LT3486EFE [Linear]
Dual 1.3A White LED Step-Up Converters with Wide Dimming; 双1.3A白光LED升压型转换器具有宽调光
| 型号： | LT3486EFE |
| 厂家： | 
Linear |
| 描述： | Dual 1.3A White LED Step-Up Converters with Wide Dimming |
| 文件： | 总20页 (文件大小：840K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
LT3486
Dual 1.3A White LED
Step-Up Converters with
Wide Dimming
U
FEATURES
DESCRIPTIO
The LT®3486 is a dual step-up DC/DC converter
specifically designed to drive up to 16 White LEDs (8 in
series per converter) at constant current from a single
Li-Ion cell. Series connection of the LEDs provides identi-
cal LED currents resulting in uniform brightness. The two
independentconvertersarecapableofdrivingasymmetric
LED strings.
■
Wide (1000:1) PWM Dimming Range with No
ColorShift
■
Independent Dimming and Shutdown Control of the
LED Drivers
■
Drives Up to 16 White LEDs at 25mA (8 per Driver)
from a Single Li-Ion Cell
■
Drives Up to 16 White LEDs at 100mA (8 per Driver)
from 12V Supply
The dimming of the two LED strings can be controlled
independently via the respective CTRL pins. An internal
dimmingsystemallowsthedimmingrangetobeextended
up to 1000:1 by feeding a PWM signal to the respective
PWMpins.TheLT3486operatingfrequencycanbesetwith
an external resistor over a 200kHz to 2MHz range. A low
200mVfeedbackvoltage( 3ꢀaccuracy)minimizespower
loss in the current setting resistor for better efficiency.
Additional features include output voltage limiting when
LEDs are disconnected and overtemperature protection.
■
±±3 LED Current Programming Aꢀꢀuraꢀy
■
Open LED Proteꢀtion: ±6V Clamp Voltage
■
Fixed Frequency Operation: Up to 2MHz
■
Wide Input Voltage Range: 2.5V to 24V
■
Low Shutdown Current: I < 1µA
CC
■
■
Overtemperature Protection
Available in (5mm × 3mm × 0.75mm) 16-Pin DFN
and 16-Pin Thermally Enhanced TSSOP Packages
U
APPLICATIO S
The LT3486 is available in a space saving 16-pin DFN
(5mm × 3mm × 0.75mm) and 16-pin thermally enhanced
TSSOP packages.
■
Notebook PC Display
■
LED Camera Light for Cell Phones
■
Car Dashboard Lighting
Avionics Displays
, LTC and LT are registered trademarks of Linear Technology Corporation.
All other trademarks are the property of their respective owners. Patent Pending.
■
U
TYPICAL APPLICATIO
Li-Ion Powered Driver for Camera Flash and LCD Baꢀklighting
V
IN
3V TO 4.2V
Effiꢀienꢀy vs V
IN
10µF
90
85
80
75
MOVIE MODE
L1
10µH
L2
10µH
2.2µF
LED1
I
= 175mA
LED1
2.2µF
8 LEDs
25mA
SW1
SW2
V
IN
FLASH MODE
= 320mA
AOT3218
OVP2
OVP1
I
LED1
DIMMING 1
CTRL1
CTRL2
REF
DIMMING 2
OFF ON
SHDN
PWM1
FB1
LT3486
0.1µF
PWM2
FB2
70
65
OFF ON
V
C1
R
V
C2
T
8 LEDS/25mA
3.4
R
R
FB2
FB1
0.62Ω
2.8k
4.7nF
100k
63.4k
3
3.6
(V)
3.8
4
4.2
3.2
8.06Ω
3486 TA01a
V
IN
0.1µF
3486 TA01b
3486f
1
LT3486
W W U W
(Note 1)
ABSOLUTE AXI U RATI GS
Input Voltage (V ) ...................................................25V
Operating Temperature Range (Note 2) ...–40°C to 85°C
Storage Temperature Range
DFN ...................................................–65°C to 125°C
TSSOP ............................................... –65°C to 150°C
Maximum Junction Temperature .......................... 125°C
Lead Temperature (Soldering, 10sec, TSSOP)...... 300°C
IN
SHDN Voltage..........................................................25V
SW1, SW2 Voltages .................................................40V
OVP1, OVP2 Voltages...............................................40V
CTRL1, CTRL2 Voltages ...........................................10V
PWM1, PWM2 Voltages ...........................................10V
FB1, FB2 Voltages.....................................................10V
U
W
U
PACKAGE/ORDER I FOR ATIO
ORDER PART
NUMBER
ORDER PART
TOP VIEW
SW1
1
2
3
4
5
6
7
8
16 SW2
15 REF
NUMBER
1
2
3
4
5
6
7
8
SW1
16 SW2
15 REF
V
IN
V
IN
OVP1
14 OVP2
13 SHDN
LT3486EDHC
LT3486EFE
OVP1
14 OVP2
13 SHDN
R
T
17
R
T
17
V
12 V
C2
C1
V
12
V
C2
C1
FB1
11 FB2
FB1
11 FB2
CTRL1
PWM1
10 CTRL2
DHC PART
MARKING
FE PART
MARKING
CTRL1
PWM1
CTRL2
10
9
9
PWM2
PWM2
FE PACKAGE
16-LEAD PLASTIC TSSOP
EXPOSED PAD IS GND (PIN 17)
MUST BE SOLDERED TO PCB
DHC PACKAGE
3486
3486EFE
16-LEAD (5mm × 3mm) PLASTIC DFN
EXPOSED PAD (PIN 17) IS GND
MUST BE SOLDERED TO PCB
T
= 125°C, θ = 38°C/W, θ = 10°C/W
JA JC
JMAX
T
= 125°C, θ = 43°C/W, θ = 4°C/W
JA JC
JMAX
Order Options Tape and Reel: Add #TR
Lead Free: Add #PBF Lead Free Tape and Reel: Add #TRPBF
Lead Free Part Marking: http://www.linear.com/leadfree/
Consult LTC Marketing for parts specified with wider operating temperature ranges.
ELECTRICAL CHARACTERISTICS The
●
denotes the speꢀifiꢀations whiꢀh apply over the full operating
temperature range, otherwise speꢀifiꢀations are at T = 25°C. V = ±V, V
= ±V, V
= ±V, V
= ±V, V
= ±V,
A
IN
CTRL1
CTRL2
PWM1
PWM2
V
= ±V, unless otherwise noted.
