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LT3496

3496ff

Features

applications

Description

Triple Output LED Driver

The LT

3496 is a triple output DC/DC converter designed

to operate as a constant-current source and is ideal for

driving LEDs. The LT3496 works in buck, boost or buck-

boost mode. The LT3496 uses a fixed frequency, current

mode architecture resulting in stable operation over a

wide range of supply and output voltages. A frequency

adjust pin allows the user to program switching frequency

between 330kHz and 2.1MHz to optimize efficiency and

external component size.

The LT3496 supports 3000:1 dimming control on each

channel. Each of the three regulators is independently

operated by that channel’s PWM signal. The PWM feature

allows precise adjustment of the color mixing or dimming

ratio of the LED source. Each of the three channels has

a built-in gate driver to drive an external LED-disconnect

P-channel MOSFET, allowing high dimming range. The

output current range of each channel of the LT3496 is

programmed with an external sense resistor.

The CTRL pins are used to adjust the LED currents either

for analog dimming or overtemperature protection.

L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks and

ThinSOT and True Color PWM are trademarks of Linear Technology Corporation. All other

trademarks are the property of their respective owners. Protected by U.S. Patents, including

7199560, 7321203, and others pending.

True Color PWM™ Dimming Delivers Up to 3000:1

Dimming Ratio

Built-In Gate Driver for PMOS LED Disconnect

Three Independent Driver Channels with 750mA,

45V Internal Switches

Operates in Buck, Boost, Buck-Boost Modes

CTRL Pin Accurately Sets LED Current Sense

Threshold Over a Range of 10mV to 100mV

Adjustable Frequency: 330kHz to 2.1MHz

Open LED Protection

Wide V

Supply Range:

Operation from 3V to 30V

Transient Protection to 40V

Surface Mount Components

28-Lead (4mm × 5mm) QFN and TSSOP Packages

RGB Lighting

Billboards and Large Displays

Automotive and Avionic Lighting

Constant-Current Sources

High Dimming Ratio Triple Output LED Power Supply

3000:1 PWM Dimming at 120Hz

typical application

PWM

5V/DIV

0.5µs/DIV

3496 TA01b

LED

0.5A/DIV

0.5A

0.47µF

LED1

200mΩ 200mΩ

TG1

42V

7 LEDs

18µH

CAP1

0.5A

LED2

TG2

18µH

CAP2

0.5A

0.47µF

LED3

1µF

200mΩ

470pF

3496 TA01a

TG3

18µH

CAP3

SW1 SW2

LT3496

GND

SW3

TG1, TG2, TG3

VC1, VC2, VC3

REF

CTRL1, CTRL2, CTRL3

ADJ

OVP1, OVP2, OVP3

CAP1, CAP2, CAP3

LED1, LED2, LED3

PWM1, PWM2, PWM3

SHDN

PWM1, PWM2, PWM3

SHDN

3V TO 24V

1µF

22k

Summary of content (20 pages)

