MP2358DS-LF-Z

MP28313 2A, 16V, 340KHz Synchronous Rectified Step-Down Converter The Future of Analog IC Technology DESCRIPTION FEATURES The MP28313 is a monolithic synchronous buck regulator. The device integrates 130mΩ MOSFETS that provide 2A continuous load current over a wide operating input voltage of 5V to 16V. Current mode control provides fast transient response and cycle-by-cycle current limit. • • • • • • • • • • An adjustable soft-start prevents inrush current at turn-on. Shutdown mode drops the supply current to 1µA. This device, available in an 8-pin SOIC package, provides a very compact system solution with minimal reliance on external components. 2A Output Current Wide 5V to 16V Operating Input Range Integrated 130mΩ Power MOSFET Switches Output Adjustable from 0.923V to 13V Up to 93% Efficiency Programmable Soft-Start Stable with Low ESR Ceramic Output Capacitors Fixed 340KHz Frequency Cycle-by-Cycle Over Current Protection Input Under Voltage Lockout APPLICATIONS • • • • • Distributed Power Systems Networking Systems FPGA, DSP, ASIC Power Supplies Green Electronics/ Appliances Notebook Computers “MPS” and “The Future of Analog IC Technology” are Registered Trademarks of Monolithic Power Systems, Inc. TYPICAL APPLICATION C5 10nF INPUT 5V to 16V Efficiency vs Load Current 100 VOUT = 3.3V 95 1 IN BS 3 SW EN MP28313 8 SS GND 4 FB COMP 5 6 C3 3.3nF OUTPUT 3.3V 2A EFFICIENCY (%) 2 7 90 85 VOUT = 2.5V 80 75 70 65 60 55 50 0 0.5 1.0 1.5 2.0 LOAD CURRENT (A) 2.5 MP28313_EC01 MP28313 Rev. 1.5 9/27/2010 www.MonolithicPower.com MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited. © 2010 MPS. All Rights Reserved. 1 MP28313 – 2A, 16V, 340KHz SYNCHRONOUS RECTIFIED, STEP-DOWN CONVERTER ORDERING INFORMATION Part Number MP28313CS* MP28313DS Package SOIC8 Top Marking Free Air Temperature (TA) MP28313CS 0°C to +85°C MP28313DS –40°C to +85°C * For Tape & Reel, add suffix –Z (e.g. MP28313CS–Z) For RoHS compliant packaging, add suffix –LF (e.g. MP28313CS–LF–Z) PACKAGE REFERENCE TOP VIEW BS 1 8 SS IN 2 7 EN SW 3 6 COMP GND 4 5 FB MP28313_PD01 ABSOLUTE MAXIMUM RATINGS (1) Thermal Resistance Supply Voltage VIN .......................–0.3V to +22V Switch Voltage VSW .................. –1V to VIN +0.3V Boost Voltage VBS ..........VSW – 0.3V to VSW + 6V All Other Pins .................................–0.3V to +6V Continuous Power Dissipation (TA = +25°C)(2) …………………………………………………1.4W Junction Temperature ...............................150°C Lead Temperature ....................................260°C Storage Temperature ............. –65°C to +150°C SOIC8 .....................................90 ...... 45 ... °C/W Recommended Operating Conditions (3) Input Voltage VIN .................................5V to 16V Output Voltage VOUT .....................0.923V to 13V MP28313CS Operating Junct. Temp (TJ)............. ……………………………………….0°C to +85°C MP28313DS Operating Junct. Temp (TJ)............. ……………………………………...-40°C to +85°C MP28313 Rev. 1.5 9/27/2010 (4) θJA θJC 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 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. 3) The device is not guaranteed to function outside of its operating conditions. 4) Measured on JESD51-7, 4-layer PCB.. www.MonolithicPower.com MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited. © 2010 MPS. All Rights Reserved. 