz
10kHz
ILED
20mA/DIV
VIN = 48V
4 LEDs
2ms/DIV
3590 F06
1
10
100
1000
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
signal sets the commanded sense voltage across the sense
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
dimmed first, modulating the duty cycle of the PWM signal.
Once the minimum duty cycle is reached, the height of the
PWM signal can be decreased below 1.5V down to 150mV.
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 shutdown. It is required to place a 0.1μF capacitor from VREG
to ground. The regulator current is limited to 1.5mA.
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 essential. Minimize the length and area of all traces connected
to the switching node pin (SW). Keep the sense voltage
pins (VIN and LED) away from the switching node. Place
the output capacitor, C2, next to the VIN pin. Always use
a ground plane under the switching regulator to minimize
interplane coupling. Recommended component placement
is shown in Figure 8.
C3
VREG
GND
GND
C3
VREG
GND
GND
CTRL
CTRL
VIN
VIN
5
4
6
3
7
2
8
1
CTRL
CTRL
6
1
4
3
C1
C2
5
7
2
VIN
C1
GND
R1
VREG
VREG
VIN
R1
LED
SW
C2
L1
OUT
LED
L1
OUT
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
C2
1μF
90
R1
4Ω
6
LEDs
C1
1μF
VIN
CONTROL
>1.5V
LED
L1
470μH
CTRL
EFFICIENCY (%)
VIN
48V
50mA
LT3590
70
60
50
VREG
C3
0.1μF
80
SW
3590 TA02a
40
GND
10
0
20
30
LED CURRENT (mA)
40
50
3590 TA02b
L1: MURATA LQH32CN221K03
48V Supply for 5 LED String, 30mA Current
Conversion Efficiency
100
C2
1μF
90
R1
6.8Ω
C1
1μF
VIN
CONTROL
>1.5V
LED
L1
470μH
CTRL
EFFICIENCY (%)
VIN
48V
30mA
LT3590
70
60
50
VREG
C3
0.1μF
80
SW
3590 TA03a
40
GND
0
5
20
15
10
LED CURRENT (mA)
25
30
3590 TA03b
L1: MURATA LQH32CN-391
24V Supply for a 5 LED String, 30mA Current
Conversion Efficiency
100
C2
1μF
90
R1
6.8Ω
C1
1μF
CONTROL
>1.5V
VIN
LED
L1
220μH
CTRL
LT3590
VREG
C3
0.1μF
80
70
60
50
SW
GND
EFFICIENCY (%)
VIN
24V
30mA
3590 TA04a
40
0
5
20
15
10
LED CURRENT (mA)
25
30
3590 TA04b
L1: MURATA LQH32CN-221
3590f
12
LT3590
TYPICAL APPLICATIONS
12V or 24V Supply for a Single LED, 50mA Current
Conversion Efficiency
80
C2
2.2μF
75
R1
4Ω
C1
1μF
VIN
CONTROL
>1.5V
LED
L1
220μH
CTRL
VREG
65
24V
60
55
50
LT3590
45
SW
C3
0.1μF
12V
70
EFFICIENCY (%)
VIN
12V OR 24V
50mA
3590 TA05a
40
GND
0
10
20
30
LED CURRENT (mA)
40
50
3590 TA05b
48V Supply for Two Strings of 10 LEDs, 25mA Current
Conversion Efficiency
100
C2
1μF
90
EFFECIENCY (%)
25mA
R1
4Ω
25mA
VIN
48V
C1
1μF
80
70
60
50
VIN
CONTROL
>1.5V
LED
LT3590
VREG
C3
0.1μF
40
L1
470μH
CTRL
SW
0
5
10
15
LED CURRENT (mA)
20
25
3590 TA06b
3590 TA06a
GND
12V Supply for a 3 LED String, 50mA Current
Conversion Efficiency
C2
1μF
100
90
R1
4Ω
C1
1μF
CONTROL
>1.5V
VIN
LED
L1
220μH
CTRL
LT3590
VREG
C3
0.1μF
L1: MURATA LQH32CN-221
80
70
60
50
SW
GND
EFFICIENCY (%)
VIN
12V
50mA
3590 TA07a
40
0
10
20
30
LED CURRENT (mA)
40
50
3590 TA07b
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)
0.675 ±0.05
2.50 ±0.05
1.15 ±0.05 0.61 ±0.05
(2 SIDES)
PACKAGE
OUTLINE
PIN 1 BAR
TOP MARK
(SEE NOTE 6)
0.38 ± 0.05
4
2.00 ±0.10
(4 SIDES)
PIN 1
CHAMFER OF
EXPOSED PAD
3
0.25 ± 0.05
0.50 BSC
1.42 ±0.05
(2 SIDES)
0.200 REF
RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS
6
0.75 ±0.05
1
(DC6) DFN 1103
0.25 ± 0.05
0.50 BSC
1.37 ±0.05
(2 SIDES)
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
PIN 8
1.80 – 2.20
(NOTE 4)
1.00 REF
INDEX AREA
(NOTE 6)
1.80 – 2.40 1.15 – 1.35
(NOTE 4)
2.8 BSC 1.8 REF
PIN 1
RECOMMENDED SOLDER PAD LAYOUT
PER IPC CALCULATOR
0.10 – 0.40
0.50 BSC
0.15 – 0.27
8 PLCS (NOTE 3)
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
3. DIMENSIONS ARE INCLUSIVE OF PLATING
