MP1471A High-Efficiency, 3A 16V, 500kHz Synchronous, Step-Down Converter In a 6-Pin TSOT 23 DESCRIPTION FEATURES The MP1471A is a high-frequency, synchronous, rectified, step-down, switch-mode converter with internal power MOSFETs. It offers a very compact solution to achieve a 3A output current over a wide input supply range, with excellent load and line regulation. The MP1471A has synchronous-mode operation for higher efficiency over the output current-load range. Current-mode operation provides fast transient response and eases loop stabilization. Protection features include protection and thermal shutdown. over-current The MP1471A requires a minimal number of readily-available, standard, external components and is available in a space-saving 6-pin TSOT23 package. Wide 4.5V-to-16V Operating Input Range 110m/57m Low-RDS(ON) Internal Power MOSFETs Proprietary Switching-Loss-Reduction Technology High-Efficiency Synchronous-Mode Operation Fixed 500kHz Switching Frequency Internal AAM Power-Save Mode for High Efficiency at Light Load Internal Soft-Start Over-Current Protection and Hiccup Thermal Shutdown Output Adjustable from 0.8V Available in a 6-pin TSOT-23 package APPLICATIONS Game Consoles Digital Set-Top Boxes Flat-Panel Television and Monitors General Purposes All MPS parts are lead-free and adhere to the RoHS directive. For MPS green status, please visit MPS website under Products, Quality Assurance page. "MPS" and "The Future of Analog IC Technology" are registered trademarks of Monolithic Power Systems, Inc. TYPICAL APPLICATION MP1471A Rev. 1.0 www.MonolithicPower.com 8/18/2013 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. (c) 2013 MPS. All Rights Reserved. 1 MP1471A - SYNCHRONOUS, STEP-DOWN CONVERTER WITH INTERNAL MOSFETS ORDERING INFORMATION Part Number* MP1471AGJ Package TSOT23-6 Top Marking AGM * For Tape & Reel, add suffix -Z (e.g. MP1471AGJ-Z); PACKAGE REFERENCE ABSOLUTE MAXIMUM RATINGS (1) Thermal Resistance VIN ................................................ -0.3V to 17V VSW .................................................................... -0.3V (-5V for <10ns) to 17V (19V for <10ns) VBST ...................................................... VSW+6V All Other Pins .................................. -0.3V to 6V (2) Continuous Power Dissipation (TA = +25C) .......................................................... 1.25W Junction Temperature .............................. 150C Lead Temperature ................................... 260C Storage Temperature ................. -65C to 150C TSOT-23-6 ............................ 100 ..... 55 ... C/W Recommended Operating Conditions (3) Supply Voltage VIN .......................... 4.5V to 16V Output Voltage VOUT............... 0.8V to VIN*Dmax Operating Junction Temp. (TJ) . -40C to +125C (4) JA JC Notes: 1) Exceeding these ratings may damage the device. 2) The maximum allowable power dissipation is a function of the maximum junction temperature TJ (MAX), the junction-toambient thermal resistance 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 will cause excessive die temperature, and the regulator will go into thermal shutdown. Internal thermal shutdown circuitry protects the device from permanent damage. 3) The device is not guaranteed to function outside of its operating conditions. 4) Measured on JESD51-7, 4-layer PCB. MP1471A Rev. 1.0 www.MonolithicPower.com 8/18/2013 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. (c) 2013 MPS. All Rights Reserved. 