LT3592IDDB#TR [Linear]
IC LED DISPLAY DRIVER, PDSO10, 3 X 2 MM, PLASTIC, MO-229WECD-1, DFN-10, Display Driver;
| 型号： | LT3592IDDB#TR |
| 厂家： | 
Linear |
| 描述： | IC LED DISPLAY DRIVER, PDSO10, 3 X 2 MM, PLASTIC, MO-229WECD-1, DFN-10, Display Driver 驱动器 |
| 文件： | 总24页 (文件大小：304K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
LT3592
500mA Wide Input Voltage
Range Step-Down LED Driver
with 10:1 Dimming
FEATURES
DESCRIPTION
The LT®3592 is a fixed frequency step-down DC/DC con-
verter designed to operate as a constant-current source.
An external sense resistor monitors the output current
allowing accurate current regulation, ideal for driving
high current LEDs. The output current can be dimmed
by a factor of 10 using an external signal for nighttime
brake lights.
n
Wide Input Voltage Range
Operation from 3.6V to 36V
n
Resistor Adjustable 400kHz–2.2MHz Switching
Frequency
n
Shorted and Open LED Protected
n
Internal Switch Current Sense Resistor
n
External Resistor Programs LED Current, Pin
Selects 10:1 Ratio
50mA/500mA LED Current Settings
Thehighswitchingfrequencyoffersseveraladvantagesby
permitting the use of a small inductor and small ceramic
capacitors.SmallcomponentscombinedwiththeLT3592’s
10-pinDFNleadlesssurfacemountpackagesavespaceand
cost versus alternative solutions. The constant switching
frequencycombinedwithlow-impedanceceramiccapaci-
tors result in low, predictable output ripple.
n
n
Catch Diode Current Sense to Prevent Runaway at
High V
IN
n
Small Thermally Enhanced 10-Lead DFN
(2mm × 3mm) and MSOP-10 Packages
APPLICATIONS
A wide input voltage range of 3.6V to 36V makes the
LT3592 useful in a variety of applications. Current mode
PWM architecture provides fast transient response and
cycle-by-cyclecurrentlimiting.Thermalshutdownprovides
additional protection.
n
Automotive Signal Lighting
Industrial Lighting
n
n
Constant-Current, Constant Voltage Supplies
L, LT, LTC and LTM are registered trademarks of Linear Technology Corporation.
All other trademarks are the property of their respective owners.
TYPICAL APPLICATION
50/500mA Two Series Red LED Driver
Efficiency for 2 Red LEDs, L = 10μH, 900kHz
100
95
V
IN
V
BOOST
LT3592
IN
7V TO 32V
1μF
0.1μF
10μH
90
SW
BRIGHT 500mA
85
80
75
70
65
60
55
50
DA
CAP
+
SHDN
ON
200/20mV
–
0.4Ω
4.7μF
BRIGHT
OUT
BRAKE
51k
10k
R
T
V
FB
GND
140k
900kHz
4
8
12
16
20
24
28
INPUT VOLTAGE (V)
3592 TA01a
3592 TA01b
3592fa
1
LT3592
(Note 1)
ABSOLUTE MAXIMUM RATINGS
V , BRIGHT Voltages ................................ –0.3V to 36V
SHDN Voltage ............................................................V
IN
DA Pin Current (Average)..................... –1.2A (sourcing)
Operating Temperature Range (Notes 2, 3)
LT3592E............................................. –40°C to 125°C
LT3592I.............................................. –40°C to 125°C
Storage Temperature Range................... –65°C to 150°C
IN
BOOST Voltage .........................................................60V
BOOST above SW pin ...............................................30V
CAP, OUT Voltages (OUT ≤ CAP) ...............................30V
V
Voltage .................................................................4V
FB
R Voltage...................................................................6V
T
PIN CONFIGURATION
TOP VIEW
TOP VIEW
R
1
2
3
4
5
10
9
V
FB
T
R
1
2
3
4
5
10
9
V
FB
T
BRIGHT
OUT
BRIGHT
OUT
11
11
SHDN
8
CAP
BOOST
SW
SHDN
8
CAP
V
7
6
IN
V
IN
7
BOOST
SW
DA
DA
6
MSE PACKAGE
10-LEAD PLASTIC MSOP
DDB PACKAGE
θ
JA
= 38°C/W, θ = 8°C/W
JC
EXPOSED PAD (PIN 11) IS GND, MUST BE SOLDERED TO PCB
10-LEAD (3mm s 2mm) PLASTIC DFN
θ
= 76°C/W, θ = 13.5°C/W
JC
EXPOSED PAD (PIN 11) IS GND, MUST BE SOLDERED TO PCB
JA
ORDER INFORMATION
LEAD FREE FINISH
LT3592EDDB#PBF
LT3592IDDB#PBF
LT3592EMSE#PBF
LT3592IMSE#PBF
LEAD BASED FINISH
LT3592EDDB
TAPE AND REEL
PART MARKING*
LDCQ
PACKAGE DESCRIPTION
TEMPERATURE RANGE
LT3592EDDB#TRPBF
LT3592IDDB#TRPBF
LT3592EMSE#TRPBF
LT3592IMSE#TRPBF
TAPE AND REEL
–40°C to 125°C
–40°C to 125°C
–40°C to 125°C
–40°C to 125°C
TEMPERATURE RANGE
–40°C to 125°C
–40°C to 125°C
–40°C to 125°C
–40°C to 125°C
10-Lead (3mm × 2mm) Plastic DFN
10-Lead (3mm × 2mm) Plastic DFN
10-Lead Plastic MSOP
LDCQ
LTDCR
LTDCR
10-Lead Plastic MSOP
PART MARKING
LDCQ
PACKAGE DESCRIPTION
LT3592EDDB#TR
LT3592IDDB#TR
10-Lead (3mm × 2mm) Plastic DFN
10-Lead (3mm × 2mm) Plastic DFN
10-Lead Plastic MSOP
LT3592IDDB
LDCQ
LT3592EMSE
LT3592EMSE#TR
LT3592IMSE#TR
LTDCR
LT3592IMSE
LTDCR
10-Lead Plastic MSOP
Consult LTC Marketing for parts specified with wider operating temperature ranges. *The temperature grade is identified by a label on the shipping container.
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/
3592fa
2
LT3592
ELECTRICAL CHARACTERISTICS The l denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C. VIN = 12V, VBOOST = 16V, VOUT = 4V unless otherwise noted. (Note 2)
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
l
Minimum Input Voltage
3.25
3.6
V
Input Quiescent Current
- in Shutdown
Not Switching
SHDN
2
0.1
3
2
mA
μA
V
= 0.3V
CAP to OUT Voltage
0.4ꢀ CAP to OUT
BRIGHT = 1.4V
BRIGHT = 0.3V
l
l
190
18
200
20
210
22
mV
mV
DA Pin Current to Stop OSC
Switching Frequency
–0.8
–1
–1.2
A
R = 357k
350
800
1.9
400
900
2.2
450
1000
2.5
kHz
kHz
MHz
T
R = 140k
T
R = 48.7k
T
Maximum Duty Cycle
R = 140k
90
94
%
V
T
SHDN Input High Voltage
SHDN Input Low Voltage
BRIGHT Input High Voltage
BRIGHT Input Low Voltage
Switch Current Limit (Note 4)
2.3
0.3
V
1.4
V
0.3
1.5
V
l
0.85
1.25
300
20
A
Switch V
I
I
= 500mA
= 500mA
mV
mA
μA
V
CESAT
SW
Boost Pin Current
30
10
SW
Switch Leakage Current
Minimum Boost Voltage
Boost Diode Forward Voltage
1
V
OUT
= 4V
1.8
800
1.21
2.5
I
= 50mA
mV
V
DIO
l
V
FB
Voltage
OUT = CAP = 4V
1.185
1.235
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 LT3592E is guaranteed to meet performance specifications
from 0°C to 125°C junction temperature. Specifications over the –40°C
to 125°C operating junction temperature range are assured by design,
characterization and correlation with statistical process controls. The
LT3592I is guaranteed over the full –40°C to 125°C operating junction
temperature range. The operating lifetime is derated at junction
temperatures greater than 125°C.