SHDN
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
V
Minimum Operating Voltage
Maximum Operating Voltage
Feedback Voltage (FB1, FB2)
Offset between FB1 and FB2
Feedback Pin Bias Current (FB1, FB2)
Quiescent Current
2.5
24
206
6
V
●
194
0
200
3
mV
mV
nA
V
V
V
= |FB1-FB2|
OS
= V = 0.2V (Note 3)
10
45
100
FB1
FB2
= V = 1V
9
0.1
14
1
mA
µA
FB1
FB2
SHDN = 0V, CTRL1 = CTRL2 = 0V
Switching Frequency
R = 53.6k
0.75
200
1
1.25
MHz
kHz
V
T
Oscillator Frequency Range
(Note 4)
2000
Nominal R Pin Voltage
R = 53.6k
T
0.54
T
3486f
2
LT3486
The
●
denotes the speꢀifiꢀations whiꢀh apply over the full operating
ELECTRICAL CHARACTERISTICS
SHDN
temperature range, otherwise speꢀifiꢀations are at T = 25°C. V = ±V, V
= ±V, V
= ±V, V
= ±V, V
= ±V,
A
IN
CTRL1
CTRL2
PWM1
PWM2
V
= ±V, unless otherwise noted.
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
Maximum Duty Cycle
R = 53.6k
●
90
96
90
98
ꢀ
ꢀ
ꢀ
T
R = 20.5k
T
R = 309k
T
Switch Current Limit (SW1, SW2)
1
1.3
300
0.1
220
120
0.85
1.5
25
A
mV
Switch V
I
= I
= 0.75A
CESAT
SW1
SW2
Switch Leakage Current
V
= V
= 10V
SW2
5
µA
SW1
Error Amplifier Transconductance
Error Amplifier Voltage Gain
∆I = 5µA
µA/V
V
V
V
V
V
, V Switching Threshold
V
V
C1 C2
, V Clamp Voltage
C1 C2
, V Source Current
C1 C2
V
V
V
= V = 0V
µA
µA
nA
V
FB1
FB2
, V Sink Current
C1 C2
= V = 1V
25
FB1
FB2
, V Pin Leakage Current
C1 C2
= V = 1V, V
= V = 0V
PWM2
1
10
38
75
C1
C2
PWM1
OVP1, OVP2 Overvoltage Threshold Voltage
CTRL1, CTRL2 Voltages to Turn Off LED1, 2 Currents
CTRL1, CTRL2 Voltages to Turn On LED1, 2 Currents
CTRL1, CTRL2 Voltages for Full LED1, 2 Currents
CTRL1, CTRL2 Pin Bias Current
PWM1, PWM2 Voltage High
34
36
●
mV
mV
V
150
1.8
20
V
V
V
= V
= V
= 3V
= 3V
●
●
●
30
40
µA
V
CTRL1
PWM1
SHDN
CTRL2
PWM2
0.9
PWM1, PWM2 Voltage Low
0.4
1
V
PWM1, PWM2 Pin Bias Current
SHDN Voltage High
0.1
µA
V
1.6
SHDN Voltage Low
0.4
1.3
V
SHDN Pin Bias Current
= 3V
20
1.25
80
µA
V
REF Voltage
I
= 10µA
1.2
50
REF
REF Source Current
●
µA
Note 1: Absolute maximum ratings are those beyond which the life of a
device may be impaired.
Note ±: Current flows out of the pin.
Note 4: Guaranteed by design and test correlation, not production tested.
Note 2: The LT3486E is guaranteed to meet specified performance from
0°C to 70°C and is designed, characterized and expected to meet these
extended temperature limits, but is not tested at –40°C and 85°C.
3486f
3
LT3486
U W
TYPICAL PERFOR A CE CHARACTERISTICS
T = 25°C unless otherwise speꢀified.
A
Switꢀhing Waveforms
PWM Dimming Wavforms
I
V
LED
SW2
200mA/DIV
50V/DIV
I
L2
500mA/DIV
I
L
500mA/DIV
V
SW1
10V/DIV
PWM
5V/DIV
I
L1
1A/DIV
3486 G17
3486 G18
V
= 3.6V
0.5µs/DIV
V
= 12V
IN
0.2ms/DIV
IN
8 LEDs/25mA
2 LEDs/320mA
8/8 LEDs
PWM FREQ = 1kHz
CIRCUIT OF FRONT PAGE APPLICATION
LED Current vs PWM Duty Cyꢀle
Wide Dimming Range (1000:1)
V
vs V
CTRL
FB
V
vs V
(Temperature Variation)
FB
CTRL
100
10
1
250
200
150
100
50
250
200
150
100
50
V
= 12V
IN
V
T
= 3.6V
= 25°C
IN
A
T
= 85°C
A
8/8 LEDs
5mV
PWM FREQ = 100Hz
T
= 25°C
A
T
= –50°C
A
0.1
0.01
0
0
0.01
0.1
1
10
100
1
1.5
0
0.5
1
1.5
0
0.5
2
2
PWM DUTY CYCLE (%)
CONTROL VOLTAGE (V)
CONTROL VOLTAGE (V)
3486 G01
3486 G03
3486 G04
Open-Cirꢀuit Output Clamp
Voltage vs Temperature
Open-Cirꢀuit Output Clamp
SHDN Pin Bias Current
(CTRL1 = CTRL2 = ±V)
Voltage vs V
IN
37
36
35
34
33
140
120
100
80
37
36
35
34
V = 3.6V
IN
R = 63.4k
T
V
= 3.6V
V
= 3.6V
= 63.4k
IN
IN
T
R
T
T
= 50°C
= 25°C
A
A
V
OUT2
V
OUT1
V
OUT1
V
T
= 100°C
OUT2
A
60
40
20
0
33
2
4
6
8
10 12 14 16 18 20 22 24
(V)
16
SHDN PIN VOLTAGE (V)
24
0
4
8
12
20
–50 –25
0
25
50
75 100 125
V
TEMPERATURE (°C)
IN
3486 G07
3486 G05
3486 G06
3486f
4
LT3486
U W
T = 25°C unless otherwise speꢀified.
TYPICAL PERFOR A CE CHARACTERISTICS
A
Input Current with Output 1 and
Output 2 Open Cirꢀuit
R vs Osꢀillator Frequenꢀy
T
Osꢀillator Frequenꢀy vs V
IN
1100
1050
1000
950
20
15
10
5
1000
100
10
R = 53.6k
T
T
= 25°C
A
T
R
= 63.4k
900
0
2
4
6
8
10 12 14 16 18 20 22 24
0
500
1000
1500
2000
2500
2
4
6
8
10 12 14 16 18 20 22 24
(V)
V
(V)
OSCILLATOR FREQUENCY (kHz)
V
IN
IN
3486 G09
3486 G10
3486 G08
Osꢀillator Frequenꢀy vs
Temperature
Quiesꢀent Current vs V
PWM Pin Input Bias Current
IN
12
10
8
10000
1000
1.0
0.5
V
IN
= 3.6V
UVLO
R
R
= 22.1k
= 53.6k
T
T
PWM 1
PWM 2
6
0
4
–0.5
–1.0
R
= 309k
T
2
SHDN = 3V
CTRL1 = CTRL2 = 3V
100
0
0
2
8
10 12 14 16 18 20 22 24
(V)
IN
–50 –25
0
25
50
75 100 125
4
6
0
2
4
6
8
10
TEMPERATURE (°C)
V
PWM PIN VOLTAGE (V)
3486 G12
3486 G11
3486 G13
Switꢀh Current Limit vs
Duty Cyꢀle
REF Voltage Load Regulation
REF Voltage vs Temperature
1.30
1.28
1.26
1.24
1.22
1.20
1.30
1.25
1.20
1.15
1.10
1.05
1.00
0.95
0.90
1800
1700
1600
1500
1400
1300
1200
V
= 3.6V
IN
V
= 3.6V
IN
T
= –50°C
A
T
= 85°C
= 25°C
A
T
A
V
A
= 3.6V
IN
T
= 25°C
50
75 100 125
0
20 40 60 80 100 120 140 160 180 200
70 80
DUTY CYCLE (%)
–50 –25
0
25
20 30 40 50 60
90 100
TEMPERATURE (°C)
REF LOAD CURRENT (µA)
3468 G16
3486 G15
3486 G14
3486f
5
LT3486
U
U
U
PI FU CTIO S
SW1, SW2 (Pins 1, 16): The SW Pins are the Collectors
of the Internal Power Transistors. Connect the inductors
and Schottky diodes to these pins. Minimize trace area
at these pins to minimize EMI.
