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LTM8042/LTM8042-1

80421fa

TYPICAL APPLICATION

FEATURES DESCRIPTION

µModule Boost LED Driver

and Current Source

The LTM

8042 is a complete µModule

Boost LED Driver

specifically designed to drive LEDs up to 1A, while the

LTM8042-1 drives up to 350mA. It combines a boost

power topology with a unique current loop to operate as

a constant-current source. The PWM input provides as

much as 3000:1 LED dimming, while 10:1 analog dimming

can be accomplished by a single resistor or analog voltage

applied to the CTL pin. As with any boost topology, the

LTM8042/LTM8042-1 has an uninterrupted current path

between its input and output and is thus intolerant to a

short-circuit or overload from the output to ground.

# WHITE LEDS LED CURRENT 12V

24V

6 1A LTM8042

7 350mA LTM8042-1

8 1A LTM8042

9 350mA LTM8042-1

The LTM8042/LTM8042-1 is packaged in a thermally

enhanced, compact overmolded land grid array (LGA)

package. The LTM8042/LTM8042-1 is Pb-free and a RoHS

compliant.

µModule Boost LED Driver, Driving 8 White LEDs at 1A

APPLICATIONS

True Color PWM™ with 3000:1 Dimming Ratio

Operates in Boost, Buck Mode or Buck-Boost Mode

Wide Input Voltage Range:

Operation from 3V to 30V

Transient Protection to 40V

Gate Driver for Optional PWM Dimming with

P-channel MOSFET

Adjustable Frequency: 250kHz to 2MHz

Constant-Current and Constant-Voltage Regulation

Low Shutdown Current: <1A

RoHS Compliant Package with Gold Pad Finish

Tiny, Low Profile (9mm × 15mm × 2.82mm)

Surface Mount LGA Package

Display Backlighting

Automotive and Avionic Lighting

Illumination

Scanners

Efficiency vs V

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

and True Color PWM is a trademark of Linear Technology Corporation. All other trademarks are

the property of their respective owners.

(V)

EFFICIENCY (%)

1918

80421 TA01b

17 20 232221 2524 26

80421 TA01a

LTM8042

RT GND CTL

RUN

BSTIN/BKLED

–

PWM

SYNC

TGEN

16V TO 26V

LED

BSTOUT/BKIN

4.7µF

33.2k

= 550kHz

4.7µF

UP TO 26.8V

Summary of content (32 pages)