Note 3: 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 result in
device degradation or failure.
Note 4: Switch Current Measurements are performed when the outputs
are not switching. Slope compensation reduces current limit at higher duty
cycles.
3592fa
3
LT3592
(TA = 25°C, unless otherwise noted)
TYPICAL PERFORMANCE CHARACTERISTICS
Efficiency (2 Red LEDS,
L = 10μH, 900kHz)
Efficiency (1 Red LED,
L = 6.8μH, 900kHz)
Efficiency (2 Red LEDs,
L = 22μH, 400kHz)
100
100
95
90
85
80
75
70
65
60
55
50
45
40
100
95
90
85
80
75
70
65
60
55
50
45
40
95
90
BRIGHT (500mA)
BRIGHT (500mA)
85
80
75
70
65
60
55
50
BRIGHT (500mA)
4
8
12
16
20
24
28
4
8
12
16
20
24
28
4
8
12
16
20
24
28
INPUT VOLTAGE (V)
INPUT VOLTAGE (V)
INPUT VOLTAGE (V)
3592 G01
3592 G03
3592 G02
Minimum VIN for 500mA Output
Current vs VOUT, L = 22μH,
f = 400kHz (LED Loads)
Minimum VIN for 500mA Output
Current vs VOUT, L = 6.8μH,
f = 900kHz (LED Loads)
Efficiency (2 Red LEDs,
L = 4.7μH, 2.2MHz)
100
95
90
85
80
75
70
65
60
55
50
12
11
10
9
12
11
10
9
BRIGHT (500mA)
8
8
7
7
6
6
5
5
4
4
3
3
2
2
4
8
12
16
20
24
28
2
4
6
8
10
12
2
4
6
8
10
12
INPUT VOLTAGE (V)
INPUT VOLTAGE (V)
INPUT VOLTAGE (V)
3592 G04
3592 G06
3592 G05
Minimum VIN for 500mA Output
Current vs VOUT, L = 22μH,
f = 400kHz (LED Loads)
Switch Voltage Drop
vs Switch Current
Switch Voltage Drop at 500mA
vs Temperature
500
450
400
350
300
250
200
150
100
50
400
375
350
325
300
275
250
12
11
10
9
8
7
6
5
4
3
0
2
0
100 200 300 400 500 600 700 800
–50
0
50
100
150
2
4
6
8
10
12
14
16
SWITCH CURRENT (mA)
TEMPERATURE (°C)
INPUT VOLTAGE (V)
3592 G08
3592 G09
3592 G07
3592fa
4
LT3592
(TA = 25°C, unless otherwise noted)
TYPICAL PERFORMANCE CHARACTERISTICS
Undervoltage Lockout
vs Temperature
Switching Frequency
vs Temperature
Current Limit During Soft Start
3.4
3.3
3.2
3.1
2300
2100
1900
1700
1500
1300
1100
900
1400
1200
1000
800
600
400
200
0
R
= 48.7k
T
R
R
= 140k
= 357k
T
700
500
T
300
–50
0
50
100
150
–50 –30 –10 10 30 50 70 90 110 130
0.5
1
1.5
2
2.5
TEMPERATURE (°C)
TEMPERATURE (°C)
V
(V)
SHDN
3592 G10
3592 G11
3592 G12
Switch Current Limit
Frequency Foldback
Switch Current Limit
1.4
2500
2000
1500
1000
500
1.50
1.45
1.40
1.35
1.30
1.25
1.20
1.15
1.10
1.05
1.00
R
T
= 48.7k
1.3
1.2
1.1
1
TYPICAL
0.9
0.8
0.7
0.6
0.5
0
0
20
40
60
80
100
600 800 1000 1200 1400 1600 1800 2000 2200
–50 –30 –10 10 30 50 70 90 110 130
DUTY CYCLE (%)
SHDN VOLTAGE (mV)
TEMPERATURE (°C)
3592 G14
3592 G13
3592 G15
Operating Waveforms,
Discontinuous Mode
Operating Waveforms
V
V
SW
5V/DIV
SW
5V/DIV
V
V
CAP
CAP
10mV/DIV
10mV/DIV
AC COUPLED
AC COUPLED
I
I
L
L
500mA/DIV
500mA/DIV
3592 G16
3592 G17
500ns/DIV
500ns/DIV
3592fa
5
LT3592
(TA = 25°C, unless otherwise noted)
TYPICAL PERFORMANCE CHARACTERISTICS
VBRIGHT vs VOUT
VDIM vs VOUT
210
205
200
195
190
25
24
23
22
21
20
19
18
17
16
15
V
(mV)
BRIGHT
V
(mV)
DIM
0
2
4
6
8
10
12
0
2
4
6
8
10
12
V
(V)
V
(V)
OUT
OUT
3592 G18
3592 G19
Boost Diode Voltage vs Current
Switching Frequency vs RT
1.0
0.9
0.8
0.7
0.6
0.5
0.4
3000
2500
2000
1500
1000
500
V
BSTDIO
0
0
50
100
150
200
30 60 90 120 150 180 210 240 270 300 330 360
(kΩ)
DIODE CURRENT (mA)
R
T
3592 G20
3592 G21
3592fa
6
LT3592
PIN FUNCTIONS
R (Pin1):Programsthefrequencyoftheinternaloscillator.
capacitor. An internal Schottky is provided for the boost
function and an external diode is not needed. An external
Schottky diode should be connected between BOOST and
CAP for single LED applications or whenever a higher
BOOST voltage is desired.
T
Connect a resistor from R to ground. Refer to Table 1 or
T
theTypicalPerformanceCharacteristicsforresistorvalues
that result in desired oscillator frequencies.
BRIGHT (Pin 2): Used to program a 10:1 dimming ratio
for theLED current. Drivethispinabove1.4Vtocommand
maximum intensity or below 0.3V to command minimum
intensity. This pin can be PWMed at 150Hz for brightness
control between the 1x and 10x current levels.
CAP (Pin 8): Output of the step-down converter and also
an input to the LED current sense amplifier. Connect the
filter capacitor, inductor, and the top of the external LED
current sense resistor to this pin.
SHDN (Pin 3): Used to shutdown the switching regulator
and the internal bias circuits. This pin can be PWMed at
150Hz for brightness control.