2 MP28313 – 2A, 16V, 340KHz SYNCHRONOUS RECTIFIED, STEP-DOWN CONVERTER ELECTRICAL CHARACTERISTICS VIN = 12V, TA = +25°C, unless otherwise noted. Parameter Symbol Condition Shutdown Supply Current Supply Current Feedback Voltage VEN = 0V VEN = 2.0V; VFB = 1.0V VFB Feedback Overvoltage Threshold Error Amplifier Voltage Gain (5) High-Side Switch On Resistance (5) Low-Side Switch On Resistance (5) High-Side Switch Leakage Current Upper Switch Current Limit Oscillation Frequency Short Circuit Oscillation Frequency Maximum Duty Cycle Minimum On Time (5) EN Shutdown Threshold Voltage EN Shutdown Threshold Voltage Hysteresis EN Lockout Threshold Voltage EN Lockout Hysterisis Input Under Voltage Lockout Threshold Input Under Voltage Lockout Threshold Hysteresis Soft-Start Current Soft-Start Period Thermal Shutdown (5) Min 5V ≤ VIN ≤ 16V, TA =+25°C TA = 0°C to +85°C TA = -40°C to +85°C 0.909 Typ Max Units 1 1.3 10 1.8 µA mA 0.923 0.937 V .941 .941 V .906 .905 1.1 V AEA 400 V/V RDS(ON)1 130 mΩ RDS(ON)2 130 mΩ VEN = 0V, VSW = 0V Minimum Duty Cycle Fosc1 Fosc2 VFB = 0V DMAX VFB = 1.0V VEN Rising 10 2.6 300 87 1.1 3.4 340 A KHz 100 KHz 90 220 1.5 % ns V 340 2.0 210 VIN Rising µA mV 2.2 2.5 210 2.7 V mV 3.80 4.10 4.40 V VSS = 0V CSS = 0.1µF 145 210 mV 6 15 160 µA ms °C Note: 5) Guaranteed by design, not tested. MP28313 Rev. 1.5 9/27/2010 www.MonolithicPower.com MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited. © 2010 MPS. All Rights Reserved. 3 MP28313 – 2A, 16V, 340KHz SYNCHRONOUS RECTIFIED, STEP-DOWN CONVERTER PIN FUNCTIONS Pin # Name 1 BS 2 IN 3 SW 4 GND 5 FB 6 COMP 7 EN 8 SS MP28313 Rev. 1.5 9/27/2010 Description High-Side Gate Drive Boost Input. BS supplies the drive for the high-side N-Channel MOSFET switch. Connect a 0.01µF or greater capacitor from SW to BS to power the high side switch. Power Input. IN supplies the power to the IC, as well as the step-down converter switches. Drive IN with a 5V to 16V power source. Bypass IN to GND with a suitably large capacitor to eliminate noise on the input to the IC. See Input Capacitor. Power Switching Output. SW is the switching node that supplies power to the output. Connect the output LC filter from SW to the output load. Note that a capacitor is required from SW to BS to power the high-side switch. Ground. Feedback Input. FB senses the output voltage to regulate that voltage. Drive FB with a resistive voltage divider from the output voltage. The feedback threshold is 0.923V. See Setting the Output Voltage. Compensation Node. COMP is used to compensate the regulation control loop. Connect a series RC network from COMP to GND to compensate the regulation control loop. In some cases, an additional capacitor from COMP to GND is required. See Compensation Components. Enable Input. EN is a digital input that turns the regulator on or off. Drive EN high to turn on the regulator, drive it low to turn it off. Pull up with 100kΩ resistor for automatic startup. Soft-Start Control Input. SS controls the soft start period. Connect a capacitor from SS to GND to set the soft-start period. A 0.1µF capacitor sets the soft-start period to 15ms. To disable the soft-start feature, leave SS unconnected. www.MonolithicPower.com MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited. © 2010 MPS. All Rights Reserved. 4 MP28313 – 2A, 16V, 340KHz SYNCHRONOUS RECTIFIED, STEP-DOWN CONVERTER TYPICAL PERFORMANCE CHARACTERISTICS VIN = 12V, VO = 3.3V, L = 10µH, C1 = 10µF, C2 = 22µF, TA = +25°C, unless otherwise noted. Shutdown through Enable Startup through Enable Steady State Test VIN = 12V, VOUT = 3.3V IOUT = 1A (Resistance Load) VIN = 12V, VOUT = 3.3V IOUT = 1A (Resistance Load) VIN = 12V, VOUT = 3.3V IOUT = 0A, IIN= 8.2mA VIN 20mV/div. VOUT 20mV/div. IL 1A/div. VEN 5V/div. VEN 5V/div. VOUT 2V/div. VOUT 2V/div. IL 1A/div. IL 1A/div. VSW 10V/div. VSW 10V/div. VSW 10V/div. 2ms/div. 2ms/div. MP28313-TPC01 MP28313-TPC03 MP28313-TPC02 Heavy Load Operation Medium Load Operation Light Load Operation 2A Load 1A Load No Load VIN, AC 200mV/div. VIN, AC 200mV/div. VIN, AC 20mV/div. VO, AC 20mV/div. VO, AC 20mV/div. VO, AC 20mV/div. IL 1A/div. IL 1A/div. VSW 10V/div. VSW 10V/div. IL 1A/div. VSW 10V/div. MP28313-TPC04 MP28313-TPC05 Short Circuit Recovery Short Circuit Protection Load Transient VOUT 2V/div. VOUT 2V/div. VOUT 200mV/div. IL 1A/div. IL 2A/div. IL 2A/div. MP28313-TPC07 MP28313 Rev. 1.5 9/27/2010 MP28313-TPC06 ILOAD 