4. DIMENSIONS ARE EXCLUSIVE OF MOLD FLASH
AND METAL BURR
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
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 representation 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
C1
1μF
CONTROL
>1.5V
VIN
90
LED
L1
220μH
CTRL
LT3590
VREG
C3
0.1μF
EFFICIENCY (%)
VIN
24V
50mA
85
80
75
70
65
SW
3590 TA08a
GND
60
0
L1: MURATA LQH32CN-221
10
20
30
LED CURRENT (mA)
40
50
3590 TA08b
RELATED PARTS
PART NUMBER DESCRIPTION
COMMENTS
LT1932
Constant Current, 1.2MHz, High Efficiency White LED Boost
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VIN: 1.0V to 10.0V, VOUT(MAX) = 34V, Dimming Analog/PWM,
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LT3003
Three Channel LED Ballaster with PWM Dimming
VIN: 3.0V to 48.0V, Dimming 3,000:1 True Color PWM™,
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LT3465/A
Constant Current, 1.2/2.7MHz, High Efficiency White LED Boost
Regulator with Integrated Schottky Diode
VIN: 2.7V to 16.0V, VOUT(MAX) = 34V, Dimming Analog/PWM,
ISD <1μA, ThinSOT Package
LT3466/-1
Dual Constant Current, 2MHz, High Efficiency White LED Boost
Regulator with Integrated Schottky Diode
VIN: 2.7V to 24.0V, VOUT(MAX) = 40V, Dimming 5mA, ISD <16μA,
3mm × 3mm DFN-10
LT3474
36V, 1A (ILED), 2MHz,Step-Down LED Driver
VIN: 4.0V to 36V, VOUT(MAX) = 13.5V, Dimming 400:1 True Color
PWM, ISD <1μA, TSSOP16E Package
LT3475
Dual 1.5A(ILED), 36V, 2MHz, Step-Down LED Driver
VIN: 4.0V to 36V, VOUT(MAX) = 13.5V, Dimming 3,000:1 True Color
PWM, ISD <1μA, TSSOP20E Package
LT3476
Quad Output 1.5A, 2MHz High Current LED Driver with 1,000:1
Dimming
VIN: 2.8V to 16.0V, VOUT(MAX) = 36.0V, Dimming 1,000:1 True
Color PWM, ISD <10μA, 5mm × 7mm QFN-10
LT3478/-1
4.5A, 2MHz High Current LED Driver with 3,000:1 Dimming
VIN: 2.8V to 36.0V, VOUT(MAX) = 40.0V, Dimming 1,000:1 True
Color PWM, ISD <10μA, 5mm × 7mm QFN-10
LT3486
Dual 1.3A, 2MHz High Current LED Driver
VIN: 2.5V to 24.0V, VOUT(MAX) = 36.0V, Dimming 1,000:1 True
Color PWM, ISD <1μA, 5mm × 3mm DFN, TSSOP-16E Package
LT3491
Constant Current, 2.3MHz, High Efficiency White LED Boost
Regulator with Integrated Schottky Diode
VIN: 2.5V to 12.0V, VOUT(MAX) = 27V, Dimming 300:1 True Color
PWM, ISD <8μA, 2mm × 2mm DFN-6, SC70 Package
LT3496
Triple Output 750mA, 2.1 MHz High Current LED Driver with 3,000:1
Dimming
VIN: 3.0V to 30.0V, VOUT(MAX) = 40.0, Dimming 3,000:1 True
Color PWM, ISD <1μA, 4mm × 5mm QFN-28
LT3497
Dual 2.3MHz, Full Function LED Driver with Integrated Schottkys and VIN: 2.5V to 10.0V, VOUT(MAX) = 32, Dimming 250:1 True Color
250:1 True Color PWM Dimming
PWM, ISD <12μA, 2mm × 3mm DFN-10
LT3498
20mA LED Driver and OLED Driver Integrated Schottkys
VIN: 2.5 to 12.0V, VOUT(MAX) = 32, Dimming Analog/PWM,
ISD <8.5μA, 2mm × 3mm DFN-12
LT3517
1.3A, 2.5MHz High Current LED Driver with 3,000:1 Dimming
VIN: 3.0V to 30.0V, Dimming 3,000:1 True Color PWM, ISD <1μA,
4mm × 4mm QFN-16
LT3518
2.3A, 2.5MHz High Current LED Driver with 3,000:1 Dimming
VIN: 3.0V to 30.0V, Dimming 3,000:1 True Color PWM, ISD <1μA,
4mm × 4mm QFN-16
LT3591
Constant Current, 1MHz, High Efficiency White LED Boost Regulator
with Integrated Schottky Diode and 80:1 True Color PWM Dimming
VIN: 2.5V to 12.0V, VOUT(MAX) = 40, Dimming 80:1 True Color
PWM, ISD <9μA, 2mm × 3mm DFN-8
ThinSOT and True Color PWM are trademarks of Linear Technology Corporation.
3590f
16 Linear Technology Corporation
LT 0707 • PRINTED IN USA
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408) 432-1900 ● FAX: (408) 434-0507
●
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© LINEAR TECHNOLOGY CORPORATION 2007