OUT (Pin 9): Drives the LED or LEDs and is the other
input to the LED current sense amplifier. Connect this pin
to the anode of the top LED in the string, the bottom of
the external LED current sense resistor, and the top of the
V (Pin 4): Supplies current to the LT3592’s internal cir-
IN
V
resistor divider.
FB
cuitry and to the internal power switches. Must be locally
bypassed.Forautomotiveapplications,apinetworkwitha
V
(Pin 10): The feedback node for the output voltage
FB
capfromV toGND, aseriesinductorconnectedbetween
controlloop.TiethisnodetoaresistordividerbetweenOUT
and GND to set the maximum output voltage of the step-
down converter according to the following formula:
IN
V and the power source, and another cap from the far
IN
end of the inductor to GND is recommended.
DA (Pin 5): Allows the external catch diode current to be
R1+R2
VOUT =1.21•
R2
sensed to prevent current runaway, such as when V is
IN
high and the duty cycle is very low. Connect this pin to
the anode of the external catch Schottky diode.
whereR1connectsbetweenOUTandV andR2connects
FB
between V and GND.
FB
SW (Pin 6): The SW pin is the output of the internal power
switch. Connect this pin to the inductor and the cathode
of the switching diode.
GND, EXPOSED PAD (Pin 11): The underside exposed
pad metal of the package provides both electrical contact
to ground and good thermal contact to the printed circuit
board. The device must be soldered to the circuit board
for proper operation.
BOOST (Pin 7): Provides a drive voltage, higher than the
input voltage to the internal bipolar NPN power switch.
BOOST will normally be tied to the SW pin through a 0.1μF
3592fa
7
LT3592
BLOCK DIAGRAM
L2
C2C
L2
BATT
C2B
C2A
4
V
IN
BRIGHT
BRAKE
2
R
CAP
OUT
+
–
8
9
10R
R
RS
R1
R2
SENSE
BOOST
7
6
–
–
+
g
=
m
LED1
LED2
R
V
R
S
C3
D1
FB
10
Q
Q1
1.21V
L1
SW
DA
6
5
C1
GND
+
–
REG/UVLO
OSC
1
R
T
SHDN
GND
3
11
R3
V
IN
R
T
C4
3592 BD
3592fa
8
LT3592
OPERATION
error amplifier output means less output current. Current
The LT3592 is a constant frequency, current mode step-
limit is provided by an active clamp on the V node, and
downLEDdriver.Aninternaloscillatorthatisprogrammed
C
this node is also clamped to the SHDN pin. Soft-start is
implemented by ramping the SHDN pin using an external
resistor and capacitor.
by a resistor from the R pin to ground enables an RS
T
flip-flop, turning on the internal 1A power switch Q1. An
amplifier and comparator monitor the current flowing
between the V and SW pins, turning the switch off when
IN
An internal regulator provides power to the control
circuitry and also includes an undervoltage lockout to
this current reaches a level determined by the voltage at
V . An error amplifier that servos the V node has two
C
C
prevent switching when V is less than 3.25V. If SHDN
IN
inputs, one from a voltage measurement and one from a
is low, the output is disconnected and the input current
current measurement.
is less than 2μA.
An instrumentation amplifier measures the drop across
an external current sense resistor between the CAP and
OUT pins and applies a gain of 60 (BRIGHT low for dim
mode) or 6 (BRIGHT high for bright mode) to this signal
andpresentsittoonenegativeerrorampinput.Theoutput
of a external resistor divider between OUT and ground is
The switch driver operates from the input of the BOOST
pin. An external capacitor and internal diode are used to
generate a voltage at the BOOST pin that is higher than the
input supply, which allows the driver to fully saturate the
internal bipolar NPN power switch for efficient operation.
An external diode can be used to make the BOOST drive
more effective at low output voltage.
tiedtotheV pinandpresentedtoasecondnegativeerror
FB
ampinput. Whicheverinputishigherinvoltagewillendup
controlling the loop, so a circuit in which current control
is desired (as for driving a LED) will be set up such that
the output of the instrumentation amp will be higher than
The oscillator reduces the LT3592’s operating frequency
when the voltage at the OUT pin is low. This frequency
foldbackhelpstocontroltheoutputcurrentduringstartup
and overload.
the V pin at the current level that is desired. The voltage
FB
feedbackloopwillacttolimittheoutputvoltageandprevent
The anode of the catch diode for the step-down circuit is
connected to the DA pin to provide a direct sense of the
current in this device. If this diode’s current goes above a
level set by an internal catch diode current limit circuit, the
oscillatorfrequencyissloweddown.Thispreventscurrent
circuit damage if an LED should go open circuit.
The positive input to the error amp is a 1.21V reference,
so the voltage loop forces the V pin to 1.21V and the
FB
current loop forces the voltage difference between CAP
and OUT to be 200mV for BRIGHT mode and 20mV for
DIM mode. A rise in the output of the error amplifier
results in a increase in output current, and a fall in the
runaway due to minimum on time limitations at high V
IN
voltages. This function can easily be disabled by tying the
DA pin and the catch diode anode to ground.
3592fa
9
LT3592
APPLICATIONS INFORMATION
Oscillator
The BRIGHT mode current is given by:
= 200mV/R
The frequency of operation is programmed by an external
I
BRIGHT
SENSE
resistor from R to ground. Table 1 shows R values for
T
T
The DIM mode current is 10% of the BRIGHT mode value.
The maximum allowed DC value of the BRIGHT mode cur-
rentis500mA.Whentherecommendedcomponentvalues
are used in a 900kHz 2 LED application, the transient from
switching between BRIGHT and DIM currents will be less
than 50μs in duration.
commonlyusedoscillatorfrequencies,andrefertotheTypi-
cal Performance Characteristics curve for other values.
Table 1. RT Values for Selector Oscillator Frequencies
f
R
T
OSC
400kHz
900kHz
2.2MHz
357k
140k
48.7k
The sense resistor used should exhibit a low TC to keep
theLEDcurrentfromdriftingastheoperatingtemperature
changes.
FB Resistor Network
The BRIGHT pin can tolerate voltages as high as 36V and
The output voltage limit is programmed with a resistor
can be safely tied to V even in high voltage applications,
IN
divider between the output and the V pin. This is the
but it also has a low threshold voltage (~0.7V) that allows
FB
voltage that the output will be clamped to in case the LED
it to interface to logic level control signals.
goes open circuit. Choose the resistors according to
Input Voltage Range
R1 = R2([V /1.21V] – 1)
OUT
The maximum allowed input voltage for the LT3592 is
36V. The minimum input voltage is determined by either
the LT3592’s minimum operating voltage of 3.6V 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:
Be sure to choose V
such that it does not interfere with
OUT
the operation of the current control loop; it should be set
at least 10% above the maximum expected LED voltage
for the selected BRIGHT output current. R2 should be 20k
or less to avoid bias current errors. An optional phase-
lead capacitor of 22pf between V
light-load ripple.
and V reduces
OUT
FB
VOUT + VD
DC =
V – VSW + VD
IN
Output Current Selection
where V is the forward voltage drop of the catch diode
D
The output current levels are programmed by the value of
the external current sense resistor between CAP and OUT.
