MPQ3386-AEC1 50V, 6 String White LED Driver AEC-Q100 Qualified DESCRIPTION FEATURES The MPQ3386 is a step-up converter with 6channel current sources designed for driving the white LED arrays for large size LCD panel backlighting applications. • The MPQ3386 uses current mode, fixed frequency architecture. The switching frequency can be selected at 1.25MHz or 625kHz. It generates an output voltage up to 50V from a 4.5V to 25V input supply. The MPQ3386 regulates the current in each LED string to the user programmed value set by an external current setting resistor. • • • • • • • Guaranteed Industrial/Automotive Temp Range Limits 4.5V to 25V Input Voltage Range 50V Maximum Step-up Voltage Balanced Driver for 6 Strings of WLED 3% Current Matching Accuracy Between Strings Selectable Switching Frequency: 1.25MHz or 625kHz PWM or DC Input Burst PWM Dimming Programmable Over-voltage Protection Threshold Under Voltage Lockout Open and Short LED Protection Thermal Shutdown Small QFN24 (4x4mm) Package Available in AEC-Q100 Qualified Grade 1 The MPQ3386 applies 6 internal current sources in each LED string terminal to get current balance. And the current matching achieves 3% regulation accuracy between strings. Its low 600mV regulation voltage on LED current sources reduces power loss and improves efficiency. • • • • • The MPQ3386 features external PWM dimming or DC input PWM dimming, which allows the flexible control of the backlighting luminance under wide range of the ambient brightness, and also avoids the possibility of PWM dimming audible noise. The dimming PWM signal can be generated internally, and the dimming frequency is programmed by an external setting capacitor. APPLICATIONS • • • • Notebook & Netbook PC Small LCD TV Portable Terminals Display Automotive System and Tablet Computer 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. TYPICAL APPLICATION MPQ3386 Rev. 1.0 www.MonolithicPower.com 5/24/2016 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2016 MPS. All Rights Reserved. 1 MPQ3386- 50V, 6 STRINGS WHITE LED DRIVERS, AEC-Q100 QUALIFIED ORDERING INFORMATION Part Number Top Marking MPQ3386DR* Package QFN-24 (4mmx4mm) MPQ3386DR-AEC1** QFN-24 (4mmx4mm) 3386DR 3386DR * For Tape & Reel, add suffix –Z (e.g. MPQ3386DR–Z). For RoHS Compliant Packaging, add suffix –LF (e.g. MPQ3386DR–LF–Z) * * For Tape & Reel, add suffix –Z (e.g. MPQ3386DR-AEC1–Z). For RoHS Compliant Packaging, add suffix –LF (e.g. MPQ3386DR-AEC1–LF–Z) PACKAGE REFERENCE QFN24 (4x4mm) ABSOLUTE MAXIMUM RATINGS (1) VIN ................................................ -0.3V to +30V VVFAULT ......................................... VIN - 6V to VIN VSW, VOUT, VLED1 to VLED6 ................. -1V to +50V All Other Pins ................................. -0.3V to +6V (2) Continuous Power Dissipation (TA = +25°C) …………………………………………………2.9W Junction Temperature 150°C Lead Temperature ................................... 260°C Storage Temperature ............... -65°C to +150°C Recommended Operating Conditions (3) Supply Voltage VIN .......................... 4.5V to 25V Operating Junction Temp. (TJ). -40°C to +125°C (4) θJA θJC QFN-24 (4mmx4mm) ............. 42 ....... 9 .... °C/W Thermal Resistance 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 is not guaranteed to function outside of its operating conditions. 4) Measured on JESD51-7, 4-layer PCB. MPQ3386 Rev. 1.0 www.MonolithicPower.com 5/24/2016 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2016 MPS. All Rights Reserved. 2 MPQ3386- 50V, 6 STRINGS WHITE LED DRIVERS, AEC-Q100 QUALIFIED ELECTRICAL CHARACTERISTICS VIN =12V, VEN = 5V, TJ = -40ºC to + 125°C, unless otherwise noted. Typical values are at TJ=25ºC Parameters Symbol Condition Min Operating Input Voltage VIN Supply Current (Quiescent) IQ VIN=12V, VEN=5V, no load. Supply Current (Shutdown) IST VEN=0V, VIN=12V LDO Output Voltage VCC Input UVLO Threshold VIN_UVLO Typ Max Units 25 V 1.8 2.5 mA 0.05 1 µA 4.5 5 5.5 V 3.4 3.9 4.3 V 4.5 VEN=5V, 0<IVCC<10mA Rising Edge 6V<VIN<25V, 1.1 Input UVLO Hysteresis 165 EN ON Threshold VEN_ON VEN Rising EN OFF Threshold VEN_OFF VEN Falling SW On-Resistance RDS_ON IDS=20mA SW Leakage Current