FEATURES
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LT3486
Dual 1.3A White LED
Step-Up Converters with
Wide Dimming
DESCRIPTION
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
independent converters are capable of driving asymmetric
LED strings.
The dimming of the two LED strings can be controlled
independently via the respective CTRL pins. An internal
dimming system allows the dimming range to be extended
up to 1000:1 by feeding a PWM signal to the respective
PWM pins. The LT3486 operating frequency can be set with
an external resistor over a 200kHz to 2.5MHz range. A low
200mV feedback voltage (±3% accuracy) minimizes power
loss in the current setting resistor for better efficiency.
Additional features include output voltage limiting when
LEDs are disconnected and overtemperature protection.
The LT3486 is available in a space saving 16-pin DFN
(5mm × 3mm × 0.75mm) and 16-pin thermally enhanced
TSSOP packages.
L,
LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks and
ThinSOT is a trademark of Linear Technology Corporation. All other trademarks are the property
of their respective owners.
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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
±3% LED Current Programming Accuracy
Open LED Protection: 36V Clamp Voltage
Fixed Frequency Operation: Up to 2.5MHz
Wide Input Voltage Range: 2.5V to 24V
Low Shutdown Current: ICC < 1µA
Overtemperature Protection
Available in (5mm × 3mm × 0.75mm) 16-Pin DFN
and 16-Pin Thermally Enhanced TSSOP Packages
APPLICATIONS
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Notebook PC Display
LED Camera Light for Cell Phones
Car Dashboard Lighting
Avionics Displays
TYPICAL APPLICATION
Li-Ion Powered Driver for Camera Flash and LCD Backlighting
V
IN
3V TO 4.2V
Efficiency vs V
IN
90
2.2µF
SW2
OVP2
CTRL2
DIMMING 2
25mA
MOVIE MODE
I
LED1
= 175mA
FLASH MODE
I
LED1
= 320mA
10µF
2.2µF
LED1
AOT3218
DIMMING 1
OFF ON
SW1
OVP1
CTRL1
SHDN
PWM1
OFF ON
R
FB1
0.62
FB1
V
C1
GND R
T
63.4k
0.1µF
LT3486
L1
10µH
V
IN
L2
10µH
8 LEDs
EFFICIENCY (%)
85
80
REF
PWM2
FB2
V
C2
2.8k
4.7nF
R
FB2
8.06
3486 TA01a
75
0.1µF
70
65
8 LEDS/25mA
3
3.2
3.4
3.6
V
IN
(V)
3.8
4
4.2
100k
3486 TA01b
3486fe
1
LT3486
ABSOLUTE MAXIMUM RATINGS
(Note 1)
Input Voltage (V
IN
) ....................................................25V
SHDN
Voltage ...........................................................25V
SW1, SW2 Voltages .................................................40V
OVP1, OVP2 Voltages ...............................................40V
CTRL1, CTRL2 Voltages ............................................10V
PWM1, PWM2 Voltages ............................................10V
FB1, FB2 Voltages .....................................................10V
Operating Junction Temperature Range (Note 2)
LT3486E ...............................................–40°C to 85°C
LT3486I ..............................................–40°C to 125°C
Storage Temperature Range
DFN ...................................................–65°C to 125°C
TSSOP ...............................................–65°C to 150°C
Maximum Junction Temperature........................... 125°C
Lead Temperature (Soldering, 10 sec, TSSOP) ..... 300°C
PIN CONFIGURATION
TOP VIEW
SW1
V
IN
OVP1
R
T
V
C1
FB1
CTRL1
PWM1
1
2
3
4
5
6
7
8
17
16 SW2
15 REF
14 OVP2
13
SHDN
12 V
C2
11 FB2
10 CTRL2
9
PWM2
SW1 1
V
IN
2
OVP1 3
R
T
4
V
C1
5
FB1 6
CTRL1 7
PWM1 8
17
TOP VIEW
16 SW2
15 REF
14 OVP2
13
SHDN
12 V
C2
11 FB2
10 CTRL2
9 PWM2
DHC PACKAGE
16-LEAD (5mm
×
3mm) PLASTIC DFN
EXPOSED PAD (PIN 17) IS GND
MUST BE SOLDERED TO PCB
T
JMAX
= 125°C,
θ
JA
= 43°C/W,
θ
JC
= 4°C/W
FE PACKAGE
16-LEAD PLASTIC TSSOP
EXPOSED PAD IS GND (PIN 17)
MUST BE SOLDERED TO PCB
T
JMAX
= 125°C,
θ
JA
= 38°C/W,
θ
JC
= 10°C/W
ORDER INFORMATION
LEAD FREE FINISH
LT3486EDHC#PBF
LT3486EFE#PBF
LT3486IFE#PBF
LEAD BASED FINISH
LT3486EDHC
LT3486EFE
LT3486IFE
TAPE AND REEL
LT3486EDHC#TRPBF
LT3486EFE#TRPBF
LT3486IFE#TRPBF
TAPE AND REEL
LT3486EDHC#TR
LT3486EFE#TR
LT3486IFE#TR
PART MARKING
3486
3486EFE
3486IFE
PART MARKING
3486
3486EFE
3486IFE
PACKAGE DESCRIPTION
16-Lead (5mm × 3mm) Plastic DFN
16-Lead Plastic TSSOP
16-Lead Plastic TSSOP
PACKAGE DESCRIPTION
16-Lead (5mm × 3mm) Plastic DFN
16-Lead Plastic TSSOP
16-Lead Plastic TSSOP
TEMPERATURE RANGE
–40°C to 85°C
–40°C to 85°C
–40°C to 125°C
TEMPERATURE RANGE
–40°C to 85°C
–40°C to 85°C
–40°C to 125°C
Consult LTC Marketing for parts specified with wider operating temperature ranges.
