MP4603 White LED Driver for Large LCD TV Backlights The Future of Analog IC Technology DESCRIPTION FEATURES The MP4603 is an integrated white LED driver. It uses MPS’s patent-pending technology to drive the backlights for LCD TVs measuring 60inches or larger, for LED string voltages up to 350V. This novel technology can leverage the LED drive power by regulating only a small portion of the LED drive voltage—together with a fixed high-voltage source, a low-voltage LED driver can drive high voltage LED strings. This method allows for a super-high power density, higher efficiency and lower cost due to the low voltage stress, higher switching frequencies, and smaller passive components. The MP4603 is a current-mode–controlled buck-boost regulator. With a 12V input VINL and a high voltage source VINH, it can deliver a regulated voltage (VINH to VINH+68V) to drive a LED string with up to 100 LEDs. It can drive an external switch in series with the LED string to achieve over 1:1000 dimming ratio. Analog dimming can be applied at the same time to further improve the dimming ratio. Fault protections include LED open-string protection, output short-circuit protection, cycle-by-cycle peak current limiting, and thermal shutdown. Novel Power-Leverage-Control Technology Unique Step-Up/Down Operation Up to 99.5% Efficiency 0.5Ω Internal Power MOSFET Switching Frequency Synchronization Over 1:1000 Dimming Ratio Separate Analog and PWM Dimming ±5% 200mV Reference Voltage 10μA Shutdown Mode Cycle-by-Cycle Over-Current Protection Thermal Shutdown Protection LED String Open and Short Protection FAULT Output at LED Protection Output Short-Circuit Protection Available in TSSOP16-EP and SOIC16 Packages APPLICATIONS Large LCD Panels Backlighting High Power Street LED Lighting All MPS parts are lead-free and adhere to the RoHS directive. For MPS green status, please visit MPS website under Products, Quality Assurance page. “MPS” and “The Future of Analog IC Technology” are registered trademarks of Monolithic Power Systems, Inc. The MP4603 is available in TSSOP16-EP and SOIC16 packages. MP4603 Rev. 1.0 4/27/2012 www.MonolithicPower.com MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2012 MPS. All Rights Reserved.MP4603 1 MP4603 – WHITE LED DRIVER FOR LARGE LCD TV BACKLIGHTS TYPICAL APPLICATION VINH MP4603 Fault RFAULT 100K FAULT VIN VIN BST SW CBST 100n L1 CIN INGND CLK/SYN R1 VSS SYN DGD PWM OVP COUT PWM EN EN ADIM RFST 300K MP4603 Rev. 1.0 4/27/2012 FB ADIM COMP FST SLOPE RFB CCOMP 10n R2 RSLOPE 300K www.MonolithicPower.com MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2012 MPS. All Rights Reserved.MP4603 2 MP4603 – WHITE LED DRIVER FOR LARGE LCD TV BACKLIGHTS ORDERING INFORMATION Part Number Package Top Marking MP4603ES* SOIC16 MP4603ES MP4603EF** TSSOP16-EP MP4603EF Free Air Temperature (TA) -20°C to +85°C * For Tape & Reel, add suffix –Z (e.g. MP4603ES–Z); For RoHS Compliant Packaging, add suffix –LF (e.g. MP4603ES–LF–Z) ** Contact Factory for Availability of TSSOP16-EP PACKAGE REFERENCE TOP VIEW PIN 1 ID TOP VIEW VIN 1 16 BST FAULT 2 15 SW FAULT 1 16 BST INGND 3 14 VSS VIN 2 15 SW SYN 4 13 DGD INGND 3 14 VSS PWM 5 12 OVP SYN 4 13 DGD EN 6 11 FB PWM 5 12 OVP ADIM 7 10 COMP EN 6 11 FB FST 8 9 SLOPE ADIM 7 10 COMP FST 8 9 SLOPE EXPOSED PAD FOR TSSOP20F ONLY TSSOP16-EP SOIC16 ABSOLUTE MAXIMUM RATINGS (1) Thermal Resistance VVIN – VSS ........................................ -0.3V to 85V VINGND – VSS ..................................... -0.3V to 85V VSW – VSS .............................. -0.3V to VIN + 0.3V VBST ...................................................... VSW + 6V VDGD – VSS .....................................