ISW_LK VSW =45V Switching Frequency fSW mV 2.0 V 0.4 V STEP-UP CONVERTER OSC High-Level Threshold VOSC_H OSC Low-Level Threshold VOSC_L (6) Minimum On Time Maximum Duty Cycle SW Current Limit TON_MIN TJ=25°C 0.21 0.3 -40°C to + 125°C 0.21 0.45 1 µA VOSC=VCC or Floating 1.0 1.25 1.5 MHz VOSC=0V 500 625 750 kHz 2.1 V 1.2 PWM Mode, when no pulse skipping happens DMAX ISW_LIMIT Ω Duty=90% 100 ns 90 93 TJ=25°C 2.0 2.5 -40°C to + 125°C 1.5 2.5 70 100 130 60 90 ΔICOMP=±10uA COMP Transconductance GCOMP COMP Output Current ICOMP 30 PWMI High-Level Threshold VPWMI_H 1.5 PWMI Low-Level Threshold VPWMI_L PWMO Output Impedance RPWMO 300 PWMI Leakage Current IPWMI_LK -1 V 96 % A µA/V µA PWM DIMMING DPWM Frequency fDPWM CFSET=2.2nF 1.2 V 400 1.6 MPQ3386 Rev. 1.0 www.MonolithicPower.com 5/24/2016 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2016 MPS. All Rights Reserved. 0.4 V 500 kΩ +1 µA 2 kHz 3 MPQ3386- 50V, 6 STRINGS WHITE LED DRIVERS, AEC-Q100 QUALIFIED ELECTRICAL CHARACTERISTICS (continued) VIN =12V, VEN = 5V, TJ = -40ºC to + 125°C, unless otherwise noted. Typical values are at TJ=25ºC. Parameters Symbol Condition Min Typ Max 19 20 21 Units LED CURRENT REGULATION LEDX Average Current ILED Current Matching TJ=25°C -40°C to + 125°C 18.6 ILED=20mA Maximum LED Current per String LEDX Regulation Voltage RISET=60.4kΩ (5) TJ=25°C 27 -40°C to + 125°C 24 21.4 1 3 30 33 mA % ILEDmax RISET=40.2 kΩ VLEDX ILED=20mA 520 600 680 mV 1.17 1.23 1.3 V 33 mA PROTECTION OVP Over Voltage Threshold VOVP_OV Rising Edge OVP UVLO threshold VOVP_UV Step-up Converter Fails 48 70 102 mV LEDX Over Voltage Threshold VLEDX_OV VIN>5.5V 5.1 5.5 5.9 V LEDX UVLO Threshold VLEDX_UV 130 175 230 mV Thermal Shutdown Threshold (6) TST 150 LEDX Over Voltage Fault Timer VFAULT Pull Down Current VFAULT Blocking-Off Voltage (with Respect to VIN) IFAULT VFAULT VIN =12V, VIN-VFAULT °C 1.3 1.6 1.9 ms 40 55 80 µA 4.7 6 6.7 V Notes: 5) Matching is defined as the difference of the maximum to minimum current divided by the sum of the maximum and minimum currents. 6) Design guarantee, no production test. MPQ3386 Rev. 1.0 www.MonolithicPower.com 5/24/2016 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2016 MPS. All Rights Reserved. 4 MPQ3386- 50V, 6 STRINGS WHITE LED DRIVERS, AEC-Q100 QUALIFIED TYPICAL PERFORMANCE CHARACTERISTICS VIN =12V, 10 LEDs in series, 6 strings parallel, 20mA/string, unless otherwise noted. MPQ3386 Rev. 1.0 www.MonolithicPower.com 5/24/2016 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2016 MPS. All Rights Reserved. 5 MPQ3386- 50V, 6 STRINGS WHITE LED DRIVERS, AEC-Q100 QUALIFIED TYPICAL PERFORMANCE CHARACTERISTICS VIN =12V, 10 LEDs in series, 6 strings parallel, 20mA/string, unless otherwise noted. MPQ3386 Rev. 1.0 www.MonolithicPower.com 5/24/2016 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2016 MPS. All Rights Reserved. 6 MPQ3386- 50V, 6 STRINGS WHITE LED DRIVERS, AEC-Q100 QUALIFIED PIN FUNCTIONS Pin # Name Description 1 EN 2 OSC 3 FSET 4 PWMO 5 GND Analog Ground. 6 PWMI PWM Signal Input. To use external PWM dimming mode, apply a PWM signal on this pin for brightness control. This signal is filtered and its duty cycle is converted into a DC signal to calculate the DPWM duty cycle. And the DPWM duty cycle equals to the input PWM duty cycle. To use DC input PWM dimming mode, float this pin. 7 LED6 LED String 6 Current Input. This pin is the open-drain output of an internal dimming control switch. Connect the LED String 6 cathode to this pin. If this string is not used, connect Vout to this pin. 8 LED5 9 LED4 10 LED3 LED String 3 Current Input. This pin is the open-drain output of an internal dimming control switch. Connect the LED String 3 cathode to this pin. If this string is not used, connect Vout to this pin. 11 ISET LED Current Set. Tie a current setting resistor from this pin to ground to program the current in each LED string. ILED = 1.21V / RSET 12 LED2 13 LED1 14 15 NC Vout Enable Control Input. Do not let this pin floating. Switching Frequency Selection Input. When float this pin or connect this pin to VCC, the step-up converter switching frequency is 1.25MHz. When connect this pin to GND, the