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PDF LT3466-1 Data sheet ( Hoja de datos )
| Número de pieza | LT3466-1 | |
| Descripción | White LED Driver and Boost Converter | |
| Fabricantes | Linear | |
| Logotipo |  |
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FEATURES
■ Drives Up to 10 White LEDs from a 3.6V Supply
■ Two Independent Step-Up DC/DC Converters
■ Independent Dimming and Shutdown Control
of the Outputs
■ ±1.5% Output Voltage Accuracy (Boost Converter)
■ ±4% LED Current Programming Accuracy
■ Internal Schottky Diodes
■ Internal Soft-Start Eliminates Inrush Current
■ Output Overvoltage Protection (39.5V Max VOUT)
■ Fixed Frequency Operation Up to 2MHz
■ 83% Efficiency Driving 8 White LEDs at 15mA
from a 3.6V Supply
■ Wide Input Voltage Range: 2.7V to 24V
■ Tiny (3mm × 3mm) 10-Lead DFN Package
U
APPLICATIO S
■ White LED and OLED Displays
■ Digital Cameras, Sub-Notebook PCs
■ PDAs, Handheld Computers
■ TFT - LCD Bias Supply
■ Automotive
LT3466-1
White LED Driver and Boost
Converter in 3mm × 3mm
DFN Package
DESCRIPTIO
LT®3466-1 is a dual switching regulator that combines a
white LED driver and a boost converter in a low profile,
small footprint (3mm × 3mm × 0.75mm) DFN package.
The LED driver can be configured to drive up to 10 White
LEDs in series and the boost converter can be used for
generating the LCD bias voltages or driving a secondary
OLED display. Series connection of the LEDs provides
identical LED currents resulting in uniform brightness and
eliminating the need for ballast resistors and expensive
factory calibration.
The LT3466-1 provides independent dimming and shut-
down control of the two converters. The operating fre-
quency can be set with an external resistor over a 200kHz
to 2MHz range. The white LED driver features a low 200mV
reference, thereby minimizing power loss in the current
setting resistor for better efficiency. The boost converter
achieves ±1.5% output voltage accuracy by the use of a
precision 0.8V reference. Protection features include out-
put overvoltage protection and internal soft-start. Wide
input supply range allows operation from 2.7V to 24V.
, LTC and LT are registered trademarks of Linear Technology Corporation.
All other trademarks are the property of their respective owners.
TYPICAL APPLICATIO
3V TO 5V
33µH
33µH
1µF
SW1
VIN
SW2
6 LEDs
VOUT1
LT3466-1
VOUT2
1µF
16V
1µF 30mA
FB1
CTRL1
RT GND
FB2
CTRL2
475k
10Ω SHUTDOWN 63.4k
AND DIMMING
CONTROL 1
SHUTDOWN
AND DIMMING
CONTROL 2
24.9k
34661 F01a
Figure 1. Li-Ion Powered Driver for 6 White LEDs and OLED Display
Conversion Efficiency
90
VIN = 3.6V
85
LED DRIVER
80
BOOST CONVERTER
75
70
65
60
55
50
0
5 10 15 20 25
OUTPUT CURRENT (mA)
30
34661 F01b
34661f
1
1 page  
LT3466-1
TYPICAL PERFOR A CE CHARACTERISTICS TA = 25°C unless otherwise specified
Oscillator Frequency
vs Temperature
1100
VIN = 3.6V
RT = 48.7k
1000
900
800
–50
–25 0 25 50
TEMPERATURE (°C)
75 100
34661 G12
Schottky Forward Voltage Drop
400
350
300
250
200
150
100
50
0
0 200 400 600 800 1000
SCHOTTKY FORWARD DROP (mV)
34661 G14
FB2 Pin Voltage vs Temperature
0.810
0.805
VIN = 3V
VOUT2 = 16V/30mA
0.800
0.795
0.790
0.785
0.780
–50 –25
0 25 50 75
TEMPERATURE (°C)
100 125
34661 G17
CTRL Voltages to Shut Down
the IC
150
VIN = 3.6V
125
CTRL1
100
CTRL2
75
50
25
0
–50 –25 0
25 50
TEMPERATURE (°C)
75 100
34661 G13
Schottky Leakage Current
8
6
4
VR = 36V
VR = 20V
2
0
–50 –25
0
25 50
TEMPERATURE (°C)
75 100
34661 G015
FB2 Pin Load Regulation
0
VIN = 3V
VOUT2 = 16V
–0.20
–0.40
–0.60
–0.80
–1.00
0
10 20
LOAD CURRENT (mA)
30
34661 G18
34661f
5
5 Page 
LT3466-1
APPLICATIO S I FOR ATIO
The inductor current ripple (∆IL), neglecting the drop
across the Schottky diode and the switch, is given by :
( )∆IL
=
VIN(MIN) • VOUT(MAX) – VIN(MIN)
VOUT(MAX) • f • L
where:
L = Inductor
f = Operating frequency
VIN(MIN) = Minimum input voltage
VOUT(MAX) = Maximum output voltage
The ∆IL is typically set to 20% to 40% of the maximum
inductor current.