CTRL1, CTRL2 (Pins 7, 10): The CTRL pins are used to
provide dimming and shutdown control for the individual
switching converters. Connecting these to ground shuts
down the respective converter. As the voltages on these
pins is ramped from 0V to 1.8V, the LED current in each
V (Pin 2): Input Supply Pin. Must be locally bypassed
IN
converter ramps from 0 to I
= (200mV/R ). Any volt-
LED
FB
with an X5R or X7R type ceramic capacitor.
age above 1.8V does not affect the LED current.
OVP1, OVP2 (Pins ±, 14): Output Overvoltage Protection
Pins. Connect these pins to the output capacitors. The
on-chip voltage detectors monitor the voltages at these
pins and limit it to 36V (typ) by turning off the respective
PWM1, PWM2 (Pins 8, 9): The PWM control pins can
be used to extend the dimming range for the individual
switching converter. The LED current in each string can
be controlled down to µA levels by feeding a PWM signal
to these pins. When the PWM pin voltage is taken below
switcher and pulling its V pin low.
C
R (Pin 4): Timing Resistor to Program the Switching
T
0.4V, the respective converter is turned off and its V pin
C
Frequency. The switching frequency can be programmed
is disconnected from the internal circuitry. Taking it higher
than 0.9V resumes normal operation. Connect these pins
to 0.9V supply or higher, if not in use.
from 200kHz to 2MHz.
V , V (Pins 5, 12): The V Pins are the Outputs of the
C1 C2
C
Internal Error Amplifier. The voltages at these pins control
thepeakswitchcurrents. Connectaresistorandcapacitor
compensation network from these pin to ground.
SHDN (Pin 1±): Shutdown Pin for the Device. Connect it
to 1.6V or higher to enable device; 0.4V or less to disable
device.
FB1, FB2 (Pins 6, 11): The LT3486 regulates the voltage
at each feedback pin to 200mV. Connect the cathode of
the lowest LED in the string and the feedback resistor
REF (Pin 15): The internal bandgap reference (1.25V) is
available at this pin. Bypass with a 0.1µF X5R or X7R ce-
ramic capacitor. Draw no more than 50µA from this pin.
(R ) to the respective feedback pin. The LED current in
FB
Exposed Pad (Pin 17): The exposed pad of the package
provides an electrical contact to ground and good thermal
connection to the printed circuit board (PCB). Solder the
exposed pad to the PCB system ground.
each string can be programmed by:
I
I
≅ 200mV/R , when V
> 1.8V
LED
LED
FB
CTRL
≅ V
/(5R ), when V
< 1V
CTRL
FB
CTRL
3486f
6
LT3486
W
BLOCK DIAGRA
R
V
IN
T
SW1
1
SW2
16
4
2
OVP2
14
OVP1
3
OVERVOLT
DETECTION
OVERVOLT
DETECTION
CONVERTER1
CONVERTER2
OSC
OV2
DRIVER
OSC
OV1
EN1
PWM
PWM
Q1
Q2
LOGIC
LOGIC
EN2
RAMP
GEN
+
–
+
–
OSC
OSC
A3
A3
R
SNS2
R
SNS1
PWM
COMP
PWM
COMP
+
+
+
–
+
–
A2
A2
0.2V
0.2V
EA
EA
+
REF 1.25V
+
A1
A1
–
+
–
+
V
C1
5
12
V
C2
OV1
OV2
EN1
EN2
SHDN
START-UP
CONTROL
CONVERTER1
CONTROL
80k
20k
80k
20k
CONVERTER 2
CONTROL
3486 F01
8
7
6
13
15
11
FB2
10
9
17
EXPOSED
PAD
PWM1 CTRL1
FB1
SHDN
REF
CTRL2 PWM2
Figure 1. LT±486 Bloꢀk Diagram
3486f
7
LT3486
U
OPERATIO
Main Control Loop
Ifonlyoneoftheconvertersisturnedon,theotherconverter
will stay off and its output will remain charged up to V
(input supply voltage).
IN
The LT3486 uses a constant frequency, current mode
controlschemetoprovideexcellentlineandloadregulation.
It incorporates two identical, but fully independent PWM
converters.Operationcanbebestunderstoodbyreferring
to the block diagram in Figure 1. The oscillator, start-up
biasandthebandgapreferencearesharedbetweenthetwo
converters. The control circuitry, power switch, dimming
control etc., are all identical for both converters.
Minimum Output Current
The LT3486 can drive an 8-LED string at 4mA LED current
without pulse skipping. As current is further reduced, the
device may 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 photo
in Figure 2 shows circuit operation with 8 white LEDs
at 4mA current driven from 3.6V supply. Peak inductor
current is less than 200mA and the regulator operates in
discontinuous mode implying that the inductor current
reachedzeroduringthedischargephase.Aftertheinductor
currentreacheszero, theswitchpinexhibitsringingdueto
the LC tank circuit formed by the inductor in combination
with switch and diode capacitance. This ringing is not
harmful;farlessspectralenergyiscontainedintheringing
than in the switch transitions. The ringing can be damped
by application of a 300Ω resistor across the inductors,
although this will degrade efficiency.
At power-up, the output capacitors of both converters are
chargeduptoV (inputsupplyvoltage)viatheirrespective
IN
inductor and the Schottky diode. If the SHDN pin is taken
above 1.6V, the bandgap reference, start-up bias and the
oscillator are turned on. Grounding the SHDN pin shuts
down the part.
TheCTRL1andCTRL2pinsperformindependentdimming
and shutdown control for the two converters. Taking
the CTRL pins high, enables the respective converters.
Connecting these pins to ground, shuts down each
converter by pulling their respective V pin low.