step-up converter switching frequency is 625kHz. Dimming PWM Frequency Set. Connect a capacitor between FSET and GND to set the DPWM frequency by the equation: fDPWM=3.5uF/CFSET. The frequency of DPWM is recommended to be set from 100Hz to 2kHz. PWM Filter Output. To use external PWM dimming mode, connect a capacitor between PWMO and GND to form a low-pass filter with an internal 400kΩ resistor. It filters the external PWM logic signal on PWMI pin into a DC signal whose level is inversely proportional to the duty-cycle of the input PWM signal and then the DC signal is translated into a duty-cycle of the dimming PWM. To use DC input PWM dimming mode, directly apply a DC voltage from 0.2V to 1.2V on PWMO pin for dimming PWM duty cycle control. The DC input PWM dimming polarity is negative. LED String 5 Current Input. This pin is the open-drain output of an internal dimming control switch. Connect the LED String 5 cathode to this pin. If this string is not used, connect Vout to this pin. LED String 4 Current Input. This pin is the open-drain output of an internal dimming control switch. Connect the LED String 4 cathode to this pin. If this string is not used, connect Vout to this pin. LED String 2 Current Input. This pin is the open-drain output of an internal dimming control switch. Connect the LED String 4 cathode to this pin. If this string is not used, connect Vout to this pin. LED String 1 Current Input. This pin is the open-drain output of an internal dimming control switch. Connect the LED String 3 cathode to this pin. If this string is not used, connect Vout to this pin. No Connection. Voltage Output. Connect this pin to output. MPQ3386 Rev. 1.0 www.MonolithicPower.com 5/24/2016 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2016 MPS. All Rights Reserved. 7 MPQ3386- 50V, 6 STRINGS WHITE LED DRIVERS, AEC-Q100 QUALIFIED PIN FUNCTIONS (continued) Description Pin # Name 16 OVP 17 PGND2 Step-up Converter Power Ground. 18 PGND1 Step-up Converter Power Ground. PGND1 and PGND2 should be shorted externally. 19 SW1 Step-up Converter Power Switch Output. SW1 is the drain of the internal MOSFET switch. Connect the power inductor and output rectifier to SW1. SW1 can swing between GND and 50V. SW1 and SW2 should be shorted externally. 20 SW2 Step-up Converter Power Switch Output. SW2 is the drain of the internal MOSFET switch. Connect the power inductor and output rectifier to SW2. SW2 can swing between GND and 50V. SW1 and SW2 should be shorted externally. 21 VFAULT Fault Disconnection Switch Driver Output. When the system starts up normally, this pin turns on the external PMOS. When the MPQ3386 is disabled, the external PMOS is turned off to disconnect the input and output. 22 COMP Step-up Converter Compensation Pin. This pin is used to compensate the regulation control loop. Connect a capacitor or a series RC network from COMP to GND. 23 VIN Supply Input. VIN supplies the power to the chip, as well as the step-up converter switch. Drive VIN with a 4.5V to 25V power source. Must be locally bypassed. 24 VCC The Internal 5V Linear Regulator Output. VCC provides power supply for the internal MOSFET switch gate driver and the internal control circuitry. Bypass VCC to GND with a ceramic capacitor. If VIN is less than 5.5V, apply an external 5V supply directly on VCC. Over-voltage Protection Input. Connect a resistor divider from output to this pin to program the OVP threshold. When this pin voltage reaches 1.23V, the MPQ3386 triggers OV Protection mode. MPQ3386 Rev. 1.0 www.MonolithicPower.com 5/24/2016 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2016 MPS. All Rights Reserved. 8 MPQ3386- 50V, 6 STRINGS WHITE LED DRIVERS, AEC-Q100 QUALIFIED FUNCTION DIAGRAM Figure 1—MPQ3386 Function Diagram MPQ3386 Rev. 1.0 www.MonolithicPower.com 5/24/2016 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2016 MPS. All Rights Reserved. 