MPM3515 36V, 1.5A Module, Synchronous, Step-Down Converter with an Integrated Inductor AEC-Q100 Qualified The Future of Analog IC Technology DESCRIPTION FEATURES The MPM3515 is a synchronous, rectified, stepdown converter with built-in power MOSFETs, inductors, and capacitors. The MPM3515 offers a very compact solution and requires only four external components to achieve 1.5A of continuous output current with excellent load and line regulation over a wide input supply range. The MPM3515 operates with a 2.2MHz switching frequency to achieve a fast load transient response. Full protection features include over-current protection (OCP) and thermal shutdown. The MPM3515 eliminates design and manufacturing risks while improving the time to market dramatically. The MPM3515 is available in a space-saving QFN-17 (3mmx5mmx1.6mm) package. Complete Switch-Mode Power Supply Wide 4V to 36V Operating Input Range 1.5A Continuous Load Current 90mΩ/50mΩ Low RDS(ON) Internal Power MOSFETs Fixed 2.2MHz Switching Frequency Frequency Foldback at a High Input Voltage 450kHz to 2.2MHz Frequency Sync Forced Continuous Conduction Mode (CCM ) Power Good (PG) Indicator Over-Current Protection (OCP) with ValleyCurrent Detection and Hiccup Thermal Shutdown Output Adjustable from 0.8V Available in a QFN-17 (3mmx5mmx1.6mm) Package CISPR25 Class 5 Compliant Available in a Wettable Flank Package Available in AEC-Q100 Grade 1 APPLICATIONS Industrial Controls Automotive Medical and Imaging Equipment Telecom Applications Distributed Power Systems All MPS parts are lead-free, halogen-free, and adhere to the RoHS directive. For MPS green status, please visit the MPS website under Quality Assurance. “MPS” and “The Future of Analog IC Technology” are registered trademarks of Monolithic Power Systems, Inc. TYPICAL APPLICATION VIN 4V-36V VOUT 3.3V/1.5A IN C1 4.7µF EN/ SYNC MPM3515 OUT R1 75kΩ EN/SYNC C2 47µF FB R2 24.3kΩ PGND AGND MPM3515 Rev. 1.0 www.MonolithicPower.com 8/22/2016 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2016 MPS. All Rights Reserved. 1 MPM3515 – 36V, 1.5A, SYNCHRONOUS, STEP-DOWN, MODULE CONVERTER ORDERING INFORMATION Part Number MPM3515GQV* MPM3515GQV-AEC1** MPM3515GQVE-AEC1*** Package Top Marking QFN-17 (3mmx5mmx1.6mm) See Below * For Tape & Reel, add suffix –Z (e.g. MPM3515GQV–Z) ** Under qualification. *** Under qualification, wettable flank. TOP MARKING (MPM3515GQV & MPM3515GQV-AEC1) MP: MPS prefix Y: Year code W: Week code 3515: First four digits of the part number LLL: Lot number M: Module TOP MARKING (MPM3515GQVE-AEC1) MP: MPS prefix: Y: Year code; W: Week code: 3515: First four digits of the part number; LLL: Lot number; E: Wettable lead flank M: Module MPM3515 Rev. 1.0 www.MonolithicPower.com 8/22/2016 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2016 MPS. All Rights Reserved. 2 MPM3515 – 36V, 1.5A, SYNCHRONOUS, STEP-DOWN, MODULE CONVERTER PACKAGE REFERENCE TOP VIEW QFN-17 (3mmx5mmx1.6mm) ABSOLUTE MAXIMUM RATINGS (1) Thermal Resistance VIN ................................................... -0.3V to 40V VSW, VOUT............................... -0.3V to VIN + 0.3V VBST ...................................................... VSW + 6V (2) All other pins ................................ -0.3V to 6V (3) Continuous power dissipation (TA = +25°C) ................................................................... 2.7W Junction temperature ................................150°C Lead temperature .....................................260°C Storage temperature .................. -65°C to 150°C QFN-17 (3mmx5mmx1.6mm)...46 ..... 