INTERNAL USE ONLY / DO NOT DISTRIBUTE MPQ4425M High Efficiency 1.5A, 36V, 2.2MHz Synchronous Step-Down LED Driver AEC-Q100 Qualified DESCRIPTION FEATURES The MPQ4425M is a high-frequency, synchronous, rectified, step-down, switch-mode white LED driver with built-in power MOSFETs. It offers a very compact solution to achieve a 1.5A continuous output current with excellent load and line regulation over a wide input supply range. The MPQ4425M has synchronous mode operation to get high efficiency. Current-mode operation provides fast transient response and eases loop stabilization. Full protection features include over-current protection (OCP) and thermal shut down (TSD). The MPQ4425M requires a minimal number of readily-available standard external components, and is available in a space-saving QFN-13 (2.5mmx3mm) package. EMI Reduction Technique Wide 4V-to-36V Operating Input Range 85mΩ/50mΩ Low RDS(ON) Internal Power MOSFETs High-Efficiency Synchronous Mode Operation Default 2.2MHz Switching Frequency PWM Dimming (Min 100Hz Dimming Frequency) Forced CCM Mode 0.2V Reference Voltage Internal Soft-Start Fault Indication for LED Short, Open and Thermal Shutdown Over-Current Protection (OCP) with ValleyCurrent Detection Thermal Shutdown Available in a QFN-13 (2.5mmx3mm) Package CISPR25 Class 5 Compliant Available in a Wettable Flank Package Available in AEC-Q100 Grade-1 APPLICATIONS Automotive LED Lighting All MPS parts are lead-free, halogen free, and adhere to the RoHS directive. For MPS green status, please visit MPS website under Quality Assurance. “MPS” and “The Future of Analog IC Technology” are Registered Trademarks of Monolithic Power Systems, Inc. TYPICAL APPLICATION BST MPQ4425M EN/DIM SW LED+ FB LED- EN/DIM VCC /FAULT /FAULT PGND AGND MPQ4425M Rev.1.01 www.MonolithicPower.com 9/30/2017 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2017 MPS. All Rights Reserved. 1 INTERNAL USE ONLY / DO NOT DISTRIBUTE MPQ4425M – 36V, 1.5A SYNCHRONOUS STEP-DOWN LED DRIVER ORDERING INFORMATION Part Number* MPQ4425MGQB MPQ4425MGQB-AEC1 MPQ4425MGQBE-AEC1** Package QFN-13 (2.5mmx3mm) Top Marking See Below See Below * For Tape & Reel, add suffix –Z (e.g. MPQ4425MGQB–Z) ** Wettable Flank TOP MARKING (MPQ4425MGQB & MPQ4425MGQB-AEC1) ANP: product code; Y: year code; WW: week code: LLL: lot number; TOP MARKING (MPQ4425MGQBE-AEC1) AXT: product code; Y: year code; WW: week code: LLL: lot number; MPQ4425M Rev.1.01 www.MonolithicPower.com 9/30/2017 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2017 MPS. All Rights Reserved. 2 INTERNAL USE ONLY / DO NOT DISTRIBUTE MPQ4425M – 36V, 1.5A SYNCHRONOUS STEP-DOWN LED DRIVER PACKAGE REFERENCE TOP VIEW IN IN PGND PGND PGND BST 13 12 11 10 9 SW 8 AGND 7 VCC 1 2 3 4 5 6 NC /FAULT EN /DIM FB QFN-13 (2.5mmx3mm) ABSOLUTE MAXIMUM RATINGS (1) Thermal Resistance Supply voltage (VIN) ....................... -0.3V to 40V Switch voltage (VSW) ............. -0.3V to VIN + 0.3V BST voltage (VBST) ................................ VSW+6V (2) All other pins ................................ -0.3V to 6V (3) Continuous power dissipation (TA = +25°C) QFN-13 (2.5mmx3mm) ............................ 2.08W Junction temperature ............................... 150°C Lead temperature .................................... 260°C Storage temperature .................. -65°C to 150°C QFN-13 (2.5mmx3mm) .......... 60 ...... 13 ... °C/W Recommended Operating Conditions Supply voltage (VIN) ........................... 4V to 36V LED current (ILED) .............................. Up to 1.5A Operating junction temp. (TJ). .. -40°C to +125°C (4) θJA θJC Notes: 1) Absolute maximum ratings are rated under room temperature unless otherwise noted. Exceeding these ratings may damage the device. 