C
Working of the main control loop can be understood by
following the operation of converter 1. At the start of
each oscillator cycle, the power switch Q1 is turned 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 A2. When this
voltage exceeds the level at the negative input of A2, the
PWM logic turns off the power switch. The level at the
negative input of A2 is set by the error amplifier A1, and
is simply an amplified version of the difference between
the feedback voltage and the 200mV reference voltage. In
this manner, the error amplifier A1 regulates the feedback
voltage to 200mV reference voltage. The output of the
error amplifier A1 sets the correct peak current level in
inductor L1 to keep the output in regulation. The CTRL1
pin voltage is used to adjust the reference voltage.
V
OUT2
10mV/DIV
V
SW2
20V/DIV
I
L2
200mA/DIV
3486 F02
V
LED2
= 3.6V
0.5µs/DIV
IN
I
= 4mA (8 LEDs)
CIRCUIT OF FRONT PAGE APPLICATION
Figure 2. Switꢀhing Waveforms
Open-Cirꢀuit Proteꢀtion
The LT3486 has internal open-circuit protection for both
the converters. Connect the overvoltage protection pins
(OVP1, OVP2) to the output of the respective converter.
When the LEDs are disconnected from the circuit or fail
open,theon-chipvoltagedetectorsmonitorthevoltagesat
the OVP1 and OVP2 pins and limits these voltages to 36V
(typ) by turning off the respective switcher. The converter
will then switch at a very low frequency to minimize the
input current. Output voltage and input current during
ThePWM1, 2controlpinsareusedtoextendthedimming
range for the individual converter. The LED current in each
string can be controlled down to µA levels by feeding
a PWM signal to these pins. Refer to the Applications
Information section for more detail.
3486f
8
LT3486
U
OPERATIO
output open circuit are shown in the Typical Performance
Characteristics graphs.
eight LEDs at 25mA. Converter 1 starts switching at a very
low frequency, reducing its input current.
Figure 3a shows the transient response of switcher 1 with
the LEDs disconnected from the output. When the LED1
string is disconnected from the output, the voltage at
the feedback pin (FB1) drops to 0V. As a result, the error
Soft-Start
The LT3486 has a separate internal soft-start circuitry for
each converter. Soft-start helps to limit the inrush current
during start-up. Soft-start is achieved by clamping the
output of the error amplifier during the soft-start period.
This limits the peak inductor current and ramps up the
output voltage in a controlled manner.
amplifier charges up the V node to the clamp voltage
C
level of 1.5V (typ). The converter starts switching at peak
current limit and ramps up the output voltage. When the
output voltage reaches the OVP clamp voltage level of
36V (typ), the LT3486 shuts off the converter by pulling
The converter enters into soft-start mode whenever the
respective CTRL pin is pulled from low to high. Figure 4
shows the start-up waveforms with converter 2 driving
eight LEDs at 25mA. The filtered input current, as shown
in Figure 4, is well controlled. The soft-start circuit is more
effective when driving a smaller number of LEDs.
the V node to ground. The converter then regulates the
C
output voltage at 36V (typ) by switching at a very low
frequency.
In the event one of the converters has an output open-
circuit, its output voltage will be clamped at 36V (typ).
However, the other converter will continue functioning
properly. The photo in Figure 3b shows circuit operation
withconverter1outputopen-circuitandconverter2driving
Undervoltage Loꢀkout
The LT3486 has an undervoltage lockout circuit which
shuts down both the converters when the input voltage
drops below 2.1V (typ). This prevents the converter to
operate in an erratic mode when powered from low supply
voltages.
I
L1
1A/DIV
Overtemperature Proteꢀtion
V
OUT1
20V/DIV
ThemaximumallowablejunctiontemperatureforLT3486is
125°C. In normal operation, the IC’s junction temperature
should be kept below 125°C at an ambient temperature of
85°Corless.Ifthejunctiontemperatureexceeds150°C,the
internal thermal shutdown circuitry kicks in and turns-off
both the converters. The converters will remain off until
the die temperature falls below 150°C.
V
C1
2V/DIV
3486 F03a
V
= 3.6V
100µs/DIV
IN
CIRCUIT OF
LED1 DISCONNECTED
AT THIS INSTANT
FRONT PAGE
APPLICATION
Figure ±a. Transient Response of Switꢀher 1 with LED1
Disꢀonneꢀted from the Output
I
IN
200mA/DIV
I
L1
1A/DIV
V
OUT2
10V/DIV
V
OUT1
1V/DIV
AC COUPLED
V
FB2
200mV/DIV
I
L2
CTRL2
5V/DIV
500mA/DIV
3486 F04
V
= 3.6V
0.5ms/DIV
3486 F03b
IN
V
= 3.6V
2ms/DIV
IN
8 LEDs, 25mA
CIRCUIT OF FRONT PAGE APPLICATION
LED1 DISCONNECTED
CIRCUIT OF FRONT PAGE APPLICATION
Figure ±b. Switꢀhing Waveforms with Output 1 Open Cirꢀuit
Figure 4. Start-Up Waveforms
3486f
9
LT3486
U
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APPLICATIO S I FOR ATIO
Duty Cyꢀle
Operating Frequenꢀy Seleꢀtion
The duty cycle for a step-up converter is given by:
The choice of operating frequency is determined by sev-
eral factors. There is a tradeoff between efficiency and
component size. Higher switching frequency allows the
use of smaller inductors albeit at the cost of increased
switching losses and decreased efficiency.
VOUT + VD – V
VOUT + VD – VCESAT
IN
D =
where:
Another consideration is the maximum duty cycle
achievable. In certain applications the converter needs to
operate at the maximum duty cycle in order to light up
the maximum number of LEDs. The LT3486 has a fixed
oscillator off-time and a variable on-time. As a result, the
maximumdutycycleincreasesastheswitchingfrequency
is decreased.
V
= Output voltage
OUT
V = Schottky forward voltage drop
D
V
CESAT
= Saturation voltage of the switch
V = Input battery voltage
IN
The maximum duty cycle achievable for LT3486 is 96ꢀ
(typ) when running at 1MHz switching frequency. It in-
creases to 98ꢀ (typ) when run at 200kHz and drops to
90ꢀ (typ) at 2MHz. Always ensure that the converter is
not duty-cycle limited when powering the LEDs at a given
switching frequency.
The circuit of Figure 6a is operated with different values of
timingresistor(R ).R ischosensoastoruntheconverters
T
T
at 800kHz (R = 63.4k), 1.25MHz (R = 39.1k) and 2MHz
T
T
(R = 21.5k). The CTRL pins are used to provide dimming
T
for the respective LED strings. The efficiency comparison
for different R values is shown in Figure 6b.
T
Setting the Switꢀhing Frequenꢀy
The LT3486 uses a constant frequency architecture that
can be programmed over a 200kHz to 2MHz range with a
C
10µF
5V
IN
single external timing resistor from the R pin to ground.
