MP1477H 17V, 3A, 1.2MHz, High-Efficiency, Synchronous, Step-Down Converter in a SOT563 Package DESCRIPTION FEATURES The MP1477H is a fully integrated, highfrequency, synchronous, rectified, step-down, switch-mode converter with internal power MOSFETs. The MP1477H offers a very compact solution that achieves 3A of continuous output current with excellent load and line regulation over a wide input range. The MP1477H uses synchronous-mode operation for higher efficiency over the output current-load range. Constant-on-time (COT) control operation provides very fast transient response, easy loop design, and very tight output regulation. Full protection features include short-circuit protection (SCP), over-current protection (OCP), under-voltage protection (UVP), and thermal shutdown. Wide 4.2V to 17V Operating Input Range 58m/25m Low RDS(ON) Internal Power MOSFETs 200A Low IQ High-Efficiency Synchronous Mode Operation Forced PWM Mode Operation Fast Load Transient Response 1.2MHz Switching Frequency Internal Soft Start (SS) Over-Current Protection (OCP) and Hiccup Thermal Shutdown Output Adjustable from 0.8V Available in a SOT563 (1.6mm1.6mm) Package APPLICATIONS The MP1477H requires a minimal number of readily available, standard, external components and is available in a space-saving SOT563 (1.6mm1.6mm) package. Security Camera Digital Set-Top Boxes Flat-Panel Television and Monitors General Purposes 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 Efficiency R4 10 VIN BST L1 1.5H 3.3V/3A VOUT SW R1 40.2k C1 22F MP1477H FB EN GND R2 R3 75k 13k C2 22F x 2 EFFICIENCY(%) 12V VIN EN VOUT = 3.3V, L = 1.5H, DCR = 4.3m C3 1F 100 90 80 70 60 50 40 30 20 10 0 Vin=5V Vin=12V Vin=16V 0.01 0.1 1 LOAD CURRENT(A) MP1477H Rev. 1.0 www.MonolithicPower.com 11/10/2017 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. (c) 2017 MPS. All Rights Reserved. 10 1 MP1477H - SYNCHRONOUS, STEP-DOWN CONVERTER WITH INTERNAL MOSFETS ORDERING INFORMATION Part Number* MP1477HGTF Package SOT563(1.6mm1.6mm) Top Marking See Below * For Tape & Reel, add suffix -Z (e.g. MP1477HGTF-Z). TOP MARKING BEC: Product code of MP1477HGTF Y: Year code LLL: Lot number PACKAGE REFERENCE SOT563(1.6mm1.6mm) MP1477H Rev. 1.0 www.MonolithicPower.com 11/10/2017 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. (c) 2017 MPS. All Rights Reserved. 2 MP1477H - SYNCHRONOUS, STEP-DOWN CONVERTER WITH INTERNAL MOSFETS ABSOLUTE MAXIMUM RATINGS (1) VIN ................................................ -0.3V to 18V VSW ................................ -0.6V (-6.5V for <10ns) to VIN + 0.3V (19V for <10ns) VBST .....................................................VSW + 5V (2) VEN .............................................. -0.3V to 5V All other pins .................................... -0.3V to 5V (3)(5) Continuous power dissipation (TA = +25C) ..................................................................2.2W Junction temperature ............................... 150C Lead temperature .................................... 260C Storage temperature .................. -65C to 150C Recommended Operating Conditions (4) Supply voltage (VIN) ....................... 4.2V to 17V Output voltage (VOUT) ............ 0.8V to VIN DMAX or 10V max Operating junction temp. (TJ) ... -40C to +125C Thermal Resistance SOT563 JA JC EV1477H-TF-00B (5) .............. 