10... °C/W Recommended Operating Conditions Supply voltage (VIN) ............................ 4V to 36V Output voltage (VOUT) ................ 0.8V to VIN*DMax Operating junction temp. (TJ). .. -40°C to +125°C (4) θJA θJC NOTES: 1) Exceeding these ratings may damage the device. 2) For details on EN/SYNC’s ABS MAX rating, please refer to the EN/SYNC section on page 13. 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 produces an excessive die temperature, causing the regulator to go into thermal shutdown. Internal thermal shutdown circuitry protects the device from permanent damage. 4) Measured on JESD51-7, 4-layer PCB. MPM3515 Rev. 1.0 www.MonolithicPower.com 8/22/2016 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2016 MPS. All Rights Reserved. 3 MPM3515 – 36V, 1.5A, SYNCHRONOUS, STEP-DOWN, MODULE CONVERTER ELECTRICAL CHARACTERISTICS VIN = 12V, TJ = -40°C to +125°C, unless otherwise noted. Typical values are at TJ = +25°C. Parameter Supply (shutdown) Symbol current IIN Supply current (quiescent) Iq HS switch on resistance LS switch on resistance Inductor DC resistance Switch leakage Current limit (5) Low-side valley current limit Reverse current limit Oscillator frequency Foldback frequency during soft start (5) Maximum duty cycle Minimum on time (5) HSRDS(ON) LSRDS(ON) LDCR SWLKG ILIMIT Min Typ Max Units 8 μA 0.6 0.8 mA 90 50 75 155 105 VEN/SYNC = 0V VEN/SYNC = 2V , VFB = 1V, no switching VBST-SW = 5V VCC = 5V VEN/SYNC = 0V, VSW = 12V 20% duty cycle 2.4 4.0 1 5.5 mΩ mΩ mΩ μA A 1.5 2.5 3.5 A 1800 1.2 2200 2600 A kHz fSW VFB = 700mV fFB VFB = 200mV 0.2 fSW DMAX TON MIN VFB = 700mV 85 40 807 807 10 819 824 50 % ns mV mV nA Feedback voltage VFB Feedback current EN/SYNC rising threshold EN/SYNC falling threshold EN/SYNC input current IFB EN/SYNC turn off delay EN/SYNC frequency range VIN under-voltage lockout threshold rising VIN under-voltage lockout threshold hysteresis PG rising threshold PG falling threshold PG rising delay PG falling delay PG sink current capability PG leakage current VCC regulator VCC load regulation Soft-start time Thermal shutdown (5) Thermal hysteresis (5) Condition TA = 25°C TA = -40°C to 125°C VFB = 820mV 795 790 VEN_RISING 1.2 1.45 1.7 V VEN_FALLING 0.8 1 1.3 V 5 10 μA IEN VEN/SYNC = 2V ENTd_off 3 450 INUVVth 3 tSS 2200 kHz 3.8 V 330 INUVHYS PGVth Hi PGVth Lo PGTD RISING PGTD FALLING VPG IPG LEAK VCC 3.5 μs 0.83 0.78 40 30 0.88 0.83 90 55 4.5 4.8 1.5 1.7 170 20 Sink 4mA ICC = 5mA VOUT from 10% to 90% 0.5 mV 0.93 0.88 160 95 0.4 100 5.1 4 3 VFB VFB μs μs V nA V % ms °C °C NOTE: 5) Not tested in production and guaranteed by over-temperature correlation. MPM3515 Rev. 1.0 www.MonolithicPower.com 8/22/2016 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2016 MPS. All Rights Reserved. 4 MPM3515 – 36V, 1.5A, SYNCHRONOUS, STEP-DOWN, MODULE CONVERTER TYPICAL PERFORMANCE CHARACTERISTICS MPM3515 Rev. 1.0 www.MonolithicPower.com 8/22/2016 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2016 MPS. All Rights Reserved. 5 MPM3515 – 36V, 1.5A, SYNCHRONOUS, STEP-DOWN, MODULE CONVERTER TYPICAL PERFORMANCE CHARACTERISTICS (CONTINUED) MPM3515 Rev. 1.0 www.MonolithicPower.com 8/22/2016 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2016 MPS. All Rights Reserved. 6 MPM3515 – 36V, 1.5A, SYNCHRONOUS, STEP-DOWN, MODULE CONVERTER TYPICAL PERFORMANCE CHARACTERISTICS (CONTINUED) MPM3515 Rev. 1.0 www.MonolithicPower.com 8/22/2016 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2016 MPS. All Rights Reserved. 