2 MP1471A - SYNCHRONOUS, STEP-DOWN CONVERTER WITH INTERNAL MOSFETS ELECTRICAL CHARACTERISTICS (5) VIN = 12V, TA = 25C, unless otherwise noted. Parameter Supply Current (Shutdown) Supply Current (Quiescent) HS Switch-On Resistance LS Switch-On Resistance Switch Leakage Current Limit Oscillator Frequency Maximum Duty Cycle (5) Minimum On Time Feedback Voltage EN Rising Threshold EN Falling Threshold EN Input Current Symbol IIN Iq HSRDS-ON LSRDS-ON SW LKG ILIMIT fSW DMAX Condition 3.9 410 4.6 500 VFB=700mV 88 92 60 804 1.5 1.32 0.84 110 57 788 1.4 1.23 VEN=2V INUVVth 3.9 INUVHYS SS Vout from 0% to 100% Max Units 1 1.1 590 A mA m m A A kHz 820 1.6 1.41 % ns mV V V 1 VEN=0 VIN Under-Voltage Lockout Threshold, Rising VIN Under-Voltage Lockout Threshold Hysteresis Soft-Start Period (5) Thermal Shutdown (5) Thermal Hysteresis Typ VEN = 0V VEN = 2V, VFB = 1V VBST-SW =5V Vcc=5V VEN = 0V, VSW =12V Duty=40% VFB=0.75V ON_MIN VFB VEN_RISING VEN_FALLING IEN Min 1.8 A 0 A 4.15 4.4 V 340 mV 1.5 150 20 ms C C Notes: 5) Derived from bench characterization. Not tested in production. MP1471A Rev. 1.0 www.MonolithicPower.com 8/18/2013 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. (c) 2013 MPS. All Rights Reserved. 3 MP1471A - SYNCHRONOUS, STEP-DOWN CONVERTER WITH INTERNAL MOSFETS TYPICAL CHARACTERISTICS VIN = 12V, VOUT = 3.3V, L = 4.7H, TA = +25C, unless otherwise noted. MP1471A Rev. 1.0 www.MonolithicPower.com 8/18/2013 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. (c) 2013 MPS. All Rights Reserved. 4 MP1471A - SYNCHRONOUS, STEP-DOWN CONVERTER WITH INTERNAL MOSFETS TYPICAL PERFORMANCE CHARACTERISTICS Performance waveforms are tested on the evaluation board of the Design Example section. VIN = 12V, VOUT = 3.3V, L = 4.7H, TA = +25C, unless otherwise noted. MP1471A Rev. 1.0 www.MonolithicPower.com 8/18/2013 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. (c) 2013 MPS. All Rights Reserved. 5 MP1471A - SYNCHRONOUS, STEP-DOWN CONVERTER WITH INTERNAL MOSFETS TYPICAL PERFORMANCE CHARACTERISTICS (continued) Performance waveforms are tested on the evaluation board of the Design Example section. VIN = 12V, VOUT = 3.3V, L = 4.7H, TA = +25C, unless otherwise noted. MP1471A Rev. 1.0 www.MonolithicPower.com 8/18/2013 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. (c) 2013 MPS. All Rights Reserved. 6 MP1471A - SYNCHRONOUS, STEP-DOWN CONVERTER WITH INTERNAL MOSFETS TYPICAL PERFORMANCE CHARACTERISTICS (continued) Performance waveforms are tested on the evaluation board of the Design Example section. VIN = 12V, VOUT = 3.3V, L = 4.7H, TA = +25C, unless otherwise noted. MP1471A Rev. 1.0 www.MonolithicPower.com 8/18/2013 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. (c) 2013 MPS. All Rights Reserved. 7 MP1471A - SYNCHRONOUS, STEP-DOWN CONVERTER WITH INTERNAL MOSFETS PIN FUNCTIONS Package Pin # Name Description 1 GND System Ground. Reference ground of the regulated output voltage: requires extra care during PCB layout. Connect to GND with copper traces and vias. 2 SW 3 IN 4 FB 5 EN 6 BST Switch Output. Connect using wide a PCB trace. Supply Voltage. The MP1471A operates from a 4.5V-to-16V input rail. Requires C1 to decouple the input rail. Connect using a wide PCB trace. Feedback. Connect to the tap of an external resistor divider from the output to GND to set the output voltage. The frequency fold-back comparator lowers the oscillator frequency when the FB voltage drops below 140mV to prevent current-limit runaway during a short circuit fault. EN=HIGH to enable the MP1471A. For automatic start-up, connect EN to VIN using a 100k resistor. Bootstrap. Connect a capacitor and a resistor between SW and BST pins to form a floating supply across the high-side switch driver. Use a 1F BST capacitor. MP1471A Rev. 1.0 www.MonolithicPower.com 8/18/2013 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. (c) 2013 MPS. All Rights Reserved. 8 MP1471A - SYNCHRONOUS, STEP-DOWN CONVERTER WITH INTERNAL MOSFETS BLOCK DIAGRAM Figure 1: Functional Block Diagram MP1471A Rev. 1.0 www.MonolithicPower.com 8/18/2013 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. (c) 2013 MPS. All Rights Reserved. 9 MP1471A - SYNCHRONOUS, STEP-DOWN CONVERTER WITH INTERNAL MOSFETS OPERATION The MP1471A is a high-frequency, synchronous, rectified, step-down, switch-mode converter with internal power MOSFETs. It offers a very compact solution to achieve a 3A output current over a wide input supply range, with excellent load and line regulation. The MP1471A operates in a fixed-frequency, peak-current-control mode to regulate the output voltage. An internal clock initiates the PWM cycle to turn on the integrated high-side power MOSFET. This MOSFET remains on until its current reaches the value set by the COMP voltage. 