1A/div. MP28313-TPC08 www.MonolithicPower.com MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited. © 2010 MPS. All Rights Reserved. MP28313-TPC09 5 MP28313 – 2A, 16V, 340KHz SYNCHRONOUS RECTIFIED, STEP-DOWN CONVERTER OPERATION FUNCTIONAL DESCRIPTION The MP28313 is a synchronous rectified, current-mode, step-down regulator. It regulates input voltages from 5V to 16V down to an output voltage as low as 0.923V, and supplies up to 2A of load current. The MP28313 uses current-mode control to regulate the output voltage. The output voltage is measured at FB through a resistive voltage divider and amplified through the internal transconductance error amplifier. The voltage at the COMP pin is compared to the switch current measured internally to control the output voltage. The converter uses internal N-Channel MOSFET switches to step-down the input voltage to the regulated output voltage. Since the high side MOSFET requires a gate voltage greater than the input voltage, a boost capacitor connected between SW and BS is needed to drive the high side gate. The boost capacitor is charged from the internal 5V rail when SW is low. When the MP28313 FB pin exceeds 20% of the nominal regulation voltage of 0.923V, the over voltage comparator is tripped and the COMP pin and the SS pin are discharged to GND, forcing the high-side switch off. + CURRENT SENSE AMPLIFIER OVP 1.1V -OSCILLATOR + FB 5 100/340KHz 0.3V RAMP + + + ERROR AMPLIFIER S Q BS R Q 3 SW 4 GND CURRENT COMPARATOR COMP 6 2.5V 1 5V --- 0.923V IN -- CLK -- SS 8 + 2 1.2V + EN EN OK -- OVP IN < 4.10V LOCKOUT COMPARATOR IN + EN 7 INTERNAL REGULATORS 1.5V -- SHUTDOWN COMPARATOR 5V MP28313_F01_BD01 Figure 1—Functional Block Diagram MP28313 Rev. 1.5 9/27/2010 www.MonolithicPower.com MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited. © 2010 MPS. All Rights Reserved. 6 MP28313 – 2A, 16V, 340KHz SYNCHRONOUS RECTIFIED, STEP-DOWN CONVERTER APPLICATIONS INFORMATION COMPONENT SELECTION INPUT 5V to 16V 2 7 1 IN OUTPUT 3.3V 2A BS 3 SW EN MP28313 8 SS GND FB COMP 4 5 6 Figure 2—Application Circuit Setting the Output Voltage The output voltage is set using a resistive voltage divider from the output voltage to FB pin. The voltage divider divides the output voltage down to the feedback voltage by the ratio: VFB = VOUT R2 R1 + R2 Where VFB is the feedback voltage and VOUT is the output voltage. Thus the output voltage is: VOUT = 0.923 × R1 + R2 R2 R2 can be as high as 100kΩ, but a typical value is 10kΩ. Using the typical value for R2, R1 is determined by: R1 = 10.83 × ( VOUT − 0.923 ) (kΩ) For example, for a 3.3V output voltage, R2 is 10kΩ, and R1 is 26.1kΩ. Inductor The inductor is required to supply constant current to the output load while being driven by the switched input voltage. A larger value inductor will result in less ripple current that will result in lower output ripple voltage. However, the larger value inductor will have a larger physical size, higher series resistance, and/or lower saturation current. A good rule for MP28313 Rev. 1.5 9/27/2010 determining the inductance to use is to allow the peak-to-peak ripple current in the inductor to be approximately 30% of the maximum switch current limit. Also, make sure that the peak inductor current is below the maximum switch current limit. The inductance value can be calculated by: L= ⎛ VOUT V × ⎜⎜1 − OUT f S × ∆I L ⎝ VIN ⎞ ⎟⎟ ⎠ Where VOUT is the output voltage, VIN is the input voltage, fS is the switching frequency, and ∆IL is the peak-to-peak inductor ripple current. Choose an inductor that will not saturate under the maximum inductor peak current. The peak inductor current can be calculated by: ILP = ILOAD + ⎛ VOUT V × ⎜1 − OUT 2 × f S × L ⎜⎝ VIN ⎞ ⎟⎟ ⎠ Where ILOAD is the load current. The choice of which style inductor to use mainly depends on the price vs. size requirements and any EMI requirements. www.MonolithicPower.com MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited. © 2010 MPS. All Rights Reserved. 