7 MPM3515 – 36V, 1.5A, SYNCHRONOUS, STEP-DOWN, MODULE CONVERTER TYPICAL PERFORMANCE CHARACTERISTICS (CONTINUED) VIN = 12V, Vout = 3.3V, IOUT = 1.5A, L = 2.2μH, FSW = 2.2MHz, with EMI filters, TA = +25°C, unless otherwise noted.(6) CISPR25 Class 5 Peak Radiated Emissions (150kHz - 30MHz) 0.15 5.15 10.15 15.15 20.15 Frequency (MHz) Amplitude (dBuV/m) 100 200 300 400 500 600 700 800 0 400 500 600 700 800 900 100 200 300 400 500 600 Frequency (MHz) 700 1000 50 45 40 35 30 25 20 15 10 5 0 -5 -10 -15 Amplitude (dBuV/m) Amplitude (dBuV/m) 300 Frequency (MHz) 25.15 800 900 1000 CISPR25 Class 5 Average Radiated Emissions (Horizontal, 30MHz - 1GHz) Class 5 Avg 200 20.15 Data Class 5 Peak Class 5 Avg 900 1000 Data Class 5 Peak 100 15.15 50 45 40 35 30 25 20 15 10 5 0 -5 -10 -15 CISPR25 Class 5 Peak Radiated Emissions (Horizontal, 30MHz - 1GHz) 0 10.15 CISPR25 Class 5 Average Radiated Emissions (Vertical, 30MHz - 1GHz) Frequency (MHz) 50 45 40 35 30 25 20 15 10 5 0 -5 -10 -15 5.15 Frequency (MHz) Data Class 5 Peak Class 5 Avg 0 Data Class 5 Peak Class 5 Avg 0.15 25.15 CISPR25 Class 5 Peak Radiated Emissions (Vertical, 30MHz - 1GHz) 50 45 40 35 30 25 20 15 10 5 0 -5 -10 -15 Amplitude (dBuV/m) Data Class 5 Peak Class 5 Avg 50 45 40 35 30 25 20 15 10 5 0 -5 -10 -15 Amplitude (dBuV/m) Amplitude (dBuV/m) 50 45 40 35 30 25 20 15 10 5 0 -5 -10 -15 CISPR25 Class 5 Average Radiated Emissions (150kHz - 30MHz) Data Class 5 Peak Class 5 Avg 0 100 200 300 400 500 600 700 Frequency (MHz) 800 900 1000 NOTE: 6) The EMC test results are based on the application circuit with EMI filters (see Figure 12). MPM3515 Rev. 1.0 www.MonolithicPower.com 8/22/2016 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2016 MPS. All Rights Reserved. 8 MPM3515 – 36V, 1.5A, SYNCHRONOUS, STEP-DOWN, MODULE CONVERTER TYPICAL PERFORMANCE CHARACTERISTICS (CONTINUED) VOUT 1V/div. VIN 5V/div. VOUT 1V/div. PG 5V/div. VIN 5V/div. SW 5V/div. IL 500mA/div. VOUT 2V/div. PG 5V/div. VIN 5V/div. SW 5V/div. IL 1A/div. VEN 5V/div. VOUT 1V/div. PG 5V/div. SW 5V/div. IL 1A/div. VOUT 1V/div. PG 5V/div. VIN 5V/div. SW 5V/div. PG 5V/div. SW 5V/div. IL 1A/div. IL 1A/div. VOUT 1V/div. PG 5V/div. VEN 5V/div. VOUT 1V/div. PG 5V/div. VEN 5V/div. SW 10V/div. SW 5V/div. IL 1A/div. IL 1A/div. VOUT 2V/div. VOUT 1V/div. PG 5V/div. VEN 5V/div. SW 10V/div. IL 1A/div. PG 5V/div. VIN 5V/div. SW 10V/div. IL 2A/div. MPM3515 Rev. 1.0 www.MonolithicPower.com 8/22/2016 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2016 MPS. All Rights Reserved. 9 MPM3515 – 36V, 1.5A, SYNCHRONOUS, STEP-DOWN, MODULE CONVERTER TYPICAL PERFORMANCE CHARACTERISTICS (CONTINUED) MPM3515 Rev. 1.0 www.MonolithicPower.com 8/22/2016 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2016 MPS. All Rights Reserved. 10 MPM3515 – 36V, 1.5A, SYNCHRONOUS, STEP-DOWN, MODULE CONVERTER PIN FUNCTIONS Package Pin # 1 Name PG 2 EN/SYNC 3 FB 4 VCC 5 AGND 6, 7, 8, 12 SW 9, 10, 11 OUT 13, BST 14,15 PGND 16 IN 17 NC Description Power good indicator. PG is an open-drain structure. Enable/sync. Pull EN/SYNC high to enable the MPM3515. Float EN/SYNC or connect EN/SYNC to ground to disable the MPM3515. Apply an external clock to EN/SYNC to change the switching frequency. Feedback. Connect FB to the tap of an external resistor divider from the output to AGND to set the output voltage. The frequency foldback comparator lowers the oscillator frequency when the FB voltage is below 400mV to prevent current-limit runaway during a short-circuit fault. Place the resistor divider as close to FB as possible. Avoid placing vias on the FB traces. Internal 4.8V LDO output. Since an internal circuit integrates the LDO output capacitor, there is no need to add an external capacitor. 