55 ....... 21 ... C/W JESD51-7 (6) ......................... 130 ...... 60 ... C/W NOTES: 1) Exceeding these ratings may damage the device. 2) For details on EN's ABS max rating, please refer to the EN 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 JA, and the ambient temperature TA. The maximum allowable continuous power dissipation at any ambient temperature is calculated by PD (MAX) = (TJ (MAX)-TA)/JA. 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) The device is not guaranteed to function outside of its operating conditions. 5) Measured on EV1477H-TF-00B, 2-layer PCB. 6) Measured on JESD51-7, 4-layer PCB. MP1477H Rev. 1.0 www.MonolithicPower.com 11/10/2017 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. (c) 2017 MPS. All Rights Reserved. 3 MP1477H - SYNCHRONOUS, STEP-DOWN CONVERTER WITH INTERNAL MOSFETS ELECTRICAL CHARACTERISTICS VIN = 12V, TJ = -40C to +125C (7), typical value is tested at TJ = +25C, unless otherwise noted Parameter Symbol Supply current (shutdown) Supply current (quiescent) HS switch on resistance LS switch on resistance IIN IQ HSRDS(ON) LSRDS(ON) Switch leakage Valley current limit Oscillator frequency (8) Minimum on time SW LKG ILIMIT fSW TON_MIN (8) TOFF_MIN Minimum off time Feedback voltage Feedback voltage Feedback current FB UV threshold (H to L) (8) Hiccup duty cycle VREF VREF IFB VUV_th DHiccup EN rising threshold EN hysteresis EN input current VIN under-voltage lockout threshold rising VIN under-voltage lockout threshold hysteresis Soft-start period (8) Thermal shutdown (8) Thermal hysteresis VEN_RISING VEN_HYS IEN Condition Min Typ VEN = 0V VEN = 2V, VFB = 0.85V VBST-SW = 3.3V 170 200 58 25 VEN = 0V, VSW = 12V VOUT = 0V VFB = 0.75V 1000 4 1200 45 Max Units 10 250 A A m m 10 A A kHz ns 1500 180 TJ = +25C TJ = -40C to 125C 793 789 805 805 10 44% 25 817 821 100 mV mV nA Vref % 1.14 1.2 100 2 1.26 V mV A 3.7 4 4.18 V Hiccup entry VEN = 2V INUVVth INUVHYS TSS TSD TSDHYS ns 330 1.6 2.5 150 20 mV 3 ms C C NOTES: 7) Guaranteed by over-temperature correlation, not tested in production. 8) Guaranteed by design and engineering sample characterization. MP1477H Rev. 1.0 www.MonolithicPower.com 11/10/2017 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. (c) 2017 MPS. All Rights Reserved. 4 MP1477H - SYNCHRONOUS, STEP-DOWN CONVERTER WITH INTERNAL MOSFETS TYPICAL PERFORMANCE CHARACTERISTICS VIN = 12V, VOUT = 3.3V, L = 1.5H, TA = +25C, unless otherwise noted. Efficiency Efficiency 100 90 80 70 60 50 40 30 20 10 0 VOUT = 3.3V, L = 1.5H, DCR = 4.3m EFFICIENCY(%) EFFICIENCY(%) VOUT = 5V, L = 2.2H, DCR = 11.4m Vin=6.5V Vin=12V Vin=16V 0.01 0.1 1 LOAD CURRENT(A) 100 90 80 70 60 50 40 30 20 10 0 10 0.01 Efficiency 0.1 1 LOAD CURRENT(A) EFFICIENCY(%) EFFICIENCY(%) 100 90 80 70 60 50 40 30 20 10 0 EFFICIENCY(%) EFFICIENCY(%) 10 VOUT = 1V, L = 0.68H, DCR = 3.1m Vin=5V Vin=12V Vin=16V 0.1 1 LOAD CURRENT(A) 0.1 1 LOAD CURRENT(A) Efficiency VOUT = 1.2V, L = 0.68H, DCR = 3.1m 0.01 Vin=5V Vin=12V Vin=16V 0.01 10 Efficiency 100 90 80 70 60 50 40 30 20 10 0 10 VOUT = 1.8V, L = 1.2H, DCR = 1.8m Vin=5V Vin=12V Vin=16V 0.01 0.1 1 LOAD CURRENT(A) Efficiency VOUT = 2.5V, L = 1.5H, DCR = 4.3m 100 90 80 70 60 50 40 30 20 10 0 Vin=5V Vin=12V Vin=16V 10 100 90 80 70 60 50 40 30 20 10 0 Vin=5V Vin=12V Vin=16V 0.01 0.1 1 LOAD CURRENT(A) MP1477H Rev. 1.0 www.MonolithicPower.com 11/10/2017 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. (c) 2017 MPS. All Rights Reserved. 