MP1484ME/TR

MP1484 3A, 18V, 340KHz Synchronous Rectified Step-Down Converter FEATURES  3A Continuous Output Current  Wide 4.75V to 18V Operating Input Range  Integrated 85mΩ Power MOSFET Switches  Output Adjustable from 0.925V to 15V  Up to 95% Efficiency  Programmable Soft-Start  Stable with Low ESR Ceramic Output Capacitors  Fixed 340KHz Frequency  Cycle-by-Cycle Over Current Protection  Input Under Voltage Lockout  Thermally Enhanced 8-Pin SOP Package ESOP-8 Ordering Information DEVICE MP1484ME/TR Package Type MARKING Packing Packing Qty ESOP-8 MP1484 REEL 2500pcs/Reel DESCRIPTION The MP1484 is a monolithic synchronous buck regulator. The device integrates top and bottom 85mΩ MOSFETS that provide 3A of continuous load current over a wide operating input voltage of 4.75V to 18V. Current mode control provides fast transient response and cycle-by-cycle current limit. An adjustable soft-start prevents inrush current at turn-on and in shutdown mode, the supply current drops below 1µA. The MP1484 is PIN compatible to the MP1482 2A/18V/Synchronous Step-Down Converter. APPLICATIONS  FPGA, ASIC, DSP Power Supplies  Green Electronics/Appliances  LCD TV  Notebook Computers http://www.hgsemi.com.cn 1 / 13 2016 MAR MP1484 Efficiency vs Load Current TYPICAL APPLICATION MP1484 PACKAGE REFERENCE ESOP8 PIN FUNCTIONS Pin # Name 1 BS 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. 2 IN Power Input. IN supplies the power to the IC, as well as the step-down converter switches.Drive IN with a 4.75V to 18V power source. See Input Capacitor. 3 SW 4 GND 5 FB Description Power Switching Output. SW is the switching node that supplies power to the output. Connectthe 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 (Connect the exposed pad to Pin 4). Feedback Input. FB senses the output voltage and regulates it. Drive FB with a resistive voltage divider connected to it from the output voltage. The feedback threshold is 0.925V. SeeSetting the Output Voltage. Compensation Node. COMP is used to compensate the regulation control loop. Connect a series RC network from COMP to GND. In some cases, an additional capacitor from COMP toGND is required. See Compensation Components. 6 COMP 7 EN Enable Input. EN is a digital input that turns the regulator on or off. Drive EN high to turn on the regulator; low to turn it off. Attach to IN with a 100kΩ pull up resistor for automatic startup. 8 SS Soft-Start Control Input. SS controls the soft-start period. Connect a capacitor from SS to GNDto 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. http://www.hgsemi.com.cn 2 / 13 2016 MAR MP1484 ABSOLUTE MAXIMUM RATINGS (1) Condition Min Max Unit Supply Voltage VIN -0.3 +24 V Switch Voltage VSW -1 VIN+0.3 V Boost Voltage VBS VSW – 0.3 VSW + 6 V -0.3 +6 V Junction Temperature - 150 ℃ Lead Temperature - 260 ℃ -65 +150 ℃ Min Max Unit Input Voltage VIN 4.75 18 V Output Voltage VOUT 0.925 15 V -20 +85 ℃ θJA θJC Unit 50 10 ℃/W All Other Pins Storage Temperature Recommended Operating Conditions (2) Condition Ambient OperatingTemp Thermal Resistance (3) Condition ESOP8 (Exposed Pad) Notes: 1) Exceeding these ratings may damage the device. 2) The device is not guaranteed to function outside of its operating conditions. 3) Measured on approximately 1” square of 1 oz copper. http://www.hgsemi.com.cn 3 / 13 2016 MAR MP1484 ELECTRICAL CHARACTERISTICS VIN = 12V, TA = +25°C, unless otherwise noted. Parameter Symbol Condition Min Typ Max Units Shutdown Supply Current VEN = 0V 0.3 3.0 µA Supply Current VEN = 2.0V, VFB = 1.0V 1.3 1.5 mA 0.925 0.950 V VFB Feedback Voltage 4.75V VIN 18V 0.900 Feedback Overvoltage Threshold Error Amplifier Voltage Gain (4) Error Amplifier Transconductance AEA GEA IC = 10µA High-Side/Low-Side Switch OnResistance (4) High-Side Switch Leakage Current VEN = 0V, VSW = 0V Upper Switch Current Limit Minimum Duty Cycle Lower Switch Current Limit From Drain to Source COMP to Current Sense Transconductance Fosc1 Short Circuit Oscillation Frequency Fosc2 Maximum Duty Cycle DMAX Minimum On Time TON (4) EN Shutdown Threshold Voltage 3.8 300 µA/V 85 mΩ 10 µA 5.3 A 0.9 A 5.2 A/V 340 380 KHz KHz 90 % 220 ns VEN Rising 1.1 1.5 2.0 V 220 2.2 2.5 mV 2.7 V 210 VIN Rising Input Under Voltage LockoutThreshold Hysteresis Thermal Shutdown 820 110 EN Lockout Hysterisis Soft-Start Period V/V VFB = 1.0V EN Lockout Threshold Voltage Soft-Start Current 400 VFB = 0V EN