9 MPQ3386- 50V, 6 STRINGS WHITE LED DRIVERS, AEC-Q100 QUALIFIED OPERATION The MPQ3386 employs a constant frequency, peak current mode step-up converter and 6channels regulated current sources architecture to regulate the array of 6 strings white LEDs. The operation of the MPQ3386 can be understood by referring to the block diagram of Figure 1. Internal 5V Regulator The MPQ3386 includes an internal linear regulator (VCC). When VIN is greater than 5.5V, this regulator offers a 5V power supply for the internal MOSFET switch gate driver and the internal control circuitry. The VCC voltage drops to 0V when the chip shuts down. In the application of VIN smaller than 5.5V, tie VCC and VIN together and connect them to an external 5V power supply. The MPQ3386 features Under Voltage Lockout. The chip is disabled until VCC exceeds the UVLO threshold. And the hysteresis of UVLO is approximately 200mV. System Startup When the MPQ3386 is enabled, the chip checks the topology connection first. The VFAULT pin drives the external Fault Disconnection PMOS to turn on slowly. And after 400us delay, the chip monitors the OVP pin to see if the Schottky diode is not connected or the boost output is short to GND. If the OVP voltage is lower than 70mV, the chip will be disabled and the external PMOS is turned off together. The MPQ3386 will also check other safety limit, including UVLO and OTP after the OVP test is passed. If they are all in function, it then starts boosting the step-up converter with an internal soft-start. It is recommended on the start up sequence that the enable signal comes after input voltage and PWM dimming signal established. output of the current sense amplifier and the result is fed into the PWM comparator. When this voltage equals to the output voltage of the error amplifier (VCOMP) the power FET is turned off. The voltage at the output of the internal error amplifier is an amplified signal of the difference between the 600mV reference voltage and the feedback voltage. The converter automatically chooses the lowest active LEDX pin voltage for providing enough bus voltage to power all the LED arrays. If the feedback voltage drops to smaller than the 600mV reference, the output of the error amplifier increases. This results in more current flowing through the power FET, thus increasing the power delivered to the output. In this way it forms a close loop to make the output voltage in regulation. At light-load or Vout near to Vin operation, the converter runs into the pulse-skipping mode, the FET is turned on for a minimum on-time of approximately 100ns, and then the converter discharges the power to the output in the remnant period. The FET will keep off until the output voltage needs to be boosted again. Dimming Control The MPQ3386 provides several PWM dimming methods: external PWM signal from PWMI pin or DC input PWM Dimming mode (see Figure 2). These methods results in PWM chopping of the current in the LEDs for all 6 channels to provide an average LED current. DC Input Ex-PWM Input DPWM Comparator 1.2V 400 k? PWMI PWMO CPWMO + 0.2V Step-up Converter The converter operation frequency is selectable (1.25MHz or 625kHz), which is helpful for optimizing the external components sizes and improving the efficiency. At the beginning of each oscillator cycle, the power FET is turned on. To prevent subharmonic oscillations at duty cycles greater than 50 percent, a stabilizing ramp is added to the DPWM Output - 1.2V DPWM Oscillator 0.2V FSET C FSET Figure 2—PWM Dimming Method MPQ3386 Rev. 1.0 www.MonolithicPower.com 5/24/2016 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2016 MPS. All Rights Reserved. 10 MPQ3386- 50V, 6 STRINGS WHITE LED DRIVERS, AEC-Q100 QUALIFIED When applying a PWM signal to the PWMI pin, the MPQ3386 generates a DC voltage on PWMO pin which is proportional to the duty cycle of the PWMI pin signal. By comparing the PWMO pin signal with the FSET pin triangle waveform, the converter gets a low frequency chopping signal that the duty cycle is same as the input signal. This low frequency chopping signal will modulate the LED current. A DC analog signal can be directly applied at the PWMO pin to modulate the LED current. And the DC signal is translated into the duty-cycle of the low frequency chopping signal. The polarity is negative. The brightness of the LED array is proportional to the duty cycle of the DPWM signal. The DPWM signal frequency is set by the cap at