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/
3486fe
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LT3486
ELECTRICAL CHARACTERISTICS
PARAMETER
Minimum Operating Voltage
Maximum Operating Voltage
Feedback Voltage (FB1, FB2)
Offset between FB1 and FB2
Feedback Pin Bias Current (FB1, FB2)
Quiescent Current
Switching Frequency
Oscillator Frequency Range (Typical Value)
Nominal R
T
Pin Voltage
Maximum Duty Cycle
V
OS
= |FB1-FB2|
V
FB1
= V
FB2
= 0.2V (Note 3)
V
FB1
= V
FB2
= 1V
SHDN
= 0V, CTRL1 = CTRL2 = 0V
R
T
= 53.6k
R
T
= 20.5k
(Note 4)
R
T
= 53.6k
R
T
= 53.6k
R
T
= 20.5k
R
T
= 309k
I
SW1
= I
SW2
= 0.75A
V
SW1
= V
SW2
= 10V
∆I = ±5µA
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l
The
l
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. V
IN
= 3V, V
CTRL1
= 3V, V
CTRL2
= 3V, V
PWM1
= 3V, V
PWM2
= 3V,
V
SHDN
= 3V, unless otherwise noted.
CONDITIONS
MIN
2.5
24
194
0
10
200
3
45
9
0.1
0.75
1.7
200
0.54
90
96
90
98
1.3
300
0.1
220
120
0.85
1.5
V
FB1
= V
FB2
= 0V
V
FB1
= V
FB2
= 1V
V
C1
= V
C2
= 1V, V
PWM1
= V
PWM2
= 0V
34
l
TYP
MAX
UNITS
V
V
mV
mV
nA
mA
µA
MHz
MHz
kHz
V
%
%
%
206
6
100
14
1
1.25
2.7
2500
1
2.2
Switch Current Limit (SW1, SW2)
Switch V
CESAT
Switch Leakage Current
Error Amplifier Transconductance
Error Amplifier Voltage Gain
V
C1
, V
C2
Switching Threshold
V
C1
, V
C2
Clamp Voltage
V
C1
, V
C2
Source Current
V
C1
, V
C2
Sink Current
V
C1
, V
C2
Pin Leakage Current
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
PWM1, PWM2 Voltage Low
PWM1, PWM2 Pin Bias Current
SHDN
Voltage High
SHDN
Voltage Low
SHDN
Pin Bias Current
REF Voltage
REF Source Current
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 LT3486E is guaranteed to meet specified performance
from 0°C to 85°C and is designed, characterized and expected to meet
V
SHDN
= 3V
I
REF
= 10µA
l
1
1.6
5
A
mV
µA
µA/V
V
V
µA
µA
25
25
1
35
10
36
75
150
1.8
nA
V
mV
mV
V
V
CTRL1
= V
CTRL2
= 3V
l
l
l
20
0.9
30
40
0.4
µA
V
V
µA
V
V
µA
V
µA
V
PWM1
= V
PWM2
= 3V
1.6
0.1
1
0.4
20
1.2
50
1.25
80
1.3
these extended temperature limits, but is not tested at –40°C and 85°C.
The LT3486I specifications are guaranteed over the –40°C to 125°C
temperature range.
Note 3:
Current flows out of the pin.
Note 4:
Guaranteed by design and test correlation, not production tested.
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LT3486
TYPICAL PERFORMANCE CHARACTERISTICS
Switching Waveforms
V
SW2
50V/DIV
I
L2
500mA/DIV
V
SW1
10V/DIV
I
L1
1A/DIV
0.5µs/DIV
V
IN
= 3.6V
8 LEDs/25mA
2 LEDs/320mA
CIRCUIT OF FRONT PAGE APPLICATION
3486 G17
T
A
= 25°C unless otherwise specified.