10 5 MP1477H - SYNCHRONOUS, STEP-DOWN CONVERTER WITH INTERNAL MOSFETS TYPICAL PERFORMANCE CHARACTERISTICS (continued) VIN = 12V, VOUT = 3.3V, L = 1.5H, TA = +25C, unless otherwise noted. Line Regulation Load Regulation 0.3 0.3 0.2 LOAD RRGULATION(%) LINE REGULATION(%) Iout=0.01A Iout=1.5A Iout=3A 0.1 0 -0.1 0.2 0.1 0 Vin=5V Vin=12V Vin=16V -0.1 -0.2 -0.2 4 6 8 10 12 14 INPUT VOLTAGE(V) 16 0 18 Enabled Supply Current vs. Input Voltage 1 1.5 2 LOAD CURRENT(A) 2.5 3 16 18 Disabled Supply Current vs. Input Voltage VEN = 2V, VFB = 0.85V VEN = 0V 6 220 DISABLED SUPPLY CURRENT(uA) ENABLED SUPPLY CURRENT(uA) 0.5 210 200 190 180 170 160 150 4 6 8 10 12 14 INPUT VOLTAGE(V) 16 18 5 4 3 2 1 0 4 6 8 10 12 14 INPUT VOLTAGE(V) Case Temperature Rise vs. Load Current TA = 25C, board size: 6.3cm x 4.7cm CASE TEMPERATURE RISE() 40 35 30 25 20 15 10 5 0 0 0.5 1 1.5 2 LOAD CURRENT(A) 2.5 3 MP1477H Rev. 1.0 www.MonolithicPower.com 11/10/2017 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. (c) 2017 MPS. All Rights Reserved. 6 MP1477H - SYNCHRONOUS, STEP-DOWN CONVERTER WITH INTERNAL MOSFETS TYPICAL PERFORMANCE CHARACTERISTICS (continued) VIN = 12V, VOUT = 3.3V, L = 1.5H, TA = +25C, unless otherwise noted. Input/Output Ripple Input/Output Ripple IOUT = 0A IOUT = 3A CH1: CH1: VOUT/AC 20mV/div. VOUT/AC 20mV/div. CH2: VIN/AC 50mV/div. CH2: VIN/AC 100mV/div. CH3: VSW 10V/div. CH3: VSW 10V/div. CH4: IL 2A/div. CH4: IL 2A/div. 1s/div. 1s/div. Short-Circuit Entry Short-Circuit Recovery IOUT = 0A IOUT = 0A CH1: VOUT 2V/div. CH1: VOUT 2V/div. CH2: VIN 10V/div. CH2: VIN 10V/div. CH3: VSW 5V/div. CH3: VSW 5V/div. CH4: IL 5A/div. CH4: IL 5A/div. 4ms/div. 4ms/div. Start-Up through Input Voltage Start-Up through Input Voltage IOUT = 0A IOUT = 3A CH1: VOUT 2V/div. CH1: VOUT 2V/div. CH2: VIN 5V/div. CH2: VIN 5V/div. CH3: VSW 5V/div. CH3: VSW 5V/div. CH4: IL 1A/div. CH4: IL 2A/div. 1ms/div. 1ms/div. MP1477H Rev. 1.0 www.MonolithicPower.com 11/10/2017 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. (c) 2017 MPS. All Rights Reserved. 7 MP1477H - SYNCHRONOUS, STEP-DOWN CONVERTER WITH INTERNAL MOSFETS TYPICAL PERFORMANCE CHARACTERISTICS (continued) VIN = 12V, VOUT = 3.3V, L = 1.5H, TA = +25C, unless otherwise noted. Shutdown through Input Voltage Shutdown through Input Voltage IOUT = 0A IOUT = 3A CH1: VOUT 2V/div. CH1: VOUT 2V/div. CH2: VIN 5V/div. CH2: VIN 5V/div. CH3: VSW 5V/div. CH3: VSW 5V/div. CH4: IL 2A/div. CH4: IL 2A/div. 100ms/div. 1ms/div. Start-Up through Enable Start-Up through Enable IOUT = 0A IOUT = 3A CH1: VOUT 2V/div. CH1: VOUT 2V/div. CH2: VEN 5V/div. CH2: VEN 5V/div. CH3: VSW 5V/div. CH4: IL 5A/div. CH3: VSW 5V/div. CH4: IL 5A/div. 2ms/div. 2ms/div. Shutdown through Enable Shutdown through Enable IOUT = 0A IOUT = 3A CH1: VOUT 2V/div. CH1: VOUT 2V/div. CH2: VEN 5V/div. CH2: VEN 5V/div. CH3: VSW 5V/div. CH4: IL 5A/div. CH3: VSW 5V/div. CH4: IL 5A/div. 200ms/div. 20s/div. MP1477H Rev. 1.0 www.MonolithicPower.com 11/10/2017 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. (c) 2017 MPS. All Rights Reserved. 