MP4600 High-Voltage WLED Driver For Large Panel TV Backlighting The Future of Analog IC Technology DESCRIPTION FEATURES The MP4600 is an integrated white LED driver. It can be applied with MPS patent pending technology to drive up to 55 inch LCD TV backlighting, in which the LED string voltage can be up to 300V. The novel technology can leverage the LED drive power by regulating only a small part of the LED drive voltage. As a result, working together with a fixed high voltage source, a low voltage LED driver can be used to drive the high voltage LED strings with super high power density, high efficiency and low cost due to the low voltage stress, high switching frequency, and smaller size of passive components. • • • • • • • • MP4600 is a current mode controlled buckboost regulator. With a 12V input VINL and a high voltage source VINH, it can deliver a regulated voltage (VINH to VINH+43V) to drive a LED string with up to 85 LEDs. It incorporates both DC and PWM dimming onto a single control pin. Fault protection includes LED open strings protection, output short circuit protection, input over voltage protection, cycle-by-cycle peak current limiting, and thermal shutdown. • • • • • • Novel Power Leverage Control Technology Unique Step-up/down Operation 0.28Ω Internal Power MOSFET Switch Adjustable Switching Frequency Analog and PWM Dimming 0.198V Reference Voltage 5μA Shutdown Mode Stable with Low ESR Output Ceramic Capacitors Cycle-by-Cycle Over Current Protection Thermal Shutdown Protection Open Strings Protection Input Over Voltage Protection Output Short Circuit Protection Available in 10-Pin 3x3mm QFN Packages APPLICATIONS • • TV Backlighting Large LCD Panels Backlighting “MPS” and “The Future of Analog IC Technology” are Trademarks of Monolithic Power Systems, Inc. The MP4600 is available in 10-pin 3x3mm QFN packages. MP4600 Rev. 0.91 1/6/2012 www.MonolithicPower.com MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited. © 2012 MPS. All Rights Reserved. 1 MP4600 – WHITE LED DRIVER FOR UP TO 55 INCH TV BACKLIGHTING ORDERING INFORMATION Part Number* Package Top Marking Free Air Temperature (TA) MP4600DQ QFN10 (3x 3mm) 9M -40°C to +85°C For Tape & Reel, add suffix –Z (e.g. MP4600DQ–Z); For RoHS Compliant Packaging, add suffix –LF (e.g. 4600DQ–LF–Z) PACKAGE REFERENCE TOP VIEW VDD 1 10 SW VSS 2 9 BST OVP 3 8 INGND FB 4 7 EN/DIM COMP 5 6 RSET EXPOSED PAD ON BACKSIDE (Connect to VSS) ABSOLUTE MAXIMUM RATINGS (1) Thermal Resistance Supply Voltage VDD – VSS............................. 60V VSW – VSS ..............................-0.3V to VIN + 0.3V VBST ...................................................... VSW + 6V VOVP – VSS .......................................-0.3V to +6V VEN – VINGND.....................................-0.3V to +6V VDIM – VINGND....................................-0.3V to +6V VINGND – VSS .....................................-0.3V to 60V Continuous Power Dissipation (TA = +25°C)(2) ............................................................. 2.5W Junction Temperature ...............................150°C Lead Temperature ....................................260°C Storage Temperature............... -65°C to +150°C 3x3 QFN10 ............................. 50 ...... 12... °C/W Recommended Operating Conditions (3) (4) θJA θJC Notes: 1) Exceeding these ratings may damage the device. 2) The maximum allowable power dissipation is a function of the maximum junction temperature TJ (MAX), the junction-toambient thermal resistance θJA, and the ambient temperature TA. The maximum allowable continuous power dissipation at any ambient temperature is calculated by PD (MAX) = (TJ (MAX)-TA)/θJA. Exceeding the maximum allowable power dissipation will cause excessive die temperature, and the regulator will go into thermal shutdown. Internal thermal shutdown circuitry protects the device from permanent damage. 3) The device function is not guaranteed outside of the recommended operating conditions. 4) Measured on JESD5 1-7, 4-layer PCB. Supply Voltage VDD – VSS.................4.5V to 55V Ambient Junct. Temp (TJ) ........ -40°C to +125°C MP4600 Rev. 0.91 1/6/2012 www.MonolithicPower.com MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited. © 2012 MPS. All Rights Reserved. 