the FSET pin. Short String Protection The MPQ3386 monitors the LEDX pin voltage to judge if the short string occurs. If one or more strings are short, the respective LEDX pins will be pulled up to the boost output and tolerate high voltage stress. If the LEDX pin voltage is higher than 5.5V when the internal dimming control logic is on, the short string condition is detected on the respective string. When the short string fault (LEDX over-voltage fault) continues for greater than 1.6ms, the string is marked off and disabled. Once a string is marked off, its current regulation is forced to disconnect from the output voltage loop regulation. The marked-off LED strings are shut off totally until the part restarts. If all strings in use are short, the MPQ3386 shuts down the step-up converter. Open String Protection The open string protection is achieved through the over voltage protection. If one or more strings are open, the respective LEDX pins are pulled to ground and the IC keeps charging the output voltage until it reach OVP threshold. Then the part will mark off the open strings whose LEDX pin voltage is less than 175mV. Once the markoff operation completes, the remaining LED strings will force the output voltage back into tight regulation. The string with the highest voltage drop is the ruling string during output regulation. The MPQ3386 always tries to light at least one string and if all strings in use are open, the MPQ3386 shuts down the step-up converter. The part will maintain mark-off information until the part shuts down. MPQ3386 Rev. 1.0 www.MonolithicPower.com 5/24/2016 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2016 MPS. All Rights Reserved. 11 MPQ3386- 50V, 6 STRINGS WHITE LED DRIVERS, AEC-Q100 QUALIFIED APPLICATION INFORMATION Selecting the Switching Frequency The switching frequency of the step-up converter is alternative from 1.25MHz and 625kHz. A bilevel Switching Frequency Selection (OSC) input sets the internal oscillator frequency for the stepup converter. Tie OSC pin to GND corresponds to the frequency 625kHz and tie OSC pin to VCC or floating corresponds to 1.25MHz. Setting the LED Current The LED string currents are identical and set through the current setting resistor on the ISET pin. ILED = 1000 x1.21V / RSET For RSET=60.4kΩ, the LED current is set to 20mA. The ISET pin can not be open. Setting the Over Voltage Protection The open string protection is achieved through the over voltage protection (OVP). In some cases, an LED string failure results in the feedback voltage always zero. The part then keeps boosting the output voltage higher and higher. If the output voltage ever exceeds the programmed OVP threshold, the protection will be triggered. Figure 3—PWM Dimming with Internal Triangle Waveform Generator 2, Direct PWM dimming with positive logic An external PWM dimming signal is directly employed to achieve PWM dimming control. Connect a 100kΩ resistor from FSET pin to GND and apply the 100Hz to 2kHz PWM dimming signal to PWMI pin. The minimum recommended amplitude of the PWM signal is 1.5V (See Figure 4). To make sure the chip functions properly, the OVP setting resistor divider must be set with proper value. The recommended OVP point is about 1.3 times higher than the output voltage for normal operation. Figure 4—Direct PWM Dimming VOVP=1.23V x (R1+R2)/R2 with Positive Logic Selecting Dimming Control Mode The MPQ3386 provides 4 different dimming methods 1, PWM dimming mode with internal triangle waveform generator Apply a 100Hz to 50kHz square waveform to the PWMI pin. The internal 400kΩ and external capacitor on PWMO pin filters the dimming signal to a DC voltage(0.2V~1.2V).Then DC voltage is modulated to a internal PWM dimming signal whose frequency is set via the capacitor on FSET pin according to the equation: 3, Direct PWM dimming with negative logic It is similar to method 2. Apply a 100Hz to 2 kHz external square waveform to the PWMO pin for negative logic PWM dimming. The minimum recommended amplitude of the PWM signal is 1.5V (See Figure 5) fDPWM = 3.5uF / CFSET The minimum recommended amplitude of the PWM signal is 2.1V (See Figure 3) MPQ3386 Rev. 1.0 www.MonolithicPower.com 5/24/2016 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2016 MPS. All Rights Reserved. 