8 MP1477H - SYNCHRONOUS, STEP-DOWN CONVERTER WITH INTERNAL MOSFETS TYPICAL PERFORMANCE CHARACTERISTICS (continued) VIN = 12V, VOUT = 3.3V, L = 1.5H, TA = +25C, unless otherwise noted. Load Transient Response IOUT = 1.5A to 3A, 2.5A/s CH1: VOUT/AC 50mV/div. CH4: IOUT 1A/div. 100s/div. MP1477H Rev. 1.0 www.MonolithicPower.com 11/10/2017 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. (c) 2017 MPS. All Rights Reserved. 9 MP1477H - SYNCHRONOUS, STEP-DOWN CONVERTER WITH INTERNAL MOSFETS PIN FUNCTIONS Package Pin # Name 1 VIN 2 SW 3 GND 4 BST 5 EN 6 FB Description Supply voltage. The MP1477H operates from a 4.2V to 17V input rail. A capacitor (C1) is required to decouple the input rail. Connect VIN using a wide PCB trace. Switch output. Connect SW using a wide PCB trace. System ground. GND is the reference ground of the regulated output voltage. GND requires careful consideration during the PCB layout. Connect GND with copper traces and vias. Bootstrap. Connect a 1F BST capacitor and a resistor between SW and BST to form a floating supply across the high-side switch driver. Enable. Drive EN high to enable the MP1477H. For automatic start-up, connect EN to VIN with a 100k pull-up resistor. Feedback. Connect FB to the tap of an external resistor divider from the output to GND to set the output voltage. MP1477H Rev. 1.0 www.MonolithicPower.com 11/10/2017 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. (c) 2017 MPS. All Rights Reserved. 10 MP1477H - SYNCHRONOUS, STEP-DOWN CONVERTER WITH INTERNAL MOSFETS BLOCK DIAGRAM VIN EN 1M Bias & Voltage Reference Bootstrap Regulator BST VCC Regulator HS Driver On Timer Main Switch (NCH) Iss SW Logic Control VCC PWM FB LS Driver Current Modulator Synchronous Rectifier (NCH) Current Sense Amplifier GND Figure 1: Functional Block Diagram MP1477H Rev. 1.0 www.MonolithicPower.com 11/10/2017 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. (c) 2017 MPS. All Rights Reserved. 11 MP1477H - SYNCHRONOUS, STEP-DOWN CONVERTER WITH INTERNAL MOSFETS OPERATION The MP1477H is a fully integrated, synchronous, rectified, step-down, switch mode converter. Constant-on-time (COT) control is employed to provide fast transient response and ease loop stabilization. At the beginning of each cycle, the high-side MOSFET (HS-FET) is turned on when the FB voltage (VFB) drops below the reference voltage (VREF). The HSFET is turned on for a fixed interval determined by the one-shot on-timer. The on-timer is determined by both the output voltage and input voltage to make the switching frequency fairly constant over the input voltage range. After the on period elapses, the HS-FET is turned off until the next period. By repeating operation this way, the converter regulates the output voltage. The low-side MOSFET (LS-FET) is turned on when the HS-FET is in its off state to minimize conduction loss. There is a dead short between the input and GND if both the HS-FET and LSFET are turned on at the same time. This is called shoot-through. To avoid shoot-through, a dead time is generated internally between the HS-FET off and LS-FET on period or the LSFET off and HS-FET on period. Enable Control (EN) EN is a digital control pin that turns the regulator on and off. Drive EN high to turn on the regulator. Drive EN low to turn off the regulator. An