PAGE 1
LTM8042/LTM8042-1 µModule Boost LED Driver and Current Source FEATURES DESCRIPTION n The LTM®8042 is a complete μModule® Boost LED Driver specifically designed to drive LEDs up to 1A, while the LTM8042-1 drives up to 350mA. It combines a boost power topology with a unique current loop to operate as a constant-current source. The PWM input provides as much as 3000:1 LED dimming, while 10:1 analog dimming can be accomplished by a single resistor or analog voltage applied to the CTL pin.
PAGE 2
LTM8042/LTM8042-1 ABSOLUTE MAXIMUM RATINGS PIN CONFIGURATION (Note 1) VCC, RUN, PWM, TGEN, BSTIN/BKLED– ...................40V BSTOUT/BKIN, TG, LED+ ..........................................43V TG Pin Below LED+ ...................................................10V CTL, SYNC, SS............................................................6V RT ...............................................................................3V Internal Operating Temperature (Notes 3, 4) ....................................
PAGE 3
LTM8042/LTM8042-1 ELECTRICAL CHARACTERISTICS The l denotes the specifications which apply over the full internal operating temperature range, otherwise specifications are at TA = 25°C. VCC = 5V, buck mode with 4Ω load. SYMBOL PARAMETER VCC(MIN) Minimum Input DC Voltage ILED LTM8042 LED Current CONDITIONS MIN l CTL Open CTL Open, RCTL = 6.81k LTM8042-1 LED Current RCTL = 6.81k TYP MAX 3 0.9 0.45 0.34 0.17 UNITS V 0.5 1.05 0.55 0.39 0.
PAGE 4
LTM8042/LTM8042-1 TYPICAL PERFORMANCE CHARACTERISTICS TA = 25°C, unless otherwise noted. LTM8042 Efficiency vs VIN, Boost Operation, 6.8V at 1A LED String Efficiency vs VIN, Boost Operation, 10.1V at 1A LED String 90 Efficiency vs VIN, Boost Operation, 13.
PAGE 5
LTM8042/LTM8042-1 TYPICAL PERFORMANCE CHARACTERISTICS TA = 25°C, unless otherwise noted. LTM8042 Efficiency vs VIN, Buck Mode, 13.4V at 1A LED String Efficiency vs VIN, Buck Mode, 16.7V at 1A LED String 97 97 94 96 96 93 95 95 92 94 94 91 90 89 88 EFFICIENCY (%) 95 EFFICIENCY (%) EFFICIENCY (%) Efficiency vs VIN, Buck Mode, 10.
PAGE 6
LTM8042/LTM8042-1 TYPICAL PERFORMANCE CHARACTERISTICS TA = 25°C, unless otherwise noted. LTM8042 Maximum LED Current vs VIN, Buck Mode Maximum LED Current vs Input Voltage, Buck-Boost Mode 1000 1200 MAXIMUM LED CURRENT (mA) 900 LED CURRENT (mA) 800 700 600 500 400 3.8V AT 1A 7.4V AT 1A 10.9V AT 1A 14.5V AT 1A 18.1V AT 1A 21.4V AT 1A 24.8V AT 1A 300 200 100 0 0 5 10 15 VIN (N) 20 25 1000 800 600 7.4V AT 1A 10.9V AT 1A 14.5V AT 1A 18.1V AT 1A 21.4V AT 1A 24.8V AT 1A 28.
PAGE 7
LTM8042/LTM8042-1 TYPICAL PERFORMANCE CHARACTERISTICS TA = 25°C, unless otherwise noted. LTM8042 Junction Temperature Rise vs Load, Buck Mode, 3.
PAGE 8
LTM8042/LTM8042-1 TYPICAL PERFORMANCE CHARACTERISTICS TA = 25°C, unless otherwise noted. LTM8042 Junction Temperature Rise vs Load, Buck-Boost Mode, 10.9V at 1A LED String Junction Temperature Rise vs Load, Buck-Boost Mode, 13.6V at 1A LED String 50 Junction Temperature Rise vs Load, Buck-Boost Mode, 15.
PAGE 9
LTM8042/LTM8042-1 TYPICAL PERFORMANCE CHARACTERISTICS TA = 25°C, unless otherwise noted. LTM8042-1 Efficiency vs VIN, Boost Operation, 18.6V at 350mA LED String 95 90 90 90 85 85 85 80 75 EFFICIENCY (%) 95 70 80 75 5 6 7 8 9 10 11 12 13 14 15 VIN (V) 75 65 65 4 80 70 70 65 5 6 7 8 9 10 11 12 13 14 15 16 17 18 VIN (V) 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 VIN (V) 80421 G42 80421 G44 80421 G43 Efficiency vs VIN, Boost Operation, 24.