T
D1
D2
The nominal voltage on the R pin is 0.54V, and the
T
L1
10µH
L2
10µH
C
C
OUT1
OUT2
2.2µF
currentthatflowsintothetimingresistorisusedtocharge
2.2µF
and discharge an internal oscillator capacitor. A graph for
SW1
OVP1
CTRL1
SHDN
PWM1
FB1
V
IN
SW2
selecting the value of R for a given operating frequency
T
OVP2
25mA
25mA
1.25V
is shown in the Figure 5.
CTRL2
REF
OFF ON
REF
LT3486
PWM2
FB2
C
REF
0.1µF
1000
V
C1
R
V
C2
T
2.8k
4.7nF
R
2.8k
4.7nF
T
8.06Ω
8.06Ω
C
C
: 10V, X7R
IN
3486 F06a
, C
: 35V, X5R
OUT1 OUT2
100
D1, D2: ZETEX ZHCS400
L1, L2: TOKO D53LC TYPE A
Figure 6a. 5V to 8/8 White LEDs
10
0
500
1000
1500
2000
2500
OSCILLATOR FREQUENCY (kHz)
3486 G09
Figure 5. Timing Resistor (R ) Value
T
3486f
10
LT3486
U
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APPLICATIO S I FOR ATIO
90
Several inductors that work well with the LT3486 are listed
inTable1.Consulteachmanufacturerformoredetailedin-
formation and for their entire selection of related parts.
V
= 5V
IN
8/8 LEDs
80
R
= 63.4k
T
70
60
Table 1. Reꢀommended Induꢀtors
R
= 21.5k
T
MAX
DCR
(Ω)
CURRENT
RATING
(A)
R
= 39.1k
T
L
(µH)
PART
VENDOR
50
40
30
LQH55DN150M
LQH55DN220M
15
22
0.150
0.190
1.40
1.20
Murata
(814) 237-1431
www.murata.com
A915AY-4R7M
A915AY-6R8M
A915AY-100M
A918CY-100M
A918CY-150M
4.7
6.8
10
10
15
0.045
0.068
0.090
0.098
0.149
2.49
2.01
1.77
1.22
0.94
Toko
(847) 297-0070
www.toko.com
0
5
10
15
20
25
LED CURRENT (mA)
3486 F06b
Figure 6b. Effiꢀienꢀy Comparison for Different R Resistors
T
CDRH4D28-100
CDRH5D18-150
10
15
0.048
0.145
1.30
0.97
Sumida
(847) 956-0666
www.sumida.com
Induꢀtor Seleꢀtion
The choice of the inductor will depend on the selection of
switching frequency of LT3486. The switching frequency
canbeprogrammedfrom200kHzto2MHz.Higherswitch-
ing frequency allows the use of smaller inductors albeit
at the cost of increased switching losses.
Capaꢀitor Seleꢀtion
The small size of ceramic capacitors make them ideal
for LT3486 applications. Use only X5R and X7R types
because they retain their capacitance over wider voltage
and temperature ranges than other types such as Y5V
or Z5U. A 4.7µF or larger input capacitor is sufficient for
most applications. Always use a capacitor with sufficient
voltage rating.
Theinductorcurrentripple(ΔI ),neglectingthedropacross
L
the Schottky diode and the switch, is given by:
V
• VOUT(MAX) – V
(
)
IN(MIN)
IN(MIN)
∆IL =
Table 2 shows a list of several ceramic capacitor manufac-
turers. Consultthemanufacturersfordetailedinformation
on their entire selection of ceramic parts.
VOUT(MAX) • f •L
where:
L = Inductor
f = Operating frequency
Table 2. Ceramiꢀ Capaꢀitor Manufaꢀturers
Taiyo Yuden
AVX
(408) 573-4150
www.t-yuden.com
(803) 448-9411
www.avxcorp.com
V
V
= Minimum input voltage
IN(MIN)
= Maximum output voltage
OUT(MAX)
Murata
(714) 852-2001
www.murata.com
The ΔI is typically set to 20ꢀ to 40ꢀ of the maximum
L
inductor current.
Diode Seleꢀtion
Theinductorshouldhaveasaturationcurrentratinggreater
thanthepeakinductorcurrentrequiredfortheapplication.
Also, ensure that the inductor has a low DCR (copper wire
Schottky diodes with their low forward voltage drop and
fast reverse recovery, are the ideal choices for LT3486
applications. The diode conducts current only during the
switch off time. The peak reverse voltage that the diode
must withstand is equal to the regulator output voltage.
2
resistance) to minimize I R power losses. Recommended
inductor values range from 4.7µH to 22µH.
3486f
11
LT3486
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APPLICATIO S I FOR ATIO
The average forward current in normal operation is equal
to the output current, and the peak current is equal to the
peak inductor current. A Schottky diode rated at 1A is suf-
ficientformostLT3486applications.Somerecommended
Schottky diodes are listed in Table 3.
200mV
ILED1
200mV
ILED2
RFB1
RFB2
=
=
Table ±. Reꢀommended Sꢀhottky Diodes
Table 4. R Value Seleꢀtion
FB
PART NUMBER
V (V)
R
I
(A)
MANUFACTURER
I
(mA)
R
FB
(Ω)
AVG
LED
5
40.2
20.0
13.3
10.0
8.06
MBR0530
30
20
0.5
On Semiconductor
www.onsemi.com
10
15
20
25
MBRM120E
1
ZLLS400
ZLLS1000
ZHCS400
ZHCS1000
40
40
40
40
0.4
1
0.4
1
Zetex
www.zetex.com
Most low power white LEDs are driven at maximum cur-
rents of 15mA to 25mA. The LT3486 can be used to power
high power LEDs as well. Refer to the Typical Applications
for more detail.
When the LT3486 is set up for PWM dimming operation,
choose a Schottky diode with low reverse leakage current.
During PWM dimming operation, the output capacitor is
required to hold up the charge in the PWM “off” period.
A low reverse leakage Schottky helps in that mode of op-
eration. The Zetex ZLLS400 and ZLLS1000 are available
in a small surface mount package and are a good fit for
this application.
Dimming Control
The dimming of the two LED strings can be controlled
independently by modulating the respective CTRL and
PWM pins. There are two ways to control the intensity
of the LEDs.
MOSFET Seleꢀtion
ThepowerMOSFETusedinLT3486applicationswithwide
dimming range requirements should be chosen based on
the maximum drain-source voltage. The maximum drain
Adjusting the LED Current Value
Controlling the current flowing through the LEDs controls
the intensity of the LEDs.This is the easiest way to control
the intensity of the LEDs. The LED forward current can be
controlled by modulating the DC voltage at the respective
CRTL pin. The PWM pins are not in use when appying
this scheme. They must be connected to a 0.9V supply or
higher. The DC voltage at the CTRL pin can be modulated
in two ways.
current I
and gate-to-source voltages should also
D(MAX)
be considered when choosing the FET.