The inductor should have a saturation current rating
greater than the peak inductor current required for the
application. Also, ensure that the inductor has a low DCR
(copper wire resistance) to minimize I2R power losses.
Recommended inductor values range from 10µH to 68µH.
Several inductors that work well with the LT3466-1 are listed
in Table 1. Consult each manufacturer for more detailed
information and for their entire selection of related parts.
Table 1. Recommended Inductors
PART
MAX CURRENT
L DCR RATING
(µH) (Ω) (mA)
LQH32CN100
LQH32CN150
LQH43CN330
10 0.44
15 0.58
33 1.00
300
300
310
ELL6RH330M
ELL6SH680M
33 0.38
68 0.52
600
500
A914BYW330M
A914BYW470M
A920CY680M
CDRH2D18150NC
CDRH4D18-330
CDRH5D18-680
33 0.45
47 0.73
68 0.40
15 0.22
33 0.51
68 0.84
440
360
400
0.35A
0.31A
0.43A
VENDOR
Murata
(814) 237-1431
www.murata.com
Panasonic
(714) 373-7939
www.panasonic.com
Toko
www.toko.com
Sumida
(847) 956-0666
www.sumida.com
CAPACITOR SELECTION
The small size of ceramic capacitors make them ideal for
LT3466-1 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 1µF input capacitor is sufficient for most applica-
tions. Always use a capacitor with sufficient voltage rating.
Table 2 shows a list of several ceramic capacitor manufac-
turers. Consult the manufacturers for detailed information
on their entire selection of ceramic parts.
Table 2. Ceramic Capacitor Manufacturers
Taiyo Yuden
(408) 573-4150
www.t-yuden.com
AVX (803) 448-9411
www.avxcorp.com
Murata
(714) 852-2001
www.murata.com
INRUSH CURRENT
The LT3466-1 has built-in Schottky diodes. When supply
voltage is applied to the VIN pin, an inrush current flows
through the inductor and the Schottky diode and charges
up the output capacitor. Both Schottky diodes in the
LT3466-1 can sustain a maximum of 1A current. The
selection of inductor and capacitor value should ensure
the peak of the inrush current to be below 1A.
For low DCR inductors, which is usually the case for this
application, the peak inrush current can be simplified as
follows:
IPK
=
VIN – 0.6
ωL
where:
ω= 1
LCOUT
Table 3 gives inrush peak current for some component
selections.
Table 3. Inrush Peak Current
VIN (V)
5
L (µH)
15
5 33
5 47
5 68
9 47
12 33
COUT (µF)
0.47
1.00
2.2
1.00
0.47
0.22
IP (A)
0.78
0.77
0.95
0.53
0.84
0.93
34661f
11
11 Page | ||
| Páginas | Total 20 Páginas | |
| PDF Descargar | [ Datasheet LT3466-1.PDF ] | |
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