7 MP28313 – 2A, 16V, 340KHz SYNCHRONOUS RECTIFIED, STEP-DOWN CONVERTER Optional Schottky Diode During the transition between high-side switch and low-side switch, the body diode of the lowside power MOSFET conducts the inductor current. The forward voltage of this body diode is high. An optional Schottky diode may be paralleled between the SW pin and GND pin to improve overall efficiency. Table 1 lists example Schottky diodes and their Manufacturers. Table 1—Diode Selection Guide Part Number Voltage/Current Rating B130 SK13 MBRS130 30V, 1A 30V, 1A 30V, 1A Vendor Diodes, Inc. Diodes, Inc. International Rectifier Input Capacitor The input current to the step-down converter is discontinuous, therefore a capacitor is required to supply the AC current to the step-down converter while maintaining the DC input voltage. Use low ESR capacitors for the best performance. Ceramic capacitors are preferred, but tantalum or low-ESR electrolytic capacitors may also suffice. Choose X5R or X7R dielectrics when using ceramic capacitors. Since the input capacitor (C1) absorbs the input switching current it requires an adequate ripple current rating. The RMS current in the input capacitor can be estimated by: I C1 = ILOAD ⎛ ⎞ V V × OUT ×⎜⎜1− OUT ⎟⎟ VIN ⎝ VIN ⎠ The worst-case condition occurs at VIN = 2VOUT, where IC1 = ILOAD/2. For simplification, choose the input capacitor whose 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, a small, high quality ceramic capacitor, i.e. 0.1µF, should be placed as close to the IC as possible. When using ceramic capacitors, make sure that they have enough capacitance to provide sufficient charge to prevent excessive voltage ripple at input. The input voltage ripple for low ESR capacitors can be estimated by: MP28313 Rev. 1.5 9/27/2010 ∆VIN = ⎛ ILOAD V V × OUT × ⎜⎜1 − OUT C1 × fS VIN ⎝ VIN ⎞ ⎟⎟ ⎠ Where C1 is the input capacitance value. Output Capacitor The output capacitor is required to maintain the DC output voltage. Ceramic, tantalum, or low ESR electrolytic capacitors are recommended. Low ESR capacitors are preferred to keep the output voltage ripple low. The output voltage ripple can be estimated by: ∆VOUT = VOUT ⎛ V × ⎜1 − OUT f S × L ⎜⎝ VIN ⎞ ⎞ ⎛ 1 ⎟ ⎟⎟ × ⎜ R ESR + ⎜ 8 × f S × C2 ⎟⎠ ⎠ ⎝ Where C2 is the output capacitance value and RESR is the equivalent series resistance (ESR) value of the output capacitor. In the case of ceramic capacitors, the impedance at the switching frequency is dominated by the capacitance. The output voltage ripple is mainly caused by the capacitance. For simplification, the output voltage ripple can be estimated by: ∆VOUT = ⎛ V × ⎜⎜1 − OUT VIN × L × C2 ⎝ VOUT 8 × fS 2 ⎞ ⎟⎟ ⎠ In the case of tantalum or electrolytic capacitors, the ESR dominates the impedance at the switching frequency. For simplification, the output ripple can be approximated to: ∆VOUT = VOUT ⎛ V × ⎜⎜1 − OUT fS × L ⎝ VIN ⎞ ⎟⎟ × R ESR ⎠ The characteristics of the output capacitor also affect the stability of the regulation system. The MP28313 can be optimized for a wide range of capacitance and ESR values. Compensation Components MP28313 employs current mode control for easy compensation and fast transient response. The system stability and transient response are controlled through the COMP pin. COMP pin is the output of the internal transconductance error amplifier. A series capacitor-resistor combination sets a pole-zero combination to control the characteristics of the control system. www.MonolithicPower.com MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited. © 2010 MPS. All Rights Reserved. 