MP1593 3A, 28V, 385kHz Step-Down Converter

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1 The Future of Analog IC Technology MP59 A,, 5kHz Step-Down Converter DESCRIPTION The MP59 is a step-down regulator with an internal Power MOSFET. It achieves A of continuous output current over a wide input supply range with excellent load and line regulation. Current mode operation provides fast transient response and eases loop stabilization. Fault condition protection includes cycle-by-cycle current limiting and thermal shutdown. An adjustable soft-start reduces the stress on the input source at startup. In shutdown mode the regulator draws 0µA of supply current. The MP59 requires a minimum number of readily available external components, providing a compact solution. EALUATION BOARD REFERENCE Board Number Dimensions E59DN-00A. X x. Y x 0. Z FEATURES A Output Current Programmable Soft-Start 00mΩ Internal Power MOSFET Switch Stable with Low ESR Output Ceramic Capacitors Up to 95% Efficiency 0μA Shutdown Mode Fixed 5kHz Frequency Thermal Shutdown Cycle-by-Cycle Over Current Protection Wide.75 to Operating Input Range Output Adjustable from. Under-oltage Lockout Available in -Pin SOIC Package APPLICATIONS Distributed Power Systems Battery Chargers Pre-Regulator for Linear Regulators Flat Panel Ts Set-Top Boxes Cigarette Lighter Powered Devices DD/PR Devices 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 PUT.75 to OFF ON C 0μ F/5 CERAMIC x 7 EN MP59 GND 5 C 0.μ F C6 (optional) 6 C.nF R 5.6kΩ C5 0nF D B0A L 0μ H A R 6.9kΩ % R 0kΩ % PUT. A C μ F/6. CERAMIC x EFFICIENCY (%) Efficiency vs Load Current = = 0 = LOAD CURRENT (A) MP59 Rev.. /0/0 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. 0 MPS. All Rights Reserved.

2 MP59 A,, 5kHz STEP-DOWN CONERTER ORDERG FORMATION Part Number* Package Top Marking Free Air Temperature (T A ) MP59DN SOICE MP59DN -0C to +5C * For Tape & Reel, add suffix Z (e.g. MP59DN Z). For RoHS Compliant packaging, add suffix LF (e.g. MP59DN LF Z) PACKAGE REFERENCE TOP IEW 7 EN 6 GND 5 EXPOSED PAD ON BACKSIDE CONNECT TO P AOLUTE MAXIMUM RATGS () Supply oltage to +0 Switch oltage to + 0. Boost oltage to + 6 All Other Pins to +6 Continuous Power Dissipation (T A = +5 C) ()...5W Junction Temperature...50C Lead Temperature...60C Storage Temperature C to +50C Recommended Operating Conditions () Input oltage...75 to Operating Junct. Temp (T J )...-0C to +5C Thermal Resistance () θ JA θ JC SOICE (Exposed Pad) C/W Notes: ) Exceeding these ratings may damage the device. ) The maximum allowable power dissipation is a function of the maximum junction temperature T J (MAX), the junction-toambient thermal resistance θ JA, and the ambient temperature T A. The maximum allowable continuous power dissipation at any ambient temperature is calculated by P D (MAX) = (T J (MAX)-T A )/θ 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. ) The device is not guaranteed to function outside of its operating conditions. ) Measured on JESD5-7, -layer PCB. MP59 Rev.. /0/0 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. 0 MPS. All Rights Reserved.

3 MP59 A,, 5kHz STEP-DOWN CONERTER ELECTRICAL CHARACTERISTICS =, T A = +5C, unless otherwise noted. Parameter Symbol Condition Min Typ Max Units Shutdown Supply Current EN = μa Supply Current EN =, =..0. ma Feedback oltage.75 < Error Amplifier oltage Gain A EA 00 / Error Amplifier Transconductance High-Side Switch On-Resistance Low-Side Switch On-Resistance High-Side Switch Leakage Current G EA I = 0μA μa/ R DS(ON) 00 0 mω R DS(ON) 0 Ω EN = 0, = μa Current Limit A Current Sense to Transconductance G CS 5. A/ Oscillation Frequency f OSC khz Short Circuit Oscillation Frequency f OSC = khz Maximum Duty Cycle D MAX =.0 90 % Minimum Duty Cycle D M =.5 0 % EN Rising Threshold EN Threshold Hysteresis 50 m Enable Pull Up Current EN = μa Under-oltage Lockout Threshold Under-oltage Lockout Threshold Hysteresis Rising m Soft-Start Period C = 0.μF 0 ms Thermal Shutdown 60 C MP59 Rev.. /0/0 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. 0 MPS. All Rights Reserved.