PAGE 10
LTM8042/LTM8042-1 TYPICAL PERFORMANCE CHARACTERISTICS TA = 25°C, unless otherwise noted. LTM8042-1 Efficiency vs VIN, Buck Mode, 18.6V at 350mA LED String Efficiency vs VIN, Buck-Boost Mode, 3.7V at 350mA LED String 97 Efficiency vs VIN, Buck-Boost Mode, 6.
PAGE 11
LTM8042/LTM8042-1 TYPICAL PERFORMANCE CHARACTERISTICS TA = 25°C, unless otherwise noted. LTM8042-1 Maximum LED Current vs Input Voltage, Buck-Boost Mode 400 120 300 250 200 150 3.2V AT 350mA 6.3V AT 350mA 9.4V AT 350mA 12.4V AT 350mA 15.5V AT 350mA 18.
PAGE 12
LTM8042/LTM8042-1 TYPICAL PERFORMANCE CHARACTERISTICS TA = 25°C, unless otherwise noted. LTM8042-1 Junction Temperature Rise vs Load, Buck Mode, 9.4V at 350mA LED String Junction Temperature Rise vs Load, Buck Mode, 6.8V at 350mA LED String 10 TEMPERATURE (°C) TEMPERATURE (°C) 24VIN 8 6 12VIN 4 14 14 12 12 10 TEMPERATURE (°C) 12 Junction Temperature Rise vs Load, Buck Mode, 11.
PAGE 13
LTM8042/LTM8042-1 TYPICAL PERFORMANCE CHARACTERISTICS TA = 25°C, unless otherwise noted. LTM8042-1 Junction Temperature Rise vs Load, Buck-Boost Mode, 11.2V at 350mA LED String Junction Temperature Rise vs Load, Buck-Boost Mode, 15.
PAGE 14
LTM8042/LTM8042-1 PIN FUNCTIONS TG (Pin J7): Top Gate Driver Output. In response to an active high PWM signal, this pin will drive the gate of an external series P-channel MOSFET device low. An internal 7V clamp protects the PFET gate. This pin can also be used to disconnect the load when RUN is pulled low. Leave TG unconnected if not used. PWM (Pin K1): Pulse Width Modulation Input Pin. A low signal turns off the LED string, disables the main switch and pulls the TG pin high. Drive above 1.
PAGE 15
LTM8042/LTM8042-1 OPERATION The LTM8042/LTM8042-1 is a complete, full featured, current mode regulator specifically designed to drive light emitting diodes (LEDs) or other loads where a constant current up to 1A (350mA for the LTM8042-1) is required. The LTM8042/LTM8042-1 can operate in any of three LED drive topologies: boost, buck mode and buck-boost mode.
PAGE 16
LTM8042/LTM8042-1 APPLICATIONS INFORMATION For most applications, the design process is straight forward, summarized as follows: 1. Decide whether the LTM8042/LTM8042-1 should operate in boost, buck, or buck-boost mode. 2. Look at Tables 1 through 6 and find the line that best matches the input and output conditions of the system under consideration. 3. Connect CIN, COUT, CVCC and RT as indicated in the appropriate table. 4. Connect the remaining pins as needed by the system requirements.
PAGE 17
LTM8042/LTM8042-1 APPLICATIONS INFORMATION Which mode to use depends upon the operating conditions. Boost is generally selected when the voltage across the LED string is always higher than the input voltage. Buck mode is the dual of boost, used when the voltage across the LED string is always lower than VIN. Finally, buck-boost mode is used when the VIN can vary both above and below the voltage across the LED string.
PAGE 18
LTM8042/LTM8042-1 APPLICATIONS INFORMATION PCB Layout Most of the headaches associated with PCB layout have been alleviated or even eliminated by the high level of integration of the LTM8042/LTM8042-1. The device is nevertheless a switching power supply, and care must be taken to minimize EMI and ensure proper operation. Even with the high level of integration, you may fail to achieve specified operation with a haphazard or poor layout.