8 MP28313 – 2A, 16V, 340KHz SYNCHRONOUS RECTIFIED, STEP-DOWN CONVERTER The DC gain of the voltage feedback loop is given by: A VDC = R LOAD × G CS × A EA × VFB VOUT in slower line and load transient responses, while higher crossover frequencies could cause system instability. A good rule of thumb is to set the crossover frequency below one-tenth of the switching frequency. Where AVEA is the error amplifier voltage gain; GCS is the current sense transconductance and RLOAD is the load resistor value. To optimize the compensation components, the following procedure can be used. The system has two poles of importance. One is due to the compensation capacitor (C3, Figure2) and the output resistor of the error amplifier, and the other is due to the output capacitor and the load resistor. These poles are located at: Determine the R3 value by the following equation: fP1 = GEA 2π × C3 × A VEA fP2 = 1 2π × C2 × R LOAD Where GEA is transconductance. the error amplifier 1 2π × C3 × R3 1 2π × C2 × R ESR In this case, a third pole set by compensation capacitor (C6, Figure2) and compensation resistor (R3) is used compensate the effect of the ESR zero on loop gain. This pole is located at: fP 3 = 2π × C2 × fC VOUT 2π × C2 × 0.1 × fS VOUT × < × GEA × GCS VFB GEA × GCS VFB 2. Choose the compensation capacitor (C3, Figure2) to achieve the desired phase margin. For applications with typical inductor values, setting the compensation zero, fZ1, below oneforth of the crossover frequency provides sufficient phase margin. Determine the C3 value by the following equation: C3 > The system may have another zero of importance, if the output capacitor has a large capacitance and/or a high ESR value. The zero, due to the ESR and capacitance of the output capacitor, is located at: fESR = R3 = Where fC is the desired crossover frequency which is typically below one tenth of the switching frequency. The system has one zero of importance, due to the compensation capacitor (C3) and the compensation resistor (R3). This zero is located at: f Z1 = 1. Choose the compensation resistor (R3, Figure2) to set the desired crossover frequency. the the to the 1 2π × C6 × R3 4 2π × R3 × f C Where R3 is the compensation resistor. 3. Determine if the second compensation capacitor (C6, Figure2) is required. It is required if the ESR zero of the output capacitor is located at less than half of the switching frequency, or the following relationship is valid: f 1 < S 2π × C2 × R ESR 2 If this is the case, then add the second compensation capacitor (C6, Figure2) to set the pole fP3 at the location of the ESR zero. Determine the C6 value by the equation: C6 = C2 × R ESR R3 The goal of compensation design is to shape the converter transfer function to get a desired loop gain. The system crossover frequency where the feedback loop has the unity gain is important. Lower crossover frequencies result MP28313 Rev. 1.5 9/27/2010 www.MonolithicPower.com MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited. © 2010 MPS. All Rights Reserved. 9 MP28313 – 2A, 16V, 340KHz SYNCHRONOUS RECTIFIED, STEP-DOWN CONVERTER External Bootstrap Diode An external bootstrap diode may enhance the efficiency of the regulator, the applicable conditions of external BST diode are: z VOUT=5V or 3.3V; and z Duty cycle is high: D= VOUT >65% VIN In these cases, an external BST diode is recommended from the output of the voltage regulator to BST pin, as shown in Figure3 External BST Diode IN4148 BST MP28313 SW CBST L + COUT 5V or 3.3V Figure 3—Add Optional External Bootstrap Diode to Enhance Efficiency The recommended external BST diode is IN4148, and the BST cap is 0.1~1µF. MP28313 Rev. 1.5 9/27/2010 www.MonolithicPower.com MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited. © 2010 MPS. All Rights Reserved. 10 MP28313 – 2A, 16V, 340KHz SYNCHRONOUS RECTIFIED, STEP-DOWN CONVERTER PACKAGE INFORMATION SOIC8 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. MP28313 Rev. 1.5 9/27/2010 www.MonolithicPower.com MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited. © 2010 MPS. All Rights Reserved. 11