internal 1M resistor from EN to GND allows EN to be floated to shut down the chip. EN is clamped internally using a 2.8V series Zener diode (see Figure 2). Connecting the EN input through a pull-up resistor to VIN limits the EN input current below 100A to prevent damaging the Zener diode. For example, when connecting 12V to VIN, RPULLUP (12V - 2.8V) / (100k + 35k) = 68A. EN 1M GND 35k 2.8V Under-Voltage Lockout (UVLO) Under-voltage lockout (UVLO) protects the chip from operating at an insufficient supply voltage. The MP1477H UVLO comparator monitors the output voltage of the internal regulator (VCC). The UVLO rising threshold is about 4V, while its falling threshold is 3.67V. Internal Soft Start (SS) Soft start prevents the converter output voltage from overshooting during start-up. When the chip starts up, the internal circuitry generates a soft-start voltage (SS) that ramps up from 0V to 1.2V. When SS is lower than REF, SS overrides REF so the error amplifier uses SS as the reference. When SS exceeds REF, the error amplifier uses REF as the reference. The SS time is set to 2.5ms internally. Over-Current Protection (OCP) and ShortCircuit Protection (SCP) The MP1477H has a valley current-limit control. During the LS-FET on state, the inductor current is monitored. When the sensed inductor current reaches the valley current limit, the lowside limit comparator turns over, the MP1477H enters over-current protection (OCP) mode, and the HS-FET waits until the valley current limit is removed before turning on again. Meanwhile, the output voltage drops until VFB is below the under-voltage (UV) threshold (typically 44% below the reference). Once UV is triggered, the MP1477H enters hiccup mode to restart the part periodically. During OCP, the device attempts to recover from the over-current fault with hiccup mode. In hiccup mode, the chip disables the output power stage, discharges the soft start, and attempts to soft start again automatically. If the over-current condition still remains after the soft start ends, the device repeats this operation cycle until the over-current condition is removed. The output rises back to the regulation level. OCP is a non-latch protection. EN Logic Figure 2: Zener Diode between EN and GND MP1477H Rev. 1.0 www.MonolithicPower.com 11/10/2017 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. (c) 2017 MPS. All Rights Reserved. 12 MP1477H - SYNCHRONOUS, STEP-DOWN CONVERTER WITH INTERNAL MOSFETS Pre-Bias Start-Up The MP1477H is designed for monotonic startup into pre-biased loads. If the output is prebiased to a certain voltage during start-up, the BST voltage is refreshed and charged, and the voltage on the soft start is charged as well. If the BST voltage exceeds its rising threshold voltage and the soft-start voltage exceeds the sensed output voltage at FB, the MP1477H starts working normally. Thermal Shutdown Thermal shutdown prevents the chip from operating at exceedingly high temperatures. When the silicon die temperature exceeds 150C, the entire chip shuts down. When the temperature falls below its lower threshold (typically 130C), the chip is enabled again. Start-Up and Shutdown Circuit If both VIN and EN exceed their respective 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 circuits. Three events can shut down the chip: EN low, VIN low, and thermal shutdown. The shutdown procedure starts by blocking the signaling path initially to avoid any fault triggering. The internal supply rail is then pulled down. 