High Power LED Driver

® ISL97801 Data Sheet April 2, 2007 FN6428.1 High Power LED Driver The ISL97801 is a high-power LED backlight driver with an integrated 36V FET designed to drive up to 8 high-power LEDs in series. The PWM converter runs from an internally generated 1MHz clock. With efficiencies over 90% the regulator provides tight control of LED current and may be configured in either boost or buck topologies, allowing from 3 to 8 series diodes to be driven from wide input voltages. LED light level may be controlled either by: 1. LED DC bias current set via the LEVEL pin, or 2. External low frequency PWM control via the ENABLE/PWM pin. In both control modes optional over temperature thermal protection of the LED reduces the LED DC bias current above an adjustable set temperature, protecting the LED from thermal damage. An optional fault monitor drives an external FET between the input supply and inductor, providing short circuit current protection for the LED and inductor as well as load dump protection for automotive applications. For low cost applications the pass transistor may be omitted and the fault pin bypassed. The ISL97801 is packaged in a 20 Ld 4mm x 4mm QFN package and is specified for operation over the -40°C to +105°C temperature range. Features • Drives 3-8 high-power LEDs in series, up to 32V • 2.7V to 16V input voltage range • Boost or Buck configurable switch • 3A integrated FET • Automotive load dump protection • Light output temperature compensation • LED over-temperature protection • LED disconnect • PWM/analog light level control • Small, 20 Ld 4mm x 4mm QFN package • Pb-free plus anneal available (RoHS compliant) Applications • Display backlighting - Automotive - LCD monitor - Notebook displays • LED accent lighting • Automotive lighting Ordering Information PART NUMBER (Note) ISL97801ARZ TAPE & REEL/ PART MARKING QTY 978 01ARZ 13”/ 1,000 13”/ 6,000 PACKAGE (Pb-free) PKG. DWG. # Pinout ISL97801 (20 LD 4X4 QFN) TOP VIEW 19 FAULT 16 VBAT 15 ENL 14 MODE THERMAL PAD 13 EN/PWM 12 SWS1 11 SWS2 BUCK/BOOSTN 6 LEVEL 7 TMAX 10 TEMP 8 FB 9 18 GND 20 Ld 4x4 QFN L20.4x4C 20 VIN ISL97801ARZ-TK 978 01ARZ ISL97801ARZ-T 978 01ARZ 20 Ld 4x4 QFN L20.4x4C 20 Ld 4x4 QFN L20.4x4C VDC 1 VHI 2 OVP 3 SWD1 4 SWD2 5 NOTE: Intersil Pb-free plus anneal products employ special Pb-free material sets; molding compounds/die attach materials and 100% matte tin plate termination finish, which are RoHS compliant and compatible with both SnPb and Pb-free soldering operations. Intersil Pb-free products are MSL classified at Pb-free peak reflow temperatures that meet or exceed the Pb-free requirements of IPC/JEDEC J STD-020. 1 CAUTION: These devices are sensitive to electrostatic discharge; follow proper IC Handling Procedures. 1-888-INTERSIL or 1-888-468-3774 | Intersil (and design) is a registered trademark of Intersil Americas Inc. Copyright Intersil Americas Inc. 2007. All Rights Reserved All other trademarks mentioned are the property of their respective owners. 17 NC ISL97801 Absolute Maximum Ratings (TA = +25°C) Maximum pin voltage, all pins except below 6.5V VIN, SWS1, SWS2, EN/PWM . . . . . . . . . . . . . . . . . . . . . . . . . . .18V VBAT, FAULT, FB . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .24V |VHI - SWS1, SWS2| . