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LT3497のメーカーはLinearです、この部品の機能は「Dual Full Function White LED Driver」です。 |
部品番号 | LT3497 |
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部品説明 | Dual Full Function White LED Driver | ||
メーカ | Linear | ||
ロゴ | |||
このページの下部にプレビューとLT3497ダウンロード(pdfファイル)リンクがあります。 Total 20 pages
FEATURES
■ Drives Up to 12 White LEDs (6 in Series per
Converter) from a 3V Supply
■ Two Independent Boost Converters Capable of
Driving Asymmetric LED Strings
■ Independent Dimming and Shutdown Control of the
Two LED Strings
■ High Side Sense Allows “One Wire Current Source”
per Converter
■ Internal Schottky Diodes
■ Open LED Protection (32V)
■ 2.3MHz Switching Frequency
■ ±5% Reference Accuracy
■ VIN Range: 2.5V to 10V
■ Dual Wide 250:1 True Color PWMTM Dimming
■ Requires Only 1µF Output Capacitor per Converter
■ Available in a 3mm × 2mm 10-Pin DFN Package
APPLICATIONS
■ Cellular Phones
■ PDAs, Handheld Computers
■ Digital Cameras
■ MP3 Players
■ GPS Receivers
LT3497
Dual Full Function White
LED Driver with Integrated
Schottky Diodes
DESCRIPTION
The LT®3497 is a dual full function step-up DC/DC con-
verter specifically designed to drive up to 12 white LEDs
(6 white LEDs in series per converter) from a Li-Ion cell. Se-
ries connection of the LEDs provides identical LED currents
resulting in uniform brightness and eliminating the need
for ballast resistors and expensive factory calibration.
The two independent converters are capable of driving
asymmetric LED strings. Accurate LED dimming and
shutdown of the two LED strings can also be controlled
independently. The LT3497 features a unique high side LED
current sense that enables the part to function as a “one
wire current source;” one side of the LED string can be
returned to ground anywhere, allowing a simpler 1-wire
LED connection. Traditional LED drivers use a grounded
resistor to sense LED current, requiring a 2-wire connec-
tion to the LED string.
The 2.3MHz switching frequency allows the use of tiny
inductors and capacitors. Few external components are
needed for the dual white LED Driver: open-LED protection
and the Schottky diodes are all contained inside the 3mm
× 2mm DFN package. With such a high level of integra-
tion, the LT3497 provides a high efficiency dual white LED
driver solution in the smallest of spaces.
, LT, LTC and LTM are registered trademarks of Linear Technology Corporation.
True Color PWM is a trademark of Linear Technology Corporation.
All other trademarks are the property of their respective owners.
TYPICAL APPLICATION
Li-Ion Power Driver for 4/4 White LEDs
VIN
3V TO 5V
15µH
15µH
1µF
SW1 VIN SW2
CAP1
CAP2
10Ω LT3497
10Ω
1µF 1µF
LED1
LED2
CTRL1 GND CTRL2
OFF ON
SHUTDOWN
AND DIMMING
CONTROL 1
OFF ON
SHUTDOWN
AND DIMMING
CONTROL 2
3497 TA01a
80
VIN = 3.6V
4/4LEDs
75
Efficiency
70
65
60
55
50
0
5 10 15 20
LED CURRENT (mA)
3497 TA01b
3497f
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1 Page LT3497
ELECTRICAL CHARACTERISTICS The ● denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C. VIN = 3V, VCTRL1 = VCTRL2 = 3V.
PARAMETER
CONDITIONS
MIN TYP MAX UNITS
VCTRL1 Voltage for Full LED Current
VCTRL2 Voltage for Full LED Current
VCTRL1 or VCTRL2 Voltage to Turn On the IC
VCTRL1 and VCTRL2 Voltages to Shut Down the IC
CTRL1, CTRL2 Pin Bias Current
VCAP1 = 16V
VCAP2 = 16V
● 1.5
● 1.5
● 100
50
100
V
V
mV
mV
nA
CAP1 Pin Overvoltage Protection
● 30 32 34
V
CAP2 Pin Overvoltage Protection
● 30 32 34
V
Schottky 1 Forward Drop
Schottky 2 Forward Drop
Schottky 1 Reverse Leakage Current
Schottky 2 Reverse Leakage Current
ISCHOTTKY1 = 100mA
ISCHOTTKY2 = 100mA
VR1 = 25V
VR2 = 25V
0.8
0.8
4
4
V
V
µA
µA
Note 1: Stresses beyond those listed under Absolute Maximum Ratings
may cause permanent damage to the device. Exposure to any Absolute
Maximum Rating condition for extended periods may affect device
reliability and lifetime.
Note 2: The LT3497E is guaranteed to meet performance specifications
from 0°C to 85°C. Specifications over the –40°C to 85°C operating
temperature range are assured by design, characterization and correlation
with statistical process controls.
3497f
3
3Pages LT3497
PIN FUNCTIONS
LED1 (Pin 1): Connection point for the anode of the first
LED of the first set of LEDs and the sense resistor (RSENSE1).
The LED current can be programmed by:
ILED1
=
200mV
RSENSE1
CTRL1 (Pin 2): Dimming and Shutdown Pin. Connect
CTRL1 below 50mV to disable converter 1. As the pin volt-
age is ramped from 0V to 1.5V, the LED current ramps from
0 to (ILED1 = 200mV/RSENSE1). The CTRL1 pin must not
be left floating.
GND (Pin 3): Connect the GND pin to the PCB system
ground plane.
CTRL2 (Pin 4): Dimming and Shutdown Pin. Connect
CTRL2 below 50mV to disable converter 2. As the pin volt-
age is ramped from 0V to 1.5V, the LED current ramps from
0 to (ILED2 = 200mV/RSENSE2). The CTRL2 pin must not
be left floating.
LED2 (Pin 5): Connection point for the anode of the first
LED of the second set of LEDs and the sense resistor
(RSENSE2). The LED current can be programmed by:
ILED2
=
200mV
RSENSE2
CAP2 (Pin 6): Output of Converter 2. This pin is connected
to the cathode of internal Schottky diode 2. Connect the
output capacitor to this pin and the sense resistor (RSENSE2)
from this pin to LED2 pin.
SW2 (Pin 7): Switch Pin. Minimize trace area at this pin
to minimize EMI. Connect the inductor at this pin.
VIN (Pin 8): Input Supply Pin. This pin must be locally
bypassed.
SW1 (Pin 9): Switch Pin. Minimize trace area at this pin
to minimize EMI. Connect the inductor at this pin.
CAP1 (Pin 10): Output of Converter 1. This pin is connected
to the cathode of internal Schottky diode 1. Connect the
output capacitor to this pin and the sense resistor (RSENSE1)
from this pin to LED1 pin.
Exposed Pad (Pin 11): Ground. Must be soldered to
PCB.
3497f
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6 Page | |||
ページ | 合計 : 20 ページ | ||
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PDF ダウンロード | [ LT3497 データシート.PDF ] |
データシートを活用すると、その部品の主な機能と仕様を詳しく理解できます。 ピン構成、電気的特性、動作パラメータ、性能を確認してください。 |
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