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. There is no need to connect these SW pins, but a large copper plane is recommended on pins 6, 7, and 8 for better heat sinking. Power output. Connect the load to OUT. An output capacitor is required. Bootstrap. The bootstrap capacitor is integrated internally. There is no need for external connections. 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. Supply voltage. IN supplies power for the internal MOSFET and regulator. The MPM3515 operates from a +4V to +36V input rail. A low-ESR and low-inductance capacitor is required to decouple the input rail. Place the input capacitor very close to IN and connect it with wide PCB traces and multiple vias. Do not connect. NC must be left floating. MPM3515 Rev. 1.0 www.MonolithicPower.com 8/22/2016 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2016 MPS. All Rights Reserved. 11 MPM3515 – 36V, 1.5A, SYNCHRONOUS, STEP-DOWN, MODULE CONVERTER BLOCK DIAGRAM Figure 1: Functional Block Diagram MPM3515 Rev. 1.0 www.MonolithicPower.com 8/22/2016 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2016 MPS. All Rights Reserved. 12 MPM3515 – 36V, 1.5A, SYNCHRONOUS, STEP-DOWN, MODULE CONVERTER OPERATION The MPM3515 is a high-frequency, synchronous, rectified, step-down, switch-mode converter with built-in power MOSFETs, an integrated inductor, and two capacitors. The MPM3515 offers a very compact solution that achieves 1.5A of continuous output current with excellent load and line regulation over a 4V to 36V input supply range. The MPM3515 operates in a fixed-frequency, peak-current-control mode to regulate the output voltage. An internal clock initiates a PWM cycle. The integrated high-side power MOSFET (HS-FET) turns on and remains on until the current reaches the value set by the COMP voltage (VCOMP). When the power switch is off, it remains off until the next clock cycle begins. If the current in the power MOSFET does not reach the value set by VCOMP within 85% of one PWM period, the power MOSFET is forced off. Internal Regulator A 4.8V internal regulator powers most of the internal circuitries. This regulator takes VIN and operates in the full VIN range. When VIN is higher than 4.8V, the output of the regulator is in full regulation. When VIN is lower than 4.8V, the output decreases. The MPM3515 integrates an internal decoupling capacitor, so there is no need to add an external VCC output capacitor. CCM Operation The MPM3515 uses continuous conduction mode (CCM) to ensure that the part works with a 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 MPM3515 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 voltage to the internal 0.807V 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 count and simplifies the control loop design. 