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 a hysteresis of 150mV. VIN regulates the bootstrap capacitor voltage internally through D1, M1, C3, L1, and C2 (see Figure 3). If VIN - VSW exceeds 3.3V, U2 regulates M1 to maintain a 3.3V BST voltage across C3. Figure 3: Internal Bootstrap Charger MP1477H Rev. 1.0 www.MonolithicPower.com 11/10/2017 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. (c) 2017 MPS. All Rights Reserved. 13 MP1477H - SYNCHRONOUS, STEP-DOWN CONVERTER WITH INTERNAL MOSFETS APPLICATION INFORMATION Setting the Output Voltage The external resistor divider is used to set the output voltage. First, choose a value for R2. R2 should be chosen reasonably, since a small R2 leads to considerable quiescent current loss, while a large R2 makes FB noise-sensitive. R2 is recommended be within 5 - 100k. Typically, set the current through R2 to be between 5 30A for a good balance between system stability and no-load loss. Then determine R1 with Equation (2): R1 VOUT VREF R2 VREF (2) The feedback circuit is shown in Figure 4. VOUT MP1477H RT R1 FB R2 Figure 4: Feedback Network Table 1 lists the recommended parameters for common output voltages. Table 1: Parameter Selection for Common (9) Output Voltages, COUT = 22F*2 Vout (V) 5 3.3 2.5 1.8 1.5 1.2 1 R1 (k) 40.2 40.2 40.2 40.2 40.2 40.2 20.5 R2 (k) 7.68 13 19.1 32.4 45.3 82 84.5 RT (k) 75 75 100 110 249 249 348 L (H) 2.2 1.5 1.5 1.2 1 0.68 0.68 NOTE: 9) For the detail design circuit, please refer to the Typical Application Circuits on page 17 to 19. Selecting the Inductor An inductor is necessary for supplying constant current to the output load while being driven by the switched input voltage. A larger-value inductor results in less ripple current and a lower output ripple voltage but also has a larger physical footprint, higher series resistance, and lower saturation current. A good rule for determining the inductance value is to design the peak-to-peak ripple current in the inductor to be in the range of 30 - 60% of the maximum output current. The inductance value can be calculated with Equation (3): L VOUT V (1 OUT ) FSW IL VIN (3) Where IL is the peak-to-peak inductor ripple current. The inductor should not saturate under the maximum inductor peak current. The peak inductor current can be calculated with Equation (4): ILP IOUT VOUT V (1 OUT ) 2FSW L VIN (4) 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 step-down converter while maintaining the DC input voltage. For best results, use ceramic capacitors placed as close to VIN as possible. Capacitors with X5R and X7R ceramic dielectrics are recommended because they are fairly stable with temperature fluctuations. The capacitors must also have a ripple current rating greater than the maximum input ripple current of the converter. The input ripple current can be estimated with Equation (5): ICIN IOUT VOUT V (1 OUT ) VIN VIN (5) The worst-case condition occurs at VIN = 2VOUT, shown in Equation (6): ICIN IOUT 2 (6) For simplification, choose an input capacitor with an RMS current rating greater than half of the maximum load current. MP1477H Rev. 1.0 www.MonolithicPower.com 11/10/2017 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. (c) 2017 MPS. All Rights Reserved. 