MP2565DQ-LF-P

MP2565 2.5A, 4MHz, 50V Step-Down Converter The Future of Analog IC Technology FEATURES DESCRIPTION • • • • The MP2565 is a high frequency step-down switching regulator with an integrated internal high-side high voltage power MOSFET. It provides 2.5A output with current mode control for fast loop response and easy compensation. • • • • The wide 4.5V to 50V input range accommodates a variety of step-down applications, including those in an automotive input environment. A 12µA shutdown mode supply current allows use in battery-powered applications. • • • High power conversion efficiency over a wide load range is achieved by scaling down the switching frequency at light load condition to reduce the switching and gate driving losses. 120μA Quiescent Current Wide 4.5V to 50V Operating Input Range 220mΩ Internal Power MOSFET Up to 4MHz Programmable Switching Frequency High-Efficiency, Light-Load operation Stable with Ceramic Capacitor Internal Soft-Start Internally Set Current Limit without external Current Sensing Resistor Up to 95% Efficiency Output Adjustable from 0.8V to 47V Available in 3x3 QFN10 and Thermally Enhanced SOIC8 Packages APPLICATIONS The frequency foldback helps prevent inductor current runaway during startup and thermal shutdown provides reliable, fault tolerant operation. • • • • • By switching at 4MHz, the MP2565 is able to prevent EMI (Electromagnetic Interference) noise problems, such as those found in AM radio and ADSL applications. High Voltage Power Conversion Automotive Systems Industrial Power Systems Distributed Power Systems Battery Powered Systems All MPS parts are lead-free, halogen free, and adhere to the RoHS directive. For MPS green status, please visit MPS website under Quality Assurance. “MPS” and “The Future of Analog IC Technology” are Registered Trademarks of Monolithic Power Systems, Inc. The MP2565 is available in small 3mm x 3mm QFN10 and thermally enhanced SOIC8 packages. TYPICAL APPLICATION C4 100nF Efficiency @VOUT=3.3V fs=500kHz 10 C1 50V VIN BST L1 SW 1,2 C2 D1 R5 3 EN EN R6 7 MP2565 R2 COMP FREQ GND R4 FB 6 6.3V 5 4 R1 VOUT 3.3V VIN=8V 80 70 VIN=36V 60 C3 220pF 50 R3 40 VIN=24V VIN=50V 0 MP2565 Rev. 1.01 12/9/2015 VIN=12V 90 EFFICIENCY (%) 8,9 VIN 100 0.5 1 1.5 IOUT (A) www.MonolithicPower.com MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2015 MPS. All Rights Reserved. 2 2.5 1 MP2565 – 2.5A, 4MHz, 50V STEP-DOWN CONVERTER ORDERING INFORMATION Part Number* Package Top Marketing Free Air Temperature (TA) MP2565DQ MP2565DN 3x3 QFN10 SOIC8E 8D MP2565DN –40°C to +85°C For Tape & Reel, add suffix –Z (eg. MP2565DQ–Z); For RoHS Compliant Packaging, add suffix –LF; (eg. MP2565DQ–LF–Z) For Tape & Reel, add suffix –Z (eg. MP2565DN–Z); For RoHS Compliant Packaging, add suffix –LF; (eg. MP2565DN–LF–Z) PACKAGE REFERENCE TOP VIEW TOP VIEW SW 1 10 BST SW 1 8 BST SW 2 9 VIN EN 2 7 VIN EN 3 8 VIN COMP 3 6 FREQ COMP 4 7 FREQ FB 4 5 GND FB 5 6 GND EXPOSED PAD CONNECT TO GND EXPOSED PAD ON BACKSIDE CONNECT TO GND ABSOLUTE MAXIMUM RATINGS (1) Thermal Resistance Supply Voltage (VIN).....................–0.3V to +55V Switch Voltage (VSW)........................................... ……………..–0.3V (-9V for 20μA (R1 + R2) Current Comparator and Current Limit The power MOSFET current is accurately sensed via a current sense MOSFET. It is then fed to the high speed current comparator for the current mode control purpose. The current comparator takes this sensed current as one of its inputs. When the power MOSFET is turned on, the comparator is first blanked till the end of the turn-on transition to avoid noise issues. The comparator then compares the power switch current with the COMP voltage. When the sensed current is higher than the COMP voltage, the comparator output is low, turning off the power MOSFET. The cycle-by-cycle maximum current of the internal power MOSFET is internally limited. MP2565 Rev. 1.01 12/9/2015 Startup and Shutdown If both VIN and EN are higher than their appropriate thresholds, the chip starts. The reference block starts first, generating stable reference voltage and currents, and then the internal regulator is enabled. The regulator provides stable supply for the remaining circuitries. While the internal supply rail is up, an internal timer holds the power MOSFET OFF for about 50µs to blank the startup glitches. When the internal soft-start block is enabled, it first holds its SS output low to ensure the remaining circuitries are ready and then slowly ramps up. Three events can shut down the chip: EN low, VIN low and thermal shutdown. In the shutdown procedure, power MOSFET is turned off first to avoid any fault triggering. The COMP voltage and the internal supply rail are then pulled down. Programmable Oscillator The MP2565 oscillating frequency is set by an external resistor, Rfreq from the FREQ pin to ground. The value of Rfreq can be calculated from: R freq (KΩ) = 180000 fs (KHz)1.1 www.MonolithicPower.com MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2015 MPS. All Rights Reserved. 