2 MP4600 – WHITE LED DRIVER FOR UP TO 55 INCH TV BACKLIGHTING ELECTRICAL CHARACTERISTICS VDD = 12V, TA = +25°C, all voltages with respect to VSS, unless otherwise noted. Parameters Feedback Voltage Feedback Current Switch-On Resistance Switch Leakage Current Limit Symbol VFB IFB RDS(ON) ISW-LK ILIMIT Oscillator Frequency fS Default Oscillator Frequency fS-Default Fold-back Frequency Maximum Duty Cycle Minimum On-Time Under Voltage Lockout Threshold Rising Under Voltage Lockout Threshold Hysteresis fS-FB DMAX tON VDD-TH VDD-HYS EN Input Current IEN EN OFF Threshold (w/Respect to INGND) EN ON Threshold (w/Respect to INGND) Minimum EN Dimming Threshold Maximum EN Dimming Threshold PWM Dimming Frequency (5) Supply Current (Quiescent) Supply Shut Down Current Thermal Shutdown Thermal Shutdown Hysteresis Open LED OV Threshold Open LED OV Hysteresis Condition VDD=4.5V to 55V VFB = 0.22V Min 0.188 -50 Typ 0.198 Max 0.208 50 3.0 Units V nA Ω μA A 0.5 MHz 1.35 MHz 250 90 100 3.3 100 2.1 0.1 kHz % ns V mV 0.28 VEN = 0V, VSW = 0V 1 VFB = 0.1V, RST=100kΩ VFB = 0.1V, RST open VFB = 0V, VOVP=0V VFB = 0.1V 3.0 VEN = 2V VEN = 0V VEN Falling VEN Rising VENL VENH VDIML VDIMH fPWM IQ VEN = 2V, VFB = 1V IOFF VEN = 0V TTH THYS VOVP-TH VOVP-HYS 3.6 μA 0.4 0.6 1.25 100 1.1 0.7 1.4 0.8 3.4 150 20 1.2 60 0.6 0.8 1.5 20k 1.0 15 1.3 V V V V Hz mA μA °C °C V mV Note: 5) Guaranteed by design. MP4600 Rev. 0.91 1/6/2012 www.MonolithicPower.com MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited. © 2012 MPS. All Rights Reserved. 3 MP4600 – WHITE LED DRIVER FOR UP TO 55 INCH TV BACKLIGHTING PIN FUNCTIONS Pin # Name 1 VDD 2 VSS 3 OVP 4 FB 5 COMP 6 RSET 7 EN/DIM 8 INGND 9 BST 10 SW MP4600 Rev. 0.91 1/6/2012 Description Positive Voltage Input Pin. A decoupling cap is needed to prevent large voltage spikes from appearing at the input. Negative Voltage Output Pin. This pin is the voltage reference for OVP, FB, COMP and RSET pins. This node should be placed away from switching noise sources. The exposed pad is connected to this pin. Over Voltage Protection Pin. Use one external resistor voltage divider across INGND and VSS to program OVP threshold. Its voltage is referred to VSS. When the OVP pin voltage reaches the shutdown threshold 1.2V, the switch will be turned off and will recover when OVP voltage decreases sufficiently. When the OVP pin voltage is lower than 0.4V and FB pin voltage is lower than 0.1V, the chip frequency will be folded back. Program the OVP pin voltage from 0.4V to 1.2V for normal operation. LED Current Feedback Input. MP4600 regulates the voltage across the current sensing resistor between FB and VSS. Connect the current sensing resistor from the bottom of the LED strings to VSS. The FB pin is connected to the bottom of the LED strings. The regulation voltage is 0.198V. Output of error amplifier. Connect a 1nF or larger capacitor on COMP to improve the stability and to provide a soft on at start up or PWM dimming. Connect to a resistor to VSS to set the switching frequency. On/Off Control Input and Dimming Command Input. Its voltage is referred to INGND. A voltage greater than 0.7V will turn on the chip. When the EN/DIM pin voltage rises from 0.7V to 1.4V, the LED current will change from 0% to 100% of the maximum LED current. To use PWM dimming, apply a 100Hz to 20kHz square wave signal with amplitude greater than 1.5V to this pin. Input Ground Reference. This pin is the reference for the EN/DIM signal. Bootstrap. A capacitor is connected between SW and BST pins to form a floating supply across the power switch driver. Switch Output. SW is the source of the internal MOSFET switch. Connect to the power inductor and cathode of the Schottky rectifier. Exposed pad should be connected to VSS. www.MonolithicPower.com MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited. © 2012 MPS. All Rights Reserved. 4 MP4600 – WHITE LED DRIVER FOR UP TO 55 INCH TV BACKLIGHTING OPERATION The MP4600 is a current mode controlled BuckBoost regulator. The sensing resistor senses the LED current and feeds it back to an error amplifier, which regulates it to 198mV with an inside compensation network. The COMP pin is the output of the error amplifier. The inductor peak current is proportional to the COMP pin voltage. An increase of the COMP voltage increases the current delivered to the output. Open LED Protection If the LED is open, there is no voltage on the FB pin. The duty cycle will increase until VDD- VSS reaches to 55V or VOVP-VSS reaches the shutdown threshold set by the external resistor. The top switch will turn off until the voltage VDDVSS and VOVP-VSS decreases sufficiently. Dimming Control The MP4600 allows both DC and PWM dimming. When the voltage on EN is <0.6V, the chip is turned off. For analog dimming, when the voltage on EN is from 0.7V to 1.4V, the LED current will change from 0% to 100% of the maximum LED current. If the voltage on EN pin is higher than 1.4, maximum LED current will be generated. For PWM dimming, its amplitude (VDIM – VINGND) must exceed 1.5V. The PWM waveform is internally clamped to 0.198V. COMP Figure 1—Functional Block Diagram MP4600 Rev. 0.91 1/6/2012 www.MonolithicPower.com MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited. © 2012 MPS. All Rights Reserved. 