-0.3V to +12V VVIN – VOCP ......................................-0.3V to +6V VOVP, VFB, VCOM, VFST – VSS .............-0.3V to +6V VADIM, VEN, VPWM, VSYN– VINGND .........-0.3V to +6V Continuous Power Dissipation (TA = +25°C) (2) TSSOP16-EP ............................................. 2.7W SOIC16 ...................................................... 1.6W Junction Temperature ...............................150°C Lead Temperature ....................................260°C Storage Temperature ............... -65°C to +150°C TSSOP16-EP ......................... 45 ...... 10... °C/W SOIC16 .................................. 80 ...... 30... °C/W Recommended Operating Conditions (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. (3) Supply Voltage VVIN – VSS ................... 5V to 80V VADIM, VEN, VPWM, VSYN – VINGND .............. 0V to 5V Maximum Junction Temp. (TJ) ............. +125°C MP4603 Rev. 1.0 4/27/2012 www.MonolithicPower.com MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2012 MPS. All Rights Reserved.MP4603 3 MP4603 – WHITE LED DRIVER FOR LARGE LCD TV BACKLIGHTS ELECTRICAL CHARACTERISTICS VVIN = 12V, PWM and AD Pins floating, RFST=51kΩ, TA = +25°C, VVSS=VINGND=0V, unless otherwise noted. Parameters FB Feedback Voltage Symbol Condition VFB Min Typ Max Units 190 200 210 mV VFB = 0.2V -0.1 0.1 μA 4.3 V FB Input Current IFB VIN UVLO Rising VVINTH VIN UVLO Hysteresis VVINHYS 3.6 Shut Down Current Ioff VEN=0V Supply Current (Quiescent) IQ VPWM = 0V, VFB = 250mV Switch-On Resistance (5) ISWLK Switch Current Limit (5) IS_MAX Oscillator Frequency fSW FST Output Voltage VFST Fold-back Frequency fSWFB Slope Compensation SSLOPE SLOPE Pin Output Voltage VSLOPE Maximum Duty Cycle Minimum ON-Time (5) SYN Input Current DMAX μA 1.2 FST pin open RFST = 200kΩ VFB = VOVP = 0V, FST pin open VFB = VOVP = 0V, RFST = 200kΩ SLOPE pin open RSLOPE = 200kΩ 1 1.2 390 MHz kHz 1 1.1 1.2 V 160 kHz 40 0.3 0.12 0.5 0.17 0.7 0.235 V/μs 1 1.1 1.2 V 88 % 270 ns 400 VSYN = 0V -750 VPWM Falling PWM Dimming ON Threshold PWM Dimming Frequency Minimum Analog Dimming Threshold VPWMH VPWM Rising VADMIN VFB = 5mV Maximum Analog Dimming Threshold VADMAX A 0.9 280 VSYN = 3.3V VPWML μA 0.65 180 VFB = 0.15V,FST pin open PWM Dimming OFF Threshold mA Ω 2.5 fSW 0.1 μA 2 MHz 1.65 V 50k 0 V Hz mV VFB = 200mV 1.2 V VADIM= 3.3V 36 SYN 2.2 100 VADIM= 0V EN OFF Threshold VENL VEN Falling EN ON Threshold VENH VEN Rising EN Input Current IEN VEN = 3.3V MP4603 Rev. 1.0 4/27/2012 10 0.5 Frequency Synchronization Range (5) ADIM Input Current mV VVIN=80V, VEN=0V, VPWM=0V, VSW=0V tON ISYN 400 1.05 RDS(ON) Switch Leakage 4 μA -3.5 0.9 1.5 V V 3.8 www.MonolithicPower.com MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2012 MPS. All Rights Reserved.MP4603 μA 4 MP4603 – WHITE LED DRIVER FOR LARGE LCD TV BACKLIGHTS ELECTRICAL CHARACTERISTICS (continued) VVIN = 12V, PWM and AD Pins floating, RFST=51kΩ, TA = +25°C, VVSS=VINGND=0V, unless otherwise noted. Parameters Symbol Condition Dim Gate Driver Sourcing Current IDGD+ Dim Gate Driver Sinking Current IDGD- LED Open OV Threshold LED Short Threshold for Immediate Latch-Off LED Short Delay for Latch-Off Thermal Shutdown (5) Thermal Shutdown Hysteresis (5) VDGD–VSS= 0V, Min Typ Max Units -25 mA 45 mA VOVPTH 1.2 V VFBS 600 mV 450 150 20 μs °C °C τD FBS VPWM=3V VDGD–VSS=10V, VPWM=1.5V 300mV < VFBS < 600mV Note: 5) Guaranteed by design. MP4603 Rev. 1.0 4/27/2012 www.MonolithicPower.com MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2012 MPS. All Rights Reserved.MP4603 5 MP4603 – WHITE LED DRIVER FOR LARGE LCD TV BACKLIGHTS TYPICAL CHARACTERISTICS MP4603 Rev. 1.0 4/27/2012 www.MonolithicPower.com MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2012 MPS. All Rights Reserved.MP4603 6 MP4603 – WHITE LED DRIVER FOR LARGE LCD TV BACKLIGHTS TYPICAL PERFORMANCE CHARACTERISTICS Performance waveforms are tested on the evaluation board of the Design Example section. VIN = 12V, VINH = 125V, VLED=180V ILED = 120mA, TA = 25°C, unless otherwise noted. Analog Dimming Curve 140 140 120 120 LED CURRENT (mA) LED CURRENT (mA) PWM Dimming Curve 100 80 60 40 20 0 0 20 40 60 80 VSW 50V/div. 100 VIN 10V/div. VSS 50V/div. 80 60 40 20 0 100 Steady State IL 500mA/div. 0 0.2 0.4 0.6 0.8 1 1.2 VADIM_EVB (V) VIN Start EN Start PWM Dimming fPWM=200Hz, DPWM=50% VSW 50V/div. VSW 50V/div. VSW 50V/div. VIN 10V/div. VSS 50V/div. VEN 5V/div. VSS 50V/div. VPWM 5V/div. VSS 50V/div. ILED 100mA/div. ILED 100mA/div. ILED 100mA/div. Open LED Load @ Working VSW 50V/div. VSW 50V/div. VFAULT 5V/div. VSS 50V/div. VFAULT 5V/div. VSS 50V/div. IL 500mA/div. ISHORT 5A/div. MP4603 Rev. 1.0 4/27/2012 Short LED- to GND @ Working www.MonolithicPower.com MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2012 MPS. All Rights Reserved.MP4603 7 MP4603 – WHITE LED DRIVER FOR LARGE LCD TV BACKLIGHTS PIN FUNCTIONS Pin # SOIC16 Pin # TSSOP 16-EP Name 2 1 VIN 1 2 FAULT 3 3 INGND 4 4 SYN 5 5 PWM 6 6 EN 7 7 ADIM 8 8 FST 9 9 SLOPE 10 10 COMP 11 11 FB 12 12 OVP 13 13 DGD 14 14 VSS 15 15 SW 16 16 BST MP4603 Rev. 1.0 4/27/2012 Description Positive Voltage Input. Requires a decoupling capacitor to prevent large inputvoltage spikes. Fault Condition Output. Open drain with reference to INGND. FAULT is high-Z during normal operation, and pulled to INGND when LED short protection or LED open protection trigger. Input Ground Reference. Frequency Synchronization Input. The switching frequency can be synchronized with an external clock. Multiple ICs’ frequencies can also be synchronized without the external clock by connecting all the SYN pins together. They follow the highest set frequency. PWM Dimming Input. Apply a 100Hz to 50kHz square wave signal with amplitude greater than 2.2V. The PWM pin voltage is high if left floating. Enable Input Pin. A voltage greater than 1.5V will turn on the chip. Analog Dimming Input. A voltage in range of 0V to 1.2V on ADIM pin adjusts the LED current from 0 to 100%. The ADIM pin voltage is high (about 3.3V) if left floating. Frequency Set. A resistor from FST to VSS sets the switching frequency if there is no SYN input. If left open, switching frequency reverts to an internal default value. Programmable Slope Compensation. Connect a resistor from SLOPE to VSS to set the slope-compensation peak amplitude. If left open, slope compensation reverts to an internal default value. Error Amplifier Output. Connect a capacitor ≥1nF from the COMP pin to VSS to improve the stability and to provide a soft-start on start-up or for PWM dimming. LED Current Feedback. The MP4603 regulates the voltage across the current sensing resistor between FB and VSS with 200mV. If the FB voltage exceeds 300mV for 450µs or exceeds 600mV, LED short protection triggers. Over Voltage Protection. Use one external resistor voltage divider from the output to VSS to program the OVP threshold. This voltage references VSS. When the OVP pin voltage reaches the 1.2V threshold, the switch turns off and the IC latches off. When the OVP pin voltage falls below 0.4V and the FB pin voltage is less than 0.1V, the chip frequency folds back. Program the OVP pin voltage from 0.4V to 1.2V for normal operation. LED Dimming-Switch Gate Drive Output. Negative Voltage Output. The voltage reference for OVP, FB, COMP, SLOPE, DGD and FST. Switch Output. The source of the