2) About the details of EN/DIM pin’s ABS MAX rating, please refer to page 14, Enable control section. 3) 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. 4) Measured on JESD51-7, 4-layer PCB. MPQ4425M Rev.1.01 www.MonolithicPower.com 9/30/2017 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2017 MPS. All Rights Reserved. 3 INTERNAL USE ONLY / DO NOT DISTRIBUTE MPQ4425M – 36V, 1.5A SYNCHRONOUS STEP-DOWN LED DRIVER ELECTRICAL CHARACTERISTICS VIN = 12V, VEN = 2V, TJ=-40°C to +125°C, unless otherwise noted, typical values are at TJ=+25°C Parameter Symbol Supply current (shutdown) Supply current (quiescent) HS switch-on resistance LS switch-on resistance Switch leakage (5) Current limit Reverse current limit Oscillator frequency Maximum duty cycle (5) IIN IQ HSRDS-ON LSRDS-ON SW LKG ILIMIT VCC =5V VEN = 0V, VSW =12V Under 40% Duty Cycle 50 fSW DMAX Feedback voltage VFB IFB VEN_RISING VEN_FALLING VEN_HYS IEN EN turn-off delay VIN under-voltage lockout threshold-rising VIN under-voltage lockout threshold-falling VIN under-voltage lockout threshold-hysteresis Over voltage detection (/FAULT pulled low) Over voltage detection hysteresis /FAULT delay /FAULT sink current capability /FAULT leakage current VCC regulator VCC load regulation (5) Soft-start time Typ 12 0.6 85 τON_MIN EN input current Min VEN = 0V VEN = 2V, VFB = 1V, no switching VBST-SW =5V Minimum on time Feedback current EN rising threshold EN falling threshold EN threshold hysteresis Condition VFB=100mV VFB=100mV 2.5 1800 80 4 1.2 2200 87 Max Units 0.8 150 μA mA mΩ 105 1 5.5 2600 mΩ μA A A kHz % 46 200 200 30 1.45 1 450 208 216 100 1.8 1.3 VEN=2V 5 10 μA VEN=0 0.2 50 μA ms TJ=+25°C TJ=-40°C to +125°C VFB=250mV 192 184 1.1 0.7 ns mV nA V V mV ENtd-off 10 0 25 INUVVth 3.2 3.5 3.8 V 2.8 3.1 3.5 V INUVHYS 400 mV FTVth-Hi 140% VFB 20% VFB 10 μs FTTd VFT Sink 4mA IFT-LEAK VCC tSS ICC=0mA ICC=5mA ILED=1.5A, L=2.2uH, load=2 series LED, ILED from 10% to 90% (5) Thermal shutdown (5) Thermal hysteresis 4.6 150 4.9 1.5 0.4 V 100 nA 5.2 4 V % 0.9 ms 170 30 °C °C Note: 5) Derived from bench characterization. Not tested in production MPQ4425M Rev.1.01 www.MonolithicPower.com 9/30/2017 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2017 MPS. All Rights Reserved. 4 INTERNAL USE ONLY / DO NOT DISTRIBUTE MPQ4425M – 36V, 1.5A SYNCHRONOUS STEP-DOWN LED DRIVER PIN FUNCTIONS Package Pin # Name 1, 2 IN 3 NC 4 /FAULT 5 EN/DIM 6 FB 7 VCC 8 AGND 9 SW 10 BST 11, 12, 13 PGND Description Supply Voltage. The MPQ4425M operates from a 4V to 36V input rail. Requires CIN to decouple the input rail. Connect using a wide PCB trace. Do not connect. Fault indicator. Open Drain output, pulled to low when LED short, open or thermal shutdown happening. Enable/Dimming Control. Pull EN high to enable the MPQ4425M. Apply a 100Hz to 2kHz external clock to the EN/DIM pin for the PWM dimming. LED Current Feedback Input. Internal bias Supply. Decouple VCC with a 0.1μF-to-0.22μF capacitor. The capacitance should be no more than 0.22μF. Analog ground. Reference ground of the logic circuit. AGND is connected to PGND internally. There is no need to add external connections to PGND. Switch Output. Connect using a wide PCB trace. Bootstrap. Requires a capacitor connected between SW and BST pins to form a floating supply across the high-side switch driver. A 20Ω resistor placed between SW and BST cap is strongly recommended to reduce SW spike voltage. Power Ground. PGND is the reference ground of the power device and requires careful consideration during PCB layout. For best results, connect PGND with copper pours and vias. MPQ4425M Rev.1.01 www.MonolithicPower.com 9/30/2017 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2017 MPS. All Rights Reserved. 