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). The UVLO rising threshold is about 3.5V, while its falling threshold is 3.17V. Enable/SYNC EN/SYNC is a control pin that turns the regulator on and off. Drive EN/SYNC high to turn on the regulator; drive EN/SYNC low to turn off the regulator. An internal 500kΩ resistor from EN/SYNC to GND allows EN/SYNC to be floated to shut down the chip. EN/SYNC is clamped internally using a 6.5V series Zener diode (see Figure 2). Connecting the EN/SYNC input through a pull-up resistor to the voltage on VIN limits the EN/SYNC input current below 100µA. For example, with 12V connected to VIN, RPULLUP ≥ (12V - 6.5V) ÷ 100µA = 55kΩ. Connecting EN/SYNC 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. EN/SYNC EN/SYNC Figure 2: 6.5V Zener Diode Connection Connect an external clock with a range of 450kHz to 2.2MHz to synchronize the internal clock rising edge to the external clock rising edge. The pulse wide of the external clock MPM3515 Rev. 1.0 www.MonolithicPower.com 8/22/2016 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2016 MPS. All Rights Reserved. 13 MPM3515 – 36V, 1.5A, SYNCHRONOUS, STEP-DOWN, MODULE CONVERTER signal should be below 350ns, and the off time of external clock signal should be below 1.9µs. drops below its lower threshold (typically 150°C), the power supply resumes operation. Internal Soft Start (SS) 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 (SS) voltage that ramps up from 0V to 4.8V. When SS is lower than REF, the error amplifier uses SS as the reference. When SS is higher than REF, the error amplifier uses REF as the reference. The SS time is set to 1.7ms internally. Floating Driver and Bootstrap Charging An internal bootstrap capacitor powers the floating power MOSFET driver. A dedicated internal regulator charges and regulates the bootstrap capacitor voltage to ~4.8V (see Figure 3). When the voltage between the BST and SW nodes drops below the regulation voltage, a PMOS pass transistor connected from VIN to BST turns on. The charging current path is from VIN to BST to SW. The external circuit should provide enough voltage headroom to facilitate charging. As long as VIN is higher than SW significantly, the bootstrap capacitor remains charged. When the HS-FET is on, VIN ≈ VSW, so the bootstrap capacitor cannot charge. When the LS-FET is on, VIN VSW reaches its maximum for fast charging. When there is no inductor current, VSW is equal to VOUT, so the difference between VIN and VOUT can charge the bootstrap capacitor. The floating driver has its own UVLO protection with a rising threshold of 2.2V and hysteresis of 150mV. Over-Current Protection (OCP) and Hiccup The MPM3515 has cycle-by-cycle peak-currentlimit protection and valley-current detection protection. The inductor current is monitored during the 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. The low-side MOSFET (LS-FET) then turns on to discharge the energy, and the inductor current decreases. The HSFET 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 HSFET 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. If the output voltage drops below the undervoltage (UV) threshold (typically 50% below the reference), the MPM3515 enters hiccup mode to restart the part periodically. Simultaneously, the peak-current limit is reached. This protection mode is useful when the output is dead-shorted to ground and reduces the average short-circuit current greatly to alleviate thermal issues and protect the regulator. The MPM3515 exits hiccup mode once the overcurrent condition is removed. Thermal Shutdown Thermal shutdown prevents the chip from operating at exceedingly high temperatures. When the die temperatures exceed 170°C, the device stops switching. When the temperature Figure 3: Internal Bootstrap Charging