internal MOSFET switch. Connect to the power inductor and cathode of the Schottky rectifier. Bootstrap. Connect a capacitor between the SW and BST pins to form a floating supply across the power switch driver. www.MonolithicPower.com MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2012 MPS. All Rights Reserved.MP4603 8 MP4603 – WHITE LED DRIVER FOR LARGE LCD TV BACKLIGHTS BLOCK DIAGRAM VIN SYN 20X SYN EN DDIM ADIM INGND EN VIN INGND INGND Dimming ADIM Control INGND ENI FBREF V0P20 V0P20 DIMIN VSS VBG Bandgap & Bias EN V0P20 VBG BST BST OSC DDIM VBG SC FST CLK VBG VBG HSG BST Regulator DRVIN SW VSS SCST SW OverVoltage Protection OV OVP VSS Current Limit ILIM FST VSS OV SoftStart SLOPE OVP VSS CLK FALTDRV Logic FAULT INGND ILIM REF FB PWM EA HSON FB DIMIN PWM Level Shift Diming FET Gate Drive DIMIN DGD COMP Control Loop COMP VSS Figure 1: Functional Block Diagram MP4603 Rev. 1.0 4/27/2012 www.MonolithicPower.com MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2012 MPS. All Rights Reserved.MP4603 9 MP4603 – WHITE LED DRIVER FOR LARGE SIZE TV BACKLIGHTING OPERATION The MP4603 is a current mode regulator. The sensing resistor senses the LED current and the signal goes an error amplifier, which regulates it to 200mV through an internal compensation network—The COMP pin is the output of the error amplifier. The inductor peak current is proportional to the COMP voltage. Increasing the COMP voltage increases the current delivered to the output. LED Open Protection If the LED is open, there is no voltage on the FB pin. The duty cycle increases until VOVP-VVSS reaches the shutdown threshold. The top switch turns off, and the IC latches off. At LED open protection, the Fault pin goes low. LED Short Protection If the FB voltage exceeds 600mV, the IC immediately latches off and DGD goes low. If the FB voltage exceeds 300mV for around 450µs, IC latches off and DGD goes low. The EN pin must reset to restart the IC. The Fault pin goes low when the IC latches off. Dimming Control The MP4603 allows for both Analog and PWM dimming. The analog dimming voltage range on ADIM goes from 0V to1.2V to change the LED current from 0% to 100% of the maximum LED current. If the voltage on the ADIM pin exceeds 1.2V or is floating, LED current goes to its maximum. PWM dimming uses a square-wave signal with a 100Hz-to-50kHz frequency range and an amplitude over 2.2V applied to the PWM pin. PWM dimming can achieve over 1:1000 dimming ratio with PWM frequency less than 200Hz During the PWM dimming OFF interval, an internal switch disconnects the COMP pin capacitor from the output of the error amplifier: This holds the COMP voltage during the PWM OFF interval and increases the LED current response speed to achieve a high dimming ratio. Combine PWM and analog dimming to increase the dimming ratio. Apply a 100Hz to 50kHz PWM signal on PWM pin and a analog dimming signal in range of 0V to 1.2V on ADIM pin. . MP4603 Rev. 1.0 4/27/2012 www.MonolithicPower.com MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2012 MPS. All Rights Reserved.MP4603 10 MP4603 – WHITE LED DRIVER FOR LARGE SIZE TV BACKLIGHTING APPLICATION INFORMATION The MP4603 is a buck-boost LED driver. Its novel power leverage control technology provides a highly efficient, low-cost solution for LCD TV LED drivers. It has a high bus voltage and a low supply voltage (typically 12V or 24V, up to 60V) to drive LED backlight strings of >350V for LCD TVs measuring 60-inch or more. Setting the LED Current An external resistor (RFB) sets the maximum LED current as per: RFB 0.200V ILED Setting the Switching Frequency An external resistor RFST can set the switching frequency (fS) as per: fS 0.95MHz 60k RFST This equation applies to a programmable frequency range between 200kHz and 2MHz. If FST pin is floating or RFST exceeds 400k, the switching frequency is set to default value of 0.9MHz. Setting the Slope Compensation The MP4603 employs peak-current–mode control, which needs slope compensation to avoid sub-harmonic oscillation when the duty cycle exceeds 50%. The current loop has effective sense resistance of 0.4Ω. Given a desired input/output voltage relationship, estimate the sense current rampdown slope as: SDOWN VL 0.4V/s L Where VL is the voltage across the inductor in volt; and L is the inductor value in μH. Ensuring current loop stability requires a compensation slope of at least half of the rampdown slope: SSC MP4603 Rev. 1.0 4/27/2012 1 SDOWN 2 An external resistor (RSLOPE) can set the slope compensation for the current loop as per: SSC = 0.6 V 60k * s R SLOPE The equation is effective only for a resistor range from 20kΩ to 400kΩ for RSLOPE. If SLOPE pin is floating or RSLOPE exceeds 400k, the slope compensation is set to default value of 0.5V/μs. Selecting the Inductor The input voltage, output voltage, and LED current factor into inductor selection. In addition, select the inductor so that the circuit always operates in continuous current mode (CCM). Estimate the inductor value using the following equation: L VIN VOUT fS (VIN VOUT ) IL Where IL is the inductor peak-to-peak current ripple. Design IL somewhere around 40% to 60% of the inductor average current, which is: IL _ AVG ILED (1 VOUT ). VIN Select an inductor that does not saturate at the maximum peak current, which is: IL _ PK IL _ AVG 0.5 IL . Selecting the Input Capacitor The input capacitor reduces the surge current drawn from the input supply and the switching noise from the device. Use ceramic capacitors with X5R or X7R dielectrics because they have low ESR values and small temperature coefficients. Select a sufficiently-large capacitance to limit the input voltage ripple (VIN), which is normally less than 5%-10% of the DC value. CIN IL _ AVG VOUT fs VIN (VIN VOUT ) www.MonolithicPower.com MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2012 MPS. All Rights Reserved.MP4603 11 MP4603 – WHITE LED DRIVER FOR LARGE SIZE TV BACKLIGHTING Selecting the Output Capacitor The output capacitor normally limits the output voltage ripple (VOUT) to less than 1%-to-5% of the DC value, and ensures a stable feedback loop. Select an output capacitor value with low impedance at the switching frequency. Use ceramic capacitors with X5R or X7R dielectrics for their low ESR characteristics. COUT ILED VOUT fs VOUT (VIN VOUT ) switching loop is composed of the input capacitor, the internal switch of IC (VIN pin to SW pin) and the diode. Place the input capacitor and the diode close to the IC. For buck-boost applications, the high frequency switching loop is composed of the input capacitor, the internal switch, the diode and the output capacitor. Place the input and output capacitors close together, close to the IC, and to the diode. Setting the Over Voltage Protection The output voltages of some converters, such as buck-boost and boost converters, can rise to very high levels without a limiting function. Overvoltage protection (OVP) limits the output voltage to below the operating rating. Use a voltage divider to set the OVP point. VOVP 1.2V (1 R1 ) R2 Where R1 and R2 are the voltage divider (refer the TYPICAL APPLICATION). For most applications, set the OVP point around 10% to 30% higher than the output voltage. Check that the set OVP point will not exceed the operation rating. Top Layer FAULT Condition Output The MP4603 