(~0.4V) and V is the voltage drop of the internal switch
SW
Table 2. Inductor Vendor Information
SUPPLIER
Panasonic
Vishay
PHONE
FAX
WEBSITE
www.panasonic.com/industrial/components/components.html
www.vishay.com/resistors
(800) 344-2112
(402) 563-6866
(847) 639-6400
(800) 227-7040
(402) 563-6296
(847) 639-1469
(650) 361-2508
(814) 238-0490
Coilcraft
www.coilcraft.com
CoEv Magnetics
Murata
www.circuitprotection.com/magnetics.asp
www.murata.com
(814) 237-1431
(800) 831-9172
Sumida
USA: (847) 956-0666
USA: (847) 956-0702
www.sumida.com
Japan: 81(3) 3607-5111 Japan: 81(3) 3607-5144
TDK
(847) 803-6100
(847) 297-0070
(847) 803-6296
(847) 699-7864
www.component.tdk.com
www.tokoam.com
TOKO
3592fa
10
LT3592
APPLICATIONS INFORMATION
(~0.4V at maximum load). This leads to a minimum input
voltage of:
the V absolute maximum range (36V) during overload
IN
conditions (short circuit or startup).
VOUT + VD
DCMAX
Minimum On Time
V
=
– VD + VSW
IN(MIN)
The LT3592 will still regulate the output properly at input
voltages that exceed V
(up to 36V); however, the
IN(MAX)
with DCmax = 0.90.
output voltage ripple increases as the input voltage is
The maximum input voltage is determined by the absolute
maximum ratings of the V and BOOST pins. The con-
tinuous mode operation, the maximum input voltage is
determinedbytheminimumdutycycle,whichisdependent
upon the oscillator frequency:
increased.
IN
Figure1illustratesswitchingwaveformsina2.2mHzsingle
red LED application near V
= 24V.
IN(MAX)
As the input voltage is increased, the part is required to
switch for shorter periods of time. Delays associated with
turning off the power switch dictate the minimum on time
of the part. The minimum on time for the LT3592 is ~70ns.
Figure 2 illustrates the switching waveforms when the
DC
= F
• 70nsec
MIN
OSC
VOUT + VD
DCMIN
V
=
– VD + VSW
IN(MAX)
input voltage is increased to V = 26V.
IN
Notethatthisisarestrictionontheoperatinginputvoltage
for continuous mode operation. The circuit will tolerate
transient inputs up to the absolute maximum of the V
and BOOST pins. The input voltage should be limited to
Now the required on time has decreased below the mini-
mum on time of 70ns. Instead of the switch pulse width
becoming narrower to accommodate the lower duty
cycle requirement, the switch pulse width remains fixed
at 70ns. In Figure 2, the inductor current ramps up to a
value exceeding the load current and the output ripple
increases to about 70mV. The part then remains off until
the output voltage dips below the programmed value
before it switches again.
IN
V
OUT
50mV/DIV
I
L
500mA/DIV
Provided that the load can tolerate the increases output
voltage ripple and the the components have been properly
V
SW
20V/DIV
selected,operationaboutV
issafeandwillnotdam-
3592 F01
IN(MAX)
1μs/DIV
age the part. Figure 3 illustrates the switching waveforms
when the input voltage is increased to 36V.
Figure 1.
V
V
OUT
OUT
50mV/DIV
50mV/DIV
I
L
I
L
500mA/DIV
500mA/DIV
V
V
SW
20V/DIV
SW
20V/DIV
3592 F02
3592 F03
1μs/DIV
1μs/DIV
Figure 2.
Figure 3.
3592fa
11
LT3592
APPLICATIONS INFORMATION
As the input voltage increases, the inductor current ramps
up more quickly, the number of skipped pulses increases,
and the output voltage ripple increases. For operation
Characteristics section of this data sheet that show the
maximum load current as a function of input voltage and
inductor value for several popular output voltages. Low
inductance may result in discontinuous mode operation,
which is acceptable, but further reduces maximum load
current. For details of the maximum output current and
discontinuous mode operation, see Linear Technology
Application Note 44.
above V
, the only component requirement is that
IN(MAX)
they be adequately rated for operation at the intended
voltage levels.
The LT3592 is robust enough to survive prolonged opera-
tion under these conditions as long as the peak inductor
current does not exceed 1.2A. Inductor saturation due to
high current may further limit performance in this operat-
ing regime.
Catch Diode
Depending on load current, a 500mA to 1A Schottky di-
ode is recommended for the catch diode, D1. The diode
must have a reverse voltage rating equal to or greater
than the maximum input voltage. The ON Semiconductor
MBRA140T3andCentralSemiconductorCMMSH1-40are
good choices, as they are rated for 1A continuous forward
current and a maximum reverse voltage of 40V.
Inductor Selection and Maximum Output Current
A good first choice for the inductor value is:
V
OUT + 0.2V + VD
(
)
L =1.2A •
ƒ
Input Filter Network
where V is the forward voltage drop of the catch diode
D
(~0.4V), f is the switching frequency in MHz and L is in μH.
Withthisvalue,therewillbenosubharmonicoscillationfor
applications with 50% or greater duty cycle. For low duty
For applications that only require a capacitor, bypass V
IN
with a 1μF or higher ceramic capacitor of X7R or X5R
type. Y5V types have poor performance over tempera-
ture and applied voltage and should not be used. A 1μF
ceramic capacitor is adequate to bypass the LT3592 and
will easily handle the ripple current. However, if the input
power source has high impedance, or there is significant
inductance due to long wires or cables, additional bulk
capacitance might be necessary. The can be provided
with a low performance (high ESR) electrolytic capacitor
in parallel with the ceramic device.
cycle applications in which V is more than three times
IN
V
, a good guide for the minimum inductor value is
OUT
ꢁ
ꢄ ꢁ
ꢄ
V ꢀ V ꢀ 0.2V
VOUT + 0.2V + VD
(
)
(
)
IN
OUT
L =1.7 •
•
ꢃ
ꢆ ꢃ
ꢆ
V ꢀ VSW + VD
ƒ
ꢂ
ꢅ ꢂ
ꢅ
IN
where V
is the switch voltage drop (about 0.3V at
SW
500mA).Theinductor’sRMScurrentratingmustbegreater
thanyourmaximumloadcurrentanditssaturationcurrent
should be about 30% higher. For robust operation in fault
conditions,thesaturationcurrentshouldbeabove1.5A.To
keepefficiencyhigh,theseriesresistance(DCR)shouldbe
less than 0.1ꢀ. Table 2 lists several inductor vendors.
Some applications, such as those in automobiles, may
require extra filtering due to EMI/EMC requirements. In
these applications, very effective EMI filtering can be pro-
vided by a capacitor to ground right at the source voltage,
aseriesferritebead, andapifiltercomposedofacapacitor
toground, aseriesinductor, andanothercapacitordirectly
from the device pin to ground (see the Block Diagram for
an example). Typical values for the filter components are
10nF for C2C, a ferrite bead that is ~220ꢀ at 100MHz for
L2, 3.3μF for C2B, 10μH for L3, and 1μF for C2A.