PAGE 19
LTM8042/LTM8042-1 APPLICATIONS INFORMATION TO LED STRING COUT VIN CVCC VIN LED+ CIN BSTIN/BKLED– TG LED+ VCC BSTOUT/BKIN GND TGEN CTL 80421 F03 PWM SS SYNC RUN GND RT THERMAL VIAS TO GROUND PLANE Figure 3. Suggested Layout for Buck Mode TO LED STRING TO LED STRING COUT2 COUT1 LED+ CIN VIN BSTIN/BKLED– TG LED+ VCC BSTOUT/BKIN CVCC TGEN CTL PWM SS SYNC RUN GND 80421 F04 RT THERMAL VIAS TO GROUND PLANE Figure 4.
PAGE 20
LTM8042/LTM8042-1 APPLICATIONS INFORMATION Table 1. LTM8042 Recommended Values and Configuration for Boost (TA = 25°C) VIN RANGE (BSTIN/ BKLED–) 3V to 3.6V 3V to 5.1V 3V to 6.3V 3V to 9.3V 3V to 10V 3V to 12.6V 3.7V to 15V 3V to 3.85V 3V to 5.6V 3V to 7V 3V to 10.2V 4V to 12.6V 4V to 14.5V 6.3V to 18.7V 3V to 3.8V 3V to 5.5V 3.3V to 7V 4.1V to 10V 5.5V to 12.5V 6.4V to 15V 9V to 20.8V 3V to 3.8V 3.3V to 5.7V 4V to 7.2V 5.2V to 10.4V 7V to 13V 8.2V to 15.5V 11.8V to 21.2V 3.3V to 3.5V 4V to 5.8V 5V to 7.
PAGE 21
LTM8042/LTM8042-1 APPLICATIONS INFORMATION Table 2. LTM8042 Recommended Values and Configuration for Buck Mode (TA = 25°C) VIN RANGE (BSTOUT/BKIN) VCC CVCC CIN (BSTOUT/BKIN TO GND) 4.4V to 5.5V 3V to 30V 1μF 0805 X7R 50V 1μF 1206 X7R 50V LED STRING VOLTAGE (LED+ TO RT f COUT LED BSTIN/ (OPTI- (OPTI- RT f (BSTOUT/BKIN TO STRING BKLED–) CURRENT RCTL MAL) MAL) (MIN) (MAX) BSTIN/BKLED–) 2.2μF 1206 X7R 10V 2V to 4V 35mA 523 86.6k 250k 86.6k 250k 6.
PAGE 22
LTM8042/LTM8042-1 APPLICATIONS INFORMATION Table 3. LTM8042 Recommended Values and Configuration for Buck-Boost Mode (TA = 25°C) VIN RANGE (BSTIN/ BKLED–) 3V to 6V LED STRING VOLTAGE LED (LED+ to STRING RT f BSTIN/ CURR(OPTI- (OPTI- RT f BKLED–) ENT RCTL MAL) MAL) (MIN) (MAX) VCC CVCC (VCC to GND) CIN (BSTIN/BKLED– TO GND) COUT1 (BSTOUT/BKIN TO BSTIN/ BKLED–) COUT2 (BSTOUT/BKIN TO GND) 3V to 30V 1μF 0805 X7R 50V 1μF 0805 X7R 10V 1μF 0805 X7R 10V 1μF 0805 X7R 10V 2V to 4V 35mA 523 86.
PAGE 23
LTM8042/LTM8042-1 APPLICATIONS INFORMATION Table 4. LTM8042-1 Recommended Values and Configuration for Boost (TA = 25°C) VCC CIN (BSTIN/BKLED– TO GND) COUT (BSTOUT/BKIN TO GND) LED STRING VOLTAGE (LED+ TO GND) 1V to 3.3V 3V to 30V 1μF 0805 X7R 10V 1μF 0805 X7R 10V 4V to 6V 1.2V to 5V 3V to 30V 1μF 0805 X7R 10V 1μF 0805 X7R 10V 6V to 9V 35mA 1.27k 76.8k 275k 61.9k 330k 1.6V to 6V 3V to 30V 1μF 0805 X7R 10V 1μF 0805 X7R 16V 8V to 12V 35mA 1.27k 69.8k 300k 57.
PAGE 24
LTM8042/LTM8042-1 APPLICATIONS INFORMATION Table 5. LTM8042-1 Recommended Values and Configuration for Buck Mode (TA = 25°C) VIN RANGE (BSTOUT/ BKIN) VCC CVCC CIN (BSTOUT/BKIN TO GND) COUT (BSTOUT/BKIN TO BSTIN/BKLED–) LED STRING VOLTAGE (LED+ TO R f LED BSTIN/ (OPTI- (OPTI- RT f STRING BKLED–) CURRENT RCTL MAL) MAL) (MIN) (MAX) 4.3V to 8.3V 3V to 30V 1μF 0805 X7R 50V 1μF 1206 X7R 50V 2.2μF 1206 X7R 10V 2V to 4V 35mA 1.27k 86.6k 250k 86.6k 250k 6.
PAGE 25
LTM8042/LTM8042-1 APPLICATIONS INFORMATION Table 6. LTM8042-1 Recommended Values and Configuration for Buck-Boost Mode (TA = 25°C) VIN RANGE (BSTIN/ BKLED–) 1V to 9.5V VCC CVCC (VCC TO GND) CIN (BSTIN/BKLED– TO GND) COUT1 (BSTOUT/BKIN TO BSTIN/ BKLED–) LED STRING VOLTAGE LED (LED+ TO STRING RT f COUT2 (OPTI- (OPTI- RT f (BSTOUT/BKIN BSTIN/ CURBKLED–) RENT RCTL MAL) MAL) (MIN) (MAX) TO GND) 3V to 30V 1μF 0805 X7R 50V 1μF 0805 X7R 10V 1μF 0805 X7R 10V 1μF 0805 X7R 10V 2V to 4V 35mA 1.27k 86.