has an open drain output as a FAULT indicator. Under normal conditions, FAULT is a high-Z output and can be set to any desired voltage with external resistors. However, if VFB exceeds VSS by 600mV, or VFB exceeds VSS by 300mV for ~450μs, or OVP triggers at 1.2V, FAULT drops to the INGND level. The Rdson for this pull down switch is ~100Ω. PC Board Layout Place the high-current paths (VSS, VIN and SW) very close to the device with short, direct, and wide traces. Place the input capacitor as close as possible to the VIN and VSS pins. Place the external feedback resistors next to the FB pin. Keep the switch node traces short and far away from the feedback network. Bottom Layer Figure 2: PCB Layout Pay attention to the layout of the high frequency switching loop, which should be placed as small as possible. For buck MP4603 Rev. 1.0 4/27/2012 applications, the high frequency www.MonolithicPower.com MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2012 MPS. All Rights Reserved.MP4603 12 MP4603 – WHITE LED DRIVER FOR LARGE SIZE BACKLIGHTING TYPICAL APPLICATION CIRCUITS VINH LED+ 150V VIN 12V VLED 180V MP4603 Fault VIN 12V RFAULT100K FAULT VIN Block1 BST SW CBST 100n L1 CIN INGND CLK/ SYN SYN DGD PWM PWM OVP EN EN ADIM RFST 300K LEDCOUT FB ADIM COMP FST SLOPE RSLOPE 300K Fault R1 VSS RFB VIN 12V Block2 LED- CLK/ SYN PWM CCOMP 10n R2 EN ADIM Figure 3: White LED Driver for TV Applications MP4603 Rev1.0 4/27/2012 www.MonolithicPower.com MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2012 MPS. All Rights Reserved.MP4603 13 MP4603 – WHITE LED DRIVER FOR LARGE SIZE BACKLIGHTING Design Example This design example shows an LCD TV LED backlight application. Figure 4 shows the system power structure block diagram. MPS’s HFC0100 flyback controller controls the flyback, offering 2 outputs: 12VIN and VINH. The high output, VINH, provides a bias voltage (less than the LED string voltage) for all LED strings and connects to the anodes. The low output, 12VIN, is about 12V and supplies the MP4603 LED driver; the MP4603 generates a negative voltage and connects to the cathode of the LED strings to drive the LED strings. V INH HFC0100 Flyback AC Input 12VIN MP4603 LED Driver INGND MP4603 LED Driver LED1- INGND LED2- Figure 4: System Power Block Diagram Specifications Flyback Output: VINH = typical 145V (140V to 160V): crossregulation in the multiple output flyback is the primary cause of the large tolerance. 12VIN is 12V; Output: 2 outputs of 120mA for every string LED voltage is typical 180V (165V to 195V) Protections: Open LED string protection Short LED string protection MP4603 Operating Range: Input voltage = 12V Output voltage = -5V to -55V LED current = 120mA. Figure 5 shows the schematic of the MP4603 LED driver stage. JP1 is short and JP2 is open. Switching frequency: ~200kHz MP4603 Rev1.0 4/27/2012 www.MonolithicPower.com MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2012 MPS. All Rights Reserved.MP4603 14 MP4603 – WHITE LED DRIVER FOR LARGE SIZE BACKLIGHTING Figure 5: LED Driver Schematic Used for Evaluation (EV4603-S-00A) IL _ PK IL _ AVG 0.5 IL Setting Current Sense Resistor The sense resistor RFB is: RFB Select L1=100μH with a saturation current of 1.5A 0.200V ILED Use two 3.32Ω resistor in parallel (R15 and R16) as the LED current sensor resistor. Setting the Frequency Set Resistor The following equation determines frequency set resistor, R18: R18 the 0.95MHz 60k fS Select 300kΩ to set the switching frequency to about 200kHz. Selecting the Inductor Select an inductor such that the circuit always operates in CCM as per the following equation: VIN_min VOUT_max L1 fS (VIN_min VOUT_max ) η ILED (1 VOUT_max