Shutdown Threshold Voltage Hysterisis Input Under Voltage LockoutThreshold V 0 GCS Oscillation Frequency 1.1 3.80 4.05 mV 4.40 V 210 mV VSS = 0V 6 µA CSS = 0.1µF 15 ms 160 °C (4) Note: 4) Guaranteed by design, not tested. http://www.hgsemi.com.cn 4 / 13 2016 MAR MP1484 TYPICAL PERFORMANCE CHARACTERISTICS C1 = 4.7µF, C2 = 2 x 10µF, L= 10µH, CSS= 0.1µF, TA = +25°C, unless otherwise noted. http://www.hgsemi.com.cn 5 / 13 2016 MAR MP1484 OPERATION FUNCTIONAL DESCRIPTION The MP1484 regulates input voltages from 4.75V to 18V down to an output voltage as low as 0.925V, and supplies up to 3A of load current. The MP1484 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 FB pin voltage exceeds 20% of the nominal regulation value of 0.925V, the over voltage comparator is tripped and the COMP pin and the SS pin are discharged to GND, forcing the high-side switch off. Figure 1—Functional Block Diagram http://www.hgsemi.com.cn 6 / 13 2016 MAR MP1484 APPLICATIONS INFORMATION COMPONENT SELECTION Setting the Output Voltage The output voltage is set using a resistive voltage divider connected from the output voltage to FB. The voltage divider divides the output voltage down to the feedback voltage by the ratio: VFB = VOUT Thus the output voltage is: R2 R1 + R2 VOUT = 0.925 × 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 = 10.81 × (VOUT − 0.925)(KΩ) For example, for a 3.3V output voltage, R2 is 10kΩ, and R1 is 26.1kΩ. Table 1 lists recommended resistance values of R1 and R2 for standard output voltages. Table 1—Recommended Resistance Values VOUT 1.8V 2.5V 3.3V 5V 12V R1 9.53kΩ 16.9kΩ 26.1kΩ 44.2kΩ 121kΩ R2 10kΩ 10kΩ 10kΩ 10kΩ 10kΩ Inductor The inductor is required to supply constant current to the load while being driven by the switched input voltage. A larger value inductor will result in less ripple current that will in turn 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 determining inductance is to allow the peak-to- peak ripple current 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 VOUT × 1− fs × ∆IL 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, calculated by: Where ILOAD is the load current. ILP = ILOAD + VOUT VOUT × 1− 2 × fs × L VIN The choice of which style inductor to use mainly depends on the price vs. size requirements and any EMI constraints. http://www.hgsemi.com.cn 7 / 13 2016 MAR MP1484 Table 2—Diode Selection Guide Part Number Voltage/CurrentRating Vendor B130 30V, 1A Diodes, Inc. SK13 30V, 1A Diodes, Inc. MBRS130 30V, 1A InternationalRectifier Input Capacitor The input current to the step-down converter is discontinuous, therefore a capacitor is required to supply the AC current 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 will 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: IC1 = ILOAD × VOUT VOUT × 1− VIN VIN The worst-case condition occurs at VIN = 2VOUT, where IC1 = ILOAD/2. For simplification, use an input capacitor with a 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: ∆VIN = Where C1 is the input capacitance value. ILOAD VOUT VOUT × × 1− C1 × fs VIN VIN Output Capacitor The output capacitor (C2) is required to maintain the DC output voltage. Ceramic, tantalum, or low ESR electrolytic capacitors are recommended. Under typical application conditions,a minimum ceramic capacitor value of 20 µF is recommended on the output. Low ESR capacitors are preferred to keep the output voltage ripple low. The output voltage ripple can be estimated by: ∆VOUT = VOUT VOUT 1 × 1− × RESR + 8 × fs × CS fs × L VIN Where C2 is the output capacitance value and RESR is the equivalent series resistance (ESR) value of the output capacitor. When using ceramic capacitors, the impedance at the switching frequency is dominated by the capacitance which is the main cause for the output voltage ripple. For simplification, the output voltage ripple can be estimated by: ∆VOUT = http://www.hgsemi.com.cn VOUT 2 8 × fs × L × C2 8 / 13 × 1− VOUT VIN 2016 MAR MP1484 When using tantalum or electrolytic capacitors, the ESR dominates the impedance at the switching frequency. For simplification, the output ripple can be approximated to: ∆VOUT = VOUT VOUT × 1− × RESR fs × L VIN The characteristics of the output capacitor also affect the stability of the regulation system. The MP1484 can be optimized for a wide range of capacitance and ESR values. Compensation Components MP1484 employs current mode control for easy