Datasheet LT3475, LT3475-1 (Analog Devices)
| Fabricante | Analog Devices |
| Descripción | Dual Step-Down 1.5A LED Driver |
| Páginas / Página | 20 / 1 — FEATURES. DESCRIPTIO. True Color PWM. Delivers Constant Color with. … |
| Formato / tamaño de archivo | PDF / 249 Kb |
| Idioma del documento | Inglés |
FEATURES. DESCRIPTIO. True Color PWM. Delivers Constant Color with. 3000:1 Dimming Range
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LT3475/LT3475-1 Dual Step-Down 1.5A LED Driver
U FEATURES DESCRIPTIO
■
True Color PWM
TM
Delivers Constant Color with
The LT®3475/LT3475-1 are dual step-down DC/DC
3000:1 Dimming Range
converters designed to operate as a constant-current ■
Wide Input Range: 4V to 36V Operating, 40V
source. An internal sense resistor monitors the output
Maximum
current allowing accurate current regulation ideal for ■
Accurate and Adjustable Control of LED Current
driving high current LEDs. The high side current sense al-
from 50mA to 1.5A
lows grounded cathode LED operation. High output current ■
High Side Current Sense Allows Grounded Cathode
accuracy is maintained over a wide current range, from
LED Operation
50mA to 1.5A, allowing a wide dimming range. Unique ■
Open LED (LT3475) and Short Circuit Protection
PWM circuitry allows a dimming range of 3000:1, avoid- ■
LT3475-1 Drives LED Strings Up to 25V
ing the color shift normally associated with LED current ■ Accurate and Adjustable 200kHz to 2MHz dimming. Switching Frequency The high switching frequency offers several advantages, ■ Anti-Phase Switching Reduces Ripple permitting the use of small inductors and ceramic capaci- ■ Uses Small Inductors and Ceramic Capacitors tors. Small inductors combined with the 20 lead TSSOP ■ Available in the Compact 20-Lead TSSOP Thermally surface mount package save space and cost versus Enhanced Surface Mount Package alternative solutions. The constant switching frequency
U
combined with low-impedance ceramic capacitors result
APPLICATIO S
in low, predictable output ripple. ■ Automotive and Avionic Lighting With its wide input range of 4V to 36V, the LT3475/LT3475-1 ■ Architectural Detail Lighting regulate a broad array of power sources. A current mode ■ Display Backlighting PWM architecture provides fast transient response and ■ Constant-Current Sources cycle-by-cycle current limiting. Frequency foldback and , LT, LTC and LTM are registered trademarks of Linear Technology Corporation. All other trademarks are the property of their respective owners. Patents Pending. thermal shutdown provide additional protection.
U TYPICAL APPLICATIO Dual Step-Down 1.5A LED Driver
VIN
Effi ciency
5V TO 36V 4.7μF V 95 IN SHDN VIN = 12V TWO SERIES CONNECTED BOOST1 BOOST2 WHITE 1.5A LEDS 90 0.22μF 0.22μF LT3475 10μH 10μH 85 SW1 SW2 80 SINGLE WHITE 1.5A LED OUT1 OUT2 75 LED1 LED2 *DIMMING DIMMING* 70 PWM1 PWM2 EFFICIENCY (%) CONTROL CONTROL VC1 VC2 65 REF R 2.2μF 0.1μF T 0.1μF 2.2μF 60 1.5A LED 1.5A LED VADJ1 VADJ2 CURRENT CURRENT 24.3k GND 55 0 0.5 1 1.5 LED CURRENT (A) 3475 TA01 *SEE APPLICATIONS SECTION FOR DETAILS fSW = 600kHz 3475 TA01b 3475fb 1
U FEATURES DESCRIPTIO
■
True Color PWM
TM
Delivers Constant Color with
The LT®3475/LT3475-1 are dual step-down DC/DC
3000:1 Dimming Range
converters designed to operate as a constant-current ■
Wide Input Range: 4V to 36V Operating, 40V
source. An internal sense resistor monitors the output
Maximum
current allowing accurate current regulation ideal for ■
Accurate and Adjustable Control of LED Current
driving high current LEDs. The high side current sense al-
from 50mA to 1.5A
lows grounded cathode LED operation. High output current ■
High Side Current Sense Allows Grounded Cathode
accuracy is maintained over a wide current range, from
LED Operation
50mA to 1.5A, allowing a wide dimming range. Unique ■
Open LED (LT3475) and Short Circuit Protection
PWM circuitry allows a dimming range of 3000:1, avoid- ■
LT3475-1 Drives LED Strings Up to 25V
ing the color shift normally associated with LED current ■ Accurate and Adjustable 200kHz to 2MHz dimming. Switching Frequency The high switching frequency offers several advantages, ■ Anti-Phase Switching Reduces Ripple permitting the use of small inductors and ceramic capaci- ■ Uses Small Inductors and Ceramic Capacitors tors. Small inductors combined with the 20 lead TSSOP ■ Available in the Compact 20-Lead TSSOP Thermally surface mount package save space and cost versus Enhanced Surface Mount Package alternative solutions. The constant switching frequency
U
combined with low-impedance ceramic capacitors result
APPLICATIO S
in low, predictable output ripple. ■ Automotive and Avionic Lighting With its wide input range of 4V to 36V, the LT3475/LT3475-1 ■ Architectural Detail Lighting regulate a broad array of power sources. A current mode ■ Display Backlighting PWM architecture provides fast transient response and ■ Constant-Current Sources cycle-by-cycle current limiting. Frequency foldback and , LT, LTC and LTM are registered trademarks of Linear Technology Corporation. All other trademarks are the property of their respective owners. Patents Pending. thermal shutdown provide additional protection.
U TYPICAL APPLICATIO Dual Step-Down 1.5A LED Driver
VIN
Effi ciency
5V TO 36V 4.7μF V 95 IN SHDN VIN = 12V TWO SERIES CONNECTED BOOST1 BOOST2 WHITE 1.5A LEDS 90 0.22μF 0.22μF LT3475 10μH 10μH 85 SW1 SW2 80 SINGLE WHITE 1.5A LED OUT1 OUT2 75 LED1 LED2 *DIMMING DIMMING* 70 PWM1 PWM2 EFFICIENCY (%) CONTROL CONTROL VC1 VC2 65 REF R 2.2μF 0.1μF T 0.1μF 2.2μF 60 1.5A LED 1.5A LED VADJ1 VADJ2 CURRENT CURRENT 24.3k GND 55 0 0.5 1 1.5 LED CURRENT (A) 3475 TA01 *SEE APPLICATIONS SECTION FOR DETAILS fSW = 600kHz 3475 TA01b 3475fb 1