9 MP2565 – 2.5A, 4MHz, 50V STEP-DOWN CONVERTER APPLICATION INFORMATION COMPONENT SELECTION 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 Thus the output voltage is: VOUT = VFB (R1 + R2) R2 About 20µA current from high side BS circuitry can be seen at the output when the MP2565 is at no load. In order to absorb this small amount of current, keep R2 under 40KΩ. A typical value for R2 can be 40.2kΩ. With this value, R1 can be determined by: R1 = 50.25 × ( VOUT − 0.8)(kΩ) For example, for a 3.3V output voltage, R2 is 40.2kΩ, and R1 is 127kΩ. 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. MP2565 Rev. 1.01 12/9/2015 A good rule for 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: L1 = ⎛ ⎞ V VOUT × ⎜1 − OUT ⎟⎟ fS × ΔIL ⎜⎝ VIN ⎠ Where VOUT is the output voltage, VIN is the input voltage, fS is the switching frequency, and ΔIL 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 × fS × L1 ⎝ VIN ⎠ Where ILOAD is the load current. Table 1 lists a number of suitable inductors from various manufacturers. The choice of which style inductor to use mainly depends on the price vs. size requirements and any EMI requirement. www.MonolithicPower.com MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2015 MPS. All Rights Reserved. 10 MP2565 – 2.5A, 4MHz, 50V STEP-DOWN CONVERTER Table 1—Inductor Selection Guide Inductance (µH) Max DCR (Ω) Current Rating (A) Dimensions L x W x H (mm3) 7447789004 4.7 0.033 2.9 7.3x7.3x3.2 744066100 10 0.035 3.6 10x10x3.8 744771115 15 0.025 3.75 12x12x6 744771122 22 0.031 3.37 12x12x6 Part Number Wurth Electronics TDK RLF7030T-4R7 4.7 0.031 3.4 7.3x6.8x3.2 SLF10145T-100 10 0.0364 3 10.1x10.1x4.5 SLF12565T-150M4R2 15 0.0237 4.2 12.5x12.5x6.5 SLF12565T-220M3R5 22 0.0316 3.5 12.5x12.5x6.5 Toko FDV0630-4R7M 4.7 0.049 3.3 7.7x7x3 919AS-100M 10 0.0265 4.3 10.3x10.3x4.5 919AS-160M 16 0.0492 3.3 10.3x10.3x4.5 919AS-220M 22 0.0776 3 10.3x10.3x4.5 Output Rectifier Diode The output rectifier diode supplies the current to the inductor when the high-side switch is off. To reduce losses due to the diode forward voltage and recovery times, use a Schottky diode. Choose a diode whose maximum reverse voltage rating is greater than the maximum input voltage, and whose current rating is greater than the maximum load current. Table 2 lists example Schottky diodes and manufacturers. 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. For simplification, choose the input capacitor with RMS current rating greater than half of the maximum load current. Table 2—Diode Selection Guide Diodes B380-13-F B390 CMSH3-100MA MP2565 Rev. 1.01 12/9/2015 Voltage/ Current Rating 80V, 3A 90V, 3A 100V, 3A Manufacturer Diodes Inc. Diodes Inc. Central Semi www.MonolithicPower.com MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2015 MPS. All Rights Reserved. 11 MP2565 – 2.5A, 4MHz, 50V STEP-DOWN CONVERTER The input capacitor (C1) 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 caused by capacitance can be estimated by: ΔVIN = ⎛ ILOAD V V × OUT × ⎜1 − OUT fS × C1 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. Low ESR capacitors are preferred to keep the output voltage ripple low. The output voltage ripple can be estimated by: ΔVOUT = VOUT ⎛ V × ⎜⎜1 − OUT fS × L ⎝ VIN ⎞ ⎞ ⎛ 1 ⎟ ⎟⎟ × ⎜ R ESR + ⎜ 8 × f S × C2 ⎟⎠ ⎠ ⎝ Where L is the inductor 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: ΔVOUT = ⎞ ⎛ 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: ΔVOUT = VOUT ⎛ V × ⎜1 − OUT f S × L ⎜⎝ VIN ⎞ ⎟⎟ × R ESR ⎠ The characteristics of the output capacitor also affect the stability of the regulation system. The MP2565 can be optimized for a wide range of capacitance and ESR values. MP2565 Rev. 1.01 12/9/2015 Compensation Components MP2565 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 error amplifier. A series capacitor-resistor combination sets a pole-zero combination to control the characteristics of the control system. The DC gain of the voltage feedback loop is given by: A VDC = R LOAD × G CS × A VEA × VFB VOUT Where AVEA is the error amplifier voltage gain, 200V/V; GCS is the current sense transconductance, 7.3A/V; RLOAD is the load resistor value. The system has two poles of importance. One is due to the compensation capacitor (C3), the output resistor of error amplifier. The other is due to the output capacitor and the load resistor. These poles are located at: fP1 = GEA 2π × C3 × A VEA fP2 = 1 2π × C2 × R LOAD Where, GEA is the transconductance, 60μA/V. error amplifier 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 2π × C3 × R3 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 × R ESR www.MonolithicPower.com MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2015 MPS. All Rights Reserved. 