ChooseaMOSFETwithmaximumV (drainsource)volt-
DS
age greater than the output clamp voltage i.e., 36V (typ).
FairchildSemiconductor’sFDN5630(60V,1.7AN-channel
FET) is a good fit for most LT3486 applications. For dim-
ming low current LEDs (~25mA), Fairchild 2N7002 is a
good alternative.
(a) Using a DC Voltage Sourꢀe
Forsomeapplications,thepreferredmethodofbrightness
control is a variable DC voltage fed to the CTRL pins. The
CTRL1, CTRL2 pin voltage can be modulated to set the
dimming of the respective LED string. As the voltage on
the CTRL1, CTRL2 pin increases from 0V to 1.8V, the LED
Programming LED Current
The current in each LED string can be set independently
by the choice of resistors R
(see front page application). The feedback reference is
200mV. In order to have accurate LED current, precision
resistors are preferred (1ꢀ is recommended).
and R
respectively
FB1
FB2
current increases from 0 to I . As the CTRL1, CTRL2
LED
pin voltage increases beyond 1.8V, it has no effect on the
LED current.
3486f
12
LT3486
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APPLICATIO S I FOR ATIO
The LED current can be set by:
Pulse-Width Modulation (PWM)
I
I
≈ (200mV/R ), when V
> 1.8V
CTRL
AdjustingtheforwardcurrentflowingintheLEDschanges
the intensity of the LEDs, as explained in the previous sec-
tion.However,achangeinforwardcurrentalsochangesthe
color of the LEDs. The chromaticity of the LEDs changes
withthechangeinforwardcurrent.Manyapplicationscan-
not tolerate any shift in the color of the LEDs. Controlling
the intensity of the LEDs via applying a PWM signal allows
dimming of the LEDs without changing the color.
LED
LED
FB
≈ (V
/5 • R ), when V
< 1V
CTRL
FB
CTRL
Feedback voltage variation versus control voltage is given
in the Typical Performance Characteristics graphs.
(b) Using a Filtered PWM Signal
A variable duty cycle PWM can be used to control the
brightness of the LED string. The PWM signal is filtered
(Figure 7) by an RC network and fed to the CTRL1, CTRL2
pins.
Dimming the LEDs via a PWM signal essentially involves
turning the LEDs on and off at the PWM frequency. The
human eye has a limit of 60 frames per second. By in-
creasing the PWM frequency to say, 80Hz, the eye can
be deceived into believing that the pulsed light source is
continously 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 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
pins, which is 100kΩ.
LT3486
R1
10k
PWM
CTRL1,2
10kHz TYP
C1
1µF
3486 F07
Figure 8(a) shows a 12V to 8/8 white LED driver. The PWM
dimming control method requires an external NMOS tied
to the cathode of the lowest LED in the string, as shown in
Figure 7. Dimming Control Using a Filtered PWM Signal
12V (TYP)
9V TO 15V 10µF
C
IN
L1
10µH
L2
10µH
C
5V
C
OUT1
OUT2
2.2µF
D1
D2
2.2µF
C1 1µF
SW1
SW2
V
IN
LUXEON
LEDs
LXCL-PWF1
LUXEON
LEDs
LXCL-PWF1
I
LED
200mA/DIV
OVP2
CTRL2
REF
OVP1
V
V
CTRL1
IN
IN
I
L
OFF ON
SHDN
PWM1
FB1
LT3486
500mA/DIV
C
100mA
REF
0.1µF
100mA
PWM2
FB2
PWM
5V/DIV
V
C1
R
V
C2
T
3486 G18
V
= 12V
0.2ms/DIV
IN
8/8 LEDs
PWM FREQ = 1kHz
22pF
DIMMING
INPUT 1
DIMMING
INPUT 2
3.65k
2.2nF
3.65k
2.2nF
21.5k
PWM
FREQ
1kHz
PWM
FREQ
1kHz
Q1
R
Q2
Figure 8b. PWM Dimming Waveforms
100k
100k
R
FB2
2Ω
D1, D2: ZETEX ZLLS1000
L1, L2: TOKO D53LC (TYPE A)
Q1, Q2: FAIRCHILD FDN5630
FB1 C
, C
: 35V, X5R OR X7R
: 25V, X5R OR X7R
OUT1 OUT2
2Ω
C
IN
C1: 10V, X5R OR X7R
: 6.3V, X5R OR X7R
3486 TA10a
C
REF
Figure 8a. 12V to 8/8 White LEDs
3486f
13
LT3486
U
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APPLICATIO S I FOR ATIO
the figure. A PWM logic input is applied to the gate of the
Figure 9 shows the LED current variation vs PWM duty
cycle. The LED current is controlled by applying a PWM
of frequency 100Hz, 1kHz and 25kHz to the circuit of
Figure 8a. As seen in the curves, the LED string is able to
getawide(1000:1)dimmingrangewithPWMfrequencyof
100Hz. The dimming range decreases as PWM frequency
goes up.
NMOS and the PWM pin of the LT3486. When the PWM
input is taken high, the LEDs are connected to the R
FB
resistor and a current I
= 200mV/R flows through
LED
FB
the LEDs. When the PWM input is taken low, the LEDs are
disconnected and turn off. The low PWM input applied to
the LT3486 ensures that the respective converter turns
off and its V pin goes high impedance. This ensures that
C
Board Layout Consideration
the capacitor connected to the V pin retains its voltage
C
which in turn allows the LEDs to turn on faster, as shown
in Figure 8(b). The CTRL pin is not used to modulate the
LEDcurrentinthescheme. Itcanbeconnectedtoasupply
voltage greater than 1.8V.
As with all switching regulators, careful attention must be
paid to the PCB board layout and component placement.
To prevent electromagnetic interference (EMI) problems,
properlayoutofhighfrequencyswitchingpathsisessential.
Minimize the length and area of all traces connected to the
switching node pins (SW1 and SW2). Keep the feedback
pins (FB1 and FB2) away from the switching nodes.
The dimming control pins (PWM1, PWM2) can be used
to extend the dimming range for the individual switching
converters. The LED current can be controlled down to
µA levels by feeding a PWM signal with frequencies in the
rangeof80Hzto50kHz. TheLEDcurrentcanbecontrolled
by PWM frequencies above 50kHz but the controllable
current decreases with increasing frequency. Pulling the
PWM pins below 0.4V disables the respective switcher.
Taking it higher than 0.9V resumes normal operation.
Connect these pins to 0.9V or higher if not in use.
The DFN and FE packages both have an exposed paddle
that must be connected to the system ground. The ground
connectionforthefeedbackresistorsshouldbetieddirectly
to the ground plane and not shared with any other compo-
nent, except the R resistor, ensuring a clean, noise-free
T
connection. Recommendedcomponentplacementforthe
DFN package is shown in the Figure 10.