Circuit Start-Up and Shutdown If VIN exceeds its thresholds, the MPM3515 starts up. The reference block starts first, generating a stable reference voltage and current. The internal regulator is then enabled. The regulator provides a stable supply for the remaining circuitries. Three events can shut down the chip: VIN low, EN/SYNC 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. MPM3515 Rev. 1.0 www.MonolithicPower.com 8/22/2016 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2016 MPS. All Rights Reserved. 14 MPM3515 – 36V, 1.5A, SYNCHRONOUS, STEP-DOWN, MODULE CONVERTER APPLICATION INFORMATION Setting the Output Voltage The external resistor divider sets the output voltage (see the Typical Application on page 1). The feedback resistor (R1) sets the feedback loop bandwidth with the internal compensation capacitor. Choose R1 to be around 75kΩ when VOUT 1V. R2 can then be calculated with Equation (1): R2 R1 VOUT 1 0.807V C3 VOUT R2 R1 Figure 4: Feedback Network Table 1 lists recommended resistor values for common output voltages. Table 1: Resistor Selection for Common Output Voltages VOUT (V) 1.5 1.8 2.5 3.3 5 R1 (kΩ) 75 75 75 75 75 IC1 ILOAD x R2 (kΩ) 87 61 35.7 24.3 14.3 Selecting the Input Capacitor The input current to the step-down converter is discontinuous and therefore requires a capacitor to supply 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 capacitor. VOUT VIN V x1 OUT VIN (2) The worst-case condition occurs at VIN = 2VOUT, shown in Equation (3): (1) Figure 4 shows the feedback network. FB Since C1 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): IC1 ILOAD 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 the input. The input voltage ripple caused by the capacitance can be estimated with Equation (4): ∆VIN ILOAD VOUT x fS xC1 VIN V x 1 OUT VIN (4) Selecting the Output Capacitor The output capacitor (C2) maintains the DC output voltage. Use ceramic, tantalum, or lowESR 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): ∆VOUT VOUT VOUT x 1 fS xL1 VIN 1 x R ESR 8xf xC2 S (5) Where L1 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. MPM3515 Rev. 1.0 www.MonolithicPower.com 8/22/2016 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2016 MPS. All Rights Reserved. 15 MPM3515 – 36V, 1.5A, SYNCHRONOUS, STEP-DOWN, MODULE CONVERTER For simplification, the output voltage ripple can be estimated with Equation (6): ∆VOUT V 1 x1 OUT VIN 8xfS xL1xC2 2 (6) 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): (7) PCB Layout Guidelines Efficient PCB layout, especially of the input capacitor placement, is critical for stable operation. For best results, refer to Figure 6 and follow the guidelines below. 1. Connect a large ground plane to PGND directly. If the bottom layer is a ground plane, add vias near PGND. 2. Ensure that the high-current paths at GND and IN have short, direct, and wide traces. 3. The characteristics of the output capacitor also affect the stability of the regulation system. The MPM3515 can be optimized for a wide range of capacitance and ESR values. Place the ceramic input capacitor close to IN and PGND. 4. Keep the connection of the input capacitor and IN as short and wide as possible. External Bootstrap Diode An external bootstrap diode can enhance the efficiency of the regulator given the following conditions: 5. Place the external feedback resistors next to FB. 6. Keep the feedback network away from the switching node. ∆VOUT V V OUT x1 OUT fS xL1 VIN VOUT is 5V or 3.3V Duty cycle is high: D = xRESR (7) NOTE: 7) The recommended layout is based on Figure 8. VOUT > 65% VIN C2 R2 R1 IN R3 In these cases, add an external BST diode from VCC to BST (see Figure 5). Top Layer Figure 5: Optional External Bootstrap Diode Added to Enhance Efficiency The recommended external BST diode is IN4148. Bottom Layer Figure 6: Recommended PCB Layout MPM3515 Rev. 1.0 www.MonolithicPower.com 8/22/2016 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2016 MPS. All Rights Reserved. 