Of course, such a simple design guide will not always re-
sult in the optimum inductor for your application. A larger
valueprovidesahighermaximumloadcurrentandreduces
output voltage ripple at the expense of a slower transient
response. If your load is lower than 500mA, then you can
decrease the value of the inductor and operate with higher
ripple current. This allows you to use a physically smaller
inductor, or one with a lower DCR resulting in higher effi-
ciency.ThereareseveralgraphsintheTypicalPerformance
Step-down regulators draw current from the input sup-
ply in pulses with very fast rise and fall times. The input
capacitor is required to reduce the resulting voltage ripple
3592fa
12
LT3592
APPLICATIONS INFORMATION
attheLT3592andtoforcethisveryhighfrequencyswitch-
ing current into a tight local loop, minimizing EMI. A 1μF
capacitor is capable of this task, but only if it is placed
close to the LT3592 and catch diode (see the PCB layout
section). Asecondprecautionregardingtheceramicinput
capacitor concerns the maximum input voltage rating of
theLT3592.Aceramicinputcapacitorcombinedwithtrace
or cable inductance forms a high quality (underdamped)
tank circuit. If the LT3592 circuit is plugged into a live
supply, the input voltage can ring to twice its nominal
value, possibly exceeding the LT3592’s voltage rating.
This situation can easily be avoided, as discussed in the
Hot Plugging Safety section. For more details, see Linear
Technology Application Note 88.
You can estimate output ripple with the following equa-
tion:
ΔILP−P
8 • ƒ •COUT
VRIPPLE
=
where ΔI
is the peak-to-peak ripple current in the in-
LP-P
ductor. The RMS content of this ripple is very low, so the
RMS current rating of the output capacitor is usually not
a concern. It can be estimated with the formula:
ΔIL
12
IC(RMS)
=
The low ESR and small size of ceramic capacitors make
them the preferred type for LT3592 applications. Not all
ceramic capacitors are the same, though. Many of the
higher value ceramic capacitors use poor dielectrics with
high temperature and voltage coefficients. In particular,
Y5VandZ5Utypeslosealargefractionoftheircapacitance
with applied voltage and at temperature extremes.
Output Capacitor
For most 2.2MHz LED applications, a 3.3μF or higher
output capacitor is sufficient for stable operation. A
900kHz application should use a 4.7μF or higher output
capacitor. 400kHz applications require a 22μF or higher
output capacitor. The minimum recommended values
shouldprovideanacceptable(ifsomewhatunderdamped)
transient response, but larger values can always be used
when extra damping is required or desired.
Because loop stability and transient response depend on
the value of C , this loss may be unacceptable. Use X7R
OUT
and X5R types. Table 3 lists several capacitor vendors.
Figure 4 shows the transient response of the LT3592 when
switching between DIM and BRIGHT current levels with
twooutputcapacitorchoices.Theoutputloadistwoseries
Luxeon K2 Red LEDs, the DIM current is 50mA and the
BRIGHT current is 500mA, and the circuit is running at
900kHz. The upper photo shows the recommended 4.7μF
value. The second photo shows the improved response
resulting from a larger output capacitor.
Theoutputcapacitorfilterstheinductorcurrenttogenerate
an output with low voltage ripple. It also stores energy in
order to satisfy transient loads and stabilizes the LT3592’s
control loop. Because the LT3592 operates at a high fre-
quency,minimaloutputcapacitanceisnecessary.Inaddition,
the control loop operates well with or without the presence
of significant output capacitor equivalent series resistance
(ESR). Ceramic capacitors, which achieve very low output
ripple and small circuit size, are therefore an option.
Table 3. Capacitor Vendor Information
SUPPLIER
AVX
PHONE
FAX
WEBSITE
www.avxcorp.com
(803) 448-9411
(619) 661-6322
(408) 573-4150
(847) 803-6100
(803) 448-1943
(619) 661-1055
(408) 573-4159
(847) 803-6296
Sanyo
www.sanyovideo.com
Taiyo Yuden
TDK
www.t-yuden.com
www.component.tdk.com
3592fa
13
LT3592
APPLICATIONS INFORMATION
V
OUT
I
LED
V
SW
100μs/DIV
C = 4.7μF
V
OUT
I
LED
V
SW
3592 F04
100μs/DIV
C = 10μF
Figure 4. Transient Load Response of the LT3592 with Different Output Capacitors
D2
D2
BOOST
BOOST
C3
C3
CAP
CAP
LT3592 SW
LT3592 SW
V
V
IN
BATT
BATT
IN
GND
DA
GND
DA
3592 F05a
3592 F05b
(5a)
(5b)
Figure 5. Two Circuits for Generating the Boost Voltage
BOOST Pin Considerations
boost diode will be effective. For 3V to 3.3V outputs, use
a 0.22μF capacitor. For outputs between 2.5V and 3V,
use a 0.47μF capacitor and and external Schottky diode
(such as a BAS70) connected in parallel with the internal
Schottky diode, anode to CAP and cathode to BOOST. For
lower input voltages, the external boost Schottky diode’s
anode can be tied to the input voltage. This connection
is not as efficient as the others because the BOOST pin
current comes from a higher voltage. The user must also
be sure that the maximum voltage rating of the BOOST
pin is not exceeded.
The capacitor C3 and an internal Schottky diode from
the CAP to the BOOST pin are used to generate a boost
voltage that is higher than the input voltage. An external
fast switching Schottky diode (such as the BAS70) can be
used in parallel with the internal diode to make this boost
circuit even more effective. In most cases, a 0.1μF capaci-
tor works well for the boost circuit. The BOOST pin must
be at least 2.5V above the SW pin for best efficiency. For
outputs of 3.3V and above, the 0.1μF cap and the internal
3592fa
14
LT3592
APPLICATIONS INFORMATION
The minimum operating voltage of an LT3592 application
islimitedbytheundervoltagelockout(UVLO, ~3.25V)and
by the maximum duty cycle as outlined above. For proper
startup, the minimum input voltage is also limited by the
boost circuit. If the input voltage is ramped slowly, or the
LT3592 is turned on with its SHDN pin when the output is
already in regulation, then the boost capacitor might not
be fully charged. Because the boost capacitor is charged
with the energy stored in the inductor, the circuit will rely
on some minimum load current to get the boost circuit
running properly. This minimum load generally goes to
zero once the circuit has started. Figure 6 shows a plot
of minimum input voltage needed to start with a 500mA
output current versus output voltage with LED loads. For
LED applications, the output voltage will typically drop
rapidly after start due to diode heating, but this is not
a concern because the voltage to run is lower than the
voltage to start. The plots show the worst case situation
this restricts the input range to one-half of the absolute
maximum rating of the BOOST pin.
Atlightloads,theinductorcurrentbecomesdiscontinuous
and the effective duty cycle can be very high. This reduces
the minimum input voltage to about 400mV above V
.
CAP
At higher load currents, the inductor current is continu-
ous and the duty cycle is limited by the maximum duty
cycle of the LT3592, requiring a higher input voltage to
maintain regulation.
