MPQ4425AGQB-AEC1-Z

MPQ4425A High Efficiency 1.5A, 36V, 2.2MHz, Synchronous Step-Down LED Driver, AEC-Q100 Qualified DESCRIPTION FEATURES The MPQ4425A 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 of continuous output current with excellent load and line regulation over a wide input supply range. The MPQ4425A 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 shutdown (TSD).     The MPQ4425A requires a minimal number of readily available, standard external components, and is available in a space-saving QFN-13 (2.5mmx3mm) package.          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 Valley Current Detection Thermal Shutdown CISPR25 Class 5 Compliant Available in a QFN-13 (2.5mmx3mm) Package 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, visit the MPS website under Quality Assurance. “MPS”, the MPS logo, and “Simple, Easy Solutions” are registered trademarks of Monolithic Power Systems, Inc. or its subsidiaries. TYPICAL APPLICATION BST MPQ4425A EN/DIM SW LED+ FB LED- EN/DIM VCC /FAULT /FAULT PGND AGND MPQ4425A Rev. 1.0 www.MonolithicPower.com 7/24/2019 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2019 MPS. All Rights Reserved. 1 MPQ4425A – 36V, 1.5A, SYNCHRONOUS STEP-DOWN LED DRIVER ORDERING INFORMATION Part Number * MPQ4425AGQB MPQ4425AGQB-AEC1 MPQ4425AGQBE-AEC1** Package Top Marking QFN-13 (2.5mmx3mm) See Below QFN-13 (2.5mmx3mm) See Below * For Tape & Reel, add suffix –Z (e.g. MPQ4425AGQB–Z). ** Wettable flank. TOP MARKING (MPQ4425AGQB&MPQ4425AGQB-AEC1) BDU: Product code of MPQ4425AGQB&MPQ4425AGQB-AEC1 Y: Year code WW : Week code LLL: Lot number TOP MARKING (MPQ4425AGQBE-AEC1) BDX: Product code of MPQ4425AGQBE-AEC1 Y: Year code WW : Week code LLL: Lot number MPQ4425A Rev. 1.0 www.MonolithicPower.com 7/24/2019 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2019 MPS. All Rights Reserved. 2 MPQ4425A – 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) MPQ4425A Rev. 1.0 www.MonolithicPower.com 7/24/2019 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2019 MPS. All Rights Reserved. 3 MPQ4425A – 36V, 1.5A, SYNCHRONOUS STEP-DOWN LED DRIVER PIN FUNCTIONS Pin # Name Description Supply voltage. The MPQ4425A operates from a 4V to 36V input rail. Requires CIN to decouple the input rail. Connect using a wide PCB trace. Do not connect. 1, 2 IN 3 NC 4 /FAULT Fault indicator. Open-drain output. This pin is pulled low when an LED short, open, or thermal shutdown occurs. 5 EN/DIM Enable/dimming control. Pull EN high to enable the MPQ4425A. Apply a 100Hz to 2kHz external clock to the EN/DIM pin for the PWM dimming. 6 FB 7 VCC 8 AGND 9 SW 10 BST 11, 12, 13 PGND LED current feedback input. Internal bias supply. Decouple VCC with a 0.1μF to 0.22μF capacitor. The capacitance should not exceed 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 the SW and BST pins to form a floating supply across the high-side switch driver. A 20Ω resistor placed between SW and the BST capacitor 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. θJA θJC ABSOLUTE MAXIMUM RATINGS (1) Thermal Resistance (4) Supply voltage (VIN) ..................... -0.3V to +40V Switch voltage (VSW) ............. -0.3V to VIN + 0.3V BST voltage (VBST) ...............................VSW + 6V All other pins ...............................-0.3V to +6V (2) Continuous power dissipation (TA = 25°C) (3) 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 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, refer to the Enable Control section on page 12. 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. MPQ4425A Rev. 1.0 www.MonolithicPower.com 7/24/2019 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2019 MPS. All Rights Reserved. 4 MPQ4425A – 36V, 1.5A, SYNCHRONOUS STEP-DOWN LED DRIVER ELECTRICAL CHARACTERISTICS VIN = 12V, VEN = 2V, TJ = -40°C to +125°C, typical values are at TJ = 25°C, unless otherwise noted. Parameter Symbol Supply current (shutdown) Supply current (quiescent) HS switch on resistance LS switch on resistance Switch leakage Current limit (5) Reverse current limit Oscillator frequency Maximum duty cycle IIN IQ Condition Min HSRDS-ON VEN = 0V VEN = 2V, VFB = 1V, no switching VBST-SW = 5V 12 0.6 85 LSRDS-ON SW LKG ILIMIT VCC = 5V VEN = 0V, VSW = 12V Under 40% duty cycle 50 fSW DMAX VFB = 100mV VFB = 100mV 2.5 1800 80 τON_MIN Minimum on time (5) Typ Feedback voltage VFB Feedback current IFB TJ = 25°C TJ = -40°C to +125°C VFB = 250mV 192 184 4 1.2 