VIAs TO V PLANE
IN
V
V
OUT1
OUT2
OVP1
REF
100
10
1
R
T
OVP2
SHDN
V
C2
V
V
C1
SW1
SW2
IN
1
2
3
4
5
6
7
8
16
15
14
13
12
11
10
9
V
IN
17
FB1
LED2
FB2
CTRL1
CTRL2
0.1
LED1
PWM FREQ = 100Hz
PWM FREQ = 1kHz
PWM FREQ = 25kHz
0.01
0.01
0.1
1
10
100
V
PWM1
VIAs TO V PLANE
IN
PWM2
VIAs TO GROUND PLANE
PWM DUTY CYCLE (%)
3486 F10
3486 F09
IN
Figure 9. LED Current Variation vs PWM Duty Cyꢀle
Figure 10. Reꢀommended Layout for LT±486
3486f
14
LT3486
U
TYPICAL APPLICATIO S
Li-Ion Cell Powered Driver for Camera Flash and LCD Baꢀklighting
V
IN
3V TO 5V
C
IN
10 F
D1
D2
L1
10 H
L2
10 H
C
C
OUT2
OUT1
LED1
AOT3218
2.2 F
2.2 F
SW1
SW2
V
IN
OVP2
OVP1
25mA
320mA
CTRL1
DIMMING 1
OFF ON
CTRL2
REF
DIMMING 2
SHDN
PWM1
FB1
LT3486
C
REF
0.1 F
PWM2
FB2
V
C1
R
T
V
5V
C2
Q1
OFF ON
0V
63.4k
2.8k
4.7nF
R
R
FB2
8.06
FB1
100k
0.1 F
0.62
3486 TA02a
L1, L2: TOKO D53LC (TYPE A)
Q1: FAIRCHILD FDN5630
C
C
: 6.3V, X5R OR X7R DIELECTRIC
IN
, C
: 35V, X5R OR X7R
OUT1 OUT2
D1: ZETEX ZHCS1000
D2: ZETEX ZHCS400
Effiꢀienꢀy vs V
IN
90
85
80
75
70
MOVIE MODE
LED1
I
= 175mA
FLASH MODE
= 320mA
I
LED1
8 LEDS/25mA
3.4
65
3
3.6
(V)
3.8
4
4.2
3.2
V
IN
3486 TA01b
3486f
15
LT3486
U
TYPICAL APPLICATIO S
1 Li-Ion Cell to 8/8 White LEDs
3V TO 5V
C
IN
10µF
D1
D2
L1
10µH
L2
10µH
C
C
OUT1
OUT2
2.2µF
2.2µF
SW1
SW2
V
IN
8 LEDs
25mA
8 LEDs
25mA
OVP2
CTRL2
REF
OVP1
V
V
CTRL1
IN
IN
OFF ON
SHDN
PWM1
FB1
LT3486
C
REF
0.1µF
PWM2
FB2
V
C1
R
V
C2
T
2.8k
4.7nF
2.8k
4.7nF
5V
63.4k
PWM2
100Hz
PWM1
100Hz
Q1
Q2
100k
C
C
, C : 35V, X5R OR X7R D1, D2: ZETEX ZLLS400
OUT1 OUT2
100k
8.06Ω
8.06Ω
: 10V, X5R OR X7R
L1, L2: TOKO D53LC (TYPE A)
Q1, Q2: FAIRCHILD 2N7002
IN
3486 TA05A
Wide (250:1) Dimming Range
(LED Current 0.1mA to 25mA)
LED Current and Effiꢀienꢀy vs PWM Duty Cyꢀle
100
10
85
35
V
= 3.6V
V
= 3.6V
IN
8/8 LEDs
IN
8/8 LEDs
80
30
PWM FREQ = 100Hz
75
70
65
60
55
50
25
20
15
10
5
EFFICIENCY
1
LED CURRENT
0.10
0.01
0
100
20
40
60
0
80
0.1
1
10
100
DUTY CYCLE (%)
PWM DUTY CYCLE (%)
3486 TA05b
3486 TA05d
PWM Dimming Waveforms
LED CURRENT
20mA/DIV
I
L
200mA/DIV
PWM
5V/DIV
3486 TA05c
V
= 3.6V
2ms/DIV
IN
CTRL1 = 3.6V
8 LEDs/25mA
PWM FREQ = 100Hz
3486f
16
LT3486
U
TYPICAL APPLICATIO S
5V to 16/16 White LEDs
5V
D5
D3
D6
D4
C
IN
C3
1 F
C4
1 F
1 F
16 LEDs
16 LEDs
L1
15 H
L2
15 H
C1
0.1 F
C2
0.1 F
D1
C
D2
C
OUT2
2.2 F
OUT1
2.2 F
SW1
SW2
V
IN
OVP2
CTRL2
REF
OVP1
CTRL1
V
V
IN
25mA
IN
25mA
OFF ON
SHDN
PWM1
FB1
LT3486
C
REF
0.1 F
PWM2
FB2
V
C1
R
V
C2
T
4.02k
4.7nF
4.02k
4.7nF
63.4k
22pF
PWM FREQ
200Hz
PWM FREQ
200Hz
Q1
Q2
100k
100k
8.06
8.06
C
C
: 6.3V, X5R OR X7R
D1, D2: ZETEX ZLLS400
D3-D6: PHILIPS BAV99W
IN
, C
: 35V, X5R OR X7R
OUT1 OUT2
3486 TA08a
C1-C4: 50V, X5R OR X7R
: 6.3V, X5R OR X7R
L1, L2: TOKO D53LC (TYPE A)
Q1, Q2: FAIRCHILD 2N7002
C
REF
LED Current and Effiꢀienꢀy vs PWM Duty Cyꢀle
PWM Dimming Waveforms
85
80
35
30
V
= 5V
IN
I
LED
16/16 LEDs
50mA/DIV
75
70
65
60
55
50
25
20
15
10
5
I
L
EFFICIENCY
500mA/DIV
PWM
5V/DIV
LED CURRENT
3486 TA08c
L = 15µH
PWM FREQ = 200Hz
1ms/DIV
0
100
20
40
60
0
80
PWM DUTY CYCLE (%)
3486 TA08b
3486f
17
LT3486
U
PACKAGE DESCRIPTIO
DHC Package
16-Lead Plastic DFN (5mm × 3mm)
(Reference LTC DWG # 05-08-1706)
0.65 0.05
3.50 0.05
1.65 0.05
2.20 0.05 (2 SIDES)
PACKAGE
OUTLINE
0.25 0.05
0.50 BSC
4.40 0.05
(2 SIDES)
RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS
R = 0.115
TYP
0.40 0.10
5.00 0.10
(2 SIDES)
9
16
R = 0.20
TYP
3.00 0.10 1.65 0.10
(2 SIDES)
(2 SIDES)
PIN 1
TOP MARK
(SEE NOTE 6)
PIN 1
NOTCH
(DHC16) DFN 1103
8
1
0.25 0.05
0.50 BSC
0.75 0.05
0.200 REF
4.40 0.10
(2 SIDES)
0.00 – 0.05
BOTTOM VIEW—EXPOSED PAD
NOTE:
1. DRAWING PROPOSED TO BE MADE VARIATION OF VERSION (WJED-1) IN JEDEC
PACKAGE OUTLINE MO-229
2. DRAWING NOT TO SCALE
3. ALL DIMENSIONS ARE IN MILLIMETERS
4. DIMENSIONS OF EXPOSED PAD ON BOTTOM OF PACKAGE DO NOT INCLUDE
MOLD FLASH. MOLD FLASH, IF PRESENT, SHALL NOT EXCEED 0.15mm ON ANY SIDE
5. EXPOSED PAD SHALL BE SOLDER PLATED