PAGE 26
LTM8042/LTM8042-1 APPLICATIONS INFORMATION Thermal Considerations The LTM8042/LTM8042-1 output current may need to be derated if it is required to operate in a high ambient temperature or deliver a large amount of continuous power. The amount of current derating is dependent upon the input voltage, output power and ambient temperature. The temperature rise curves given in the Typical Performance Characteristics section can be used as a guide.
PAGE 27
LTM8042/LTM8042-1 APPLICATIONS INFORMATION The most appropriate way to use the coefficients is when running a detailed thermal analysis, such as FEA, which considers all of the thermal resistances simultaneously. None of them can be individually used to accurately predict the thermal performance of the product, so it would be inappropriate to attempt to use any one coefficient to correlate to the junction temperature versus load graphs given in the LTM8042/LTM8042-1 data sheet.
PAGE 28
LTM8042/LTM8042-1 TYPICAL APPLICATIONS Buck-Boost Mode, Driving 5 White LEDs at 500mA with PWM Dimming Si2319DS LTM8042 VIN 7V TO 17.5V LED+ VCC UP TO 16.3V RUN PWM TG TGEN BSTOUT/BKIN SYNC BSTIN/BKLED– 500mA SS 1μF 1μF RT GND CTL 19.6k fSW = 850kHz 2.2μF 7.32k 80421 TA03 Buck Mode, Driving 4 White LEDs at 1A VIN 19V TO 30V VCC LTM8042 RUN LED+ UP TO 13.9V TG PWM BSTOUT/BKIN SYNC BSTIN/BKLED– 1A 2.2μF TGEN SS 1μF RT GND CTL 4.7μF 15.
PAGE 29
LTM8042/LTM8042-1 PACKAGE DESCRIPTION Pin Assignment Table (Arranged by Pin Number) PIN NAME PIN NAME PIN NAME PIN NAME PIN NAME PIN NAME A1 GND B1 GND C1 GND D1 GND E1 GND F1 RUN A2 GND B2 GND C2 GND D2 GND E2 GND F2 GND A3 GND B3 GND C3 GND D3 GND E3 GND F3 GND A4 GND B4 GND C4 GND D4 GND E4 GND F4 GND A5 GND B5 GND C5 BSTIN/BKLED– D5 BSTIN/BKLED– E5 GND F5 GND A6 VCC B6 VCC C6 BSTIN/BKLED– D6 BSTIN/BKLED– E6 GND F6 GND A7
PAGE 30
0.9525 1.5875 4 PACKAGE TOP VIEW 9 BSC 2.540 3.810 15 BSC Y aaa Z DETAIL A 0.27 – 0.37 SUBSTRATE eee S X Y DETAIL B 0.635 ±0.025 SQ. 76x 2.45 – 2.55 MOLD CAP DETAIL B 2.72 – 2.92 6.350 5.080 3.810 2.540 1.270 DETAILS OF PAD #1 IDENTIFIER ARE OPTIONAL, BUT MUST BE LOCATED WITHIN THE ZONE INDICATED. THE PAD #1 IDENTIFIER MAY BE EITHER A MOLD OR MARKED FEATURE 4 SYMBOL TOLERANCE aaa 0.15 bbb 0.10 eee 0.05 6. THE TOTAL NUMBER OF PADS: 77 5.
PAGE 31
LTM8042/LTM8042-1 REVISION HISTORY REV DATE DESCRIPTION A 01/11 Updated features. PAGE NUMBER 1 Updated ILED conditions in the Electrical Characteristics section. 3 Updated text in the Operation section. 15 Updated text in the Setting the Switching Frequency section. 16 80421fa Information furnished by Linear Technology Corporation is believed to be accurate and reliable. However, no responsibility is assumed for its use.
PAGE 32
LTM8042/LTM8042-1 TYPICAL APPLICATION Boost Operation, Driving 9 Red LEDs at 350mA with Analog Dimming UP TO 28V VIN 7V TO 24.8V VCC LTM8042 LED+ RUN BSTIN/BKLED– PWM TG BSTOUT/BKIN 350mA SYNC TGEN SS CTL GND RT 2.2μF ANALOG CONTROL VOLTAGE 2.2μF 19.6k fSW = 850kHz 80421 TA06 RELATED PARTS PART NUMBER DESCRIPTION COMMENTS LTM8040 36V, 1A, μModule LED Driver and Current Source 4V ≤ VIN ≤ 36V; Open LED and Short-Circuit Protection, 9mm × 15mm × 4.