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 COMP set current value within 90% of one PWM period, the power MOSFET is forced to turn off. Internal Regulator The 5V internal regulator powers most of the internal circuits. This regulator takes VIN and operates in the full VIN range. When VIN exceeds 5.0V, the regulator output is in full regulation. When VIN falls below 5.0V, the output decreases. Error Amplifier The error amplifier compares the FB voltage against the internal 0.8V reference (REF) and outputs a current proportional to the difference between the two. This output current charges or discharges the internal compensation network to form the COMP voltage, which is used to control the power MOSFET current. The optimized internal compensation network minimizes the external component counts and simplifies the control-loop design. AAM Operation The MP1471A has AAM (Advanced Asynchronous Modulation) power-save mode for light load. The AAM voltage is set at 0.5V internally. Under the heavy load condition, the VCOMP is higher than VAAM. When the clock goes high, the high-side power MOSFET turns on and remains on until VILsense reaches the value set by the COMP voltage. The internal clock resets every time when VCOMP exceed VAAM. In light-load condition, the value of VCOMP is low. When VCOMP is less than VAAM and VFB is less than VREF, VCOMP ramps up until it exceeds VAAM. During this time, the internal clock is blocked, thus the MP1471A skips some pulses for PFM (Pulse Frequency Modulation) mode and achieves the light load power save. Figure 2: Simplified AAM Control Circuit When the load current is light, the inductor peak current is set internally to about 650mA for VIN=12V, VOUT=3.3V, and L=4.7H. Figure 3 shows the inductor peak current vs. inductor value curve. Figure 3: Inductor Peak Current vs. Inductor Value Enable EN is a digital control pin that turns the regulator on and off: Drive EN HIGH to turn on the regulator, drive it LOW to turn it off. An internal 1M resistor from EN to GND allows EN to float to shut down the chip. The EN pin is clamped internally using a 6.5V series-Zener-diode as shown in Figure 4. Connecting the EN input pin through a pullup MP1471A Rev. 1.0 www.MonolithicPower.com 8/18/2013 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. (c) 2013 MPS. All Rights Reserved. 10 MP1471A - SYNCHRONOUS, STEP-DOWN CONVERTER WITH INTERNAL MOSFETS resistor to the VIN voltage limits the EN input current to less than 100A. MP1471A exits hiccup mode once the overcurrent condition is removed. For example, with 12V connected to Vin, RPULLUP (12V-6.5V) 100A =55k Thermal Shutdown Thermal shutdown prevents the chip from operating at exceedingly high temperatures. When the silicon die temperature exceeds 150C, it shuts down the whole chip. When the temperature falls below its lower threshold (typically 130C) the chip is enabled again. Connecting the EN pin directly to a voltage source without any pullup resistor requires limiting the amplitude of the voltage source to 6V to prevent damage to the Zener diode. Figure 4: 6.5V Zener Diode Under-Voltage Lockout (UVLO) Under-voltage lockout (UVLO) protects the chip from operating at an insufficient supply voltage. The MP1471A UVLO comparator monitors the output voltage of the internal regulator, VCC. The UVLO rising threshold is about 4.15V while its falling threshold is consistently 3.8V. Internal Soft-Start Soft-start prevents the converter output voltage from overshooting during startup. When the chip starts, the internal circuit generates a softstart voltage (SS) that ramps up from 0V to 1.2V: When SS falls below the internal reference (REF), SS overrides REF so that the error amplifier uses SS as the reference; when SS exceeds REF, the error amplifier resumes using REF as its reference. The SS time is internally set to 1.5ms. Over-Current-Protection and Hiccup The MP1471A has a cycle-by-cycle overcurrent limit for when the inductor current peak value exceeds the set current-limit threshold. First, when