12 MPQ3386- 50V, 6 STRINGS WHITE LED DRIVERS, AEC-Q100 QUALIFIED coefficients. For most applications, a 4.7μF capacitor is sufficient. Selecting the Output Capacitor Figure 5— Direct PWM Dimming with Negative Logic 4, DC input PWM dimming To apply DC input PWM dimming, apply an analog signal (range from 0.2V to 1.2V) at the PWMO pin to modulate the LED current directly. If the PWMO is applied with a DC voltage<0.2V, the PWM duty cycle will be 100%. If the PWMO pin is applied with a DC voltage>1.2V, the output will be 0% (See Figure 6). The capacitor on FSET pin set the frequency of internal triangle waveform. The output capacitor keeps the output voltage ripple small and ensures feedback loop stability. The output capacitor impedance should be low at the switching frequency. Ceramic capacitors with X7R dielectrics are recommended for their low ESR characteristics. For most applications, a 2.2μF ceramic capacitor will be sufficient. Layout Considerations Careful attention must be paid to the PCB board layout and components placement. Proper layout of the high frequency switching path is critical to prevent noise and electromagnetic interference problems. The loop of MPQ3386 SW to PGND pin (U1), output diode (D1), and output capacitor (C2) is flowing with high frequency pulse current. it must be as short as possible (See Figure 7). Figure 6—DC input PWM dimming Selecting the Inductor A 10μH (for 1.25MHz switching frequency) /22uH (for 625kHz switching frequency) inductor with a DC current rating of at least 40% higher than the maximum input current is recommended for most applications. For highest efficiency, the inductor’s DC resistance should be as small as possible. Figure 7—Layout Consideration The IC exposed pad is internally connected to GND pin, and all logic signals are refer to the GND. The PGND should be externally connected to GND and is recommended to keep away from the logic signals. Selecting the Input Capacitor The input capacitor reduces the surge current drawn from the input supply and the switching noise from the device. The input capacitor impedance at the switching frequency should be less than the input source impedance to prevent high frequency switching current from passing through the input. Ceramic capacitors with X5R or X7R dielectrics are highly recommended because of their low ESR and small temperature MPQ3386 Rev. 1.0 www.MonolithicPower.com 5/24/2016 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2016 MPS. All Rights Reserved. 13 MPQ3386- 50V, 6 STRINGS WHITE LED DRIVERS, AEC-Q100 QUALIFIED Design Example Below is a design example following the application guidelines for the specifications. Table 1: Design Example Parameter Input Voltage Symbol Value Units VIN 4.5 – 25 V 6 string parallel and 10 LEDs each string LEDs # LED Current The detailed application shematic is shown in Figure 8. The typical performance and sircuit waveforms have been shown in the Typical Perfomance Characteristics, please refer to the related Evaluation Board Datasheets. ILED 20/string mA Figure 8—Detail Application Schematic MPQ3386 Rev. 1.0 www.MonolithicPower.com 5/24/2016 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2016 MPS. All Rights Reserved. 14 MPQ3386- 50V, 6 STRINGS WHITE LED DRIVERS, AEC-Q100 QUALIFIED PACKAGE INFORMATION QFN24 (4mm x 4mm) 3.90 4.10 2.50 2.80 19 PIN 1 ID MARKING 18 3.90 4.10 PIN 1 ID INDEX AREA PIN 1 ID SEE DETAIL A 24 1 0.50 BSC 2.50 2.80 0.18 0.30 6 13 0.35 0.45 TOP VIEW 12 7 BOTTOM VIEW PIN 1 ID OPTION A 0.30x45º TYP. PIN 1 ID OPTION B R0.25 TYP. 0.80 1.00 0.20 REF 0.00 0.05 DETAIL A SIDE VIEW 3.90 NOTE: 2.70 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 CONFIRMS TO JEDEC MO-220, VARIATION VGGD. 5) DRAWING IS NOT TO SCALE. 0.70 0.25 0.50 RECOMMENDED LAND PATTERN NOTICE: The information in this document is subject to change without notice. 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. MP3386 Rev. 1.0 5/24/2016 www.MonolithicPower.com MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2016 MPS. All Rights Reserved. 15