5 INTERNAL USE ONLY / DO NOT DISTRIBUTE MPQ4425M – 36V, 1.5A SYNCHRONOUS STEP-DOWN LED DRIVER TYPICAL CHARACTERISTICS MPQ4425M Rev.1.01 www.MonolithicPower.com 9/30/2017 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2017 MPS. All Rights Reserved. 6 INTERNAL USE ONLY / DO NOT DISTRIBUTE MPQ4425M – 36V, 1.5A SYNCHRONOUS STEP-DOWN LED DRIVER TYPICAL PERFORMANCE CHARACTERISTICS VIN = 12V, LOAD=2 series LED, L=2.2µH, FSW=2.2MHz, TA = +25°C, unless otherwise noted. MPQ4425M Rev.1.01 www.MonolithicPower.com 9/30/2017 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2017 MPS. All Rights Reserved. 7 INTERNAL USE ONLY / DO NOT DISTRIBUTE MPQ4425M – 36V, 1.5A SYNCHRONOUS STEP-DOWN LED DRIVER TYPICAL PERFORMANCE CHARACTERISTICS (continued) VIN = 12V, LOAD=2 series LED, ILED=1.5A, L=2.2µH, FSW=2.2MHz, with EMI filters, TA = +25°C, unless otherwise noted. (6) Amplitude (dBuV/m) 50 45 40 35 30 25 20 15 10 5 0 -5 -10 -15 Data Class 5 Peak Class 5 Avg 0.15 5.15 10.15 15.15 20.15 CISPR25 Class 5 Average Radiated Emissions (150kHz-30MHz) 50 45 40 35 30 25 20 15 10 5 0 -5 -10 -15 Amplitude (dBuV/m) CISPR25 Class 5 Peak Radiated Emissions (150kHz-30MHz) 25.15 Data Class 5 Peak Class 5 Avg 0.15 5.15 Amplitude (dBuV/m) Data Class 5 Peak Class 5 Avg 0 100 200 300 400 500 600 700 800 900 50 45 40 35 30 25 20 15 10 5 0 -5 -10 -15 100 200 400 500 600 Frequency (MHz) 400 500 600 700 800 900 1000 700 800 900 1000 CISPR25 Class 5 Average Radiated Emissions (Horizontal, 30MHz-1GHz) 50 45 40 35 30 25 20 15 10 5 0 -5 -10 -15 Amplitude (dBuV/m) Amplitude (dBuV/m) Data Class 5 Peak Class 5 Avg 300 300 Frequency (MHz) 50 45 40 35 30 25 20 15 10 5 0 -5 -10 -15 200 25.15 Data Class 5 Peak Class 5 Avg 0 1000 CISPR25 Class 5 Peak Radiated Emissions (Horizontal, 30MHz-1GHz) 100 20.15 CISPR25 Class 5 Average Radiated Emissions (Vertical, 30MHz-1GHz) Frequency (MHz) 0 15.15 Amplitude (dBuV/m) CISPR25 Class 5 Peak Radiated Emissions (Vertical, 30MHz-1GHz) 50 45 40 35 30 25 20 15 10 5 0 -5 -10 -15 10.15 Frequency (MHz) Frequency (MHz) Data Class 5 Peak Class 5 Avg 0 100 200 300 400 500 600 700 800 900 1000 Frequency (MHz) MPQ4425M Rev.1.01 www.MonolithicPower.com 9/30/2017 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2017 MPS. All Rights Reserved. 8 INTERNAL USE ONLY / DO NOT DISTRIBUTE MPQ4425M – 36V, 1.5A SYNCHRONOUS STEP-DOWN LED DRIVER TYPICAL PERFORMANCE CHARACTERISTICS (continued) VIN = 12V, LOAD=2 series LED, ILED=1.5A, L=2.2µH, FSW=2.2MHz, with EMI filters, TA = +25°C, unless otherwise noted. (6) CISPR25 Class5 Peak Conducted Emissions (150kHz-108MHz) CISPR25 Class5 Average Conducted Emissions (150kHz-108MHz) Note: 6) The EMC test results are based on application circuit with EMI filters as shown in Figure 9. MPQ4425M Rev.1.01 www.MonolithicPower.com 9/30/2017 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2017 MPS. All Rights Reserved. 9 INTERNAL USE ONLY / DO NOT DISTRIBUTE MPQ4425M – 36V, 1.5A SYNCHRONOUS STEP-DOWN LED DRIVER TYPICAL PERFORMANCE CHARACTERISTICS (continued) VIN = 12V, LOAD=2 series LED, L=2.2µH, FSW=2.2MHz, TA = +25°C, unless otherwise noted. MPQ4425M Rev.1.01 www.MonolithicPower.com 9/30/2017 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2017 MPS. All Rights Reserved. 10 INTERNAL USE ONLY / DO NOT DISTRIBUTE MPQ4425M – 36V, 1.5A SYNCHRONOUS STEP-DOWN LED DRIVER TYPICAL PERFORMANCE CHARACTERISTICS (continued) VIN = 12V, LOAD=2 series LED, L=2.2µH, FSW=2.2MHz, TA = +25°C, unless otherwise noted. MPQ4425M Rev.1.01 www.MonolithicPower.com 9/30/2017 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2017 MPS. All Rights Reserved. 