2200 87 Max Units 0.8 150 μA mA mΩ 105 1 5.5 2600 46 200 200 30 208 216 100 mΩ μA A A kHz % ns mV nA EN rising threshold VEN_RISING 1.1 1.45 1.8 V EN falling threshold EN threshold hysteresis VEN_FALLING VEN_HYS 0.7 1 450 1.3 V mV 10 0.2 50 μA μA ms EN input current IEN VEN = 2V VEN = 0 EN turn-off delay ENtd-off 10 5 0 25 VIN under-voltage lockout rising threshold INUVVth 3.2 3.5 3.8 V 2.8 3.1 3.5 V VIN under-voltage lockout falling threshold VIN under-voltage lockout hysteresis threshold Over-voltage detection (/FAULT pulled low) INUVHYS 400 mV FTVth-Hi 140% VFB 20% VFB 10 μs Over-voltage detection hysteresis /FAULT delay FTTd /FAULT sink current capability VFT /FAULT leakage current VCC regulator VCC load regulation tSS ICC = 0mA 4.6 ICC = 5mA ILED = 1.5A, L = 2.2µH, load = 2 series LED, ILED from 10% to 90% Thermal shutdown (5) Thermal hysteresis 0.4 V 100 nA 4.9 5.2 V 1.5 4 % IFT-LEAK VCC Soft-start time (5) Sink 4mA (5) 150 0.9 ms 170 °C 30 °C Note: 5) Not tested in production. Guaranteed by design and characterization. MPQ4425A Rev. 1.0 www.MonolithicPower.com 7/24/2019 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2019 MPS. All Rights Reserved. 5 MPQ4425A – 36V, 1.5A, SYNCHRONOUS STEP-DOWN LED DRIVER TYPICAL CHARACTERISTICS MPQ4425A Rev. 1.0 www.MonolithicPower.com 7/24/2019 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2019 MPS. All Rights Reserved. 6 MPQ4425A – 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. MPQ4425A Rev. 1.0 www.MonolithicPower.com 7/24/2019 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2019 MPS. All Rights Reserved. 7 MPQ4425A – 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. MPQ4425A Rev. 1.0 www.MonolithicPower.com 7/24/2019 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2019 MPS. All Rights Reserved. 8 MPQ4425A – 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. MPQ4425A Rev. 1.0 www.MonolithicPower.com 7/24/2019 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2019 MPS. All Rights Reserved. 9 MPQ4425A – 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. MPQ4425A Rev. 1.0 www.MonolithicPower.com 7/24/2019 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2019 MPS. All Rights Reserved. 10 MPQ4425A – 36V, 1.5A, SYNCHRONOUS STEP-DOWN LED DRIVER FUNCTIONAL BLOCK DIAGRAM IN VCC VCC RSEN Current-Se ns e Amplif er Regula tor Boot strap Regula tor Os cillator HS Drive r Com parato r On Time Con tr ol Logic Contro l 1 pF EN/DIM Refe re nc e 6.5V 56pF 300k BST SW VCC Current Lim it Comparator LS Drive r 400k FB Error Amplifier AGND /FAULT PGND Figure 1: Functional Block Diagram MPQ4425A Rev. 1.0 www.MonolithicPower.com 7/24/2019 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2019 MPS. All Rights Reserved. 11 MPQ4425A – 36V, 1.5A, SYNCHRONOUS STEP-DOWN LED DRIVER OPERATION The MPQ4425A 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 of continuous output current with excellent load and line regulation over a 4V to 36V input supply range. 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. The MPQ4425A operates in 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. 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. Drive it low to turn the regulator off. An internal 400kΩ resistor from EN/DIM to GND allows EN/DIM to be floated to shut down the chip. Internal Regulator The 4.9V internal regulator powers most of the internal circuitries. This regulator takes VIN 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 0.1µF ceramic decoupling capacitor is needed at VCC. CCM Operation The MPQ4425A uses continuous conduction mode (CCM) to ensure that the part works with fixed frequency across a no-load to full-load range. The advantage of CCM is the controllable frequency and lower output ripple at light load. Frequency Foldback The MPQ4425A enters frequency foldback when the input voltage is greater than about 21V. Then, 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 EN/DIM is clamped internally using a 6.5V series Zener diode (see Figure 2). Connect the EN/DIM input to the voltage on VIN through a pull-up resistor to limit 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 Driving EN/DIM low for longer than 25ms will shut down the IC. PWM Dimming Apply an external 100Hz to 2kHz PWM waveform to EN/DIM for PWM dimming. The average LED current is proportional to the PWM duty. The minimum amplitude of the PWM signal is 1.8V. If the dimming signal is applied before the chip starts up, the dimming signal’s on time must be longer than 2ms to ensure soft start finishes, so the output current can be built. If the dimming signal is applied after soft start finishes, this 2ms limit is not required. MPQ4425A Rev. 1.0 www.MonolithicPower.com 7/24/2019 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2019 MPS. All Rights Reserved. 