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.5V SWD1, SWD2, OVP. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .34V Continuous Output Current . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1A Thermal Information Thermal Resistance θJA (°C/W) / θJC (°C/W) QFN-20 Package (Notes 1, 2) . . . . . . . 39 2.5 Maximum Junction Temperature . . . . . . . . . . . . . . . . . . . . . . +135°C Storage Temperature . . . . . . . . . . . . . . . . . . . . . . .-65°C to +150°C Operating Conditions Temperature Range . . . . . . . . . . . . . . . . . . . . . . . . .-40°C to +105°C CAUTION: Stresses above those listed in “Absolute Maximum Ratings” may cause permanent damage to the device. This is a stress only rating and operation of the device at these or any other conditions above those indicated in the operational sections of this specification is not implied. IMPORTANT NOTE: All parameters having Min/Max specifications are guaranteed. Typical values are for information purposes only. Unless otherwise noted, all tests are at the specified temperature and are pulsed tests, therefore: TJ = TC = TA Operating continuously at a junction temperature of +135°C will shorten the life of the device while the thermal shutdown may trigger at a higher temperature than +135°C since it is a typical number. NOTE: 1. θJA is measured in free air with the component mounted on a high effective thermal conductivity test board with “direct attach” features. See Tech Brief TB379. 2. For θJC, the “case temp” location is the center of the exposed metal pad on the package underside. Electrical Specifications PARAMETER VIN VIN VBAT VBATFAULT ISEN ISDIS RSWITCH VDC ROUTOL ROUTCL IOUT ILIMBOOST ILIMBUCK OVPH OVPL VGATE VGATE VFB VBAT = VIN = 12V, VDC = 5V, TA = -40°C to +105°C unless otherwise specified. CONDITIONS IOUT = 350mA, 8 LEDs, BUCK/BOOSTN = GND IOUT = 350mA, 5 LEDs, BUCK/BOOSTN = GND, TMAX disabled Normal operating range If VBAT > VBATFAULT, FAULT pin is switched to ground No switching, EN/PWM = 1 No switching, EN/PWM = 0 ISWITCH = 600mA 4.75 VIN < VDC VIN > 6V, F < 100Hz 4 LED output string. VIN = VBAT = 10V BUCK/BOOSTN = GND BUCK/BOOSTN = VDC Upper threshold to enter overvoltage fault mode, TA = +25°C Lower threshold to exit overvoltage fault mode, TA = +25°C VIN - VFAULT VFAULT - VIN System in regulation, VLEVEL = 1V, VIN = 12V, 6 LEDs 9.76 8.16 0.19 31 1 3.6 2.4 32 20 12.2 10.2 0.2 23 14.64 12.24 0.21 MIN 5 2.7 2.7 17.6 21 2.7 0.6 0.15 5 TYP MAX 16 12 16 24 3.5 2.5 0.25 5.25 40 6.5 UNIT V V V V mA µA Ω V Ω Ω A A A V V V V V DESCRIPTION Input Supply Voltage Input Supply Voltage Input Supply Monitor Supply Fault Threshold Supply Current in VIN Supply Current in VIN Power FET On Resistance Regulated Auxiliary Supply Auxiliary Supply Open Loop Output Resistance Auxiliary Supply Closed Loop Output Resistance Output Drive Current Power Switch Current Limit Power Switch Current Limit Over Voltage Positive Going Voltage Mode Threshold Over Voltage Negative Going Voltage Mode Threshold Protection FET VGS (gate clamp) Protection FET VGS (gate clamp) Feedback Voltage 2 FN6428.1 April 2, 2007 ISL97801 Electrical Specifications PARAMETER VLEVEL FBUV FAULT FBOV FAULT fSW fDIMMING tSWITCH RLSDRIVERL RLSDRIVERH tFAULT tDELAY VFAULTPUMP VBOOST