11 INTERNAL USE ONLY / DO NOT DISTRIBUTE MPQ4425M – 36V, 1.5A SYNCHRONOUS STEP-DOWN LED DRIVER TYPICAL PERFORMANCE CHARACTERISTICS (continued) VIN = 12V, LOAD=2 series LED, L=2.2µH, FSW=2.2MHz, TA = +25°C, unless otherwise noted. MPQ4425M Rev.1.01 www.MonolithicPower.com 9/30/2017 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2017 MPS. All Rights Reserved. 12 INTERNAL USE ONLY / DO NOT DISTRIBUTE MPQ4425M – 36V, 1.5A SYNCHRONOUS STEP-DOWN LED DRIVER BLOCK DIAGRAM Figure 1: Functional Block Diagram MPQ4425M Rev.1.01 www.MonolithicPower.com 9/30/2017 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2017 MPS. All Rights Reserved. 13 INTERNAL USE ONLY / DO NOT DISTRIBUTE MPQ4425M – 36V, 1.5A SYNCHRONOUS STEP-DOWN LED DRIVER OPERATION The MPQ4425M is a high-frequency, synchronous rectified, step-down, switch-mode white LED driver with built-in power MOSFETs. It offers a very compact solution to achieve 1.5A continuous output current with excellent load and line regulation over a 4V to 36V input supply range. The MPQ4425M operates in a fixed-frequency, peak-current–control mode to regulate the output current. An internal clock initiates a PWM cycle. The integrated high-side power MOSFET turns on and remains on until its current reaches the value set by the COMP voltage (VCOMP). When the power switch is off, it remains off until the next clock cycle starts. If the current in the power MOSFET does not reach the current value set by VCOMP within 87% of one PWM period, the power MOSFET is forced off. Internal Regulator The 4.9V internal regulator power most of the internal circuitries. This regulator takes the VIN input and operates in the full VIN range: When VIN exceeds 4.9V, the output of the regulator is in full regulation; when VIN falls below 4.9V, the output decreases following VIN. A 0.1uF decoupling ceramic capacitor is needed at the pin. CCM Operation The MPQ4425M uses continuous conduction modulation (CCM) mode to ensure that the part works with fixed frequency from a no-load to a full-load range. The advantage of CCM is the controllable frequency and lower output ripple at light load. Frequency Foldback The MPQ4425M enters frequency foldback when the input voltage is higher than about 21V. The frequency decreases to half the nominal value and changes to 1.1MHz. Frequency foldback also occurs during soft start and short-circuit protection. Error Amplifier (EA) The error amplifier compares the FB pin voltage to the internal 0.2V reference (VREF) and outputs a current proportional to the difference between the two. This output current then charges or discharges the internal compensation network to form VCOMP, which controls the power MOSFET current. The optimized internal compensation network minimizes the external component counts and simplifies the control loop design. Enable Control (EN) EN/DIM is a control pin that turns the regulator on and off. Drive EN/DIM high to turn on the regulator, and drive it low to turn it off. An internal resistor from EN/DIM to GND allows EN/DIM to be floated to shut down the chip. EN/DIM is clamped internally using a 6.5V series Zener diode (see Figure 2). Connecting the EN/DIM input through a pull-up resistor to the voltage on VIN limits the EN input current to less than 100µA. For example, with 12V connected to VIN, RPULLUP ≥ (12V – 6.5V) ÷ 100µA = 55kΩ. Connecting EN/DIM to a voltage source directly without a pull-up resistor requires limiting the amplitude of the voltage source to ≤6V to prevent damage to the Zener diode. Figure 2: 6.5V Zener Diode Connection Drive EN/DIM low longer than 25ms will shutdown the IC. PWM Dimming Apply an external 100Hz to 2kHz PWM waveform to the EN/DIM pin for PWM dimming. The average LED current is proportional to PWM duty. The minimum amplitude of the PWM signal is 1.8V. If dimming signal is applied before the chip starts up, the on time of dimming signal must be longer than 2ms to make sure the soft start is finished, so output current can be built. If dimming signal is applied after soft start is finished, the above 2ms limit is not required. Under-Voltage Lockout (UVLO) Under-voltage lockout (UVLO) protects the chip from operating at an insufficient supply MPQ4425M Rev.1.01 www.MonolithicPower.com 9/30/2017 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2017 MPS. All Rights Reserved. 14 INTERNAL USE ONLY / DO NOT DISTRIBUTE MPQ4425M – 36V, 1.5A SYNCHRONOUS STEP-DOWN LED DRIVER voltage.The UVLO comparator monitors the output voltage of the internal regulator (VCC). drops below its lower threshold (typically 140°C), the chip is enabled again. Internal Soft Start (SS) Floating Driver and Bootstrap Charging The soft start (SS) prevents the converter output voltage from overshooting during startup. When the chip starts up, the internal circuitry generates a soft start voltage (VSS). When VSS is lower than the internal reference (VREF), VSS overrides VREF, so the error amplifier uses VSS as the reference. When VSS exceeds VREF, the error amplifier uses VREF as the reference. An external bootstrap capacitor powers the floating power MOSFET driver. This floating driver has its own UVLO protection, with a rising threshold of 2.2V and hysteresis of 150mV. The bootstrap capacitor voltage is regulated internally by VIN through D1, M1, C3, L1 and C4 (see Figure 3). If (VIN - VSW) exceeds 5V, U1 regulates M1 to maintain a 5V BST voltage across C4. As long as VIN is sufficiently higher than SW, the bootstrap capacitor can be charged. When the HS-FET is on, VIN≈VSW, so the bootstrap capacitor cannot be charged. When the LS-FET is on, VIN - VSW reaches its maximum for fast charging. When there is no inductor current, VSW = VOUT, so the difference between VIN and VOUT can charge the bootstrap capacitor. A 20Ω resistor placed between SW and BST cap is strongly recommended to reduce SW spike voltage. Fault Indicator The MPQ4425M has fault indication. The /FAULT pin is the open drain of a MOSFET. It should be connected to VCC or some other voltage source through a resistor (e.g. 100kΩ). /FAULT pin is pulled high at normal operation, and LED short, open or thermal shutdown will pulled down this pin to indicate a fault status. Over-Current Protection (OCP) The MPQ4425M has cycle-by-cycle peak current-limit protection with valley-current detection. The inductor current is monitored during the high-side MOSFET (HS-FET) onstate. If the inductor current exceeds the current-limit value set by the COMP high-clamp voltage, the HS-FET turns off immediately. Then the low-side MOSFET (LS-FET) turns on to discharge the energy, and the inductor current decreases. The HS-FET remains off unless the inductor valley current is lower than a certain current threshold (the valley current limit), even though the internal clock pulses high. If the inductor current does not drop below the valley current limit when the internal clock pulses high, the HS-FET misses the clock, and the switching frequency decreases to half the nominal value. Both the peak and valley current limits assist in keeping the inductor current from running away during an overload or