4 I L A/Div. I L A/Div. I L A/Div. MP59 A,, 5kHz STEP-DOWN CONERTER TYPICAL PERFORMANCE CHARACTERISTICS Refer to Typical Application Schematic on Page FEEDBACK OLTAGE () Feedback oltage vs Temperature TEMPERATURE ( C) PEAK CURRENT LIMIT (A) Peak Current Limit vs Temperature TEMPERATURE ( C) TEMPERATURE ( C) OSCILLATION FREQUENCY (KHz) Oscillation Frequency vs Temperature Soft-Start Waveforms Turn Off Waveforms Load Transient Waveforms /Div. /Div. 00m/Div. ms/div. =, =., A - A STEP Switching Waveforms I L A/Div. 0m/Div. 00m/Div. 0/Div. EFFICIENCY (%) Efficiency vs Load Current = 5 = = LOAD CURRENT (ma) EFFICIENCY (%) Efficiency vs Load Current = = 0 = LOAD CURRENT (ma) MP59 Rev.. /0/0 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. 0 MPS. All Rights Reserved.

5 MP59 A,, 5kHz STEP-DOWN CONERTER P FUNCTIONS Pin # Name Description High-Side Gate Drive Boost Input. supplies the drive for the high-side N-Channel MOSFET switch. Connect a 0nF or greater capacitor from to to power the high-side switch. Power Input. supplies power to the IC. Drive with a.75 to power source. Bypass to GND with a suitably large capacitor to eliminate noise on the input to the IC. See Input Capacitor. Power Switching Output. is the switching node that supplies power to the output. Connect the output LC filter from to the output load. Note that a capacitor is required from to to power the high-side switch. GND Ground. Note: Connect the exposed pad to Pin EN Feedback Input. senses the output voltage and regulates it. Drive with a resistive voltage divider from the output voltage to ground. The feedback threshold is.. See Setting the Output oltage. Compensation Node. is used to compensate the regulation control loop. Connect a series RC network from to GND. In some cases, an additional capacitor from to GND is required. See Compensation. 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. An Under-oltage Lockout (ULO) function can be implemented by the addition of a resistor divider from to GND. For complete low current shutdown the EN pin voltage needs to be less than.5. For automatic startup leave EN disconnected. Soft-Start Control Input. controls the soft-start period. Connect a capacitor from to GND to set the soft-start period. A 0.μF capacitor sets the soft-start period to 0ms. To disable the soft-start feature, leave disconnected. MP59 Rev /0/0 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. 0 MPS. All Rights Reserved.

6 MP59 A,, 5kHz STEP-DOWN CONERTER OPERATION TERNAL REGULATORS CURRENT SENSE AMPLIFIER + 5 OSCILLATOR SLOPE 5/5KHz CLK + + S -- Q M EN SHUTDOWN ARATOR LOCK ARATOR -- R Q CURRENT ARATOR. M.60/ GND FREQUENCY FOLDBACK ARATOR ERROR AMPLIFIER The MP59 is a current-mode step-down regulator. It regulates input voltages from.75 to down to an output voltage as low as., and is able to supply up to A of continuous load current. The MP59 uses current-mode control to regulate the output voltage. The output voltage is measured at through a resistive voltage divider and amplified through the internal error amplifier. The output current of the transconductance error amplifier is presented at where a network compensates the regulation control system. The voltage at is compared to the internally measured switch current to control the output voltage. 6 Figure Functional Block Diagram The converter uses an internal N-Channel MOSFET switch to step-down the input voltage to the regulated output voltage. Since the MOSFET requires a gate voltage greater than the input voltage, a boost capacitor connected between and drives the gate. The capacitor is internally charged when is low. An internal 0Ω switch from to GND is used to insure that is pulled to GND when it is low to fully charge the capacitor. MP59 Rev /0/0 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. 0 MPS. All Rights Reserved.

7 MP59 A,, 5kHz STEP-DOWN CONERTER APPLICATION FORMATION ONENT SELECTION Setting the Output oltage The output voltage is set using a resistive voltage divider from the output voltage to the pin. The voltage divider divides the output voltage down to the feedback voltage by the ratio: R R R Where is the feedback voltage and is the output voltage. Thus the output voltage is: R R. R R can be as high as 00kΩ, but a typical value is 0kΩ. Using that value, R is determined by: R. (.)(k) For a. output voltage, R is 0kΩ and R is 7kΩ. 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, larger value inductors will have larger physical size, higher series resistance and/or lower saturation current. A good standard for determining the inductance to use is to allow the inductor peak-to-peak ripple current to be approximately 0% 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 fs ΔIL Where is the input voltage, f S is the switching frequency and ΔI L 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: I LP I LOAD f S L Where I LOAD is the load current. Table lists a number of suitable inductors from various manufacturers. The choice of which inductor to use mainly depends on the price vs. size requirements and any EMI requirement. Table Inductor Selection Guide endor/ Model Core Type Core Material Package Dimensions (mm) W L H Sumida CR75 Open Ferrite CDH7 Open Ferrite CDRH5D Shielded Ferrite CDRH5D Shielded Ferrite CDRH6D Shielded Ferrite CDRH0R Shielded Ferrite Toko D5LC Type A Shielded Ferrite D75C Shielded Ferrite D0C Shielded Ferrite D0FL Open Ferrite Coilcraft DO0 Open Ferrite DO6 Open Ferrite MP59 Rev /0/0 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. 0 MPS. All Rights Reserved.