Soft-Start
TheSHDNpincanbeusedtosoft-starttheLT3592,reducing
the maximum input current during startup. The SHDN pin
is driven through an external RC filter to create a voltage
ramp at this pin. Figure 7 shows the startup waveforms
with and without the soft-start circuit. By choosing a large
RC time constant, the peak startup current can be reduced
to programmed LED current, with no overshoot. Choose
the value of the resistor so that it can supply 20μA when
the SHDN pin reaches 2.3V.
when V is ramping very slowly. For a lower startup
IN
voltage, the boost diode’s anode can be tied to V , but
IN
12
11
10
9
12
11
10
9
12
11
10
9
8
8
8
7
7
7
6
6
6
5
5
5
4
4
4
3
3
3
2
2
2
2
4
6
8
10
12
2
4
6
8
10
12
2
4
6
8
10
INPUT VOLTAGE (V)
400kHz, L = 22μH
12
14
16
INPUT VOLTAGE (V)
INPUT VOLTAGE (V)
3592 F06c
400kHz, L = 22μH
900kHz, L = 6.8μH
3592 F06b
3592 F06a
Figure 6. Input Voltage Needed to Start at 500mA Output Current vs LED Voltage
3592fa
15
LT3592
APPLICATIONS INFORMATION
LT3592
I
L
500mA/DIV
RUN
SHDN
GND
V
SW
10V/DIV
3592 F07a
V
OUT
5V/DIV
50μs/DIV
RUN
15k
LT3592
SHDN
GND
I
L
500mA/DIV
0.1μF
V
SW
10V/DIV
3592 F07b
V
OUT
5V/DIV
50μs/DIV
Figure 7. To Soft-Start the LT3592, Add a Resistor and Capacitor to the SHDN Pin
Shorted and Open LED Protection
becomes shorted or the CAP pin is shorted to ground, the
peak output current will be limited by the internal switch
current limit, which could be as high as 1.5A.
In case of a shorted LED string or the OUT pin being
shorted to ground by any means, the current loop will
help to limit the output current for many conditions, but
the switch current may still reach the switch current limit
on some cycles despite the actions of the current loop.
For some conditions (especially cold), the output current
for shorted OUT will only be limited by the switch current
limit (which can be as high as 1.5A) and the switching
frequency foldback that occurs when OUT is close to
ground, and the current control loop will have little to
no effect. The total power dissipation will be quite low
in either case due to the frequency foldback and the fact
that the small current sense resistor will effectively be the
output load for shorted OUT. Peak switch and inductor
currents will be high, but the peaks will be brief and well
separated due to the lowered operating frequency. The
main concern in this condition is that the output inductor
not saturate and force the switch into an unsafe operating
condition of simultaneous high current and high voltage
drop. If the current sense resistor between CAP and OUT
If an LED goes open circuit, the voltage control loop
through the R1-R2 resistor divider to FB will take control
and prevent the output voltages from flying up close to
V . Program the desired open circuit voltage to a value
IN
below the absolute maximum for the CAP and OUT pins
but well above the maximum possible forward drop of the
LED at the programmed BRIGHT current.
Reversed Input Protection
In some systems, the output will be held high when the
input to the LT3592 is absent. This may occur in battery
charging applications or in battery backup systems where
a battery or some other supply is diode ORed with the
LT3592’s output. If the V pin is allowed to float and the
IN
SHDN pin is held high (either by a logic signal or because
it is tied to V ), then the LT3592’s internal circuitry will
IN
draw its quiescent current through its SW pin. This is fine
if the system can tolerate a few mA in this state. If you
3592fa
16
LT3592
APPLICATIONS INFORMATION
D4
V
V
V
IN
SW
IN
OUT
LT3592
SHDNB
GND
FB
+
BACKUP
3592 F08
D4: MBR0540
Figure 8. Circuit to Address Reversed Input and Backpowering Issues
CLOSING SWITCH
SIMULATES HOT PLUG
I
IN
V
LT3592
GND
IN
I
V
IN
IN
10A/DIV
+
+
1μF
V
IN
20V/DIV
LOW
STRAY
5μs/DIV
IMPEDANCE
ENERGIZED
32V SUPPLY
INDUCTANCE
DUE TO 6 FEET
(2 METERS) OF
TWISTED PAIR
(9a)
LT3592
GND
V
IN
I
IN
10A/DIV
+
+
+
10μF
35V
2.2μF
V
IN
20V/DIV
5μs/DIV
(9b)
1Ω
LT3592
GND
V
IN
I
IN
10A/DIV
+
+
0.1μF
2.2μF
V
IN
20V/DIV
5μs/DIV
(9c)
3493 F09
Figure 9. A Well Chosen Input Network Prevents Input Voltage Overshoot and
Ensures Reliable Operation When the LT3592 is Connected to a Live Supply
3592fa
17
LT3592
APPLICATIONS INFORMATION
ground the SHDN pin, the SW pin current will drop to es-
is minor, reducing it by less than one half percent for a two
red series LED load in BRIGHT mode operating from 32V.
sentially zero. However, if the V pin is grounded while
IN
the output is held high, then parasitic diodes inside the
Frequency Compensation
LT3592 can pull large currents from the output through
the SW pin and the V pin. Figure 8 shows a circuit that
IN
The LT3592 uses current mode control to regulate the
loop, whether the current control or voltage control loop
is active. This simplifies loop compensation. In particular,
the LT3592 does not require the ESR of the output capaci-
tor for stability, allowing the use of ceramic capacitors
to achieve low output ripple and small circuit size. A low
ESR output capacitor will typically provide for a greater
margin of circuit stability than an otherwise equivalent
capacitor with higher ESR, although the higher ESR will
tend to provide a faster loop response. Figure 10 shows
an equivalent circuit for the LT3592 control loops, both for
currentandvoltagemode.Bothusethesameerroramplifier
and power section, but an additional voltage gain amp is
used in conjuction with the external current sense resistor
to implement output current control. The error amplifier is
atransconductancetypewithfiniteoutputimpedance.The
power section, consisting of the modulator, power switch,
and inductor, is modeled as a transconductance amplifier
generating an output current proportional to the voltage
will run only when the input voltage is present and that
protects against a shorted or reversed input.
Hot Plugging Safely
Thesmallsize, robustness, andlowimpedanceofceramic
capacitors make them an attractive option for the input
bypasscapacitorofLT3592circuits.However,thesecapaci-
tors can cause problems if the LT3592 is plugged into a
live supply (see Linear Technology Application Note 88 for
a complete discussion). The low loss ceramic capacitor
combined with stray inductance in series with the power
source forms an underdamped tank circuit, and the volt-
age at the V pin of the LT35392 can ring to twice the
IN
nominal input voltage, possibly exceeding the LT3592’s
rating and damaging the part. If the input supply is poorly
controlled or the user will be plugging the LT3592 into an
energized supply, the input network should be designed
to prevent this overshoot.
at the V node. Note that the output capacitor integrates
C
Figure 9 shows the waveforms that result when an LT3592
circuit is connected to a 32V supply through six feet of 24
gauge twisted pair. The first plot is the response with a 1μF
ceramic capacitor at the input. The input voltage rings as
high as 56V and the input current peaks at 16A.