6. SHADED AREA IS ONLY A REFERENCE FOR PIN 1 LOCATION ON THE
TOP AND BOTTOM OF PACKAGE
3486f
18
LT3486
U
PACKAGE DESCRIPTIO
FE Package
16-Lead Plastic TSSOP (4.4mm)
(Reference LTC DWG # 05-08-1663)
Exposed Pad Variation BB
4.90 – 5.10*
(.193 – .201)
3.58
(.141)
3.58
(.141)
16 1514 13 12 1110
9
6.60 0.10
4.50 0.10
2.94
(.116)
6.40
(.252)
BSC
SEE NOTE 4
2.94
(.116)
0.45 0.05
1.05 0.10
0.65 BSC
5
7
8
1
2
3
4
6
RECOMMENDED SOLDER PAD LAYOUT
1.10
(.0433)
MAX
4.30 – 4.50*
(.169 – .177)
0.25
REF
0° – 8°
0.65
(.0256)
BSC
0.09 – 0.20
(.0035 – .0079)
0.50 – 0.75
(.020 – .030)
0.05 – 0.15
(.002 – .006)
0.195 – 0.30
FE16 (BB) TSSOP 0204
(.0077 – .0118)
TYP
NOTE:
1. CONTROLLING DIMENSION: MILLIMETERS 4. RECOMMENDED MINIMUM PCB METAL SIZE
FOR EXPOSED PAD ATTACHMENT
*DIMENSIONS DO NOT INCLUDE MOLD FLASH. MOLD FLASH
SHALL NOT EXCEED 0.150mm (.006") PER SIDE
MILLIMETERS
(INCHES)
2. DIMENSIONS ARE IN
3. DRAWING NOT TO SCALE
3486f
Information furnished by Linear Technology Corporation is believed to be accurate and reliable.
However, no responsibility is assumed for its use. Linear Technology Corporation makes no representa-
tion that the interconnection of its circuits as described herein will not infringe on existing patent rights.
19
LT3486
U
TYPICAL APPLICATIO
12V to 8/8 White LEDs
12V (TYP)
9V TO 15V 10µF
C
IN
L1
10µH
L2
10µH
LED Current and Effiꢀienꢀy
vs PWM Duty Cyꢀle
C
5V
C
OUT1
OUT2
2.2µF
D1
D2
2.2µF
90
85
120
100
C1 1µF
EFFICIENCY
SW1
SW2
V
IN
LUXEON
LEDs
LXCL-PWF1
LUXEON
LEDs
LXCL-PWF1
OVP2
CTRL2
REF
OVP1
80
75
80
60
LED CURRENT
V
V
CTRL1
IN
IN
OFF ON
SHDN
PWM1
FB1
LT3486
C
100mA
REF
0.1µF
100mA
PWM2
FB2
70
65
60
40
20
0
V
R
V
C2
C1
T
V
= 12V
IN
22pF
DIMMING
INPUT 1
DIMMING
INPUT 2
3.65k
2.2nF
3.65k
2.2nF
8/8 LEDs
21.5k
PWM
FREQ
1kHz
PWM
FREQ
1kHz
0
20
40
60
80
100
Q1
R
Q2
PWM DUTY CYCLE (%)
3486 TA10b
100k
100k
R
FB2
2Ω
FB1 C
, C
: 35V, X5R OR X7R
D1, D2: ZETEX ZLLS1000
OUT1 OUT2
: 25V, X5R OR X7R
C1: 10V, X5R OR X7R
: 6.3V, X5R OR X7R
2Ω
C
L1, L2: TOKO D53LC (TYPE A)
Q1, Q2: FAIRCHILD FDN5630
IN
3486 TA10a
C
REF
RELATED PARTS
PART NUMBER
DESCRIPTION
COMMENTS
LT1618
Constant Current, Constant Voltage 1.24MHz, High Efficiency
Boost Regulator
Up to 16 White LEDs, VIN: 1.6V to 18V, VOUT(MAX) = 34V,
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LT1932
Constant Current, 1.2MHz, High Efficiency White LED Boost
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LT1937
Constant Current, 1.2MHz, High Efficiency White LED Boost
Regulator
Up to 4 White LEDs, VIN: 2.5V to 10V, VOUT(MAX) = 34V,
IQ = 1.9mA, ISD < 1µA, ThinSOT, SC70 Packages
LTC3200
LTC3200-5
LTC3201
LTC3202
LTC3205
Low Noise, 2MHz, Regulated Charge Pump White LED Driver
MS Package
Up to 6 White LEDs, VIN: 2.7V to 4.5V, IQ = 8mA, ISD < 1µA,
Up to 6 White LEDs, VIN: 2.7V to 4.5V, IQ = 8mA, ISD < 1µA,
Up to 6 White LEDs, VIN: 2.7V to 4.5V, IQ = 6.5mA, ISD < 1µA,
Up to 8 White LEDs, VIN: 2.7V to 4.5V, IQ = 5mA, ISD < 1µA,
Low Noise, 2MHz, Regulated Charge Pump White LED Driver
ThinSOT Package
Low Noise, 1.7MHz, Regulated Charge Pump White LED Driver
MS Package
Low Noise, 1.5MHz, Regulated Charge Pump White LED Driver
MS Package
High Efficiency, Multidisplay LED Controller
Up to 4 (Main), 2 (Sub) and RGB, VIN: 2.8V to 4.5V,
IQ = 50µA, ISD < 1µA, QFN-24 Package
LT3465/LT3465A Constant Current, 1.2MHz/2.7MHz, High Efficiency White LED
Boost Regulator with Integrated Schottky Diode
Up to Six White LEDs, VIN: 2.7V to 16V, VOUT(MAX) = 34V,
IQ = 1.9mA, ISD < 1µA, ThinSOT Package
LT3466
Dual Full Function White LED Boost Regulator with Integrated
Schottky Diode
Drives Up to 20 LEDs, V : 2.7V to 24V, V
= 40V,
IN
OUT(MAX)
I = 5mA, I < 16µA, DFN Package
Q
SD
3486f
LT/TP 0705 500 • PRINTED IN USA
LinearTechnology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
20
●
●
(408) 432-1900 FAX: (408) 434-0507 www.linear.com
© LINEAR TECHNOLOGY CORPORATION 2005
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