14 MP1477H - SYNCHRONOUS, STEP-DOWN CONVERTER WITH INTERNAL MOSFETS The input capacitance value determines the input voltage ripple of the converter. If there is an input voltage ripple requirement in the system, choose an input capacitor that meets the specification. is too high, the output voltage cannot reach the design value during the soft-start time and fails to regulate. The maximum output capacitor value (Co_max) can be limited approximately with Equation (12): The input voltage ripple can be estimated with Equation (7): CO _ MAX (ILIM _ AVG IOUT ) Tss / VOUT (12) IOUT V V VIN OUT (1 OUT ) FSW CIN VIN VIN (7) The worst-case condition occurs at VIN = 2VOUT, shown in Equation (8): VIN I 1 OUT 4 FSW CIN (8) Selecting the Output Capacitor An output capacitor is required to maintain the DC output voltage. Ceramic or POSCAP capacitors are recommended. The output voltage ripple can be estimated with Equation (9): VOUT VOUT V 1 (1 OUT ) (RESR ) (9) FSW L VIN 8 FSW COUT In the case of ceramic capacitors, the impedance at the switching frequency is dominated by the capacitance. The output voltage ripple is caused mainly by the capacitance. For simplification, the output voltage ripple can be estimated with Equation (10): VOUT VOUT V (1 OUT ) 8 FSW 2 L COUT VIN Where ILIM_AVG is the average start-up current during the soft-start period, and Tss is the softstart time. PCB Layout Guidelines Efficient layout of the switching power supplies is critical for stable operation. A poor layout design can result in poor line or load regulation and stability issues. For best results, refer to Figure 5 and follow the guidelines below. 1. Place the high-current paths (GND, VIN, and SW) very close to the device with short, direct, and wide traces. 2. Place the input capacitor as close to VIN and GND as possible (recommended within 1mm). 3. Place the external feedback resistors next to FB. 4. Keep the switching node SW short and away from the feedback network. (10) The output voltage ripple caused by the ESR is very small. In the case of POSCAP capacitors, the ESR dominates the impedance at the switching frequency. For simplification, the output ripple can be approximated with Equation (11): VOUT VOUT V (1 OUT ) RESR FSW L VIN (11) A larger output capacitor can achieve a better load transient response, but consider the maximum output capacitor limitation in the design application. If the output capacitor value MP1477H Rev. 1.0 www.MonolithicPower.com 11/10/2017 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. (c) 2017 MPS. All Rights Reserved. 15 MP1477H - SYNCHRONOUS, STEP-DOWN CONVERTER WITH INTERNAL MOSFETS Design Example Table 2 shows a design example when ceramic capacitors are applied. Table 2: Design Example VIN VOUT IOUT Top Layer 12V 3.3V 3A Detailed application schematics are shown in Figure 6 through Figure 12. The typical performance and waveforms are shown in the Typical Performance Characteristics section. For more devices applications, please refer to the related evaluation board datasheet. Bottom Layer Figure 5: Recommended Layout MP1477H Rev. 1.0 www.MonolithicPower.com 11/10/2017 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. (c) 2017 MPS. All Rights Reserved. 