12 MPQ4425A – 36V, 1.5A, SYNCHRONOUS STEP-DOWN LED DRIVER Under-Voltage Lockout (UVLO) Under-voltage lockout (UVLO) protects the chip from operating at an insufficient supply voltage. The UVLO comparator monitors the output voltage of the internal regulator (VCC). Internal Soft Start (SS) Soft start (SS) prevents the converter output voltage from overshooting during start-up. When the chip starts up, the internal circuitry generates a soft-start voltage (VSS). When VSS is below 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. Fault Indicator The MPQ4425A 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 is pulled high at normal operation. An LED short, open, or thermal shutdown will pull down this pin to indicate a fault status. Over-Current Protection (OCP) The MPQ4425A has cycle-by-cycle peak current limit protection with valley-current detection. The inductor current is monitored during the highside MOSFET (HS-FET) on-state. 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 (LSFET) turns on to discharge the energy, and the inductor current decreases. The HS-FET remains off unless the inductor valley current is below 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 drops below its lower threshold (typically 140°C), the chip is enabled again. Floating Driver and Bootstrap Charging 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 the BST capacitor is strongly recommended to reduce SW spike voltage. 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 a stable reference voltage and current, 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. MPQ4425A Rev. 1.0 www.MonolithicPower.com 7/24/2019 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2019 MPS. All Rights Reserved. 13 MPQ4425A – 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). The feedback reference voltage is 0.2V, and ILED is calculated with 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): ICIN  ILED  (1) LED+ SW VOUT V  (1  OUT ) VIN VIN The worst-case scenario occurs at VIN = 2VOUT, calculated with Equation (3): ICIN  RT FB RFB LED- Figure 4: Feedback Network RT is used to set the loop bandwidth. The lower the value of RT, the higher the bandwidth. High bandwidth may cause insufficient phase margin, resulting in loop instability. Therefore, a proper RT value is needed to make a tradeoff between the bandwidth and phase margin. Table 1 lists recommended feedback resistor and RT values for common outputs with 1 or 2 series LED. Table 1: Resistor Values for Common Outputs 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 step-down converter has a discontinuous input current, and 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 applications, use a 4.7µF to 10µF capacitor. It is strongly recommended to use another, lower-value capacitor (e.g. 0.1µF) with a small package size (0603) to absorb highfrequency switching noise. Be sure to place the small capacitor as close to the IN and GND pins as possible. (2) 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 the 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 lowESR capacitors to keep the output voltage ripple low. The output voltage ripple can be estimated with Equation (5): VOUT  VOUT V 1  (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 causes the majority of the output voltage ripple. For simplification, the output voltage ripple can be estimated with Equation (6): MPQ4425A Rev. 1.0 www.MonolithicPower.com 7/24/2019 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2019 MPS. All Rights Reserved. 