12 MP2565 – 2.5A, 4MHz, 50V STEP-DOWN CONVERTER In this case (as shown in Typical Application), 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: f P3 = 1 2π × C6 × R3 1. Choose the compensation resistor (R3) to set the desired crossover frequency. Determine the R3 value by the following equation: R3 = 2π × C2 × f C VOUT × G EA × G CS VFB Where fC is the desired crossover frequency. 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 unstable. A good rule of thumb is to set the crossover frequency to approximately onetenth of the switching frequency. The Table 3 lists the typical values of compensation components for some standard output voltages with various output capacitors and inductors. The values of the compensation components have been optimized for fast transient responses and good stability at given conditions. Table 3—Compensation Values for Typical Output Voltage/Capacitor Combinations VOUT (V) L (µH) C2 (µF) R3 (kΩ) C3 (pF) C6 1.8 4.7 47 105 100 None 2.5 4.7 - 6.8 22 54.9 220 None 3.3 6.8 -10 22 51 220 None 5 15 - 22 22 100 150 None 12 22 - 33 22 147 150 None 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 the C3 value by the following equation: C3 > 4 2π × R3 × f C 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: f 1 < S 2π × C2 × R ESR 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 the C6 value by the equation: C6 = C2 × R ESR R3 To optimize the compensation components for conditions not listed in Table 3, the following procedure can be used. MP2565 Rev. 1.01 12/9/2015 www.MonolithicPower.com MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2015 MPS. All Rights Reserved. 13 MP2565 – 2.5A, 4MHz, 50V STEP-DOWN CONVERTER High Frequency Operation The switching frequency of MP2565 can be programmed up to 4MHz by an external resistor. Please pay attention to the following if the switching frequency is above 2MHz. The minimum on time of MP2565 is about 100ns (typ). Pulse skipping operation can be seen more easily at higher switching frequency due to the minimum on time. Refer to Figure 2 below for detailed information. 30 Recommended VIN (max) vs Switching Frequency VIN (MAX) (V) 25 20 15 VOUT=3.3V 10 VOUT=2.5V 5 1500 2000 2500 3000 3500 4000 fs (KHz) Figure 2—Recommend Max VIN vs. fS Since the internal bootstrap circuitry has higher impedance, which may not be adequate to charge the bootstrap capacitor during each (1D)×Ts charging period, an external bootstrap charging diode is strongly recommended if the switching frequency is above 2MHz (see External Bootstrap Diode section for detailed implementation information). Layout becomes more important when the device switches at higher frequency. It is essential to place the input decoupling capacitor, catch diode and the MP2565 (Vin pin, SW pin and PGND) as close as possible, with traces that are very short and fairly wide. This can help to greatly reduce the voltage spike on SW node, and lower the EMI noise level as well. Try to run the feedback trace as far from the inductor and noisy power traces as possible. It is often a good idea to run the feedback trace on the side of the PCB opposite of the inductor with a ground plane separating the two. The compensation components should be placed closed to the MP2565. Do not place the compensation components close to or under high dv/dt SW node, or inside the high di/dt power loop. If you have to do so, the proper ground plane must be in place to isolate those. Switching loss is expected to be increased at high switching frequency. To help to improve the thermal conduction, a grid of thermal vias can be created right under the exposed pad. It is recommended that they be small (15mil barrel diameter) so that the hole is essentially filled up during the plating process, thus aiding conduction to the other side. Too large a hole can cause ‘solder wicking’ problems during the reflow soldering process. The pitch (distance between the centers) of several such thermal vias in an area is typically 40mil. Please refer to the PCB layout guide and example on EV2565 datasheet. With higher switching frequencies, the inductive reactance (XL) of capacitor comes to dominate, so that the ESL of input/output capacitor determines the input/output ripple voltage at higher switching frequency. As a result of that, high frequency ceramic capacitor is strongly recommended as input decoupling capacitor and output filtering capacitor for such high frequency operation. MP2565 Rev. 1.01 12/9/2015 www.MonolithicPower.com MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2015 MPS. All Rights Reserved. 14 MP2565 – 2.5A, 4MHz, 50V STEP-DOWN CONVERTER External Bootstrap Diode It is recommended that an external bootstrap diode be added when the input voltage is no greater than 5V or the 5V rail is available in the system. This helps improve the efficiency of the regulator. The bootstrap diode can be a low cost one such as IN4148 or BAT54. 5V BST MP2565 0.1 SW This diode is also recommended for high duty cycle operation (when VOUT /VIN >65%) or low VIN (