16 MP1477H - SYNCHRONOUS, STEP-DOWN CONVERTER WITH INTERNAL MOSFETS TYPICAL APPLICATION CIRCUITS U1 1 VIN C1 NS GND GND GND C1A 22F GND IN BST 4 C1B 0.1F R4 10 C3 1F GND MP1477H SW FB 5V/3A C2 22F 6 C4 15pF R3 75k VOUT C2A 22F GND GND GND R1 40.2k R2 7.68k 3 GND 5 EN L1 2.2H 2 R5 100k EN SW GND GND GND Figure 6: VIN = 12V, VOUT = 5V/3A U1 1 VIN C1 NS GND GND GND C1A 22F GND IN BST 4 C1B 0.1F C3 1F GND MP1477H SW FB L1 1.5H VOUT 3.3V/3A C2 22F 6 C4 15pF R3 75k C2A 22F GND GND GND R1 40.2k R2 13k 3 EN GND 5 SW 2 R5 100k EN R4 10 GND GND GND Figure 7: VIN = 12V, VOUT = 3.3V/3A U1 1 VIN C1 NS GND GND GND C1A 22F GND IN BST 4 C1B 0.1F C3 1F GND MP1477H SW GND EN FB L1 1.5H VOUT 2.5V/3A C2 22F 6 C4 15pF R3 100k 3 5 SW 2 R5 100k EN R4 10 C2A 22F GND GND R1 40.2k R2 19.1k GND GND GND GND Figure 8: VIN = 12V, VOUT = 2.5V/3A MP1477H Rev. 1.0 www.MonolithicPower.com 11/10/2017 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. (c) 2017 MPS. All Rights Reserved. 17 MP1477H - SYNCHRONOUS, STEP-DOWN CONVERTER WITH INTERNAL MOSFETS TYPICAL APPLICATION CIRCUITS (continued) U1 1 VIN C1 NS GND GND GND C1A 22F GND IN BST 4 C1B 0.1F C3 1F GND MP1477H SW FB L1 1.2H VOUT 1.8V/3A C2 22F 6 C4 15pF R3 110k C2A 22F GND GND GND R1 40.2k R2 32.4k 3 EN GND 5 SW 2 R5 100k EN R4 10 GND GND GND Figure 9: VIN = 12V, VOUT = 1.8V/3A U1 1 VIN C1 NS GND GND GND C1A 22F GND IN BST 4 C1B 0.1F C3 1F GND MP1477H SW FB L1 1H VOUT 1.5V/3A C2 22F 6 C4 15pF R3 249k C2A 22F GND GND GND R1 40.2k R2 45.3k 3 EN GND 5 SW 2 R5 100k EN R4 10 GND GND GND Figure 10: VIN = 12V, VOUT = 1.5V/3A U1 1 VIN C1 NS GND GND GND C1A 22F GND IN BST 4 C1B 0.1F C3 1F GND MP1477H SW GND EN FB L1 0.68H VOUT 1.2V/3A C2 22F 6 C4 15pF R3 249k C2A 22F GND GND R1 40.2k R2 82k 3 5 SW 2 R5 100k EN R4 10 GND GND GND GND Figure 11: VIN = 12V, VOUT = 1.2V/3A MP1477H Rev. 1.0 www.MonolithicPower.com 11/10/2017 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. (c) 2017 MPS. All Rights Reserved. 18 MP1477H - SYNCHRONOUS, STEP-DOWN CONVERTER WITH INTERNAL MOSFETS TYPICAL APPLICATION CIRCUITS (continued) U1 1 VIN C1 NS GND GND GND C1A 22F GND IN BST 4 C1B 0.1F C3 1F GND MP1477H SW GND EN FB L1 0.68H 1V/3A C2 22F 6 C4 15pF R3 348k 3 5 SW 2 R5 100k EN R4 10 VOUT C2A 22F GND GND R1 20.5k R2 84.5k GND GND GND GND Figure 12: VIN = 12V, VOUT = 1V/3A MP1477H Rev. 1.0 www.MonolithicPower.com 11/10/2017 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. (c) 2017 MPS. All Rights Reserved. 19 MP1477H - SYNCHRONOUS, STEP-DOWN CONVERTER WITH INTERNAL MOSFETS PACKAGE OUTLINE DRAWING FOR 6L SOT563 PACKAGE INFORMATION MF-PO-D-0250 revision 1.0 SOT563 (1.6mm1.6mm) PIN 1 ID BOTTOM VIEW TOP VIEW SIDE VIEW FRONT VIEW NOTE: 1) ALL DIMENSIONS ARE IN MILLIMETERS. 2) PACKAGE LENGTH DOES NOT INCLUDE MOLD FLASH, PROTRUSION OR GATE BURR. 3) PACKAGE WIDTH DOES NOT INCLUDE INTERLEAD FLASH OR PROTRUSION. 4) LEAD COPLANARITY (BOTTOM OF LEADS AFTER FORMING) SHALL BE 0.10 MILLIMETERS MAX. 5) DRAWING IS NOT TO SCALE. 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. MP1477H Rev. 1.0 www.MonolithicPower.com 11/10/2017 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. (c) 2017 MPS. All Rights Reserved. 20