14 MPQ4425A – 36V, 1.5A, SYNCHRONOUS STEP-DOWN LED DRIVER VOUT VOUT V   (1  OUT ) (6) 2 8  fSW  L  COUT VIN For tantalum or electrolytic capacitors, the ESR dominates the impedance at the switching frequency. For simplification, the output ripple can be estimated with Equation (7): VOUT  VOUT V  (1  OUT )  RESR fSW  L VIN (7) The characteristics of the output capacitor also affect the stability of the regulation system. The MPQ4425A can be optimized for a wide range of capacitance and ESR values. Selecting the Inductor 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 a 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): L VOUT V  (1  OUT ) fSW  IL VIN (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 peak inductor current can be calculated with Equation (9): ILP  ILED  VOUT V  (1  OUT ) 2fSW  L VIN UVLO point, an external resistor divider between the IN and EN/DIM pins can be used to get a higher equivalent UVLO threshold (see Figure 5). VIN IN RUP EN/DIM RDOWN 400kΩ Figure 5: Adjustable UVLO Using EN Divider The UVLO threshold can be calculated with Equation (10) and Equation (11): INUVRISING  (1  RUP )  VEN_RISING 400k//RDOWN (10) INUVFALLING  (1  RUP )  VEN_FALLING 400k//RDOWN (11) Where VEN_RISING = 1.45V, VEN_FALLING = 1V. When choosing RUP, ensure it is big enough to limit the current flows into the EN/DIM pin below 100µA. BST Resistor and External BST Diode A 20Ω resistor in series with the BST capacitor is recommended to reduce the SW spike voltage. A higher resistance leads to better SW spike reduction, but decreases efficiency. 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. VCC or VOUT are the best choices for power supply in the circuit (see Figure 6). (9) VIN UVLO Setting The MPQ4425A has an internal, fixed undervoltage lockout (UVLO) threshold. The rising threshold is 3.5V, and the falling threshold is about 3.1V. If the application requires a higher MPQ4425A Rev. 1.0 www.MonolithicPower.com 7/24/2019 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2019 MPS. All Rights Reserved. 15 MPQ4425A – 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 the IN4148, and the recommended BST capacitor value is 0.1µF to 1μF. PCB Layout Guidelines (6) Efficient PCB layout, especially input capacitor placement, is critical for stable operation. A 4layer layout is strongly recommended to achieve better thermal performance. For best results, refer to Figure 7 and follow the guidelines below: 1. Inner 1 Layer 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 as possible to minimize high-frequency noise. 4. Keep the connection between the input capacitor and IN as short and wide as possible. 5. Place the VCC capacitor to the VCC and GND pins as close as possible. 6. Route SW and BST away from sensitive analog areas, such as FB. 7. Place the feedback resistors close to the chip to ensure the trace that connects to FB is as short as possible. 8. Use multiple vias to connect the power planes to internal layers. Inner 2 Layer Bottom Layer Figure 7: Recommended PCB Layout Note: 6) The recommended layout is based on Figure 8. MPQ4425A Rev. 1.0 www.MonolithicPower.com 7/24/2019 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2019 MPS. All Rights Reserved. 16 MPQ4425A – 36V, 1.5A, SYNCHRONOUS STEP-DOWN LED DRIVER TYPICAL APPLICATION CIRCUIT VIN U1 4V to 36V R1 1M GND C1A 10μF 1210 50V C1B 10μF 1210 50V 1, 2 C1C 0.1μF 0603 50V 5 EN/DIM 7 R2 10 BST IN 20 C3 0.1μF L1 MPQ4425A EN/DIM VCC 9 SW PGND 1.5A C4 10μF 16V 2.2μH LED+ 11,12,13 C2 0.1μF R7 100k R3 4 /FAULT FB 6 100k AGND LED- 8 /FAULT R4 R5 R6 400m 400m 400m 1206 1206 1206 Figure 8: IO = 1.5A Application Circuit VIN 4V to 36V FB1 1206 VEMI GND CIN1 1nF 50V 0603 CIN2 10nF 50V 0603 CIN3 1µF 50V 1206 U1 L1 2.2µH CIN4 10µF 50V 1210 1, 2 CIN5 10µF 50V 1210 R1 1M 0603 C1A 10µF 1206 50V C1B 10µF 1206 50V C1C 0.1µF 0603 50V 5 EN/DIM 7 R7 100k 0603 10 C3 0.1µF/16V 0603 MPQ4425A EN/DIM VCC SW PGND 9 L2 2.2µH L3 150nH 1.5A LED+ C4 10µF/16V 1210 C5 1nF/16V 0603 11,12,13 4 /FAULT FB 6 AGND 8 /FAULT C2 0.1µF/16V 0603 BST IN R2 20 0603 R3 200k 0603 R4 400m 1206 R5 400m 1206 LEDR6 400m 1206 Figure 9: IO = 1.5A Application Circuit with EMI Filters MPQ4425A Rev. 1.0 www.MonolithicPower.com 7/24/2019 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2019 MPS. All Rights Reserved. 17 MPQ4425A – 36V, 1.5A, SYNCHRONOUS STEP-DOWN LED DRIVER PACKAGE INFORMATION QFN-13 (2.5mmx3mm) Non-Wettable Flank PIN 1 ID MARKING PIN 1 ID 0.15X45º TYP 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 MPQ4425A Rev. 1.0 www.MonolithicPower.com 7/24/2019 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2019 MPS. All Rights Reserved. 18 MPQ4425A – 36V, 1.5A, SYNCHRONOUS STEP-DOWN LED DRIVER PACKAGE INFORMATION QFN-13 (2.5mmx3mm) Wettable Flank PIN 1 ID MARKING PIN 1 ID 0.15X45º TYP 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. MPQ4425A Rev. 1.0 www.MonolithicPower.com 7/24/2019 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2019 MPS. All Rights Reserved. 19