compensation and fast transient response. The system stability and transient response are controlled through the COMP pin. COMP is the output of the internal transconductance error amplifier. A series capacitor-resistor combination sets a pole-zero combination to govern the characteristics of the control system. The DC gain of the voltage feedback loop is given by: AVDC = RLOAD × GCS × AEA × VFB VOUT Where VFB is the feedback voltage (0.925V), AVEA is the error amplifier voltage gain, GCS is the current sense transconductance and RLOAD is the load resistor value. The system has two poles of importance. One is due to the compensation capacitor (C3) 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: fP1 = fP2 = GEA 2π × C3 × AVEA 1 2π × C2 × RLOAD Where GEA is the error amplifier transconductance. http://www.hgsemi.com.cn 9 / 13 2016 MAR MP1484 The system has one zero of importance, due to the compensation capacitor (C3) and the compensation resistor (R3). This zero is located at: 1 2π × C3 × R3 fZ1 = 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 = 1 2π × C2 × RESR In this case, a third pole set by the compensation capacitor (C6) and the compensation resistor (R3) is used to compensate the effect of the ESR zero on the loop gain. This pole is located at: 1 2π × C6 × R3 fP3 = 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 in slower line and load transient responses, while higher crossover frequencies could cause system instability. A good standard is to set the crossover frequency below one-tenth of the switching frequency. To optimize the compensation components, the following procedure can be used. 1. Choose the compensation resistor (R3) to set the desired crossover frequency. Determine R3 by the following equation: R3 = 2π × C2 × fc VOUT 2π × C2 × 0.1 × fs VOUT × < × GEA × GCS GEA × GCS VFB VFB Where fC is the desired crossover frequency which is typically below one tenth of the switching frequency. 2. Choose the compensation capacitor (C3) to achieve the desired phase margin. For applications with typical inductor values, setting the compensation zero (fZ1) below one-forth of the crossover frequency provides sufficient phase margin. Determine C3 by the following equation: Where R3 is the compensation resistor. C3 > 4 2π × R3 × fc 3. Determine if the second compensation capacitor (C6) 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: 1 fs < 2π × C2 × RESR 2 If this is the case, then add the second compensation capacitor (C6) to set the pole fP3 at the location of the ESR zero. Determine C6 by the equation: C6 = http://www.hgsemi.com.cn C2 × RESR R3 10 / 13 2016 MAR MP1484 External Bootstrap Diode An external bootstrap diode may enhance the efficiency of the regulator, the applicable conditions of external BS diode are:  VOUT is 5V or 3.3V:and  Duty cycle is high:D = VOUT VIN > 65% In these cases, an external BS diode is recommended from the output of the voltage regulator to BS pin, as shown in Fig.2 Figure 2—Add Optional External Bootstrap Diode to Enhance Efficiency The recommended external BS diode is IN4148, and the BS cap is 0.1~1µF. TYPICAL APPLICATION CIRCUIT Figure 3—MP1484 with 3.3V Output, 2X10µF Ceramic Output Capacitor http://www.hgsemi.com.cn 11 / 13 2016 MAR MP1484 Physical Dimensions ESOP8 A B Q E C C1 D1 D A1 a b 0.25 Dimensions In Millimeters(ESOP8) A A1 B C C1 D D1 E Q a Min： 1.35 0.05 4.90 5.80 3.80 0.40 3.20 2.31 0° 0.35 Max： 1.55 0.20 5.10 6.20 4.00 0.80 3.40 2.51 8° 0.45 Symbol： http://www.hgsemi.com.cn 12 / 13 b 1.27 BSC 2016 MAR MP1484 IMPORTANT STATEMENT: Huaguan Semiconductor reserves the right to change its products and services without notice. Before ordering, the customer shall obtain the latest relevant information and verify whether the information is up to date and complete. Huaguan Semiconductor does not assume any responsibility or obligation for the altered documents. Customers are responsible for complying with safety standards and taking safety measures when using Huaguan Semiconductor products for system design and machine manufacturing. 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You should fully compensate Huaguan Semiconductor and its agents for any claims, damages, costs, losses and debts caused by the use of these resources. Huaguan Semiconductor accepts no liability for any loss or damage caused by infringement. http://www.hgsemi.com.cn 13 / 13 2016 MAR