short-circuit condition. Thermal Shutdown (TSD) Thermal shutdown prevents the chip from operating at exceedingly high temperatures. When the die temperature exceeds 170°C, the entire chip shuts down. When the temperature Figure 3: Internal Bootstrap Charging Circuit Start-up and Shutdown If both VIN and EN exceed their appropriate thresholds, the chip starts up. The reference block starts first, generating stable reference voltage and currents, and then the internal regulator is enabled. The regulator provides a stable supply for the remaining circuitries. Three events can shut down the chip: VIN low, EN low, and thermal shutdown. During the shutdown procedure, the signaling path is first blocked to avoid any fault triggering. VCOMP and the internal supply rail are then pulled down. The floating driver is not subject to this shutdown command. MPQ4425M Rev.1.01 www.MonolithicPower.com 9/30/2017 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2017 MPS. All Rights Reserved. 15 INTERNAL USE ONLY / DO NOT DISTRIBUTE MPQ4425M – 36V, 1.5A SYNCHRONOUS STEP-DOWN LED DRIVER APPLICATION INFORMATION Setting the Output Current The output current is set by the external resistor RFB (see Figure 4). Feedback reference voltage is 0.2V, ILED is then given by Equation (1): I LED 0.2V R FB Since CIN absorbs the input switching current, it requires an adequate ripple current rating. The RMS current in the input capacitor can be estimated with Equation (2): (1) ICIN ILED LED+ SW VOUT V (1 OUT ) VIN VIN (2) The worst case condition occurs at VIN = 2VOUT, shown in Equation (3): RT ICIN FB RFB LED- Figure 4: Feedback Network RT is used to set the loop bandwidth. Basically, lower RT, higher bandwidth. But high bandwidth may cause insufficient phase margin, resulting in loop unstable. So a proper value of RT is needed to make a trade-off between bandwidth and phase margin. Table 1 lists the recommended feedback resistor and RT values for common output with 1 or 2 series LED. Table 1: Resistor Selection for Common Output ILED (A) RFB (mΩ) RT (kΩ) 0.5 400(1%) 200 (1%) 1 200(1%) 150 (1%) 1.5 133(1%) 100 (1%) Selecting the Input Capacitor The input current to the step-down converter is discontinuous, therefore it requires a capacitor to supply the AC current to the converter while maintaining the DC input voltage. For the best performance, use low ESR capacitors. Ceramic capacitors with X5R or X7R dielectrics are highly recommended because of their low ESR and small temperature coefficients. For most application, use a 4.7µF to 10µF capacitor. And it is strongly recommended to use another lower value capacitor (e.g. 0.1µF) with small package size (0603) to absorb high frequency switching noise. Make sure place the small size capacitor as close to IN and GND pins as possible. ILED 2 (3) For simplification, choose an input capacitor with an RMS current rating greater than half of the maximum load current. The input capacitor can be electrolytic, tantalum, or ceramic. When using electrolytic or tantalum capacitors, add a small, high-quality ceramic capacitor (e.g. 0.1μF) as close to the IC as possible. When using ceramic capacitors, ensure that they have enough capacitance to provide a sufficient charge to prevent excessive voltage ripple at input. The input voltage ripple caused by capacitance can be estimated with Equation (4): VIN V V ILED OUT (1 OUT ) fSW CIN VIN VIN (4) Selecting the Output Capacitor The output capacitor maintains the DC output voltage. Use ceramic, tantalum, or low-ESR electrolytic capacitors. For best results, use low ESR capacitors to keep the output voltage ripple low. The output voltage ripple can be estimated with Equation (5): V V 1 VOUT OUT (1 OUT ) (RESR ) (5) fSW L VIN 8fSW COUT Where L is the inductor value and RESR is the equivalent series resistance (ESR) value of the output capacitor. For ceramic capacitors, the capacitance dominates the impedance at the switching frequency, and the capacitance causes the majority of the output voltage ripple. For MPQ4425M Rev.1.01 www.MonolithicPower.com 9/30/2017 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2017 MPS. All Rights Reserved. 