VBUCK VMODEL VMODEH enFAULT disFAULT enTEMP disTEMP TCOMPP TCOMPN TTRIP THYS VEN/PWML VEN/PWMH VDCUVLO Rschottky . VBAT = VIN = 12V, VDC = 5V, TA = -40°C to +105°C unless otherwise specified. (Continued) CONDITIONS MIN 0.25 120 220 850 Mode = 1, modulation signal applied to EN/PWM CGATE = 2nF EN/PWM = 0 EN/PWM = 3V 40 Timed LX switching delay VBAT = VIN = 3V BUCK/BOOSTN = GND BUCK/BOOSTN = VDC MODE = GND MODE = VDC 2/3VDC 0.9VDC 0.96VDC 0.5 0.08 VTEMP/VDC = 0.80 VTEMP/VDC = 0.20 1.26 0.74 135 25 1.2 2.5 2.6 15 23 °C °C V V V Ω 0.94VDC 1/3VDC 0.85 6 0.4VDC 160 250 1000 10 100 30 30 50 1 50 50 58 1.17 TYP MAX 3 180 280 1150 UNIT V mV mV kHz kHz ns Ω Ω ms ms V V V V V V V V V DESCRIPTION Light Control Voltage Linear Input Range Mode = 1, analog control of LED current Feedback Undervoltage Fault Feedback Overvoltage Fault Switching Frequency Maximum Recommended PWM Dimming Frequency Load Switch Transition Time Load Switch Driver Impedance Low Load Switch Driver Impedance High Fault Timer Period Start-up Delay Fault Pin Charge Pump Boost Mode Threshold Buck Mode Threshold Mode Low Threshold Mode High Threshold Input Level Applied to TMAX Pin to Enable Fault Protection Input Level Applied to TMAX Pin to Disable Fault Protection Input Level Applied to TEMP Pin to Enable Temperature Compensation Input Level Applied to TEMP Pin to Disable Temperature Compensation VFB Positive Temperature Compensation; VFB/VFBnom VFB Negative Temperature Compensation; VFB/VFBnom Internal Temperature Protection Threshold Internal Temperature Protection Hysteresis EN/PWM Pin Input Low Threshold EN/PWM Pin Input High Threshold VDC Under Voltage Lockout Internal Schottky Diode for Buck VLEVEL = 1V, EN/PWM = 3V VLEVEL = 1V, EN/PWM = 3V TABLE 1. LIGHT OUTPUT CONTROL, VDC = 5.0V MODE 1 Don’t Care 0 TEMP OPERATING MODE (VDC - 0.25) > V > 0.25V Standard Mode light level to PWM modulation of EN/PWM input; LED bias current determined by LEVEL voltage, nominal 1V V < 0.25V V < (VDC - 0.25) Disable temperature compensation Fixed Bias Mode VFB level internally set to 0.4V, independent of VLEVEL 3 FN6428.1 April 2, 2007 ISL97801 Typical Performance Curves 100 8 LEDs 95 ILEDpeak = 380mA 90 85 80 75 99%@1kHz 70 65 60 6 8 10 12 VIN (V) 14 16 18 10%@10kHz 50%@100Hz 10%@1kHz 10%@100Hz 50%@1kHz 100 99%@100Hz 99%@10kHz EFFICIENCY (%) 95 90 85 80 75 70 65 60 4 6 8 99% @ 100Hz 10% @ 100Hz 10 VIN (V) 12 14 16 10% @ 10kHz 5 LEDs ILEDpeak = 380mA 99% @ 10kHz EFFICIENCY (%) 50%@10kHz FIGURE 1. 8 LEDs EFFICIENCY vs INPUT VOLTAGE vs DIMMING FREQUENCY AND DUTY CYCLE FIGURE 2. 5 LEDs EFFICIENCY vs INPUT VOLTAGE vs DIMMING FREQUENCY AND DUTY CYCLE 100 100 95 99%@100Hz EFFICIENCY (%) 99%@10kHz 90 85 80 75 70 65 10 60 0 5 LEDs ILEDpeak = 380mA PWM = 10kHz 8 LEDs, VIN = 12V 5 LEDs, VIN = 9V 20 40 60 80 PWM DIMMING DUTY CYCLE (%) 100 8 LEDs 3 LEDs 95 ILEDpeak = 380mA 90 EFFICIENCY (%) 85 80 75 70 65 60 4 6 VIN (V) 10%@100Hz 8 10%@10kHz FIGURE 3. 3 LEDs EFFICIENCY vs INPUT VOLTAGE vs DIMMING FREQUENCY AND DUTY CYCLE FIGURE 4. 8 AND 5 LEDs EFFICIENCY vs PWM DUTY CYCLE 400 350 ILEDpeak = 380mA 4 5 LEDs @ 100Hz 3 LEDs @ 100Hz ΔILED (%) 3 2 1 0 -1 -2 -3 -4 99% @ 10kHz 99% @ 100Hz 6 8 10 12 VIN (V) 14 16 18 10% @ 10kHz 10% @ 100Hz 8 LEDs ILEDpeak = 380mA 8 LEDs, VIN = 12V 5 LEDs, VIN = 9V 30