5 MP4600 – WHITE LED DRIVER FOR UP TO 55 INCH TV BACKLIGHTING APPLICATION INFORMATION Setting the LED Current An external resistor RSENSE is used to set the maximum LED current through the use of the equation: 0.198V ILED R SENSE = FREQUENCY (kHz) Series1 600 400 200 0 50 100 150 200 250 ) T U VO + N ⋅Δ ⋅ ⋅ T U ⋅Δ fs T U IL ) , > T U O T U ⋅ V OV O ⋅ + N L = N V IV I ( fS Selecting the Inductor Inductor selection is related to the input voltage, output voltage, and LED current. Select the inductor to make the circuit always operate in continuous current mode (CCM). The inductance is designed as: C If RSET pin is floating, the setting frequency is the default value 1.35MHz. Selecting the Output Capacitor The output capacitor keeps the output voltage ripple ΔVOUT small (normally less than 1~5% of the DC value) and ensures feedback loop stable. The output capacitor impedance should be low at the switching frequency. Ceramic capacitors with X5R or X7R dielectrics are recommended for their low ESR characteristics. V OV I ( D T E U IL O V 0 + T U 800 ⋅ ) 1000 VI ( 1200 ⋅Δ N I 1400 ⋅ G V A _ N > fs CI Frequency vs. RSET O TV U VO N The input capacitor reduces the surge current drawn from the input supply and the switching noise from the device. Ceramic capacitors with X5R or X7R dielectrics are highly recommended because of their low ESR and small temperature coefficients. Enough capacitance is required for limited input voltage ripple ΔVIN, which should be normally less than 5~10% of the DC value. I LV Setting the Switching Frequency An external resistor RSET is used to set the switching frequency fS according to the following curve: Selecting the Input Capacitor PC Board Layout The high current paths (VSS, VDD and SW) should be aced very close to the device with short, direct and wide traces. The input capacitor needs to be as close as possible to the VDD and VSS pins. The external feedback resistors should be placed next to the FB pin. Keep the switch node traces short and away from the feedback network. T U . N I + ) 1 ( ⋅ D E IL G V A _ IL = V OV where ΔIL is the inductor peak-to-peak current ripple. Design ΔIL as about 40% to 60% of the inductor average current, which is: IL 5 . 0 + G V A _ MP4600 Rev. 0.91 1/6/2012 = IL K P _ IL Make sure the inductor is not saturated at the maximum peak current, which is: ⋅Δ . www.MonolithicPower.com MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited. © 2012 MPS. All Rights Reserved. 6 MP4600 – WHITE LED DRIVER FOR UP TO 55 INCH TV BACKLIGHTING TYPICAL APPLICATION CIRCUITS 1 2 3 3 2 1 1 3 2 Figure 2—White LED Driver Application for TV Applications MP4600 Rev. 0.91 1/6/2012 www.MonolithicPower.com MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited. © 2012 MPS. All Rights Reserved. 7 MP4600 – WHITE LED DRIVER FOR UP TO 55 INCH TV BACKLIGHTING PACKAGE INFORMATION 3mm x 3mm QFN10 2.90 3.10 0.30 0.50 PIN 1 ID MARKING 0.18 0.30 2.90 3.10 PIN 1 ID INDEX AREA 1.45 1.75 PIN 1 ID SEE DETAIL A 10 1 2.25 2.55 0.50 BSC 5 6 TOP VIEW BOTTOM VIEW PIN 1 ID OPTION A R0.20 TYP. PIN 1 ID OPTION B R0.20 TYP. 0.80 1.00 0.20 REF 0.00 0.05 SIDE VIEW DETAIL A NOTE: 2.90 0.70 1) ALL DIMENSIONS ARE IN MILLIMETERS. 2) EXPOSED PADDLE SIZE DOES NOT INCLUDE MOLD FLASH. 3) LEAD COPLANARITY SHALL BE 0.10 MILLIMETER MAX. 4) DRAWING CONFORMS TO JEDEC MO-229, VARIATION VEED-5. 5) DRAWING IS NOT TO SCALE. 1.70 0.25 2.50 0.50 RECOMMENDED LAND PATTERN NOTICE: The information in this document is subject to change without notice. Please contact MPS for current specifications. Users should warrant and guarantee that third party Intellectual Property rights are not infringed upon when integrating MPS products into any application. MPS will not assume any legal responsibility for any said applications. MP4600 Rev. 0.91 1/6/2012 www.MonolithicPower.com MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited. © 2012 MPS. All Rights Reserved. 8