16 INTERNAL USE ONLY / DO NOT DISTRIBUTE MPQ4425M – 36V, 1.5A SYNCHRONOUS STEP-DOWN LED DRIVER simplification, the output voltage ripple can be estimated with Equation (6): VOUT VOUT V (1 OUT ) (6) 8 fSW L COUT VIN 2 For tantalum or electrolytic capacitors, the ESR dominates the impedance at the switching frequency. For simplification, the output ripple can be approximated with Equation (7): VOUT V V OUT (1 OUT ) RESR fSW L VIN A 1µH to 10µH inductor with a DC current rating at least 25% higher than the maximum load current is recommended for most applications. For higher efficiency, choose an inductor with lower DC resistance. A larger value inductor results in less ripple current and a lower output ripple voltage. However, the larger value inductor also has a larger physical size, higher series resistance, and lower saturation current. A good rule for determining the inductor value is to allow the inductor ripple current to be approximately 30% of the maximum load current. The inductance value can be then be calculated with Equation (8): (8) Where ΔIL is the peak-to-peak inductor ripple current. Choose the inductor ripple current to be approximately 30% of the maximum load current. The maximum inductor peak current can be calculated with Equation (9): ILP ILED VOUT V (1 OUT ) 2fSW L VIN IN R UP EN/DIM 500k (7) Selecting the Inductor VOUT V (1 OUT ) fSW IL VIN VIN RDOWN The characteristics of the output capacitor also affect the stability of the regulation system. The MPQ4425M can be optimized for a wide range of capacitance and ESR values. L 3.5V while falling threshold is about 3.1V. For the application needs higher UVLO point, external resistor divider between IN and EN/DIM pins can be used to get higher equivalent UVLO threshold (see Figure 5). Figure 5: Adjustable UVLO using EN divider The UVLO threshold can be computed with Equation (10) and Equation (11): INUVRISING (1 R UP ) VEN_RISING 500k//R DOWN (10) INUVFALLING (1 RUP ) VEN_FALLING 500k//RDOWN (11) Where VEN_RISING=1.45V, VEN_FALLING=1V. When choosing RUP, make sure it is big enough to limit the current flows into EN/DIM pin lower than 100uA. BST Resistor and External BST Diode A 20ohm resistor in series with BST capacitor is recommended to reduce the SW spike voltage. Higher resistance is better for SW spike reduction, but will compromise the efficiency on the other hand. An external BST diode can enhance the efficiency of the regulator when the duty cycle is high (>65%). A power supply between 2.5V and 5V can be used to power the external bootstrap diode and VCC or VOUT is the good choice of this power supply in the circuit (see Figure 6). (9) VIN UVLO Setting MPQ4425M has internal fixed under-voltage lockout (UVLO) threshold: rising threshold is MPQ4425M Rev.1.01 www.MonolithicPower.com 9/30/2017 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2017 MPS. All Rights Reserved. 