this current, and that the capacitor on the V node (C )
C
C
integrates the error amplifier output current, resulting in
g
m
= 0.7A/V
–
0.7V
SW
One method of damping the tank circuit is to add another
capacitor with a series resistor to the circuit. In Figure 9b,
atantalumchipcapacitorhasbeenadded. Thiscapacitor’s
high equivalent series resistance (ESR) damps the circuit
and eliminates the voltage overshoot. The extra capacitor
improves low frequency ripple filtering and can slightly
improve the efficiency of the circuit, thought it is likely
to be the largest component in the circuit. An alternate
solution is shown in Figure 9c. A 1ꢀ resistor is added in
series with the input to eliminate the voltage overshoot
(it also reduces the peak input current). A 0.1μF capacitor
improves high frequency filtering. This solution is smaller
and less expensive than the tantalum capacitor. For high
input voltages, the impact of the 1ꢀ resistor on efficiency
+
+
C1
BRIGHT
CAP
C1
300k
30k
ESR
–
R
L
RS
R1
OUT
+
–
–
+
g
= 1/5k
m
V
C
V
FB
1.2V
R2
R
C
g
m
= 300μA/V
C
C
GND
3592 F10
Figure 10. Model for Loop Response
3592fa
18
LT3592
APPLICATIONS INFORMATION
two poles in the loop. Rc provides a zero. With the recom-
plane below these components, and tie this ground plane
to system ground at one location (ideally at the ground
terminal of the output capacitor C1). The SW and BOOST
nodes should be as small as possible. Finally, keep the
FB node small so that the ground pin and ground traces
will shield it from the SW and BOOST nodes. Include vias
near the exposed GND pad of the LT3592 to help remove
heat from the LT3592 to the ground plane.
mendedoutputcapacitor,theloopcrossoveroccursabove
theR C zero. Thissimplemodelworkswellaslongasthe
C C
valueoftheinductorisnottoohighandtheloopcrossover
frequency is much lower than the switching frequency.
With a larger ceramic capacitor that will have lower ESR,
crossover may be lower and a phase lead capacitor (C )
PL
across the feedback divider may improve the transient
response. Large electrolytic capacitors may have an ESR
large enough to create an additional zero, and the phase
lead might not be necessary. If the output capacitor is
differentthantherecommendedcapacitor,stabilityshould
be checked across all operating conditions, including DIM
and BRIGHT current modes, voltage control via FB, input
voltage, and temperature.
High Temperature Considerations
The die temperature of the LT3592 must be lower than the
maximum rating of 125°C. This is generally not a concern
unless the ambient temperature is above 85°C. For higher
temperatures, extra care should be taken in the layout of
the circuit to ensure good heat sinking at the LT3592. The
maximum load current should be derated as the ambient
temperature approaches 125°C. The die temperature is
calculated by multiplying the LT3592 power dissipation
by the thermal resistance from junction to ambient.
Power dissipation within the LT3592 can be estimated
by calculating the total power loss from an efficiency
measurement and subtracting the catch diode loss. The
resultingtemperatureriseatfullloadisnearlyindependent
of input voltage. Thermal resistance depends upon the
layout of the circuit board, but 76°C/W is typical for the
3mm×2mmDFN(DDB10)package,and38°C/Wistypical
for the MS10E package.
PCB Layout
ForproperoperationandminimumEMI,caremustbetaken
during printed circuit board layout. Figure 11 shows the
recommended component placement with trace, ground
plane,andvialocations.Notethatlarge,switchedcurrents
flowintheLT3592’sV andSWpins,thecatchdiode(D1),
IN
and the input capacitor (C2). The loop formed by these
components should be as small as possible and tied to
systemgroundinonlyoneplace.Thesecomponents,along
withtheinductorandoutputcapacitor,shouldbeplacedon
the same side of the circuit board, and their connections
shouldbemadeonthatlayer.Placealocal,unbrokenground
BRIGHT
SHDN
V
IN
SYS GND
3592 F11
Figure 11. A Good PCB Layout Ensures Proper, Low EMI Operation
3592fa
19
LT3592
APPLICATIONS INFORMATION
Higher Output Voltages
900kHz with a 6.8μH inductor and a 4.7μF ceramic output
capacitor. The LT3592 is in BRIGHT (500mA) mode but
the current load is switched from 50mA to 450mA and
back, so the current control loop is not active for either
current level and the output voltage is regulated through
the resistive voltage divider to the FB pin.
At higher output voltages, the choice of output capacitor
becomes especially critical. Many small case size ceramic
capacitorslosemuchoftheirratedcapacitancewellbelow
their maximum voltage capability. If a capacitor with a
lower voltage rating is found to not be stable in a design,
it will often result in a smaller solution to choose a larger
capacitor value of the same voltage rating than to choose
one of the same capacitance and higher voltage rating. For
example, a 10μF, 10V ceramic capacitor might be smaller
than a 4.7μF, 16V part, if a 4.7μF, 10V capacitor is found
to not be adequate in a given application. The LT3592 can
tolerate sustained output voltages of up to 20V.
Other Linear Technology Publications
Application Notes AN19, AN35, and AN44 contain more
detaileddescriptionsanddesigninformationforStep-down
regulatorsandotherswitchingregulators.TheLT1376data
sheet has an extensive discussion of output ripple, loop
compensation, and stability testing. Design Note DN100
shows how to generate a bipolar output supply using a
Step-down regulator.
Transient Performance with Voltage Control Loop
Thevoltagecontrollooptransientcharacteristicsaresimilar
to, but not identical to the current control loop. Figure 12
shows the transient for a 12V input application running at
I
LED
200mA/DIV
V
OUT
1V/DIV
V
SW
10V/DIV
3592 F12
10μs/DIV
Figure 12. Switching Transient When Going from 50mA to 500mA Current and Back in Voltage Mode
3592fa
20
LT3592
TYPICAL APPLICATIONS
Single Red LED Driver with Boost Diode to VIN Due to Low VOUT
1N4148
V
IN
V
BOOST
LT3592
IN
5V TO 16V
1μF
0.1μF
15μH
SW
MBRA120
DA
CAP
SHDN
OFF ON
FAULT
0.4Ω
22μF
BRIGHT
OUT
30k
R
T
LUXEON
LXK2-PD12-S00
V
FB
GND
357k
10k
400kHz
3592 TA02
50mA/500mA Two Series Red LED Driver
10μH
BEAD
10nF
V
IN
V
BOOST
LT3592
IN
8V TO 32V
3.3μF
1μF
0.1μF
6.8μH
SW
CMMSHI-40
DA
CAP
+
SHDN
OFF ON
BRAKE
200/20mV
–
4.7μF
0.4Ω
BRIGHT
OUT
51k
10k
R
T
V
FB
GND
LUXEON
LXK2-PD12-S00
48.7k
2.2MHz
3592 TA03
5V Supply with 500mA Current Limit
V
IN
V
BOOST
IN
8V TO 32V
1μF
0.1μF
6.8μH
SW
LT3592
MBRA140
DA
CAP
SHDN
ON
4.7μF
0.4Ω
5V
BRIGHT
OUT
31.6k
10k
R
V
FB
T
GND
48.7k
2.2MHz
3592 TA04
3592fa
21
LT3592
PACKAGE DESCRIPTION
DDB Package
10-Lead Plastic DFN (3mm × 2mm)
(Reference LTC DWG # 05-08-1722 Rev Ø)
R = 0.115
0.64 0.05
(2 SIDES)
0.40 0.10
3.00 0.10
(2 SIDES)
TYP
6
R = 0.05
TYP
10
0.70 0.05
2.55 0.05
1.15 0.05
2.00 0.10
PIN 1 BAR
TOP MARK
PIN 1
(2 SIDES)
R = 0.20 OR
(SEE NOTE 6)
0.25 × 45°
PACKAGE
OUTLINE
0.64 0.05
(2 SIDES)
0.25 0.05
CHAMFER
5
1
(DDB10) DFN 0905 REV Ø
0.25 0.05
0.75 0.05
0.200 REF
0.50 BSC
0.50 BSC
2.39 0.05
2.39 0.05
(2 SIDES)
(2 SIDES)
0 – 0.05
RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS
BOTTOM VIEW—EXPOSED PAD
NOTE:
1. DRAWING CONFORMS TO VERSION (WECD-1) IN JEDEC PACKAGE OUTLINE M0-229
2. DRAWING NOT TO SCALE
3. ALL DIMENSIONS ARE IN MILLIMETERS
4. DIMENSIONS OF EXPOSED PAD ON BOTTOM OF PACKAGE DO NOT INCLUDE
MOLD FLASH. MOLD FLASH, IF PRESENT, SHALL NOT EXCEED 0.15mm ON ANY SIDE
5. EXPOSED PAD SHALL BE SOLDER PLATED
6. SHADED AREA IS ONLY A REFERENCE FOR PIN 1 LOCATION ON THE TOP AND BOTTOM OF PACKAGE
3592fa
22
LT3592
PACKAGE DESCRIPTION
MSE Package
10-Lead Plastic MSOP
(Reference LTC DWG # 05-08-1664)
BOTTOM VIEW OF
EXPOSED PAD OPTION
2.06 p 0.102
2.794 p 0.102
(.110 p .004)
0.889 p 0.127
(.035 p .005)
(.081 p .004)
1
0.29
REF
1.83 p 0.102
(.072 p .004)
0.05 REF
5.23
(.206)
MIN
2.083 p 0.102 3.20 – 3.45
(.082 p .004) (.126 – .136)
DETAIL “B”
CORNER TAIL IS PART OF
THE LEADFRAME FEATURE.