PAGE 1
LT3496 Triple Output LED Driver Features n n n n n n n n n n Description True Color PWM™ Dimming Delivers Up to 3000:1 Dimming Ratio Built-In Gate Driver for PMOS LED Disconnect Three Independent Driver Channels with 750mA, 45V Internal Switches Operates in Buck, Boost, Buck-Boost Modes CTRL Pin Accurately Sets LED Current Sense Threshold Over a Range of 10mV to 100mV Adjustable Frequency: 330kHz to 2.
PAGE 2
LT3496 Absolute Maximum Ratings (Note 1) VIN (Note 4)................................................................40V SW1, SW2, SW3, LED1, LED2, LED3, CAP1, CAP2, CAP3....................................................45V TG1, TG2, TG3..................................... CAP – 10V to CAP PWM1, PWM2, PWM3...............................................20V VREF , CTRL1, CTRL2, CTRL3, fADJ, VC1, VC2, VC3, OVP1, OVP2, OVP3...................................................2.5V SHDN (Note 4)...............
PAGE 3
LT3496 Electrical Characteristics The l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. VIN = 5V, VSHDN = 5V, CAP1, CAP2, CAP3 = 5V, PWM1, PWM2, PWM3 = 5V, fADJ = 0.5V, CTRL1, CTRL2, CTRL3 = 1.5V, OVP1, OVP2, OVP3 = 0V, unless otherwise noted.
PAGE 4
LT3496 Electrical Characteristics The l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. VIN = 5V, VSHDN = 5V, CAP1, CAP2, CAP3 = 5V, PWM1, PWM2, PWM3 = 5V, fADJ = 0.5V, CTRL1, CTRL2, CTRL3 = 1.5V, OVP1, OVP2, OVP3 = 0V, unless otherwise noted. PARAMETER CONDITIONS MIN TYP SHDN Input Low Voltage 0.4 SHDN Input High Voltage SHDN Pin Current MAX 1.
PAGE 5
LT3496 Typical Performance Characteristics Quiescent Current 1000 10 400 800 8 PWM1, PWM2, PWM3 = 0V 6 4 SWITCH CURRENT LIMIT (mA) SWITCH VOLTAGE (mV) INPUT CURRENT (mA) 500 PWM1, PWM2, PWM3 = 5V 12 300 200 100 2 VC = GND, NOT SWITCHING 0 10 20 30 0 40 0 200 VIN (V) 600 800 400 SWITCH CURRENT (mA) 3496 G01 200 0 1000 800 2250 2.03 2000 2.02 1750 VREF (V) 2.00 3496 G04 1.96 –50 –25 100 1000 1.97 25 50 75 100 125 150 TEMPERATURE (°C) 80 1500 1.
PAGE 6
LT3496 Typical Performance Characteristics Switch Frequency vs Temperature 120 fADJ = 1.2V 2.2 2.1 2.0 VCAP = 24V 1.8 –50 –25 0 25 50 75 100 125 150 TEMPERATURE (°C) 80 60 40 0 0 101 100 99 0.2 0.4 0.6 0.8 CTRL (V) 1 1.2 97 0 10 20 30 VCAP (V) 40 50 3496 G09 3496 G08 VCAP-LED Threshold vs Temperature VCAP-LED THRESHOLD (mV) CTRL = 1.2V 98 3496 G07 102 VCAP-LED Threshold vs VCAP 102 20 1.9 103 103 100 VCAP-LED THRESHOLD (mV) SWITCH FREQUENCY (MHz) 2.
PAGE 7
LT3496 Pin Functions PWM1, PWM2, PWM3: Pulse Width Modulated Inputs. Signal low turns off the respective converter, reduces quiescent supply current and causes the VC pin for that converter to become high impedance. PWM pin must not be left floating; tie to VREF if not used. When the PWM pin is low, the TG pin pulls up to CAP to turn off the external MOSFET. When the PWM pin is high, the external MOSFET turns on. Respective CAP-TG is limited to 6.5V to protect the MOSFET.
PAGE 8
LT3496 Block Diagram D1 VSENSE + – ILED M1 C2 LED1 L1 VIN C1 RSENSE 0.
PAGE 9
LT3496 Applications Information Operation The LT3496 uses a fixed frequency, current mode control scheme to provide excellent line and load regulation. Operation can be best understood by referring to the Block Diagram in Figure 1. The oscillator, ramp generator, reference, internal regulator and UVLO are shared among the three converters. The control circuitry, power switch etc., are replicated for each of the three converters. Figure 1 shows the shared circuits and only converter 1 circuits.
PAGE 10