17 INTERNAL USE ONLY / DO NOT DISTRIBUTE MPQ4425M – 36V, 1.5A SYNCHRONOUS STEP-DOWN LED DRIVER Top Layer Figure 6: Optional External Bootstrap Diode to Enhance Efficiency The recommended external BST diode is IN4148, and the BST capacitor value is 0.1µF to 1μF. PCB Layout Guidelines Inner1 Layer Efficient PCB layout is critical for stable operation, especially for input capacitor placement. For best results, refer to Figure 7 and follow the guidelines below: (7) 1. Use a large ground plane to connect directly to PGND. If the bottom layer is a ground plane, add vias near PGND. 2. Ensure that the high-current paths at PGND and IN have short, direct, and wide traces. 3. Place the ceramic input capacitor, especially the small package (0603) input bypass capacitor as close to IN and PGND pins as possible to minimize high frequency noise. Keep the connection of the input capacitor and IN as short and wide as possible. 4. Place the VCC capacitor to VCC pin and GND pin as close as possible. 5. Route SW, BST away from sensitive analog areas such as FB. 6. Place the feedback resistors close to chip to ensure the trace which connects to FB pin as short as possible. 7. A four-layer layout is strongly recommended to achieve better thermal performance. Use multiple vias to connect the power planes to internal layers. Inner2 Layer Bottom Layer Figure 7: Recommended PCB Layout Note: 7) The recommended layout is based on Figure 8. MPQ4425M Rev.1.01 www.MonolithicPower.com 9/30/2017 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2017 MPS. All Rights Reserved. 18 INTERNAL USE ONLY / DO NOT DISTRIBUTE MPQ4425M – 36V, 1.5A SYNCHRONOUS STEP-DOWN LED DRIVER TYPICAL APPLICATION CIRCUIT 4V-36V VIN R1 1M GND C1A 10µF 1210 50V C1B 10µF 1210 50V 1, 2 C1C 0.1µF 0603 50V 5 EN/DIM 7 C2 0.1µF R7 100k 4 R2 10 BST IN 20 C3 0.1µF L1 MPQ4425M EN/DIM PGND VCC 9 SW 1.5A C4 10µF 16V 2.2µH LED+ 11,12,13 R3 6 /FAULT FB AGND LED- 100k R4 400m 1206 8 /FAULT U1 R6 R5 400m 400m 1206 1206 Figure 8: Io=1.5A Application Circuit VIN 4V-36V FB1 1206 VEMI GND CIN1 CIN2 1nF 10nF 50V 50V 0603 0603 CIN3 1uF 50V 1206 U1 L1 2.2uH CIN4 10uF 50V 1210 1, 2 CIN5 10uF 50V 1210 R1 1M 0603 C1A 10uF 1206 50V C1B 10uF 1206 50V C1C 0.1uF 0603 50V 5 EN/DIM 7 R7 100K 0603 4 C3 0.1uF/16V 0603 MPQ4425M EN/DIM VCC SW PGND R2 20 0603 9 L3 150nH L2 2.2uH 1.5A LED+ C4 10uF/16V 1210 C5 1nF/16V 0603 11,12,13 6 /FAULT FB AGND R3 200k 0603 8 /FAULT C2 0.1uF/16V 0603 BST IN 10 LEDR4 400m 1206 R5 R6 400m 400m 1206 1206 Figure 9: Io=1.5A Application Circuit with EMI Filters MPQ4425M Rev.1.01 www.MonolithicPower.com 9/30/2017 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2017 MPS. All Rights Reserved. 19 INTERNAL USE ONLY / DO NOT DISTRIBUTE MPQ4425M – 36V, 1.5A SYNCHRONOUS STEP-DOWN LED DRIVER PACKAGE INFORMATION QFN-13 (2.5mmx3mm) Non-Wettable Flank PIN 1 ID MARKING PIN 1 ID 0.15X45ºTYP PIN 1 ID INDEX AREA BOTTOM VIEW TOP VIEW SIDE VIEW 0.15X45º NOTE: 1) ALL DIMENSIONS ARE IN MILLIMETERS. 2) LEAD COPLANARITY SHALL BE 0.10 MILLIMETERS MAX. 3) JEDEC REFERENCE IS MO-220. 4) DRAWING IS NOT TO SCALE. RECOMMENDED LAND PATTERN MPQ4425M Rev.1.01 www.MonolithicPower.com 9/30/2017 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2017 MPS. All Rights Reserved. 20 INTERNAL USE ONLY / DO NOT DISTRIBUTE MPQ4425M – 36V, 1.5A SYNCHRONOUS STEP-DOWN LED DRIVER PACKAGE INFORMATION QFN-13 (2.5mmx3mm) Wettable Flank PIN 1 ID MARKING PIN 1 ID 0.15X45ºTYP PIN 1 ID INDEX AREA TOP VIEW BOTTOM VIEW SIDE VIEW SECTION A-A NOTE: 0.15X45º 1) THE LEAD SIDE IS WETTABLE. 2) ALL DIMENSIONS ARE IN MILLIMETERS. 3) LEAD COPLANARITY SHALL BE 0.08 MILLIMETERS MAX. 4) JEDEC REFERENCE IS MO-220. 5) DRAWING IS NOT TO SCALE. 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. MPQ4425M Rev. 1.01 www.MonolithicPower.com 9/30/2017 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2017 MPS. All Rights Reserved. 21