8 MP59 A,, 5kHz STEP-DOWN CONERTER Output Rectifier Diode The output rectifier diode supplies current to the inductor when the high-side switch is off. Use a Schottky diode to reduce losses due to diode forward voltage and recovery times. 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 lists example Schottky diodes and manufacturers. Table Diode Selection Guide Diode oltage/current Rating Manufacture SK 0, A Diodes Inc. SK 0, A Diodes Inc. B0 0, A Diodes Inc. B0 0, A Diodes Inc. MBRS0 0, A On Semiconductor MBRS0 0, A On Semiconductor 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 will also suffice. Since the input capacitor (C) absorbs the input switching current it requires an adequate ripple current rating. The RMS current in the input capacitor can be estimated by: I C I LOAD The worst-case condition occurs at =, where: ILOAD IC For simplification, choose the input capacitor whose RMS current rating is 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.μF) 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 the input. The input voltage ripple caused by the capacitance can be estimated by: ILOAD fs C 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: RESR f S L fs C Where L is the inductor value, C is the output capacitance value and R ESR 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, which is the main cause of the output voltage ripple. For simplification, the output voltage ripple can be estimated by: Δ fs L C 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: Δ f S L R ESR The characteristics of the output capacitor also affect the stability of the regulation system. The MP59 can be optimized for a wide range of capacitance and ESR values. MP59 Rev.. /0/0 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. 0 MPS. All Rights Reserved.

9 MP59 A,, 5kHz STEP-DOWN CONERTER Compensation Components The MP59 employs current mode control for easy compensation and fast transient response. The system stability and transient response are controlled through the 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. The DC gain of the voltage feedback loop is given by: A DC R LOAD G CS A EA Where A EA is the error amplifier voltage gain, G CS is the current sense transconductance and R LOAD is the load resistor value. The system has two poles of importance. One is due to the compensation capacitor (C) and the output resistor of error amplifier, while the other is due to the output capacitor and the load resistor. These poles are located at: f f P P GEA C A C R EA LOAD Where G EA is the error amplifier transconductance. The system has one zero of importance, due to the compensation capacitor (C) and the compensation resistor (R). This zero is located at: f Z C R 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: f ESR C R ESR In this case (as shown in Figure ), a third pole set by the compensation capacitor (C6) and the compensation resistor (R) is used to compensate the effect of the ESR zero on the loop gain. This pole is located at: f P C6 R 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 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 to approximately one-tenth of the switching frequency. The switching frequency for the MP59 is 5KHz, so the desired crossover frequency is around KHz. Table 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. MP59 Rev /0/0 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. 0 MPS. All Rights Reserved.

10 MP59 A,, 5kHz STEP-DOWN CONERTER Table Compensation alues for Typical Output oltage/capacitor Combinations L C R C C6..7μH μH 6.- 0μH 0-5μH 5- μh..7μh μH 6.- 0μH 0-5μH.7-6.μH 6.- 0μH 0-5μH 5- μh 00μF Ceramic 7μF Ceramic μfx Ceramic μfx Ceramic μfx Ceramic 00μF SP-CAP 7μF SP-CAP 7μF SP-CAP 7μF SP CAP 560μF Al. 0mΩ ESR 560μF Al 0mΩ ESR 70μF Al. 0mΩ ESR 0μF Al. 0mΩ ESR 5.6kΩ.nF None.9kΩ 5.6nF None 5.6kΩ.nF None 7.5kΩ 0nF None 0kΩ.nF None 5.6kΩ.nF 00pF.7kΩ 5.6nF None 6.kΩ 0nF None 0kΩ 0nF None 0kΩ 5.6nF.5nF 0kΩ.nF.5nF 5kΩ 5.6nF nf 5kΩ.7nF 90pF To optimize the compensation components for conditions not listed in Table, the following procedure can be used.. Choose the compensation resistor (R) to set the desired crossover frequency. Determine R by the following equation: R C f G G EA C CS Where f C is the desired crossover frequency (which typically has a value no higher than KHz).. Choose the compensation capacitor (C) to achieve the desired phase margin. For applications with typical inductor values, setting the compensation zero, f Z, below one forth of the crossover frequency provides sufficient phase margin. Determine C by the following equation: C R Where R is the compensation resistor value.. 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 5kHz switching frequency, or the following relationship is valid: C R f C f S ESR Where C is the output capacitance value, R ESR is the ESR value of the output capacitor and f S is the switching frequency. If this is the case, then add the second compensation capacitor (C6) to set the pole f P at the location of the ESR zero. Determine C6 by the equation: C RESR C6 R Where C is the output capacitance value, R ESR is the ESR value of the output capacitor and R is the compensation resistor. PCB Layout Guide PCB layout is very important to achieve stable operation. It is highly recommended to duplicate EB layout for optimum performance. If change is necessary, please follow these guidelines and take Figure and for references. ) Keep the path of switching current short and minimize the loop area formed by Input cap, high-side MOSFET and low-side MOSFET/schottky diode. ) Keep the connection of low-side MOSFET/schottky diode between pin and input power ground as short and wide as possible. ) Bypass ceramic capacitors are suggested to be put close to the and CC Pin. ) Ensure all feedback connections are short and direct. Place the feedback resistors and compensation components as close to the chip as possible. MP59 Rev /0/0 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. 0 MPS. All Rights Reserved.