LT3496 Applications Information dimming waveforms and the start-up time should be checked across all operating conditions. Open-LED Protection Input Capacitor Selection For proper operation, it is necessary to place a bypass capacitor to GND close to the VIN pin of the LT3496. A 1µF or greater capacitor with low ESR should be used. A ceramic capacitor is usually the best choice. The LT3496 has open-LED protection for all the three converters.
PAGE 11
LT3496 Applications Information Table 2. Surface Mount Inductors Table 1. Ceramic Capacitor Manufacturers VENDOR TYPE SERIES Taiyo Yuden Ceramic X5R, X7R AVX Ceramic X5R, X7R Murata Ceramic X5R, X7R Kemet Ceramic X5R, X7R VALUE (µH) DCR (Ω MAX) IRMS (A) SIZE W × L × H (mm3) CMD4D06 2.2 0.116 0.95 3.5 × 4.3 × 0.8 3.3 0.174 0.77 CDRH3D16 2.2 0.072 1.20 3.3 0.085 1.10 4.7 0.105 0.90 CDRH4D28 10 0.128 1.00 15 0.149 0.76 CDRH5D28 22 0.122 0.9 33 0.189 0.75 2.
PAGE 12
LT3496 Applications Information Programming the LED Current The LED current of each channel is programmed by connecting an external sense resistor RSENSE in series with the LED load, and setting the voltage regulation threshold across that sense resistor using CTRL input. If the CTRL voltage, VCTRL, is less than 1V, the LED current is: ILED = VCTRL 10 • RSENSE Board Layout If VCTRL is higher than 1V, the LED current is: ILED = 100mV RSENSE The CTRL pins should not be left open.
PAGE 13
LT3496 Typical Applications Minimum BOM Buck Mode LED Driver PVIN 42V CAP1 CAP2 CAP3 330mΩ 330mΩ 330mΩ LED1 LED2 LED3 0.3A 0.3A 0.3A 7 LEDs C6 0.22µF C4 C5 0.22µF 0.
PAGE 14
LT3496 TYPICAL APPLICATIONS Triple Boost 100mA × 10 LED Driver PVIN 12V C1 2.
PAGE 15
LT3496 TYPICAL APPLICATIONS Dual Boost LED Driver PVIN 12V C1 2.
PAGE 16
LT3496 TYPICAL APPLICATIONS Buck-Boost Mode 300mA × 6 LED Driver PVIN 10V TO 16V C1 2.2µF 6 LEDs 300mA L1 10µH L2 10µH L3 10µH 825k M1 LED1 LED2 1Ω 1Ω CAP1 D1 C3 1µF CAP3 D3 C4 0.1µF C5 1µF C7 1µF PVIN SW3 TG1 SW2 CAP1, CAP2, CAP3 LED1, LED2, LED3 VIN PWM1, PWM2, PWM3 SHDN PWM SHDN C8 1µF C6 0.1µF PVIN PVIN SW1 VIN 3V TO 16V 1Ω CAP2 D2 C2 0.
PAGE 17
LT3496 Package Description FE Package 28-Lead Plastic TSSOP (4.4mm) (Reference LTC DWG # 05-08-1663) exposed pad Variation EB 9.60 – 9.80* (.378 – .386) 4.75 (.187) 4.75 (.187) 28 2726 25 24 23 22 21 20 19 18 1716 15 6.60 p 0.10 2.74 (.108) 4.50 p 0.10 SEE NOTE 4 0.45 p 0.05 EXPOSED PAD HEAT SINK ON BOTTOM OF PACKAGE 6.40 2.74 (.252) (.108) BSC 1.05 p 0.10 0.65 BSC RECOMMENDED SOLDER PAD LAYOUT 4.30 – 4.50* (.169 – .177) 0.09 – 0.20 (.0035 – .0079) 0.50 – 0.75 (.020 – .030) NOTE: 1.
PAGE 18
LT3496 Package Description UFD Package 28-Lead Plastic QFN (4mm × 5mm) (Reference LTC DWG # 05-08-1712 Rev B) 0.70 p 0.05 4.50 p 0.05 3.10 p 0.05 2.50 REF 2.65 p 0.05 3.65 p 0.05 PACKAGE OUTLINE 0.25 p 0.05 0.50 BSC 3.50 REF 4.10 p 0.05 5.50 p 0.05 RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS APPLY SOLDER MASK TO AREAS THAT ARE NOT SOLDERED 4.00 p 0.10 (2 SIDES) 0.75 p 0.05 R = 0.05 TYP PIN 1 NOTCH R = 0.20 OR 0.35 s 45o CHAMFER 2.50 REF R = 0.115 TYP 27 28 0.40 p 0.
PAGE 19
LT3496 Revision History (Revision history begins at Rev F) REV DATE DESCRIPTION PAGE NUMBER F 4/10 Added H-Grade and Revised Entire Data Sheet 1 through 20 3496ff 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 representation that the interconnection of its circuits as described herein will not infringe on existing patent rights.
PAGE 20
LT3496 Typical Application Triple Buck-Boost Mode 100mA × 6 LED Driver PVIN 10V TO 16V C1 2.2µF 6 LEDs 100mA L1 10µH L2 10µH LED1 1Ω CAP1 D1 M2 TG2 3.9M OVP2 100k CAP2 D2 C3 1µF C4 0.1µF LED3 1Ω CAP3 D3 C5 1µF SW2 CAP1, CAP2, CAP3 LED1, LED2, LED3 VIN PWM1, PWM2, PWM3 SHDN LT3496 GND 3.9M OVP3 100k C6 0.1µF PVIN PVIN PWM SHDN 3.9M 1Ω 100k SW1 3000:1 PWM Dimming at 120Hz PWM 5V/DIV M3 TG3 LED2 OVP1 C2 0.