VIN_min ) Where is about 40% to 60%. Select an inductance of 100μH and the inductor peak-topeak current of 0.49A. Setting the Slope Compensation The voltage across the inductor in the buckboost converter is the output voltage. The maximum slope compensation is: SDOWN VOUT_max 0.4V/s L To ensure current-loop stability, select a compensation slope that is at least half of the needed ramp-down slope: SSC 1 SDOWN 2 SSC≥0.11V/μs. Use the slope compensation resistor RSLOPE to set the slope compensation for the current loop as per the following equation: R19 60kΩ 0.6 V s SSC Based on this equation, the slope compensation resistor cannot exceed 330kΩ. Select an inductor that does not saturate at the maximum peak current, which is: MP4603 Rev1.0 4/27/2012 www.MonolithicPower.com MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2012 MPS. All Rights Reserved.MP4603 15 MP4603 – WHITE LED DRIVER FOR LARGE SIZE BACKLIGHTING Select R19=300kΩ resistor. as the compensation Selecting the Input and Output Capacitor Estimate the input capacitor and capacitor using the following equations. CIN COUT output IL _ AVG VOUT fs VIN (VIN VOUT ) ILED VOUT fs VOUT (VIN VOUT ) Where ΔVIN is about 5%-to-10% of the input voltage, and ΔVout is about 1%-to-5% of the output voltage. Select C2=2.2μF ceramic capacitor as the input capacitor and C8=2.2μF as the output capacitor Setting the Over Voltage Protection Set the OVP point is about 1.1x-to-1.2x of the output voltage so that the OVP point is about 60V to 66V. VOVP 1.2V (1 R5 ) R12 Select R12=20kΩ and R5=1MΩ; the OVP point is 63V. MP4603 Rev1.0 4/27/2012 www.MonolithicPower.com MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2012 MPS. All Rights Reserved.MP4603 16 MP4603 – WHITE LED DRIVER FOR LARGE SIZE BACKLIGHTING PACKAGE INFORMATION TSSOP16-EP 3.30 TYP 0.40 TYP 4.90 5.10 16 9 1.60 TYP 4.30 4.50 PIN 1 ID 1 0.65 BSC 2.80 TYP 6.20 6.60 5.80 TYP 8 TOP VIEW RECOMMENDED LAND PATTERN 0.80 1.05 1.20 MAX SEATING PLANE 0.19 0.30 0.65 BSC 0.00 0.15 0.09 0.20 SEE DETAIL "A" SIDE VIEW FRONT VIEW GAUGE PLANE 0.25 BSC 0o-8o 0.45 0.75 DETAIL “ A” NOTE: 1) ALL DIMENSIONS ARE IN MILLIMETERS. 2) PACKAGE LENGTH DOES NOT INCLUDE MOLD FLASH , PROTRUSION OR GATE BURR. 3) PACKAGE WIDTH DOES NOT INCLUDE INTERLEAD FLASH OR PROTRUSION. 4) LEAD COPLANARITY(BOTTOM OF LEADS AFTER FORMING) SHALL BE 0.10 MILLIMETERS MAX. 5) DRAWING CONFORMS TO JEDEC MO-153, VARIATION ABT. 6) DRAWING IS NOT TO SCALE. MP4603 Rev1.0 4/27/2012 www.MonolithicPower.com MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2012 MPS. All Rights Reserved.MP4603 17 MP4603 – WHITE LED DRIVER FOR LARGE SIZE BACKLIGHTING SOIC16 0.386( 9.80) 0.394(10.00) 0.024(0.61) 9 16 0.063 (1.60) 0.150 (3.80) 0.157 (4.00) PIN 1 ID 0.050(1.27) 0.228 (5.80) 0.244 (6.20) 0.213 (5.40) 8 1 TOP VIEW RECOMMENDED LAND PATTERN 0.053(1.35) 0.069(1.75) SEATING PLANE 0.050(1.27) BSC 0.013(0.33) 0.020(0.51) 0.004(0.10) 0.010(0.25) SEE DETAIL "A" SIDE VIEW FRONT VIEW 0.010(0.25) x 45o 0.020(0.50) GAUGE PLANE 0.010(0.25) BSC 0o-8o 0.016(0.41) 0.050(1.27) 0.0075(0.19) 0.0098(0.25) NOTE: 1) CONTROL DIMENSION IS IN INCHES. DIMENSION IN BRACKET IS IN MILLIMETERS. 2) PACKAGE LENGTH DOES NOT INCLUDE MOLD FLASH, PROTRUSIONS OR GATE BURRS. 3) PACKAGE WIDTH DOES NOT INCLUDE INTERLEAD FLASH OR PROTRUSIONS. 4) LEAD COPLANARITY (BOTTOM OF LEADS AFTER FORMING) SHALL BE 0.004" INCHES MAX. 5) DRAWING CONFORMS TO JEDEC MS-012, VARIATION AC. 6) DRAWING IS NOT TO SCALE. DETAIL "A" 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. MP4603 Rev. 1.0 4/27/2012 www.MonolithicPower.com MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2012 MPS. All Rights Reserved.MP4603 18