FOR REFERENCE ONLY
NO MEASUREMENT PURPOSE
DETAIL “B”
10
0.50
(.0197)
BSC
0.305 p 0.038
(.0120 p .0015)
TYP
3.00 p 0.102
(.118 p .004)
(NOTE 3)
0.497 p 0.076
(.0196 p .003)
10 9
8
7 6
RECOMMENDED SOLDER PAD LAYOUT
REF
3.00 p 0.102
(.118 p .004)
(NOTE 4)
4.90 p 0.152
(.193 p .006)
DETAIL “A”
0.254
(.010)
0o – 6o TYP
1
2
3
4 5
GAUGE PLANE
0.53 p 0.152
(.021 p .006)
0.86
(.034)
REF
1.10
(.043)
MAX
DETAIL “A”
0.18
(.007)
SEATING
PLANE
0.17 – 0.27
(.007 – .011)
TYP
0.1016 p 0.0508
(.004 p .002)
0.50
(.0197)
BSC
MSOP (MSE) 0908 REV C
NOTE:
1. DIMENSIONS IN MILLIMETER/(INCH)
2. DRAWING NOT TO SCALE
3. DIMENSION DOES NOT INCLUDE MOLD FLASH, PROTRUSIONS OR GATE BURRS.
MOLD FLASH, PROTRUSIONS OR GATE BURRS SHALL NOT EXCEED 0.152mm (.006") PER SIDE
4. DIMENSION DOES NOT INCLUDE INTERLEAD FLASH OR PROTRUSIONS.
INTERLEAD FLASH OR PROTRUSIONS SHALL NOT EXCEED 0.152mm (.006") PER SIDE
5. LEAD COPLANARITY (BOTTOM OF LEADS AFTER FORMING) SHALL BE 0.102mm (.004") MAX
3592fa
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.
23
LT3592
RELATED PARTS
PART NUMBER DESCRIPTION
COMMENTS
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V
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V
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OUT(MAX)
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SD
LT3478/
LT3478-1
4.5A, 2MHz High Current LED Driver with 3,000:1 Dimming
V
= 2.8V, V
= 36V, V
= 40V, Dimming 1,000:1 True
IN(MIN)
IN(MAX)
OUT(MAX)
Color PWM, I < 10μA, 5mm × 7mm QFN-10 Package
SD
LT3486
LT3491
LT3496
LT3497
LT3498
LT3517
LT3518
LT3590
LT3591
Dual 1.3A , 2MHz High Current LED Driver
V
= 2.5V, V
= 24V, V
= 36V, Dimming 1,000:1 True
IN(MIN)
IN(MAX)
OUT(MAX)
Color PWM, I < 1μA, 5mm × 3mm DFN, TSSOP-16E Package
SD
Constant Current, 2.3MHz, High Efficiency White LED Boost
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V
= 2.5V, V
= 12V, V
= 27V, Dimming 300:1 True
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IN(MAX)
OUT(MAX)
Color PWM, I < 8μA, 2mm × 2mm DFN-6, SC70 Package
SD
Triple Output 750mA, 2.1 MHz High Current LED Driver with
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V
= 3V, V
= 30V, V
= 40V, Dimming 3,000:1 True
OUT(MAX)
IN(MIN)
IN(MAX)
Color PWM, I < 1μA, 4mm × 5mm QFN-28 Package
SD
Dual 2.3MHz, Full Function LED Driver with Integrated
Schottkys and 250:1 True Color PWM Dimming
V
= 2.5V, V
= 10V, V
= 32V, Dimming 250:1 True
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IN(MAX)
OUT(MAX)
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1.3A, 2.5MHz High Current LED Driver with 3,000:1 Dimming
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48V, 850kHz, 50mA Step-Down LED Driver
V
SD
= 2.5V, V
= 12V, V
= 32V, Dimming Analog/PWM,
IN(MIN)
IN(MAX)
OUT(MAX)
I
< 8.5μA, 2mm × 3mm DFN-10 Package
V
SD
= 3V, V
= 30V, Dimming 3,000:1 True Color PWM,
IN(MAX)
IN(MIN)
I
< 1μA, 4mm × 4mm QFN-16 Package
V
SD
= 3V, V
= 30V, Dimming 3,000:1 True Color PWM,
IN(MAX)
IN(MIN)
I
< 1μA, 4mm × 4mm QFN-16 Package
V
= 4.5V, V
= 50V, Dimming 0.4, I < 15μA, 2mm × 2mm
IN(MAX) SD
IN(MIN)
DFN-6, SC70 Package
Constant Current, 1MHz, High Efficiency White LED Boost
V
= 2.5V, V
= 12V, V
= 40V, Dimming 80:1 True
IN(MIN)
IN(MAX)
OUT(MAX)
Regulator with Integrated Schottky Diode and 80:1 True Color Color PWM, I < 9μA, 3mm × 2mm DFN-8 Package
SD
PWM Dimming
ThinSOT is a trademark of Linear Technology Corporation.
3592fa
LT 1108 REV A • PRINTED IN USA
LinearTechnology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
24
●
●
© LINEAR TECHNOLOGY CORPORATION 2008
(408) 432-1900 FAX: (408) 434-0507 www.linear.com
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