16 MPM3515 – 36V, 1.5A, SYNCHRONOUS, STEP-DOWN, MODULE CONVERTER Design Example Table 2 is a design example following the application guidelines for the specifications below. Table 2: Design Example 12V VIN 3.3V VOUT 1.5A IOUT The typical performance and circuit waveforms are shown in the Typical Performance Characteristics section. For more device applications, please refer to the related evaluation board datasheet. MPM3515 Rev. 1.0 www.MonolithicPower.com 8/22/2016 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2016 MPS. All Rights Reserved. 17 MPM3515 – 36V, 1.5A, SYNCHRONOUS, STEP-DOWN, MODULE CONVERTER TYPICAL APPLICATION CIRCUITS Figure 7: VOUT = 5V, IOUT = 1.5A Figure 8: VOUT = 3.3V, IOUT = 1.5A MPM3515 Rev. 1.0 www.MonolithicPower.com 8/22/2016 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2016 MPS. All Rights Reserved. 18 MPM3515 – 36V, 1.5A, SYNCHRONOUS, STEP-DOWN, MODULE CONVERTER TYPICAL APPLICATION CIRCUITS (continued) Figure 9: VOUT = 2.5V, IOUT = 1.5A Figure 10: VOUT = 1.8V, IOUT = 1.5A MPM3515 Rev. 1.0 www.MonolithicPower.com 8/22/2016 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2016 MPS. All Rights Reserved. 19 MPM3515 – 36V, 1.5A, SYNCHRONOUS, STEP-DOWN, MODULE CONVERTER TYPICAL APPLICATION CIRCUITS (continued) Figure 11: VOUT = 1.5V, IOUT = 1.5A VIN BST 4V-36V FB1 1206 SW L1 2.2uH 16 VEMI CIN1 1nF CIN 2 10nF CIN3 1uF CIN 4 10uF CIN 5 10uF C1 4.7µF GND C3 R3 0.1µF 100 k 2 EN / SYNC 4 R4 100 k PG 1 IN OUT 13 6,7,8,12 L2 150nH 9,10.11 C2 MPM 3515 R1 VOUT C4 1nF 3. 3 V/ 1. 5 A 47µF 75 k EN/ SYNC FB 3 VCC R2 24.3k PG AGND PGND 5 14,15 Figure 12: VOUT = 3.3V, IOUT = 1.5A with EMI Filter MPM3515 Rev. 1.0 www.MonolithicPower.com 8/22/2016 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2016 MPS. All Rights Reserved. 20 MPM3515 – 36V, 1.5A, SYNCHRONOUS, STEP-DOWN, MODULE CONVERTER PACKAGE INFORMATION QFN-17 (3mmx5mmx1.6mm) Non-Wettable Flank 1) ALL DIMENSIONS ARE IN MILLIMETERS. 2) SHADED AREA IS THE KEEP-OUT ZONE. ANY PCB METAL TRACE AND VIA ARE NOT ALLOWED TO CONNECT TO THIS AREA ELECTRICALLY OR MECHANICALLY. 3) LEAD COPLANARITY SHALL BE 0.10 MILLIMETERS MAX. 4) JEDEC REFERENCE IS MO-220. 5) DRAWING IS NOT TO SCALE. MPM3515 Rev. 1.0 www.MonolithicPower.com 8/22/2016 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2016 MPS. All Rights Reserved. 21 MPM3515 – 36V, 1.5A, SYNCHRONOUS, STEP-DOWN, MODULE CONVERTER PACKAGE INFORMATION (CONTINUED) QFN-17 (3mmx5mmx1.6mm) Wettable Flank 1) ALL DIMENSIONS ARE IN MILLIMETERS. 2) SHADED AREA IS THE KEEP-OUT ZONE. ANY PCB METAL TRACE AND VIA ARE NOT ALLOWED TO CONNECT TO THIS AREA ELECTRICALLY OR MECHANICALLY. 3) THE LEAD SIDE IS WETTABLE. 4) LEAD COPLANARITY SHALL BE 0.10 MILLIMETERS MAX. 5) JEDEC REFERENCE IS MO-220. 6) DRAWING IS NOT TO SCALE. 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. MPM3515 Rev. 1.0 www.MonolithicPower.com 8/22/2016 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2016 MPS. All Rights Reserved. 22