the output voltage drops until FB falls below the Under-Voltage (UV) threshold (typically 140mV) to trigger a UV event, the MP1471A enters hiccup mode to periodically restart the part. This protection mode is especially useful when the output is deadshorted to ground. This greatly reduces the average short-circuit current to alleviate thermal issues and to protect the regulator. The 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, R4, C4, L1 and C2 (Figure 5). If (VIN-VSW) exceeds 5V, U2 will regulate M1 to maintain a 5V BST voltage across C4. Figure 5 : Internal Bootstrap Charging Circuit Start-Up and Shutdown If both VIN and EN exceed their respective thresholds, the chip starts. The reference block starts first, generating a stable reference voltage and currents, 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 initially blocking the signaling path to avoid any fault triggering. The COMP voltage and the internal supply rail are then pulled down. The floating driver is not subject to this shutdown command. MP1471A Rev. 1.0 www.MonolithicPower.com 8/18/2013 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. (c) 2013 MPS. All Rights Reserved. 11 MP1471A - SYNCHRONOUS, STEP-DOWN CONVERTER WITH INTERNAL MOSFETS APPLICATION INFORMATION Setting the Output Voltage The external resistor divider sets the output voltage. The feedback resistor R1 also sets the feedback-loop bandwidth through the internal compensation capacitor (see the Typical Application circuit). Choose R1 around 10k, and R2 by: R2 R1 VOUT 1 0.8V Use a T-type network for when VOUT is low. Table 1 lists the recommended T-type resistors value for common output voltages. Table 1--Resistor Selection for Common Output Voltages VOUT R1 R2 Rt LOUT COUT (V) (k) (k) (k) (H) (F) 1.05 1.2 1.8 2.5 3.3 10 20.5 40.2 40.2 40.2 32.4 41.2 32.4 19.1 13 150 120 75 59 40.2 2.2 2.2 3.3 3.3 4.7 44 44 44 44 44 5 40.2 7.68 24.9 4.7 44 Selecting the Inductor Use a 1H-to-22H inductor with a DC current rating of at least 25% percent higher than the maximum load current for most applications. For highest efficiency, select an inductor with a DC resistance less than 15m. For most designs, derive the inductance value from the following equation. VOUT (VIN VOUT ) VIN IL fOSC Where IL is the inductor ripple current. Choose an inductor current approximately 30% of the maximum load current. The maximum inductor peak current is: IL(MAX ) ILOAD IL 2 Selecting the Input Capacitor The input current to the step-down converter is discontinuous, and therefore requires a capacitor to both supply the AC current to the step-down converter and maintain the DC input voltage. Use low ESR capacitors for the best performance, such as ceramic capacitors with X5R or X7R dielectrics of their low ESR and small temperature coefficients. A 22F capacitor is sufficient for most applications. The input capacitor (C1) requires an adequate ripple current rating because it absorbs the input switching. Estimate the RMS current in the input capacitor with: Figure 6: T-Type Network L1 Under light-load conditions (below 100mA), use a larger inductance for improved efficiency. IC1 ILOAD VOUT VOUT 1 VIN VIN The worst-case condition occurs at VIN = 2VOUT, where: IC1 ILOAD 2 For simplification, choose an input capacitor with an RMS current rating greater than half the maximum load current. The input capacitor can be electrolytic, tantalum, or ceramic. Place a small, high-quality, ceramic capacitor (0.1F) as close to the IC as possible when using electrolytic or tantalum capacitors. When using ceramic capacitors, make sure that they have enough capacitance to provide sufficient charge to prevent excessive input voltage ripple. Estimate the input voltage ripple caused by the capacitance with: VIN ILOAD V V OUT 1 OUT fS C1 VIN VIN Selecting the Output Capacitor The output capacitor (C2) maintains the DC output voltage. Use ceramic, tantalum, or lowESR electrolytic capacitors. Use low ESR capacitors to limit the output voltage ripple. Estimate the output voltage ripple with: MP1471A Rev. 1.0 www.MonolithicPower.com 8/18/2013 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. (c) 2013 MPS. All Rights Reserved. 