PWM Dimming Wavforms
I
LED
200mA/DIV
I
L
500mA/DIV
PWM
5V/DIV
V
IN
= 12V
0.2ms/DIV
8/8 LEDs
PWM FREQ = 1kHz
3486 G18
LED Current vs PWM Duty Cycle
Wide Dimming Range (1000:1)
100
V
IN
= 12V
8/8 LEDs
PWM FREQ = 100Hz
FEEDBACK VOLTAGE (mV)
250
200
V
FB
vs V
CTRL
V
IN
= 3.6V
T
A
= 25°C
FEEDBACK VOLTAGE (mV)
250
V
FB
vs V
CTRL
(Temperature Variation)
± 5mV
200
T
A
= –50°C
T
A
= 25°C
T
A
= 85°C
10
I
LED
(mA)
150
100
150
100
1
0.1
50
50
0.01
0.01
1
10
0.1
PWM DUTY CYCLE (%)
100
3486 G01
0
0
1
0.5
1.5
CONTROL VOLTAGE (V)
2
3486 G03
0
0
1
0.5
1.5
CONTROL VOLTAGE (V)
2
3486 G04
SHDN
Pin Bias Current
(CTRL1 = CTRL2 = 3V)
140
SHDN
PIN BIAS CURRENT (µA)
120
100
80
60
40
20
0
0
4
16
12
8
SHDN
PIN VOLTAGE (V)
20
24
3486 G05
Open-Circuit Output Clamp
Voltage vs Temperature
37
V
IN
= 3.6V
R
T
= 63.4k
OUTPUT CLAMP VOLTAGE (V)
V
OUT2
V
OUT1
35
37
Open-Circuit Output Clamp
Voltage vs V
IN
V
IN
= 3.6V
R
T
= 63.4k
VIN = 3.6V
TA = 50°C
OUTPUT CLAMP VOLTAGE (V)
TA = 25°C
TA = 100°C
36
36
V
OUT1
35
V
OUT2
34
34
33
–50
–25
75
0
25
50
TEMPERATURE (°C)
100
125
33
2
4
6
8 10 12 14 16 18 20 22 24
V
IN
(V)
3486 G07
3486 G06
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LT3486
TYPICAL PERFORMANCE CHARACTERISTICS
Input Current with Output 1 and
Output 2 Open Circuit
20
T
A
= 25°C
R
T
= 63.4k
1000
T
A
= 25°C unless otherwise specified.
R
T
vs Oscillator Frequency
1100
OSCILLATOR FREQUENCY (kHz)
Oscillator Frequency vs V
IN
R
T
= 53.6k
INPUT CURRENT (mA)
15
1050
R
T
(k )
10
100
1000
5
950
0
2
4
6
8 10 12 14 16 18 20 22 24
V
IN
(V)
3486 G08
10
0
500
1000
1500
2000
OSCILLATOR FREQUENCY (kHz)
2500
3486 G09
900
2
4
6
8 10 12 14 16 18 20 22 24
V
IN
(V)
3486 G10
Oscillator Frequency
vs Temperature
10000
OSCILLATOR FREQUENCY (kHz)
12
10
QUIESCENT CURRENT (mA)
R
T
= 22.1k
1000
R
T
= 53.6k
8
6
4
2
0
Quiescent Current vs V
IN
1.0
PWM Pin Input Bias Current
V
IN
= 3.6V
UVLO
PWM PIN CURRENT (µA)
0.5
PWM 1
0
PWM 2
R
T
= 309k
100
–50
–0.5
SHDN
= 3V
CTRL1 = CTRL2 = 3V
0
2
4
6
8 10 12 14 16 18 20 22 24
V
IN
(V)
3486 G12
–25
0
25
50
75
TEMPERATURE (°C)
100
125
–1.0
0
2
6
8
4
PWM PIN VOLTAGE (V)
10
3486 G13
3486 G11
Switch Current Limit
vs Duty Cycle
1400
1300
CURRENT LIMIT (mA)
REF VOLTAGE (V)
1200
1100
1000
900
800
REF Voltage vs Temperature
1.30
1.30
REF Voltage Load Regulation
1.25
1.20
REF VOLTAGE (V)
1.15
1.10
1.05
1.00
0.95
T
A
= 85°C
T
A
= 25°C
T
A
= –50°C
V
IN
= 3.6V
V
IN
= 3.6V
1.28
1.26
1.24
1.22
20
30
40
50 60 70 80
DUTY CYCLE (%)
90
100
1.20
–50
–25
50
0
75
25
TEMPERATURE (°C)
100
125
0.90
V
IN
= 3.6V
T
A
= 25°C
0
20 40 60 80 100 120 140 160 180 200
REF LOAD CURRENT (µA)
3468 G16
3486 G14
3486 G15
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