11 MP59 A,, 5kHz STEP-DOWN CONERTER 5) Route away from sensitive analog areas such as. 6) Connect,, and especially GND respectively to a large copper area to cool the chip to improve thermal performance and long-term reliability. For single layer, do not solder exposed pad of the IC. C R 7 EN 6 GND 5 R R C6 C SGND SGND R C R 7 EN 6 C C6 5 R R R SGND C5 PGND C D L C GND Figure PCB Layout (Single Layer) C5 C D PGND TOP Layer L C External Bootstrap Diode An external bootstrap diode may enhance the efficiency of the regulator, the applicable conditions of external T diode are: =5 or.; and Duty cycle is high: D= >65% In these cases, an external T diode is recommended from the output of the voltage regulator to T pin, as shown in Fig. SGND MP59 T External T Diode CT out Feeback L C 5 or. Figure Add Optional External Bootstrap Diode to Enhance Efficiency The recommended external T diode is, and the T cap is 0.~µF. Bottom Layer Figure PCB Layout (Double Layer) MP59 Rev.. /0/0 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. 0 MPS. All Rights Reserved.

12 MP59 A,, 5kHz STEP-DOWN CONERTER TYPICAL APPLICATION CIRCUITS PUT.75 to C5 0nF OFF ON 7 EN GND MP59 C6 (optional) 5 6 C.nF D B0A PUT.5 A Figure 5 MP59 with AX 7μF, 6. Ceramic Output Capacitor PUT.75 to C5 0nF OFF ON 7 EN GND MP59 C6 (optional) 5 6 C.nF D B0A PUT.5 A Figure 6 MP59 with Panasonic 7μF, 6. Special Polymer Output Capacitor MP59 Rev.. /0/0 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. 0 MPS. All Rights Reserved.

13 MP59 A,, 5kHz STEP-DOWN CONERTER PACKAGE FORMATION SOICE (EXPOSED PAD) 0.9(.0) 0.97(5.00) 5 0.(.5) 0.6(.5) P ID 0.50(.0) 0.57(.00) 0.(5.0) 0.(6.0) 0.09(.6) 0.0(.56) TOP IEW BOTTOM IEW SEE DETAIL "A" 0.0(0.) 0.00(0.5) 0.05(.0) 0.067(.70) SEATG PLANE 0.000(0.00) 0.006(0.5) 0.050(.7) C SIDE IEW (0.9) 0.009(0.5) FRONT IEW 0.00(0.5) 0.00(0.50) x 5o GAUGE PLANE 0.00(0.5) C 0.0(0.6) 0.06(.60) 0.050(.7) 0 o - o 0.06(0.) 0.050(.7) DETAIL "A" 0.(.5) 0.0(.6) RECOMMENDED LAND PATTERN 0.(5.0) NOTE: ) CONTROL DIMENSION IS CHES. DIMENSION BRACKET IS MILLIMETERS. ) PACKAGE LENGTH DOES NOT CLUDE MOLD FLASH, PROTRUSIONS OR GATE BURRS. ) PACKAGE WIDTH DOES NOT CLUDE TERLEAD FLASH OR PROTRUSIONS. ) LEAD COPLANARITY (BOTTOM OF LEADS AFTER FORMG) SHALL BE 0.00" CHES MAX. 5) DRAWG CONFORMS TO JEDEC MS-0, ARIATION BA. 6) DRAWG IS NOT TO SCALE. 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. MP59 Rev.. /0/0 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. 0 MPS. All Rights Reserved.