12 MP1471A - SYNCHRONOUS, STEP-DOWN CONVERTER WITH INTERNAL MOSFETS VOUT VOUT VOUT 1 1 RESR fS L1 VIN 8 fS C2 Where L1 is the inductor value and RESR is the equivalent series resistance (ESR) of the output capacitor. For ceramic capacitors, the capacitance dominates the impedance at the switching frequency and causes most of the output voltage ripple. For simplification, estimate the output voltage ripple with: VOUT V VOUT 1 OUT VIN 8 fS2 L1 C2 For tantalum or electrolytic capacitors, the ESR dominates the impedance at the switching frequency. For simplification, the output ripple can be approximated with: VOUT VOUT V 1 OUT fS L1 VIN PC Board Layout PCB layout is very important to achieve stable operation. For best results, use the following guidelines and Figure 8 as reference. 1) Keep the connection between the input ground and GND pin as short and wide as possible. 2) Keep the connection between the input capacitor and IN pin as short and wide as possible. 3) Use short and direct feedback connections. Place the feedback resistors and compensation components as close to the chip as possible. 4) Route SW away from sensitive analog areas such as FB. RESR The characteristics of the output capacitor also affect the stability of the regulation system. The MP1471A can be optimized for a wide range of capacitance and ESR values. External Bootstrap Diode An external bootstrap (BST) diode can enhance the efficiency of the regulator given the following applicable conditions: VOUT is 5V or 3.3V; and Duty cycle is high: D= VOUT >65% VIN Connect the external BST diode from the output of voltage regulator to the BST pin, as shown in Figure 7. Figure 7 : Optional External Bootstrap Diode For most applications, use an IN4148 for the external BST diode is IN4148, and a 1F capacitor for the BST capacitor. Figure 8: Sample Layout MP1471A Rev. 1.0 www.MonolithicPower.com 8/18/2013 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. (c) 2013 MPS. All Rights Reserved. 13 MP1471A - SYNCHRONOUS, STEP-DOWN CONVERTER WITH INTERNAL MOSFETS Design Example Below is a design example following the application guidelines for the specifications: Table 2--Design Example VIN 12V VOUT 3.3V Io 3A The detailed application schematic is shown in Figure 10. The typical performance and circuit waveforms have been shown in the Typical Performance Characteristics section. For more device applications, please refer to the related Evaluation Board Datasheets. MP1471A Rev. 1.0 www.MonolithicPower.com 8/18/2013 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. (c) 2013 MPS. All Rights Reserved. 14 MP1471A - SYNCHRONOUS, STEP-DOWN CONVERTER WITH INTERNAL MOSFETS TYPICAL APPLICATION CIRCUITS Figure 9: 12VIN, 5V/3A Figure 10: 12VIN, 3.3V/3A Figure 11: 12VIN, 2.5V/3A MP1471A Rev. 1.0 www.MonolithicPower.com 8/18/2013 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. (c) 2013 MPS. All Rights Reserved. 15 MP1471A - SYNCHRONOUS, STEP-DOWN CONVERTER WITH INTERNAL MOSFETS Figure 12: 12VIN, 1.8V/3A Figure 13: 12VIN, 1.2V/3A MP1471A Rev. 1.0 www.MonolithicPower.com 8/18/2013 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. (c) 2013 MPS. All Rights Reserved. 16 MP1471A - SYNCHRONOUS, STEP-DOWN CONVERTER WITH INTERNAL MOSFETS PACKAGE INFORMATION TSOT23-6 See note 7 EXAMPLE TOP MARK PIN 1 ID IAAAA TOP VIEW RECOMMENDED LAND PATTERN SEATING PLANE SEE DETAIL'' A'' FRONT VIEW SIDE VIEW NOTE: DETAIL "A" 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 CONFORMS TO JEDEC MO-193, VARIATION AB. 6) DRAWING IS NOT TO SCALE. 7) PIN 1 IS LOWER LEFT PIN WHEN READING TOP MARK FROM LEFT TO RIGHT, (SEE EXAMPLE TOP MARK) 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. MP1471A Rev. 1.0 www.MonolithicPower.com 8/18/2013 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. (c) 2013 MPS. All Rights Reserved. 17 Mouser Electronics Authorized Distributor Click to View Pricing, Inventory, Delivery & Lifecycle Information: Monolithic Power Systems (MPS): MP1471AGJ-P MP1471AGJ-Z